Keyword: SRF
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MOFAA1 LCLS-II: Status, Issues and Plans cavity, cryomodule, linac, FEL 1
 
  • M.C. Ross
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by Department of Energy contract DE-AC02-76SF00515
The Linac Coherent Light Source II (LCLS-II) project requires the assembly, test, and installation of 37 cryomodules (CM) in order to deliver a 4 GeV CW electron beam to the FEL undulators for production of both hard and soft X-ray pulses at a repetition rate of up to 1 MHz. SRF cavity performance in the 30+ tested CM exceeds gradient and cryogenic dynamic heat-load requirements (set at 16 MV/m and 10 W resp). In this talk we present microphonics, shipping, magnetic-flux exclusion, and field emission performance. The US funding agency, DOE, has recently approved an additional 20 CM for the extension of LCLS-II to 8 GeV. This paper will also include initial cavity and heat-load performance results for the extension project, LCLS-II-HE.
 
slides icon Slides MOFAA1 [30.146 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOFAA1  
About • paper received ※ 25 June 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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MOP003 Development of Nb3Sn Cavity Coating at IMP cavity, niobium, radio-frequency, experiment 21
 
  • Z.Q. Yang, H. Guo, Y. He, C.L. Li, Z.Q. Lin, M. Lu, T. Tan, P.R. Xiong, S.H. Zhang, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  The A15 superconductor Nb3Sn is one of the most promising alternative materials to standard niobium for SRF applications. In this paper, we report our progress in the development of Nb3Sn cavity coating by vapor diffusion method at IMP. The evolutionary process of nucleation was analyzed. Influence of SnCl2 partial pressure inhomogeneity was studied. Less-nuclear zones were found on the surfaces of nucleation samples. The Nb3Sn film structure and composition were investigated and analyzed. In light of knowledge obtained above, the coating process was optimized. Finally, both 1.3 GHz and 650 MHz single cell cavities were coated and vertically tested both at 4 K and 2 K. Effect of low temperature baking (1000°C for 48 hs) on the RF performance of Nb3Sn cavity was studied. After baking, the Q drop in the low field region was eliminated and the Q in the intermediate field region was increased 8 times. The Q was 10 times larger than that of the Nb cavity at 4.2 K even in the case of the ambient field larger than 20 mGs. This study shows that the low temperature baking is an effective enrichment to the post treatment of the Nb3Sn cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP003  
About • paper received ※ 23 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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MOP005 The Facility for Rare Isotope Beams Superconducting Cavity Production Status and Findings Concerning Surface Defects cavity, linac, niobium, status 31
 
  • C. Compton
    NSCL, East Lansing, Michigan, USA
  • H. Ao, J. Asciutto, K. Elliott, W. Hartung, S.H. Kim, E.S. Metzgar, S.J. Miller, J.T. Popielarski, L. Popielarski, K. Saito, T. Xu
    FRIB, East Lansing, Michigan, USA
  • J. Craft
    SLAC, Menlo Park, California, USA
 
  Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Facility for Rare Isotope Beams (FRIB), located on the campus of Michigan State University (MSU) will require 324 Superconducting Radio Frequency (SRF) cavities in the driver linac. Four types of cavities of two classes, quarter-wave (β=0.041 and 0.085) and half-wave (β=0.29 and 0.53), will be housed in 46 cryomodules. To date, FRIB has tested over 300 cavities in vertical Dewar tests as part of the certification procedures. Incoming cavities, fabricated in industry, are sequenced through acceptance inspection and checked for non-conformance. If accepted, the cavities are processed, assembled onto a vertical test stand, and cold tested. A large database of cavity surface images has been collected with the aid of a borescope camera. Borescope inspection is a standard step that is performed at incoming inspection, post-acid bulk etch, and after failed tests (if necessary) for each cavity, in order to locate any non-conformances. Findings of surface defects relating to degraded cavity performance will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP005  
About • paper received ※ 02 July 2019       paper accepted ※ 13 August 2019       issue date ※ 14 August 2019  
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MOP010 Ab Initio Calculations on the Growth and Superconducting Properties of Nb3Sn site, cavity, niobium, electron 39
 
  • N. Sitaraman, T. Arias, P. Cueva, M.M. Kelley, D.A. Muller
    Cornell University, Ithaca, New York, USA
  • J.M. Carlson, A.R. Pack, M.K. Transtrum
    Brigham Young University, Provo, USA
  • M. Liepe, R.D. Porter, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This research was funded by the Center for Bright Beams.
In this work, we employ theoretical ab initio techniques to solve mysteries and gain new insights in Nb3Sn SRF physics. We determine the temperature dependence of Nb3Sn antisite defect formation energies, and discuss the implications of these results for defect segregation. We calculate the phonon spectral function for Nb3Sn cells with different combinations of antisite defects and use these results to determine Tc as a function of stoichiometry. These results allow for the first-ever determination of Tc in the tin-rich regime, where experimental measurements are unavailable and which is critical to understanding the impact of tin-rich grain boundaries on superconducting cavity performance. Finally, we propose a theory for the growth mechanism of Nb3Sn growth on a thick oxide, explaining the puzzling disappearing droplet behavior of Sn on Nb oxide and suggesting how in general an oxide layer reacts with Sn to produce a uniform Nb3Sn layer.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP010  
About • paper received ※ 02 July 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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MOP011 High Frequency Nb3Sn Cavities cavity, niobium, radio-frequency, factory 44
 
  • R.D. Porter, M. Liepe, J.T. Maniscalco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Niobium-3 Tin (Nb3Sn) is an alternative material to Nb for SRF cavities. This material is capable of higher temperature operation and has high theoretical maximum accelerating gradients. Cornell University is a leader in the development of this material for SRF applications, and current Nb3Sn 1.3 GHz single cells produced at Cornell achieve quality factors above 10zEhNZeHn at 4.2 K at medium fields, far above what can be reached with niobium. Most of the recent Nb3Sn cavity development has been done at 1.3 GHz. In this paper, we present new results from Nb3Sn cavities at 2.6 GHz and 3.9 GHz. We compare relative cavity performance and flux trapping sensitivities, and extract frequency dependencies. Results show that the frequency can be increased without degrading the performance of the cavities, opening the path towards a new generation of compact and efficient SRF cavities for a wide range of future applications.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP011  
About • paper received ※ 05 July 2019       paper accepted ※ 12 July 2019       issue date ※ 14 August 2019  
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MOP013 Reducing Surface Roughness of Nb3Sn Through Chemical Polishing Treatments cavity, niobium, superconductivity, controls 48
 
  • H. Hu, M. Liepe, R.D. Porter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Niobium-3 tin (Nb3Sn) is a promising alternative material for SRF cavities, with theoretical limits for critical temperatures and superheating fields reaching twice that of conventional Nb cavities. However, currently achievable accelerating gradients in Nb3Sn cavities are much lower than their theoretical limit. One limitation to the maximum accelerating gradient is surface magnetic field enhancement caused by the surface roughness of Nb3Sn. However, there are currently no standard techniques used to reduce Nb3Sn surface roughness. Since Nb3Sn is only 2-3 microns thick, it is difficult to selectively polish Nb3Sn without removing the entire layer. Here, we investigate reducing the surface roughness of Nb3Sn through applying chemical polishing treatments, including modified versions of standard techniques such as Buffered Chemical Polishing (BCP) and Electropolishing (EP). Through data acquired from Atomic Force Microscope (AFM) scans, SEM scans, and SEM-EDS analysis, we show the effects of these chemical treatments in reducing surface roughness and consider the changes in the chemical composition of Nb3Sn that may occur through the etching process. We find that BCP with a 1:1:8 solution is ineffective while EP halves the surface roughness of Nb3Sn.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP013  
About • paper received ※ 01 July 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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MOP015 RF Performance Sensitivity to Tuning of Nb3Sn Coated CEBAF Cavities cavity, simulation, experiment, factory 55
 
  • G.V. Eremeev, W. Crahen, J. Henry, F. Marhauser, C.E. Reece
    JLab, Newport News, Virginia, USA
  • U. Pudasaini
    The College of William and Mary, Williamsburg, Virginia, USA
 
  Funding: Co-Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
Nb3Sn has the potential to surpass niobium as the material of choice for SRF applications. The potential of this material stems from a larger superconducting energy gap, which leads to expectations of a higher RF critical field and a lower RF surface resistance. The appeal of better superconducting properties is offset by the relative complexity of producing practical Nb3Sn structures, and Nb3Sn sensitivity to lattice disorder challenges the use of the material for practical applications. Such sensitivity is indirectly probed during SRF cavity development, when the cavity is tuned to match the desired accelerator frequency. In the course of recent experiments we have coated and tuned several multi-cell cavities. Cold RF measurements before and after tuning showed degradation in cavity performance after tuning. The results of RF measurement were compared against strain evolution on Nb3Sn surface during tuning based on CST and ANSYS models.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP015  
About • paper received ※ 26 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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MOP016 Insights Into Nb3Sn Coating of CEBAF Cavities From Witness Sample Analysis cavity, niobium, HOM, hardware 60
 
  • G.V. Eremeev, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
  • M.J. Kelley, U. Pudasaini
    The College of William and Mary, Williamsburg, Virginia, USA
 
  Funding: Co-Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
With the progress made in the Nb3Sn coatings on single-cell SRF cavities, development is ongoing to reproduce single-cell cavity results on practical structures such as CEBAF 5-cell cavities. During CEBAF cavity coating development, several changes from the single-cell procedure to the coating setup and the heating profile were introduced to improve the quality of Nb3Sn films. To witness the properties of grown Nb3Sn films in different cavity locations, 10 mm x 10 mm samples were positioned in strategic places within the coating chamber. Composition and structure of the samples were analyzed with surface analytic techniques and correlated with sample location during coatings. Implications from sample analysis to Nb3Sn coatings on different geometries are discussed in this contribution.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP016  
About • paper received ※ 26 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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MOP018 Recent Results From Nb3Sn Single Cell Cavities Coated at Jefferson Lab cavity, experiment, factory, niobium 65
 
  • U. Pudasaini, M.J. Kelley
    The College of William and Mary, Williamsburg, Virginia, USA
  • G. Ciovati, G.V. Eremeev, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
  • I.P. Parajuli, Md.N. Sayeed
    ODU, Norfolk, Virginia, USA
 
  Funding: Partially authored by Jefferson Science Associates under contract no. DE¬AC05¬06OR23177. Supported by Office of High Energy Physics under grants DE-SC-0014475 to the College of William and DE-SC-0018918 to Virginia Tech
Because of superior superconducting properties (Tc ~ 18.3K, Hs h ~ 425 mT and delta ~ 3.1 meV) compared to niobium, Nb3Sn promise better RF performance (Q0 and Eacc) and/or higher operating temperature (2 K Vs 4.2 K) for SRF cavities. Nb3Sn-coated SRF cavities are produced routinely by depositing a few micron-thick Nb3Sn films on the interior surface of Nb cavities via tin vapor diffusion technique. Early results from Nb3Sn cavities coated with this technique exhibited precipi-tous low field Q-slope, also known as Wuppertal slope. Several Nb3Sn single cell cavities coated at JLab ap-peared to exhibit similar Q-slope. RF testing of cavi-ties and materials study of witness samples were con-tinuously used to modify the coating protocol. At best condition, we were able to produce Nb3Sn cavity with Q0 in excess of ~ 5×1010 at 2 K and ~ 2×1010 at 4 K up the accelerating gradient of ~15 MV/m, without any significant Q-slope. In this presentation, we will dis-cuss recent results from several Nb3Sn coated single-cell cavities linked with material studies of witness samples, coating process modifications and the possi-ble causative factors to Wuppertal slope.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP018  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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MOP022 Superconducting RF Cavity Materials Research at the S-DALINAC cavity, niobium, linac, simulation 74
 
  • R. Grewe, L. Alff, M. Arnold, J. Conrad, S. Flege, M. Major, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
 
  Funding: Supported by BMBF Through 05H18RDRB2
Current state-of-the-art superconducting rf (srf) accelerators are mostly using cavities made of high RRR bulk niobium (Nb). The maximum field gradients and quality factors (Q0) of these cavities are basically reached now. To further increase the srf cavity properties for future accelerator facilities, research of new materials for srf cavity applications is necessary. The current research at the S-DALINAC* is focused on the development of bake-out procedures of Nb samples and cavities in nitrogen (N) atmosphere of up to 100 mbar to nucleate the delta-phase (d-phase) of the Nb-N binary system. The d-phase has superconducting properties which exceed the properties of bulk Nb. This makes the d-phase attractive for srf applications. The vertical test cryostat (vt) at the S-DALINAC has been upgraded and recommissioned to allow investigations of the quality factor and accelerating field gradients of cavities before and after bake-out. The vt upgrade includes a newly developed variable input coupling to allow matching of the external q-factor (Qex) to Q0. The results of the ongoing research of the nitrogen atmosphere bake-out procedures and the upgrade of the vt will be presented.
*N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018)
 
poster icon Poster MOP022 [1.759 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP022  
About • paper received ※ 21 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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MOP023 Nitrogen Infusion Sample R&D at DESY cavity, niobium, vacuum, HOM 77
 
  • C. Bate, A. Dangwal Pandey, A. Ermakov, B. Foster, T.F. Keller, D. Reschke, J. Schaffran, S. Sievers, N. Walker, H. Weise, M. Wenskat
    DESY, Hamburg, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • G.D.L. Semione, V. Vonk
    DESY Nanolab, FS-NL, Hamburg, Germany
  • A. Stierle
    University of Hamburg, Hamburg, Germany
 
  The European XFEL continuous wave upgrade requires cavities with reduced surface resistance (high Q-values) for high duty cycle while maintaining high accelerating gradient for short-pulse operation. A possible way to meet the requirements is the so-called nitrogen infusion procedure. However, a fundamental understanding and a theoretical model of this method are still missing. The approach shown here is based on sample R&D, with the goal to identify key parameters of the process and establish a stable, reproducible recipe. To understand the underlying processes of the surface evolution, which gives improved cavity performance, advanced surface analysis techniques (e.g. SEM/EDX, TEM, XPS, TOF-SIMS) are utilized. Additionally, a small furnace just for samples was set up to change and explore the parameter space of the infusion recipe. Results of these analyses, their implications for the cavity R&D and next steps are presented.  
poster icon Poster MOP023 [3.759 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP023  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP025 Cavity Cut-out Studies of a 1.3 GHz Single-cell Cavity After a Failed Nitrogen Infusion Process cavity, niobium, electron, superconductivity 87
 
  • M. Wenskat, C. Bate, T.F. Keller, D. Reschke
    DESY, Hamburg, Germany
  • C. Bate
    University of Hamburg, Hamburg, Germany
  • A. Jeromin
    DESY Nanolab, FS-NL, Hamburg, Germany
  • J. Knobloch, F. Kramer, O. Kugeler, J.M. Köszegi
    HZB, Berlin, Germany
  • J. Knobloch
    University of Siegen, Siegen, Germany
 
  Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program and by the BMBF under the research grant 05H18GURB1.
R&D on the nitrogen infusion process at DESY produced at the beginning a series of 1.3 GHz single-cell cavities which have shown severe deterioration in the vertical cold test which was completely unexpected and could not be explained. To investigate the reason for the deterioration, one of those cavities was optically inspected and a T- and H-Map test was done in collaboration with HZB. Together with 2nd Sound data, regions of interests were identified and cut from the cavity. Subsequent surface analysis techniques (SEM/EDX, SIMS, PIXE, EBSD, DB-PAS, PALS, XPS) were applied in order to identify the reason for the deterioration. Especially the differences between hot and cold spots as well as quench spots identified by T-Mapping were investigated.
 
poster icon Poster MOP025 [0.975 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP025  
About • paper received ※ 20 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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MOP027 Study on Nitrogen Infusion using KEK New Furnace cavity, injection, accelerating-gradient, vacuum 95
 
  • K. Umemori, E. Kako, T. Konomi, S. Michizono, H. Sakai
    KEK, Ibaraki, Japan
  • T. Okada
    Sokendai, Ibaraki, Japan
  • J. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
 
  KEK has been carried out high-Q/high-G R&D, to realize high performance of SRF cavities toward ILC. KEK constructed a new furnace, which is dedicated for N-infusion studies. We performed more than 10 times of N-infusion trials using 1.3 GHz single-cell cavities. Some results showed better Q-values up to high field, however, some results showed degraded Q-E slopes probably due to contamination. Improvement of accelerating gradient is not observed at moment. We have tried to clean the furnace and Nitrogen injection line to reduce the effect of contamination. Details of procedures of N-infusion, results of vertical tests, condition of the furnace including RGA spectrum and Nb sample analysis results are shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP027  
About • paper received ※ 04 July 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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MOP028 Materials Science Investigations of Nitrogen-Doped Niobium for SRF Cavities cavity, niobium, superconducting-RF, collider 99
 
  • M. Major, L. Alff, M. Arnold, J. Conrad, S. Flege, R. Grewe, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by the German Federal Ministry for Education and Research (BMBF) through grant 05H18RDRB2.
Niobium is the standard material for superconducting RF (SRF) cavities for particle acceleration. Superconducting materials with higher critical temperature or higher critical magnetic field allow cavities to work at higher operating temperatures or higher accelerating fields, respectively. Enhancing the surface properties of the superconducting material in the range of the penetration depth is also beneficial. One direction of search for new materials with better properties is the modification of bulk niobium by nitrogen doping. In the Nb-N phase diagram, the cubic delta-phase of NbN has the highest critical temperature. Niobium samples were annealed and N-doped in the high-temperature furnace at TU Darmstadt and investigated at its Materials Research Department with respect to structural modifications. Secondary ion mass spectrometry showed at which conditions N-diffusion takes place. X-ray diffraction (XRD) confirmed the appearance of NbN and Nb2N phases for the optimized doping process. XRD pole figures also showed grain growth during sample annealing.
 
poster icon Poster MOP028 [2.555 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP028  
About • paper received ※ 05 July 2019       paper accepted ※ 12 July 2019       issue date ※ 14 August 2019  
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MOP029 N-Doping Studies With Single-Cell Cavities for the SHINE Project cavity, niobium, FEL, ECR 102
 
  • J.F. Chen, H.T. Hou, Y.F. Liu, D. Wang, Y. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • Y.W. Huang
    ShanghaiTech University, Shanghai, People’s Republic of China
  • Z. Wang
    SINAP, Shanghai, People’s Republic of China
 
  The SHINE SRF accelerator is designed to operate in CW mode with more than six hundred superconducting cavities. In order to reduce the high cost of construction and operation of the cryogenic system, high-Q cavities with nitrogen-doping technology together with tradition-ally treated large-grain cavities have been considered as two possible options. In this paper, we present N-doping studies on single-cell cavities fabricated with fine-grain and large-grain niobium.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP029  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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MOP030 Analysis of Surface Nitrides Created During "Doping" Heat Treatments of Niobium niobium, cavity, lattice, controls 106
 
  • J.K. Spradlin, A.D. Palczewski, C.E. Reece, H. Tian
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The benefits of reduced RF losses from interstitial "doping" of niobium are well established. Many of the details involved in the process remain yet to be elucidated. The niobium surface reacted with low-pressure nitrogen at 800°C presents a surface with chemical reactivity different than standard niobium. While standard "recipes" are being used to produce cavities, we seek additional insight into the chemical processes that may be used to remove the "undesirable" as-formed surface layer. This may lead to new processing routes or quality assurance methods to build confidence that all surface "nitrides" have been removed. We report a series of alternate chemistry treatments and subsequent morphological examinations and interpret the results. We also introduce a new standardized Nb sample system in use for efficient characterization of varying doping protocols and cross-laboratory calibration.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP030  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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MOP031 Investigation of Frequency Behavior Near Tc of Niobium Superconducting Radio-Frequency Cavities cavity, niobium, electron, ECR 112
 
  • D. Bafia, J. Zasadzinski
    IIT, Chicago, Illinois, USA
  • D. Bafia, M. Checchin, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
 
  This paper will present a systematic investigation of the resonant frequency behavior of niobium SRF cavities subject to different surface processing (nitrogen doping, nitrogen infusion, 120°C bake, EP, etc.) near the critical transition temperature. We find features occurring in frequency versus temperature (FvsT) data near Tc that seem to vary with surface processing. Emphasis is placed on one of the observed features: a dip in the superconducting resonant frequency below the normal conducting value which is prominent in nitrogen doped cavities and appears to be a signature of nitrogen doping. This gives further insights on the mechanisms responsible for the large increase in performance of cavities subject to this surface treatment. The magnitude of this dip in frequency is studied and related to possible physical parameters such as the concentration of impurities near the surface and the design resonant frequency of the cavity. A possible explanation for the meaning of this dip is discussed, namely, that it is a result of strong coupling between electrons and phonons within the resonator.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP031  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP032 Effect of Low Temperature Infusion Heat Treatments and "2/0" Doping on Superconducting Cavity Performance cavity, ECR, niobium, background 118
 
  • P.N. Koufalis, M. Ge, M. Liepe, J.T. Maniscalco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Under specific circumstances, low temperature infusion heat treatments of niobium cavities have resulted in the ubiquitous "Q-rise". This is an increase in quality factor with increasing field strength or equivalently a decrease in the temperature-dependent component of the surface resistance. We investigate the results of various infusion conditions with infusion bake time as a free parameter. To study the very near surface effects of infusion, we employ HF rinsing, light VEP, and oxypolishing to remove several or tens of nm at a time. We present results from RF performance tests of low temperature infusion heat treated niobium cavities, and correlate these with SIMS impurity depth profiles obtained from witness samples. We also present results of a cavity doped at 800 C with the "2/0" recipe.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP032  
About • paper received ※ 26 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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MOP033 The Beam Dynamics Updates of the Fermilab PIP-II 800 MeV Superconducting Linac linac, cavity, optics, emittance 123
 
  • A. Saini, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  • E. Pozdeyev
    FRIB, East Lansing, Michigan, USA
 
  The Proton Improvement Plan (PIP) -II is a high intensity proton facility being developed to support a neutrino program over the next two decades at Fermilab. At its core is the design and construction of a Continuous Wave compatible superconducting radio frequency linear accelerator that would accelerate an average beam current of 2 mA up to 800 MeV. This paper presents recent updates in the beam dynamics leading to a reliable and robust linac design and simplifying the cryo-module assembly.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP033  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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MOP034 European XFEL: Accelerating Module Repair at DESY cavity, FEL, linac, operation 127
 
  • D. Kostin, J. Eschke, K. Jensch, N. Krupka, D. Reschke, S. Saegebarth, J. Schaffran, M. Schalwat, P. Schilling, M. Schmökel, S. Sievers, N. Steinhau-Kühl, E. Vogel, H. Weise, M. Wiencek, B. van der Horst
    DESY, Hamburg, Germany
 
  The European XFEL is in operation since 2017. The design projected energy of 17.5 GeV was reached, even with the last 4 main linac accelerating modules not yet installed. 2 out of 4 not installed modules did suffer from strong cavity performance degradation, namely increased field emission, and required surface processing. The first of two modules is reassembled and tested. The module test results confirm a successful repair action. The module repair and test steps are described together with cavities performance evolution.  
poster icon Poster MOP034 [1.863 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP034  
About • paper received ※ 17 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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MOP040 Low Temperature Thermal Conductivity of Niobium and Materials for SRF Cavities niobium, cavity, experiment, controls 144
 
  • M. Fouaidy
    IPN, Orsay, France
 
  A test facility, allowing the test of 4 samples simultaneously during each run, was developed for measuring at low temperature (T= 1.5 K - 10 K) the thermal conductivity k(T) of niobium and other materials used for the fabrication of SRF cavities. The measurements are performed using steady-state axial heat flow method with a careful control of heat leaks to the surrounding. Several samples of different materials (industrial Nb sheets, Ti’) were either tested as received or/and subjected to various Heat Treatment (H.T) prior to the experiment then tested. The resulting experimental data are presented and compared to the experimental results previously reported by other groups. As expected, H.T @ 1200°C with Ti gettering improves the Nb RRR by a factor of 3 and consequently k(T). Finally, the correlation between the Niobium RRR and the thermal conductivity. at T=4.2 K is confirmed in good agreement with the Wiedemann-Franz law.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP040  
About • paper received ※ 04 July 2019       paper accepted ※ 05 July 2019       issue date ※ 14 August 2019  
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MOP045 The LCLS-II HE High Q and Gradient R&D Program cavity, cryomodule, linac, niobium 154
 
  • D. Gonnella, S. Aderhold, A. Burrill, G.R. Hays, T.O. Raubenheimer, M.C. Ross
    SLAC, Menlo Park, California, USA
  • D. Bafia, M. Checchin, A. Grassellino, M. Martinello, A.S. Romanenko
    Fermilab, Batavia, Illinois, USA
  • M. Ge, M. Liepe, S. Posen
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • A.D. Palczewski, C.E. Reece
    JLab, Newport News, Virginia, USA
 
  Funding: US DOE and the LCLS-II HE Project
The LCLS-II HE project is a high energy upgrade to the superconducting LCLS-II linac. It consists of adding twenty additional 1.3 GHz cryomodules to the linac, with cavities operating at a gradient of 20.8 MV/m with a Q0 of 2.7·1010. Performance of LCLS-II cryomodules has suggested that operations at this high of a gradient will not be achievable with the existing cavity recipe employed. Therefore a research program was developed between SLAC, Fermilab, Thomas Jefferson National Accelerator Facility, and Cornell University in order to improve the cavity processing method of the SRF cavities and reach the HE goals. This program explores the doping regime beyond what was done for LCLS-II and also has looked to further developed nitrogen-infusion. Here we will summarize the results from this R\&D program, showing significant improvement on both single-cell and 9-cell cavities compared with the original LCLS-II cavity recipe.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP045  
About • paper received ※ 25 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP047 Progress of IFMIF/EVEDA Project and Prospects for A-FNS neutron, rfq, radiation, cavity 159
 
  • S. Ishida, A. Kasugai, K. Sakamoto
    QST, Aomori, Japan
  • P. Cara
    IFMIF/EVEDA, Rokkasho, Japan
  • H. Dzitko
    F4E, Germany
 
  International Fusion Materials Irradiation Facility (IFMIF) is an accelerator-based D-Li neutron source, in which two 40 MeV Deuteron(D) beams with a total current 250 mA impact on a liquid Li stream flowing at 15 m/s. In the IFMIF/EVEDA project under the Broader Approach (BA) agreement, the Li target was continuously operated with the cold trap and satisfied the stability requirement throughout the continuous operation. The Linear IFMIF Prototype Accelerator (LIPAc) is currently under development in Rokkasho, Japan, to demonstrate the 9 MeV/125 mA D+ beam acceleration. Recently, the first proton beam was injected into the RFQ with more than 90 % of transmission, followed by the first D+ beam accelerated at 5 MeV. The SRF linac necessary for the 9-MeV D+ beam is nearing completion of the manufacturing phase and will be assembled in Rokkasho. Based on these results, a conceptual design of the Advanced Fusion Neutron Source (A-FNS) for its construction in Rokkasho is underway to obtain material irradiation data for a DEMO reactor. The A-FNS is designed to be composed of an accelerator facility with a 40 MeV/125 mA D+ beam, a test facility including a liquid Li target system and a post irradiation examination facility, and to enable multipurpose utilization for neutron application.  
poster icon Poster MOP047 [2.327 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP047  
About • paper received ※ 29 June 2019       paper accepted ※ 12 July 2019       issue date ※ 14 August 2019  
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MOP049 Prototypes Fabrication of 1.3 GHz Superconducting Rf Components for SHINE cavity, FEL, niobium, HOM 164
 
  • H.T. Hou, J.F. Chen, Z.Y. Ma, J. Shi, Y. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • F.S. He
    IHEP, Beijing, People’s Republic of China
  • S.W. Quan
    PKU, Beijing, People’s Republic of China
 
  Aiming to high repetition rate hard X-ray facility, con-struction of Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) project has been ap-proved. During the R & D phase, prototypes fabrication of key components of 1.3GHz superconducting rf system have been proposed, especially 1.3 GHz 9-cell niobium cavities. Here the paper will present the progress of the fabrication status and performance of the prototypes, together with the analysis of not only the quality factor and gradient of the cavities. Consideration of HOM feed-throughs and absorbers are also reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP049  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP054 Fabrication of 3.0-GHz Single-cell Cavities for Thin-film Study cavity, MMI, FEL, linac 177
 
  • T. Saeki, H. Hayano, H. Inoue, R. Katayama, T. Kubo
    KEK, Ibaraki, Japan
  • F.E. Hannon, R.A. Rimmer, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
  • H. Ito
    Sokendai, Ibaraki, Japan
  • Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
 
  Funding: This work is supported by JSPS KAKENHI JP17H04839, JSPS KAKENHI JP26600142, Japan-US Research Collaboration Program, and the Collaborative Research Program of ICR Kyoto Univ. (2018-13).
We fabricated 3.0-GHz single-cell cavities with Cu and Nb materials for testing thin-film creations on the inner surface of the cavities in collaboration between Jefferson Laboratory (JLab) and KEK. The cavity was designed at JLab. According to the design of cavity, the press-forming dies and trimming fixtures for the cavity-cell were also designed and fabricated at JLab. These dies and trimming fixtures were transported to KEK, and the rest of fabrication processes were done at KEK. Finally nine Cu 3.0-GHz single-cell cavities and six Nb 3.0-GHz single-cell cavities were fabricated. Two Cu 3.0-GHz single-cell cavities were mechanically polished at Jlab. All of these cavities will be utilized for the tests of various thin-film creations at JLab and KEK. This presentation describes details of the fabrication of these cavities.
 
poster icon Poster MOP054 [1.203 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP054  
About • paper received ※ 05 July 2019       paper accepted ※ 13 August 2019       issue date ※ 14 August 2019  
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MOP056 Surface Treatments for the Series Production of ESS Medium Beta Cavities cavity, recirculation, niobium, simulation 188
 
  • M. Bertucci, A. Bosotti, A. D’Ambros, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • D. Rizzetto, M. Rizzi
    Ettore Zanon S.p.A., Schio, Italy
  • A. Visentin
    Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
 
  The surface treatment of ESS 704 MHz medium beta cavities consists of a bulk BCP 200 micron removal, a 10 h 600°C heat treatment and a final 20 micron BCP performed after tank integration. The facility currently employed for the BCP treatment, settled in Ettore Zanon SpA, is here presented, together with the results so far obtained on the first series cavities in terms of frequency sensitivity, removal rate and surface external temperature. The optimization of BCP treatment by a preliminary fluid-dynamical finite element model is also discussed. Some details about the visual inspection procedure and the furnace qualification are also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP056  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP058 ESS Medium Beta Activity at INFN LASA cavity, HOM, status, controls 199
 
  • D. Sertore, M. Bertucci, A. Bignami, A. Bosotti, M. Chiodini, A. D’Ambros, G. Fornasier, P. Michelato, L. Monaco, R. Paparella
    INFN/LASA, Segrate (MI), Italy
  • S. Aurnia, O. Leonardi, A. Miraglia, G. Vecchio
    INFN/LNS, Catania, Italy
  • A. Gresele, A. Visentin
    Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • D. Reschke, A. Sulimov, M. Wiencek
    DESY, Hamburg, Germany
  • D. Rizzetto, M. Rizzi
    Ettore Zanon S.p.A., Schio, Italy
  • L. Sagliano
    ESS, Lund, Sweden
 
  The industrial production of the 36 resonators (plus 2 spares) for the ESS linac started and it is steadily progressing. Cavities are delivered by industry as fully surface-treated and dressed to AMTF facility at DESY for their qualification via vertical cold-test. This paper reports the current status of the manufacturing process from sub-components to processing of the complete cavity inner surface. It also reviews the documental control strategy deployed to preserve the fulfillment of ESS requirements as well as the cavity performances demonstrated so far.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP058  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP060 INFN-LASA for the PIP-II Project cavity, niobium, interface, linac 205
 
  • R. Paparella, M. Bertucci, A. Bignami, A. Bosotti, M. Chiodini, A. D’Ambros, P. Michelato, L. Monaco, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • J.F. Chen
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • L. Sagliano
    ESS, Lund, Sweden
 
  INFN-LASA joined the international effort for the PIP-II project in Fermilab to build the 650 MHz superconducting cavities realizing the low-beta section of the 800 MeV proton linac. After developing the electro-magnetic and mechanical design, INFN-Milano started the prototyping phase by producing five single-cells and two complete 5-cells cavities. This paper reports the status of PIP-II activities at INFN-LASA summarizing manufacturing experience and preliminary experimental results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP060  
About • paper received ※ 24 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP061 State of the Art of Niobium Machining for SRF Applications niobium, cavity, electron, alignment 210
 
  • P. Naisson, S. Atieh, K. Scibor, P. Trubacova
    CERN, Geneva, Switzerland
  • F. Dumont, D. Fabre, F. Valiorgue
    ENISE, Saint Etienne, France
 
  Niobium is a demanding material to be machined. Its low hardness, high melting temperature and abrasivity leads to poor cutting condition, and surface quality and shape accuracy could be difficult to achieve, especially for complex shapes such as HOM antennas. Recent CERN developements concerning DQW crab cavity for HL-LHC project had implied extensive research program to better understand and master the machining of this material. In this frame, the present article will introduce actual state of the art machining condition used at CERN and their consequences about the surface roughness, shape accuracy and taking into account the tool wear in order to maintain this level of quality. Morevoer, advance machning solution, such as cryogenic cooling could be used.  
poster icon Poster MOP061 [2.921 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP061  
About • paper received ※ 30 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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MOP062 Fabrication of SRF Cavity coupling, vacuum, cavity, pick-up 214
 
  • K. Kanaoka, H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa
    MHI-MS, Kobe, Japan
  • E. Kako, K. Umemori
    KEK, Ibaraki, Japan
 
  Mitsubishi Heavy Industries Machinery Systems (MHI-MS) have developed manufacturing process of superconducting cavities for a long time. In this presentation, recent progress will be reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP062  
About • paper received ※ 23 June 2019       paper accepted ※ 05 July 2019       issue date ※ 14 August 2019  
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MOP063 Beam Loading in the BESSY VSR SRF Cavities cavity, beam-loading, storage-ring, operation 217
 
  • A.V. Tsakanian, H.-W. Glock, J. Knobloch, A.V. Vélez
    HZB, Berlin, Germany
 
  The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15 ps) and short (ca. 1.7 ps) bunches in the storage ring at currents up to 300 mA. This challenging goal requires installation of four new 4-cell SRF cavities (2x1.5 GHz and 2x1.75 GHz) in one module for installation in a single straight. As far as we are aware of, this is the first installation of multi-cell L-Band cavities in a high-current storage ring. These cavities are equipped with newly developed waveguide HOM dampers necessary for stable operation. Up to 2 kW of HOM power must be absorbed. Operating two SRF cavities for each frequency will also enable transparent parking of the cavities for the beam. Based on wakefield theory, a technique for beam loading calculation will be presented. The expected beam loading both at 2 K and at room temperature has been analyzed to evaluate transparent parking for both situations. The presented study is performed for various BESSY II and VSR bunch filling patterns with 300 mA beam current.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP063  
About • paper received ※ 22 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP064 Performance of First Prototype Multi-Cell Low-Surface-Field Shape Cavity cavity, electron, niobium, experiment 222
 
  • R.L. Geng
    JLab, Newport News, Virginia, USA
  • Y. Fuwa, Y. Iwashita
    Kyoto ICR, Uji, Kyoto, Japan
  • H. Hayano
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • Z. Li
    SLAC, Menlo Park, California, USA
 
  The idea of cavity shaping for higher ultimate acceleration gradients has been proposed for some time, Low Loss/Ichiro and Re-entrant being examples, both seeking a lower Hpk/Eacc at the expense of a higher Epk/Eacc. While experimental verification in single-cell cavities of those shapes was very successful including the record gradient of 59 MV/m, pushing multi-cell cavities of those shapes to higher gradients was prevented by field emission. The Low-Surface-Field (LSF) shape seeks not only a lower Hpk/Eacc but also a lower Epk/Eacc, therefore it has the advantage of raising ultimate gradient at reduced field emission. The first multi-cell LSF shape prototype cavity was built using the standard forming and welding techniques. RF tests have been carried out, following standard ILC TDR baseline surface processing and treatment recipe. Three out of five cells achieved Hpk values corresponding to Eacc 50 MV/m. The current limit is the field emission in end cells. Instrumented testing following end-cell wiping and HPR with larger nozzles is in progress. We will present detailed experimental results and preparation procedures.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP064  
About • paper received ※ 24 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP081 Considerations for Efficient RF Operation for the Advanced cw-Linac Demonstrator at GSI cavity, linac, cryomodule, heavy-ion 267
 
  • C. Burandt, K. Aulenbacher, W.A. Barth, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, S. Yaramyshev
    HIM, Mainz, Germany
  • K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, M. Heilmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, A. Schnase, S. Yaramyshev
    GSI, Darmstadt, Germany
  • K. Aulenbacher, F.D. Dziuba, S. Lauber, J. List
    IKP, Mainz, Germany
  • M. Basten, M. Busch, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
 
  The FAIR@GSI accelerator facility will require the GSI-UNILAC to provide short heavy ion pulses of highest intensity at low repetition rate for injection into the 18 Tm synchrotron SIS18. However, successful physics programs like SHE (Super Heavy Elements) rely on the UNILAC providing for heavy ion beams of high average current and high duty factor. In the next future, a dedicated super-conducting (sc) cw-Linac should therefore deliver cw beams to the experiments associated with those programs. As a first step towards this goal, beam tests with a single sc Cross-bar H-mode (CH) cavity were successfully conducted in 2017/2018. Within the scope of an Advanced Demonstrator project, current activities now aim at a beam test of a full cryomodule with three sc CH cavities and a sc rebuncher. Given a limited amount of rf power available per cavity and the necessity to accelerate different ion species with different mass-to-charge ratios, the loaded quality factor Q of the different resonators has to be chosen very carefully. This contribution discusses the simulations performed in this context.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP081  
About • paper received ※ 21 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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MOP083 R&D of Copper Electroplating Process for Power Couplers: Effect of Microstructures on RRR experiment, target, electron, ECR 278
 
  • Y. Okii, J. Taguchi
    Nomura Plating Co, Ltd., Osaka, Japan
  • E. Kako, S. Michizono, Y. Yamamoto
    KEK, Ibaraki, Japan
  • H. Takahashi, H. Yasutake
    CETD, Tochigi, Japan
 
  Power couplers for superconducting cavities are required to have both low-thermal conductivity and high-electrical conductivity, because high-thermal conductivity and low-electrical conductivity could generate unexpected increase for heat load. In order to combine these contrary properties, power couplers are made of stainless steel and plated with copper plating. As electrical conductivity of copper layer affects dynamic heat load, it is crucial to optimize plating processes. In this study, we investigated influences of plating parameters (i.e., thickness of copper layer, plating bath composition, bath temperature, heat-treatment conditions) on RRR by collaborative work among Nomura plating, CETD, and KEK. As a result, we obtained high-RRR samples with conditions noted below; (1) electroformed copper plate, (2) copper layer thickness of over 50 µm, and (3) heat-treatment at 200deg-1h, (4) other plating bath composition. In addition, we observed microstructures of several samples, then found that microstructures of copper layer are strongly related to RRR. In this paper, we will present the recent results for this investigation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP083  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP084 A Simple Variable Coupler for the Cryogenic Test of SRF Cavities cavity, cryogenics, coupling, FEL 282
 
  • G. Ciovati, L. Turlington
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The cryogenic rf tests of SRF cavities in vertical cryostats is typically carried out using fixed-length antennae to couple rf power into the cavity and to probe the energy stored into the cavity. Although variable couplers have been designed, built and used in the past, they are often a complex, costly, not very reliable auxiliary component to the cavity test. In this contribution we present the design and implementation of a simple variable rf antenna which has about 50 mm travel, allowing to obtain about four orders of magnitude variation in Qext -value. The motion of the antenna is driven by a motorized linear feedthrough outside of the cryostat. The antenna can easily be mounted on the most common type of cavity flanges.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP084  
About • paper received ※ 18 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP087 IFMIF Resonators Development and Performance cavity, cryomodule, linac, solenoid 293
 
  • G. Devanz, M. Baudrier, P. Carbonnier, F. Éozénou, E. Fayette, D. Roudier, P. Sahuquet, C. Servouin
    CEA-DRF-IRFU, France
  • N. Bazin, S. Chel, L. Maurice
    CEA-IRFU, Gif-sur-Yvette, France
 
  The prototype IFMIF cryomodule encloses eight superconducting 175 MHz beta 0.09 Half-Wave Resonators (HWR). They are designed together with the power coupler to accelerate a high intensity deuteron beam (125 mA) from to 5 to 9 MeV. One prototype HWR and the 8 cavities to be hosted in the cryomodule have been manufactured, prepared and tested. The paper describes the phases of the cavities development, including fabrication, processing, and RF resonant frequency management. We focus on the results of the RF tests which have been performed for all bare and jacketed HWRs in a vertical cryostat.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP087  
About • paper received ※ 23 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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MOP092 Overview of LCLS-II Project Status at Fermilab cryomodule, cavity, cryogenics, controls 302
 
  • R.P. Stanek, T.T. Arkan, J.N. Blowers, C.M. Ginsburg, A. Grassellino, C.J. Grimm, B.J. Hansen, E.R. Harms, B.D. Hartsell, J.P. Holzbauer, J.A. Kaluzny, A.L. Klebaner, A. Martinez, T.H. Nicol, Y.O. Orlov, K.S. Premo, N. Solyak, J. Theilacker, G. Wu
    Fermilab, Batavia, Illinois, USA
 
  The superconducting RF Continuous-Wave (CW) Linac for the LCLS-II consists of thirty-five 1.3 GHz and two 3.9 GHz cryomodules that Fermilab and Jefferson Lab are jointly producing in collaboration with SLAC. Fermilab’s scope of work is to build, test, and deliver half the 1.3 GHz and all the 3.9 GHz cryomodules and to design and procure components for the cryogenic distribution system. Fermilab has primary responsibility for delivering a working design. The cryomodule design basis was the European XFEL but several elements evolved to meet CW operation requirements and specifics of the SLAC tunnel. There have been several challenges faced during the design, assembly, testing and transportation of the cryomodules which have required design updates. Success in overcoming these challenges is attributable to the strength of the LCLS-II SRF Collaboration (Fermilab, Jefferson Lab and SLAC with extensive help from DESY and CEA/Saclay). The cryogenic distribution system has progressed relatively well and there are valuable Lessons Learned. An overview of the status, accomplishments, problems encountered, solutions developed, and a summary of Lessons Learned will be presented.  
poster icon Poster MOP092 [0.393 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP092  
About • paper received ※ 20 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP097 Preliminary Design of the IFMIF-DONES Superconducting Linac cavity, cryomodule, linac, neutron 311
 
  • T. Plomion, N. Bazin, N. Chauvin, G. Devanz, J. Plouin, K. Romieu
    CEA-DRF-IRFU, France
  • S. Chel
    CEA-IRFU, Gif-sur-Yvette, France
 
  The linear accelerator for the DONES facility (DEMO oriented neutron source) will serve as a neutron source for the assessment of materials damage in future fusion reactors. The DONES accelerator, which is based on the design of LIPac (Linear IFMIF Prototype Accelerator, which is under construction in Rokkasho, Japan) will accelerate deuterons from 100 keV up to 40 MeV at full CW current of 125 mA. This paper will present the preliminary design of the superconducting linac which is based on five cryomodules.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP097  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP100 Design Upgrades of the Next Superconducting RF Gun for ELBE gun, cavity, cathode, cryomodule 326
 
  • J. Teichert, A. Arnold, S. Ma, P. Murcek, J. Schaber, H. Vennekate, R. Xiang, P.Z. Zwartek
    HZDR, Dresden, Germany
  • K. Zhou
    CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
 
  Funding: Funding is provided by the China Scholarship Council.
At the ELBE user facility a superconducting RF photoinjector has been in operation since several years. The injector is routinely applied for THz radiation production in user beam experiments. For future applications higher bunch charges, shorter pulses and lower transverse emittances are required. Thus it is planned to replace this SRF gun by a next version with an RF cavity reaching a higher acceleration gradient. We also present improvements concerning the SC solenoid and the photocathode exchange system and report on the status of construction and testing of this SRF gun cryomodule.
 
poster icon Poster MOP100 [2.199 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP100  
About • paper received ※ 27 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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TUFUA1 The Field-Dependent Surface Resistance of Doped Niobium: New Experimental and Theoretical Results cavity, niobium, electron, ECR 340
 
  • J.T. Maniscalco, M. Ge, P.N. Koufalis, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T. Arias, D. Liarte, J.P. Sethna, N. Sitaraman
    Cornell University, Ithaca, New York, USA
 
  We present systematic work investigating how different doping and post-doping treatments affect the BCS surface resistance at 1.3~GHz and higher frequencies. We examine the field-dependent BCS resistance at many temperatures as well as the field-dependent residual resistance and use the results to reveal how impurity species and concentration levels affect the field-dependent RF properties. We further demonstrate the importance of thermal effects and their direct dependence on doping level. We use the tools of Density Functional Theory to work towards an {\em ab initio} model of electron overheating to theoretically confirm the impact of doping, create a full model that includes thermal effects to predict the field dependent resistance, and show that the predictions of the model agree with results from doped and non-doped cavities ({\em e.g.} the strength of the anti-Q-slope and the high-field Q slope). Finally, we use our experimental results to systematically assess and compare theories of the field-dependent BCS resistance, showing that the current theory on smearing of the density of states is incomplete.  
slides icon Slides TUFUA1 [6.780 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUA1  
About • paper received ※ 01 July 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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TUFUA4 New Insights on Nitrogen Doping cavity, electron, ECR, niobium 347
 
  • D. Bafia, J. Zasadzinski
    IIT, Chicago, Illinois, USA
  • D. Bafia, M. Checchin, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
 
  This paper covers a systematic study of the quench in nitrogen doped cavities: a cavity was sequentially treated/reset with different N-doping recipes which are known to produce different levels of quench field. Analysis of cavity heating profiles using TMAP are used to gain insight on the origins of quench; new recipes demonstrate the possibility to increase quench fields well beyond 30 MV/m. In addition, a new signature of nitrogen doping is explored, namely, a dip in the superconducting resonant frequency below the normal conducting value just below the critical transition temperature, giving further insights on the mechanisms responsible for the large increase in performance of cavities subject to this surface treatment.  
slides icon Slides TUFUA4 [3.097 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUA4  
About • paper received ※ 23 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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TUFUA5 Recent Development on Nitrogen Infusion Work Towards High Q and High Gradient cavity, niobium, injection, radio-frequency 355
 
  • P. Dhakal
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A quality factor as high as 2 × 1010 at 1.5 GHz was achieved at a gradient of 35 MV/m by 800 °C annealing and N-infusion at 140 °C. A comparison of the field dependence of the surface resistance after N-infusion with a recent theoretical model that extends the calculation of the BCS surface resistance to high rf fields suggests an increase in the quasiparticles’ relaxation time with increasing infusion temperature, which could be due to a decreasing density of subgap states. Nb coupons treated similarly showed the formation of thicker oxynitride layer on the surface beneath thin dielectric Nb2O5 layer. A plausible explanation for the improved Q0 is that the oxynitride layer on the Nb surface adds additional electron scattering within RF penetration depth.
 
slides icon Slides TUFUA5 [6.077 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUA5  
About • paper received ※ 19 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUFUA7 Review of Muon Spin Rotation Studies of SRF Materials niobium, cavity, experiment, FEL 360
 
  • T. Junginger
    Lancaster University, Lancaster, United Kingdom
  • R.E. Laxdal
    TRIUMF, Vancouver, Canada
 
  Muons spin rotate in magnetic fields and emit a positron preferentially in spin direction after decay. These properties enable muon spin rotation (muSR) as a precise probe for local magnetism. muSR has been used to characterize SRF materials since 2010. At TRIUMF a so called surface beam implants muons at a material dependent depth of about 150 µm in the bulk. A dedicated spectrometer was developed for field of first vortex penetration and pinning strength measurements of SRF materials in parallel magnetic fields of up to 300 mT. A low energy beam available at PSI implants muons at variable depth in the London layer allowing for direct measurements of the London penetration depth from which the lower critical field and the superheating field can be calculated. This facility is limited to parallel magnetic fields of up to 25 mT. Here, surface and low energy muSR results on SRF materials are reviewed and cross-correlated to each other and to further results from additional experiments. Finally, we present the status of a new facility based on the similar beta-NMR technique enabling measurements in the London layer of SRF materials exposed to parallel magnetic fields above 200 mT.  
slides icon Slides TUFUA7 [4.063 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUA7  
About • paper received ※ 01 July 2019       paper accepted ※ 12 July 2019       issue date ※ 14 August 2019  
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TUFUB5 Effects of Static Magnetic Fields on a Low-frequency TEM Class Superconducting Cavity cavity, niobium, shielding, superconductivity 370
 
  • M.K. Ng, Z.A. Conway, M.P. Kelly, K.W. Shepard
    ANL, Lemont, Illinois, USA
 
  Systematic studies on the effect of magnetic fields on a 330 MHz superconducting (TEM-mode) half-wave cavity are presented. The practical application of the results is for a possible future 2 K operation in the ATLAS heavy-ion accelerator at Argonne. The low frequency and the integral stainless steel jacket, rather than titanium, provide important new data for this full production model low-beta cavity. The studies include multi-axial magnetic field measurements near the cavity surface due to ambient and applied fields. Cavity performance under different conditions is measured at temperatures ranging between 1.6 K and 4.5 K. A residual resistance of approximately 5-7 nΩ at 1.6 K is observed. Data suggest that an appreciable fraction arises from losses that are not due to flux trapping.  
slides icon Slides TUFUB5 [1.195 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUB5  
About • paper received ※ 24 June 2019       paper accepted ※ 14 August 2019       issue date ※ 14 August 2019  
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TUFUB7 Measurement of Surface Resistance Properties with Coaxial Resonators - Review cavity, multipactoring, experiment, ECR 374
 
  • H. Park, S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
 
  Achieving ever decreasing surface resistance at higher field in superconducting RF accelerating structures is one of most outstanding developments in modern accelerators. The BCS theory has been used widely to estimate the surface resistance and to direct the technology. However, recent research results show that the behavior of the surface resistance further deviates from the BCS theory. So far the study on surface resistance was performed usually with cavities of single frequency which limited the study of frequency dependent surface resistance. The Center for Accelerator Science at Old Dominion University has designed and built several half wave coaxial cavities to study the frequency, temperature, and RF field dependence of surface resistance. TRIUMF in Canada also joined this line of research using such multi frequency quarter wave and half wave coaxial cavities. This type of multi mode cavity will allow us to systematically study the parameters affecting surface resistance on the same cavity surface. In this paper, we review the results ODU and TRIUMF collected so far and proper analysis methods.  
slides icon Slides TUFUB7 [3.551 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUB7  
About • paper received ※ 01 July 2019       paper accepted ※ 12 July 2019       issue date ※ 14 August 2019  
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TUFUB8 CVD Coated Copper Substrate SRF Cavity Research at Cornell University cavity, niobium, interface, target 381
 
  • M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J.T. Maniscalco, T.E. Oseroff, R.D. Porter, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • V.M. Arrieta, S.R. McNeal
    Ultramet, Pacoima, California, USA
 
  Chemical vapor deposition (CVD) is a promising alternative to conventional sputter techniques for coating copper substrate cavities with high-quality superconducting films. Through multiple SRF-related DOE SBIR projects, Ultramet has developed CVD processes and CVD reactor designs for SRF cavities, and Cornell University has conducted extensive RF testing of CVD coated surfaces. Here we report results from thin-film CVD Nb3Sn coated copper test plates, and for thick-film CVD niobium on copper including full-scale single cell 1.3 GHz copper substrate cavities. Detailed optical inspection and surface characterization show high-quality and well-adhered coatings. No copper contamination is found. The Nb3Sn coated plates have a uniform Nb3Sn coating with a slightly low tin concentration (19 -22%), but a BCS resistance well in agreement with predictions. The CVD Nb coatings on copper plates demonstrate excellent adhesion characteristics and exceeded surface fields of 50 mT without showing signs of a strong Q-slope that is frequently observed in sputtered Nb cavities. Multiple single-cell 1.3 GHz copper cavities have been coated to date at Ultramet, and results from RF testing of these are presented and discussed.  
slides icon Slides TUFUB8 [12.488 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUB8  
About • paper received ※ 01 July 2019       paper accepted ※ 05 July 2019       issue date ※ 14 August 2019  
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TUP007 Electromagnetic Design of the Prototype Spoke Cavity for the JAEA-ADS Linac cavity, linac, proton, superconductivity 399
 
  • J. Tamura, K. Hasegawa, Y. Kondo, F.M. Maekawa, S.I. Meigo, B. Yee-Rendón
    JAEA/J-PARC, Tokai-mura, Japan
  • E. Kako, T. Konomi, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
 
  The Japan Atomic Energy Agency (JAEA) is proposing an accelerator-driven subcritical system (ADS) as a future project to transmute long-lived nuclides to short-lived or stable ones. In the JAEA-ADS, a high-power proton beam of 30 MW with a final beam energy of 1.5 GeV is required with a high reliability. Furthermore, the accelerator needs to be operated in a continuous wave mode in order to be compatible with the reactor operation. As the first step toward the detailed design of the JAEA-ADS linac, we are planning to demonstrate a high-field measurement by prototyping a low-beta single spoke resonator (SSR1). We performed the electromagnetic design, and confirmed that the cavity performances of the SSR1 model with and without dimensional constraint.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP007  
About • paper received ※ 02 July 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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TUP010 Mechanical Design and Horizontal Tests of a Dressed 166.6 MHz Quarter-wave β=1 SRF Cavity System cavity, simulation, cryomodule, superconducting-cavity 408
 
  • X.Y. Zhang, X.R. Hao, D.B. Li, Z.Q. Li, H.Y. Lin, Q. Ma, Z.H. Mi, Q.Y. Wang, P. Zhang
    IHEP, Beijing, People’s Republic of China
 
  Funding: This work has been supported by HEPS-TF project.
A 166.6 MHz quarter-wave β=1 superconducting proof-of-principle cavity has been designed and recently been dressed with a helium jacket, fundamental power coupler and tuner. The cavity was subsequently installed in a modified cryomodule and tested in a horizontal manner at both 4.2 K and 2 K. The helium jacket was successfully developed with a focus on minimizing frequency shift due to helium pressure fluctuation while retaining a reasonable tuning range. The Lorentz force detuning (LFD) and microphonics were also optimized during the design. The df/dp and LFD coefficient were measured to be -3.1 Hz/mbar and -0.8 Hz/(MV/m)2. These are in good agreement with simulations. Future work is mainly to reduce the stiffness of the cavity and further suppress the vibration mode of the inner conductor.
 
poster icon Poster TUP010 [1.245 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP010  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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TUP012 Evaluation of High Performance Large Grain Medium Purity SRF Cavity From KEK cavity, niobium, experiment, cryogenics 415
 
  • P. Dhakal, G. Ciovati, G.R. Myneni
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We presented the RF measurement on a 1.3 GHz single cell cavity fabricated at KEK using large grain ingot niobium with RRR=107. The cavity reached to 35 MV/m with Q0 = 2.0×10zEhNZeHn at 2.0 K, record performance on the cavity made from medium purity ingot niobium. The cavity was cool down with different temperature gradient along the cavity axis in order to understand the flux expulsion mechanism when the cavity does through the superconducting transition and effect of trap residual magnetic field on the residual resistance. The measurement showed the excellent flux expulsion with the flux trapping sensitivity of 0.29 nΩ/mG for electro polished surface and 0.44 nΩ/mG for cavity followed by low temperature baking at 120°C for 12 hours.
We acknowledge KEK for sending this cavity for evaluations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP012  
About • paper received ※ 17 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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TUP013 Non-Evaporative Getter-Based Differential Pumping System for SRILAC at RIBF vacuum, linac, cavity, operation 419
 
  • H. Imao
    RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama, Japan
  • O. Kamigaito, N. Sakamoto, T. Watanabe, Y. Watanabe, K. Yamada
    RIKEN Nishina Center, Wako, Japan
  • K. Oyamada
    SHI Accelerator Service Ltd., Tokyo, Japan
 
  Upgrades of the RIKEN heavy-ion linac (RILAC) involving a new superconducting linac (SRILAC) are undergoing to promote super-heavy element searches at the RIKEN radioactive isotope beam factory (RIBF). Stable ultra-high vacuum (<10-8 Pa) and particulate-free conditions are strictly necessary for keeping the performance of the superconductive radio frequency (SRF) cavities of the SRILAC. It is crucially important to develop neighboring warm sections to prevent contamination from the existing old RILAC and beamlines built almost four decades ago. In the present study, non-evaporative getter-based differential pumping systems were newly developed to achieve the pressure reduction from the existing beamline vacuum (10-5–10-6 Pa ) to the ultra-high vacuum within very limited length (<80 cm) ensuring the large beam aperture of more than 40 mm. They are also equipped with compact electrostatic particle removers. We will describe and discuss details of the design, construction and performance of the system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP013  
About • paper received ※ 03 July 2019       paper accepted ※ 14 August 2019       issue date ※ 14 August 2019  
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TUP014 Mechanical Design and Fabrication Aspects of Prototype SSR2 Jacketed Cavities cavity, interface, cryomodule, electron 424
 
  • M. Parise, D. Passarelli, F. Ruiu
    Fermilab, Batavia, Illinois, USA
  • P. Duchesne, D. Longuevergne, D. Reynet
    IPN, Orsay, France
 
  A total of 35 Superconducting SSR2 spoke cavities will be installed in the PIP II SRF linac at Fermilab and a total of 8 prototype SSR2 cavities will be manufactured for the prototype cryomodule. In this paper, the mechanical design and fabrication aspects of the prototype jacketed SSR2 cavity will be presented. RF and mechanical design activities were conducted in parallel directly on the jacketed cavity in order to minimize the number of design iterations. Also, the lessons learned from other spoke cavities experiences (i.e. SSR1 at Fermilab and ESS double spoke at IPNO) were considered since the early stage of the design.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP014  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP018 New SRF Structures Processed at the ANL Cavity Processing Facility cavity, cathode, niobium, dipole 434
 
  • T. Reid, Z.A. Conway, B.M. Guilfoyle, M. Kedzie, M.P. Kelly, M.K. Ng
    ANL, Lemont, Illinois, USA
 
  Argonne National Laboratory (ANL) has extended high quality cavity processing techniques based on those developed for the International Linear Collider to several more complex superconducting RF cavities. Recently, these include a bunch lengthening harmonic cavity, a crabbing rf-dipole cavity, a compact half-wave cavity, and both medium and high frequency elliptical cavities. These systems are an improved version of the one originally developed for 1.3 GHz 9-cell cavities and include a second rotating electrical contact that can support multiple cathodes, necessary for optimum polishing in difficult cavity geometries. All include the possibility for external water cooling.  
poster icon Poster TUP018 [4.322 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP018  
About • paper received ※ 28 June 2019       paper accepted ※ 12 July 2019       issue date ※ 14 August 2019  
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TUP019 Status of High Temperature Vacuum Heat Treatment Program at IPN Orsay cavity, niobium, MMI, vacuum 438
 
  • M. Fouaidy, F. Chatelet, V. Delpech, F. Galet, D. Le Dréan, D. Longuevergne, R. Martret, G. Olry, T. Pépin-Donat
    IPN, Orsay, France
  • M. Baudrier, P. Carbonnier, E. Fayette, X. Hanus, Th. Proslier, D. Roudier, P. Sahuquet, C. Servouin
    CEA-DRF-IRFU, France
  • E. Cenni, L. Maurice
    CEA-IRFU, Gif-sur-Yvette, France
 
  In the framework of ESS, a vacuum furnace dedicated to High Temperature Heat Treatment under Vacuum (VH2T2) of SRF bulk Nb cavities was developed and commissioned in May 2016. This furnace is currently used for interstitial hydrogen removal (10h00 @ 650 °C) of two type of cavities: 1) the whole series of 26 ESS 352 MHz spoke resonators equipped with their Ti LHe tank well, 2) some prototypes of ESS high beta and medium beta cavities. Up to know IPN Orsay VH2T2 (10h00 @ 650 °C) was successfully applied to more than 16 cavities. In this paper we will first report about these VH2T2 tests. Finally, we have just started testing nitrogen infusion and nitrogen doping processes on samples and 1.3 GHz cavities: the preliminary results will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP019  
About • paper received ※ 03 July 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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TUP020 Statistical Analysis of the 120°C Bake Procedure of Superconducting Radio Frequency Cavities cavity, accelerating-gradient, FEL, niobium 444
 
  • L. Steder, D. Reschke
    DESY, Hamburg, Germany
 
  DESY is and was very active in R&D related to SRF cavities. Many single and nine cell cavities with different surface treatment histories were tested vertically. Results of these cold tests are accelerating gradient and quality factor of the cavities. Using the large number of available datasets the parameters of the 120°C bake procedure, which is applied to avoid high-field Q-slope, are analysed. The impact of different durations and temperatures on accelerating gradient, quality factor and residual resistance is studied in detail and is compared to results obtained with the recently proposed procedure of modified low temperature bake. For this procedure additional four hours at temperatures around 75°C are implemented before the standard bake at about 120°C. Since the claim is, that cavities treated with such a modified procedure achieve extra-ordinary large accelerating gradients it is a very interesting research field for the European XFEL continuous wave mode upgrade. For this purpose cavities with high quality factors are needed, but in addition large maximal accelerating fields are required to maintain high energies in the pulsed operation mode of the accelerator.  
poster icon Poster TUP020 [0.747 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP020  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP021 Effect of Cathode Rotation and Acid Flow in Vertical Electropolishing of 1.3 GHz Niobium Nine-Cell Cavity cavity, cathode, experiment, niobium 448
 
  • V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki
    KEK, Ibaraki, Japan
 
  We have been carrying out R&D on vertical electropolishing (VEP) technique to establish it as an alternate of the horizontal EP (HEP) technique used for the surface treatment of niobium (Nb) superconducting RF (SRF) cavities. We have earlier reported on a VEP parameter study for 1.3 GHz single and nine-cell Nb cavities. The optimized VEP parameters and a unique rotating cathode yielded uniform removal and a smooth surface in the single cell cavity. The unique cathode and a dual flow mechanism for acid circulation were applied to improve the removal uniformity in the nine-cell cavity. The vertically electropolished single and nine cell cavities achieved the same RF performance as achieved after the HEP processes. We are making efforts to further improve the removal uniformity in the nine-cell cavity. Here, we report on a VEP of the 1.3 GHz Nb nine-cell cavity at a higher cathode rotation speed of 50 rpm. The VEP results reveal that the speed could be considered for improving the uniformity in removal while maintaining the surface smoothness. Required improvements in the VEP facility and acid flow condition for achieving uniform EP and a smooth surface are also described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP021  
About • paper received ※ 23 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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TUP022 Fermilab EP Facility Improvement cavity, niobium, target, controls 453
 
  • F. Furuta, D.J. Bice, A.C. Crawford, T.J. Ring
    Fermilab, Batavia, Illinois, USA
 
  Electro-chemical Polishing (EP) is one of the key technologies of surface treatments for niobium superconducting cavities. We have established a single-cell scale horizontal electro-polishing facility at Fermilab and routinely processed the niobium cavities with the frequencies of 1.3 GHz to 3.9 GHz. The precise control of EP parameters, especially the temperatures of cavity outside wall, allows the uniform removal over the cell with the variation of ±15%. Here we report the details of our EP process and recent improvements on our EP facility at Fermilab.  
poster icon Poster TUP022 [1.711 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP022  
About • paper received ※ 10 July 2019       paper accepted ※ 17 August 2019       issue date ※ 14 August 2019  
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TUP023 Experience of LCLS-II Cavities Radial Tuning at DESY cavity, HOM, FEL, linac 456
 
  • A. Sulimov, J.H. Thie
    DESY, Hamburg, Germany
  • A. Gresele
    Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
  • A. Navitski
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  • A.D. Palczewski
    JLab, Newport News, Virginia, USA
 
  Radial tuning (rolling) was applied to three LCLS-II cavities to prevent that their lengths exceed the technical limits. The cavities have a reduced frequency due to additional material removal during cavity treatment well beyond the baseline recipe. The mechanical condition of the cavities was relatively soft because of the thermal history and the niobium manufacture requirement of an optimal flux expulsion. The niobium was highly recrystallized by 3 hours annealing at 900°C and 975°C respectively. Each cavity received an inner surface treatment of 200 µm electro-polishing (EP) and an external 30 µm buffered chemical polishing (BCP) as part of the baseline recipe. Each cavity received an addition ~100 µm of chemical removal along with a second annealing treatment before the radial tuning process. Detailed information about the accuracy and homogeneity of LCLS-II cavities rolling is presented as well as results of field distribution analysis for TM011 zero-mode with a comparison to standard cavities.  
poster icon Poster TUP023 [0.521 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP023  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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TUP024 Radial Tuning Devices for 1.3 GHz TESLA Shape Cavities cavity, HOM, FEL, niobium 459
 
  • A. Sulimov, J.H. Thie
    DESY, Hamburg, Germany
 
  Radial tuning devices at DESY can be applied to any TESLA shape 1.3 GHz cavity to reduce its elongation due to excessive additional material removal (>300 µm) or to compensate critical manufacturing uncertainties. Radial deformation of cavity cells can be provided by a special chain or a rolling device with three rollers. The chain distributes the radial forces on the equator area around the cell. The rollers are moving radially in relation to the rotating cavity and provide an equator diameter reduction. Both devices have the contour close to the cell shape at the equator area. The required equator radius deviation depends on the tuning target and usually varies between (0.02…0.60) mm. Different aspects of the tuning procedure and material properties are described using the example of cavity rolling.  
poster icon Poster TUP024 [0.252 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP024  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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TUP026 Vibro-tumbling as an Alternative to Standard Mechanical Polishing Techniques for SRF Cavities cavity, experiment, framework, superconductivity 464
 
  • E. Chyhyrynets, O. Azzolini, V.A. Garcia, G. Keppel, C. Pira, F. Stivanello, L. Zanotto
    INFN/LNL, Legnaro (PD), Italy
 
  Funding: Work supported by the INFN V group experiment TEFEN, Agreement N. KE2722/BE/FCC and from the European Union’s H2020 Framework Programme under grant agreement no. 764879 (EASITrain)
Centrifugal Barrel Polishing (CBP) is a common tool in the Nb bulk SC cavities production, prior to elec-tropolishing (EP). Indeed, the mechanical polishing is fun-damental also in the superconducting thin film resonant cavities in which one of the main issues that limits the per-formances is the surface preparation. A promising vi-bro-tumbling technique is being studied and implemented with a possibility to replace or improve mechanical treat-ment steps (grinding, barrel polishing). The simplic-ity of the technology allows it to adapt to any cavity geom-etry, both for Nb and Cu materials. The presented work contains last results on 6 GHz cavities obtained at LNL-INFN, both Nb bulk and Cu cavities.
 
poster icon Poster TUP026 [5.584 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP026  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP027 Vertical Electropolishing of Niobium Nine-Cell Cavity with a Cavity Flipping System for Uniform Removal cavity, cathode, niobium, experiment 467
 
  • K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki
    KEK, Ibaraki, Japan
 
  Marui Galvanizing Co., Ltd. has been developing vertical electropolishing (VEP) technology for single and nine-cell niobium superconducting radio frequency cavities using a unique cathode namely Ninja cathode in collaboration with KEK. The VEP process usually results in non-uniform removal with a large asymmetry along the cavity length. In order to suppress the asymmetry in removal, we are making different approaches. Flipping of the cavity during the VEP process is one of the approaches applied so far. A unique VEP setup, which allows the flipping of a multi-cell cavity, has been developed as reported earlier. Here, we report the improvement in the setup with automation for cavity flipping. VEP experiments were conducted with the improved system. VEP parameters were studied and the VEP results including the removal trend are discussed in detail.  
poster icon Poster TUP027 [1.347 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP027  
About • paper received ※ 24 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP029 An Experimental Analysis of Effective EP Parameters for Low-Frequency Cylindrical Nb Cavities cavity, cathode, niobium, polarization 472
 
  • C.E. Reece
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Work supported by the U.S. DoE, Office of Science, Office of Basic Energy Sciences.
While the basic process of electropolishing niobium with 1:9 HF:H2SO4 electrolyte has been well characterized, the specific process parameters used to electropolish different superconducting radio frequency (SRF) cavity geometries requires thoughtful attention. One seeks to realize confidently local diffusion-limited polishing at each point on the surface while maximizing uniformity of removal rate. Since the reaction rate is temperature dependent, this implies that one must manage the cavity surface temperature during polishing. Too-high applied voltage aggravates temperature and thus removal non-uniformity, but too-low applied voltage risks placing the large-diameter locations "off the current plateau," yielding etching rather than polishing. The majority of recent experience has been with elliptical L-band SRF cavities and some half-wave cavities at ANL. Lower frequency cavities with increased surface area and larger cathode-to-equator distance require fresh analysis and optimization. In preparation for SNS PPU project, JLab performed some EP process development runs with SNS high beta cavities to help identify viable parameter regimes for communication to cavity vendors. Results from this study are presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP029  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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TUP030 Automation of Particulate Characterization controls, cavity, software, electron 477
 
  • J.K. Spradlin, C.E. Reece, O. Trofimova, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
 
  Funding: Notice: This manuscript has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy.
Foreign particles residing on the field carrying surface of accelerator cavities are a known mechanism for field emission. Developing the methods and tools for collecting and characterizing particles found in an accelerator enables process development towards field emission free SRF cavities. Methods are presented for sampling assemblies, components, processes, and environmental conditions utilizing forensic techniques with specialized tooling. Sampling activities to date have produced an inventory of over 850 GSR spindles. Traditional SEM + EDS analysis of this volume of spindles is challenged by labor investment, spindle sampling methods, and the subsequent data pipeline which ultimately results in a statically inadequate dataset for any particulate distribution characterization. A complete systematic analysis of the spindles is enabled by third party software controlling SEM automation for EDS data acquisition. Details of spindle creation, collection equipment, component sampling, automating particle assessment, and data analysis used to characterize samples from beamline elements in CEBAF are presented.
 
poster icon Poster TUP030 [3.257 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP030  
About • paper received ※ 21 June 2019       paper accepted ※ 14 August 2019       issue date ※ 14 August 2019  
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TUP031 Heat Treatment for Jacketed Half-wave Resonator Cavity cavity, cryomodule, vacuum, ECR 482
 
  • Y. Jung, B.H. Choi, D.H. Gil, M.O. Hyun, H. Kim, J.W. Kim, M.S. Kim, D.Y. Lee, J. Lee, S. Lee
    IBS, Daejeon, Republic of Korea
 
  Vertical tests of a prototype half-wave resonator cavity are being tested. The performance of the cavities, such as quality factor and accelerating electrical field, are measured and compared to the target design value. In previous study, we reported the effect of the heat treatment on a prototype bare HWR cavity. We baked a jacketed HWR cavity to improve a performance for 10 h at 650°C. In this study, we will report the effect of the heat treatment on the jacketed HWR cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP031  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP032 Modal Analysis and Vibration Test for Quarter Wave Resonator for RAON cavity, cryomodule, resonance, controls 485
 
  • M.O. Hyun, H.C. Jung, Y. Kim, M. Lee
    IBS, Daejeon, Republic of Korea
 
  Funding: This paper was supported by the Rare Isotope Science Project (RISP), which is funded by the Ministry of Science and ICT (MSIT) and National Research Foundation (NRF) of the Republic of Korea.
The Rare Isotope Science Project (RISP) in the Institute of Basic Science (IBS), Korea, is developing and con-structing the multi-purpose linear accelerator at the north side of Daejeon, South Korea. RISP accelerator (RAON) is composed with low-energy region (SCL3) and high-energy region (SCL2), and low-energy region is made with quarter-wave resonator (QWR) and half-wave resonator (HWR) when high-energy region is made with single spoke resonator type-1 (SSR1) and type-2 (SSR2). This paper shows about the initial resonance issues of QWR superconducting (SC) cavity during cold test and SRF disturbance measurement. Afterwards, this paper shows the modal analysis and vibration test of QWR SC cavity.
 
poster icon Poster TUP032 [0.584 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP032  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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TUP036 Commissioning of Klystron Transmitters with 270 kWCW at 1.3 GHz klystron, cavity, GUI, power-supply 499
 
  • B. Schriefer, W. Anders, A. Heugel, H. Hoffmann, G. Mielczarek, H. Stein
    HZB, Berlin, Germany
 
  In Berlin-Adlershof the Helmholtz-Zentrum Berlin (HZB) is constructing the energy recovery linac ’BERLinPro’. Three klystron transmitters each 270 kWCW at 1.3 GHz are installed at the injection path of the ERL. The RF plant includes circulators and water loads. This paper describes the commissioning of the first klystron, calibration of the RF level control system as well as comparison with calorimetric output power measurements to verify the results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP036  
About • paper received ※ 03 November 2019       paper accepted ※ 03 November 2019       issue date ※ 14 August 2019  
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TUP041 SRF testing for Mainz Energy Recovering Superconducting Accelerator MESA cavity, cryomodule, radiation, controls 508
 
  • T. Stengler, K. Aulenbacher, F. Hug, S.D.W. Thomas
    KPH, Mainz, Germany
  • K. Aulenbacher
    GSI, Darmstadt, Germany
  • K. Aulenbacher
    HIM, Mainz, Germany
 
  Funding: This work is supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA+" EXC 2118/2019
The two superconducting radio frequency acceleration cryomodules for the new multiturn ERL ’Mainz Energy Recovering Superconducting Accelerator’ MESA at Johannes Gutenberg-Universität Mainz have been fabricated and are currently under testing at the Helmholtz Institut Mainz. These modules are based on the ELBE modules of the Helmholtz Center Dresden-Rossendorf but are modified to suit the high current and energy-recovering operation at MESA. The energy gain per module per turn should be 25 MeV, provided by two TESLA cavities, which were vertically tested at DESY, Hamburg, Germany. These tests showed an excellent performance of the quench limit and quality factor for three out of the four cavities. The fourth cavity has a lower but still acceptable quench limit and quality factor. In order to validate the performance of the fully assembled cryomodules after delivery to Mainz a test stand has been set up at the Helmholtz Institut Mainz. The test stand is described in detail and the status of the module testing is reported.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP041  
About • paper received ※ 21 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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TUP043 Ab-initio Study of Atomic Scale Interaction Among Nb, Sn, Cl, and O niobium, cavity, electron, superconductivity 518
 
  • A.B. Tesfamichael, T. Arias
    Cornell University, Ithaca, New York, USA
 
  Funding: Center for Bright Beam (CBB)
We employed a combination of ab-initio calculations and statistical mechanical models to understand the nature of atomic scale interaction among Nb, Sn, Cl, and O. Because of the profound nature of the interaction, we began our study by focusing only on the interaction of Nb with Sn in the absence of Cl and O. Using Density Functional Theory (DFT) we calculated: (1), binding energy of both vacant and interstitial of the super cell for both Nb and Sn atoms (2), rate of diffusion and re-evaporation upon transportation of Sn atom across z-axis from bulk Nb layer (3), electron transfer and electric field upon transportation of Sn atom both across z-axis and xy-plane from bulk Nb layer. Our calculation indicated 30-40% difference from experimental results. Therefore, we conclude that the presence of oxides is important and also Cl impurity can not not be avoided.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP043  
About • paper received ※ 24 June 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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TUP046 Low Frequency, Low Beta Cavity Performance Improvement Studies cavity, niobium, factory, vacuum 527
 
  • P. Kolb, R.E. Laxdal, Z.Y. Yao
    TRIUMF, Vancouver, Canada
 
  In recent years, new discoveries such as N2 doping and infusion lead to a significant increases in Q0 and accelerating gradient for 1.3 GHz, β=1 elliptical cavities. To understand and to adapt these treatments for lower frequency, \beta < 1 cavities, two coaxial test cavities, one quarter-wave resonator (QWR) and one half-wave resonator (HWR), have been built and put through a systematic study of these new treatments to show the effectiveness of these treatments at different frequencies. These cavities are tested in their fundamental mode and several higher order modes to study the frequency dependence of new cavity treatments such as N2 doping and infusion. Results of these studies are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP046  
About • paper received ※ 22 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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TUP049 Maximum Performance of Cavities Affected by the High-field Q-slope (HFQS) cavity, experiment, niobium, radio-frequency 533
 
  • G. Ciovati
    JLab, Newport News, Virginia, USA
  • A.V. Gurevich, I.P. Parajuli
    ODU, Norfolk, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The work of I. P. and A. G. is supported by NSF Grant PHY 100614-010.
The performance of high-purity, bulk niobium SRF cavities treated by chemical processes such as BCP or EP is limited by the so-called high-field Q-slope (HFQS). Several models and experimental studies have been proposed and performed over the years to understand the origin of these anomalous losses but a general consensus on what these orgins are is yet to be established. In this contribution, we present the results from the RF tests of several 1.3 GHz single-cell cavities limited by the HFQS and tested using a variable input coupler. This allowed to maintain close to critical coupling even at high field and the data showed that the HFQS did not saturate and that in some cases a power dissipation of up to 200 W at 2 K could be sustained without quench.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP049  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP050 A Multi-layered SRF Cavity for Conduction Cooling Applications cavity, cryogenics, ECR, niobium 538
 
  • G. Ciovati, G. Cheng, E. Daly, G.V. Eremeev, J. Henry, R.A. Rimmer
    JLab, Newport News, Virginia, USA
  • I.P. Parajuli
    ODU, Norfolk, Virginia, USA
  • U. Pudasaini
    The College of William and Mary, Williamsburg, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Some of the work was supported by the 2008 PECASE Award of G. Ciovati. I. Parajuli is supported by NSF Grant PHYS-100614-010
Industrial application of SRF technology would favor the use of cryocoolers to conductively cool SRF cavities for particle accelerators, operating at or above 4.3 K. In order to achieve a lower surface resistance than Nb at 4.3 K, a superconductor with higher critical temperature should be used, whereas a metal with higher thermal conductivity than Nb should be used to conduct the heat to the cryocoolers. A standard 1.5 GHz bulk Nb single-cell cavity has been coated with a ~2 µm thick layer of Nb3Sn on the inner surface and with a 5 mm thick Cu layer on the outer surface for conduction cooled applications. The cavity performance has been measured at 4.3 K and 2.0 K in liquid He. The cavity reached a peak surface magnetic field of ~40 mT with a quality factor of 6×109 and 3.5×109 at 4.3 K, before and after applying the thick Cu layer, respectively.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP050  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP051 Progress Towards Commissioning the Cornell DC Field Dependence Cavity cavity, niobium, multipactoring, solenoid 543
 
  • J.T. Maniscalco, T. Gruber, A.T. Holic, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  The Cornell DC Field Dependence Cavity is a new coaxial test resonator designed to study the impact of strong (up to 200 mT or more) DC surface magnetic fields on the superconducting surface resistance, providing physical insight into the root of the ‘‘anti-Q-slope’’ and probing critical fields. In this report we report progress in the commissioning of this new apparatus, including finalized design elements and results of prototype tests.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP051  
About • paper received ※ 25 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP052 Design and Commissioning of a Magnetic Field Scanning System for SRF Cavities cavity, cryogenics, data-acquisition, experiment 547
 
  • I.P. Parajuli, J.R. Delayen, A.V. Gurevich, J. Nice
    ODU, Norfolk, Virginia, USA
  • G. Ciovati, W.A. Clemens, J.R. Delayen
    JLab, Newport News, Virginia, USA
 
  Funding: Work supported by NSF Grant 100614-010. G. C. is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Trapped magnetic vortices are one of the leading sources of residual losses in SRF cavities. Mechanisms of flux pinning depend on the materials treatment and cool-down conditions. A magnetic field scanning system using flux-gate magnetometers and Hall probes has been designed and built to allow measuring the local magnetic field of trapped vortices normal to the outer surface of 1.3 GHz single-cell SRF cavities at cryogenic temperatures. Such system will allow inferring the key information about the distribution and magnitude of trapped flux in the SRF cavities for different material, surface preparations and cool-down conditions.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP052  
About • paper received ※ 22 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP054 How Is Flux Expulsion Affected by Geometry: Experimental Evidence and Model cavity, niobium, experiment, accelerating-gradient 555
 
  • D. Longuevergne
    IPN, Orsay, France
 
  Measurements of magnetic sensitivity to trapped flux on several type of cavity geometries have been performed at IPNO showing a clear geometrical effect. Magnetic sensitivity depends not only on material quality but also on the cavity geometry and on the residual magnetic field orientation. A presentation of experimental data will be done. These will be as well compared to the theoretical magnetic sensitivities calculated thanks to a simple Labview routine  
poster icon Poster TUP054 [1.312 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP054  
About • paper received ※ 03 July 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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TUP057 Study of Flux Trapping Variability between Batches of Tokyo Denkai Niobium used for the LCLS-II Project and Subsequent 9-cell RF Loss Distribution between the Batches cavity, niobium, FEL, superconductivity 570
 
  • A.D. Palczewski
    JLab, Newport News, Virginia, USA
  • D. Gonnella
    SLAC, Menlo Park, California, USA
  • O.S. Melnychuk, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
During the LCLS-II project a second batch of niobium was procured from Tokyo Denkai Co Ltd in order to make additional cavities. The original production material came from Two vendors Tokyo Denkai Co., Ltd. (TD) and Ningxia Orient Tantalum Industry Co., Ltd. (OTIC/NX)). It was found TD niobium required a lower annealing temperature (900°C) to obtain satisfactory flux expulsion characteristics compared to NX which required a slightly higher annealing temperature (950°-975°C). In order to ensure the new TD material performed equivalent to the niobium produced 4 year before after 900°C annealing; each heat lot of niobium had its flux expulsion characteristics parametrized and custom thermal treatments developed for each lot. Subsequent pure heat lot 9 cell cavities were made and tested. We will look at the flux expulsion characteristics of each lot, and RF loss of the 9-cell cavities produced using the individual heat lots.
 
poster icon Poster TUP057 [1.446 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP057  
About • paper received ※ 25 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP058 Characterization of Small AMR Sensors in Liquid Helium to Measure Residual Magnetic Field on Superconducting Samples cavity, experiment, controls, site 576
 
  • G. Martinet
    IPN, Orsay, France
 
  Trapped residual magnetic flux is responsible of residual resistance degradation on superconducting materials used in SRF technologies. To characterize this effect on superconducting samples, compact sensors are required to mount on sample characterization devices. In this paper, we present results on AMR sensors supplied from different manufacturers in the temperature range from 4.2 K up to 300 K.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP058  
About • paper received ※ 23 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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TUP059 Investigation of Trapped Flux Dynamics via DC-Magnetic Quenching cavity, experiment, superconducting-cavity, ECR 580
 
  • P. Nuñez von Voigt, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • J. Knobloch
    University of Siegen, Siegen, Germany
 
  Trapped magnetic flux increases the surface resistance in superconducting radio-frequency cavities. A better understanding of its behaviour could help to develop a method of expelling trapped flux from the superconducting surface. Using a superconducting coil with ferrite core attached to a 3 GHz sample Niobium cavity fully immersed in liquid Helium, we were able to subject the cavity walls to unusually large magnetic fields (estimated > 150 mT) and create magnetic quenches. With Fluxgate sensors attached in three spatial directions inside the cavity, we were able to monitor the quench dynamics and extract parameters of the flux dynamics from the hysteretic behaviour of the measured fields resulting from the applied coil current. First results of manipulation of the trapped flux with high magnetic fields are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP059  
About • paper received ※ 24 June 2019       paper accepted ※ 05 July 2019       issue date ※ 14 August 2019  
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TUP061 Gradients of 50 MV/m in TESLA Shaped Cavities via Modified Low Temperature Bake cavity, niobium, ECR, site 586
 
  • D. Bafia, J. Zasadzinski
    IIT, Chicago, Illinois, USA
  • D. Bafia, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, Z-H. Sung
    Fermilab, Batavia, Illinois, USA
 
  This paper will discuss the 75/120 C modified low temperature bake capable of giving unprecedented accel-erating gradients of above 50 MV/m for 1.3 GHz TESLA-shaped niobium SRF cavities in CW operation. A bifurca-tion in the Q0 vs Eacc curve is observed after retesting cavities without disassembly in between, yielding per-formance that ranges from exceptional to above state-of-the-art. Atomic Force Microscopy studies on cavity cut-outs gives a possible mechanism responsible for this branching in performance, namely, the dissociation and growth of room temperature niobium nano-hydrides that exist near the RF surface, which are made superconduct-ing only through the proximity effect. In-situ low temper-ature baking of cavity cutouts reveals a dissociation of these room temperature nano-hydrides, which could ex-plain the higher performance of cavities subject to similar in-situ heating in the dewar.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP061  
About • paper received ※ 23 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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TUP062 New Insights in the Quench Mechanisms in Nitrogen Doped Cavities cavity, accelerating-gradient, niobium, factory 592
 
  • D. Bafia, J. Zasadzinski
    IIT, Chicago, Illinois, USA
  • D. Bafia, D.J. Bice, A. Grassellino, O.S. Melnychuk, A.S. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  • D. Gonnella
    SLAC, Menlo Park, California, USA
  • A.D. Palczewski
    JLab, Newport News, Virginia, USA
 
  This paper will cover a systematic study of the quench in nitrogen doped cavities: three cavities were sequentially treated/reset with different doping recipes which are known to produce different levels of quench field. Analysis of mean free path and TMAP coupled with sample analysis reveals new insights on the physics of the premature quench in nitrogen doped cavities; new recipes demonstrate the possibility to increase quench fields well beyond 30 MV/m.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP062  
About • paper received ※ 23 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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TUP064 Flashover on RF Window of HWR SRF Cavity cavity, pick-up, electron, linac 597
 
  • X. Liu, Z. Gao, Y. He, G. Huang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Breakdown on the RF ceramic windows always happen in different kinds of accelerator. It is one of the main limitations in current day superconducting cavities and couplers. The PT signal trip caused by discharge on the surface of RF ceramic window lead LLRF control system trip which affect the stable operation of the superconducting linac. Simulation of field emission electron trajectory in superconducting cavity and experimental measurements of the frequency of the pickup signal trip have been performed. A lot of aged window with characteristics of flashover were studied by means of material characterization. The flashover on the surface of RF ceramic window caused by electrons and field emission provide the origin of initial electrons. A modified design of the pickup antenna have solved the PT pickup trip problem.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP064  
About • paper received ※ 23 June 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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TUP068 Study of Surface Treatment of 1.3 GHz Single-cell Copper Cavity for Niobium Sputtering cavity, niobium, experiment, MMI 605
 
  • F.Y. Yang, J. Dai, P. He, Z.Q. Li, Y. Ma, P. Zhang
    IHEP, Beijing, People’s Republic of China
 
  Funding: This work has been supported in part by PAPS project and National Key Programme for S&T Research and Development (Grant NO.: 2016YFA0400400)
A R&D program on niobium sputtering on copper cavities has started at IHEP in 2017. Single-cell 1.3 GHz copper cavity has been chosen as a substrate. A chemical polishing system has subsequently developed and commissioned recently to accommodate the etching of both copper samples and a cavity. Different polishing agents have been tested on copper samples and later characterized. The results of these surface treatment tests are presented.
 
poster icon Poster TUP068 [1.228 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP068  
About • paper received ※ 20 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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TUP070 The SRF Thin Film Test Facility in LHe-Free Cryostat cavity, cryogenics, vacuum, controls 610
 
  • O.B. Malyshev, J.A. Conlon, P. Goudket, N. Pattalwar, S.M. Pattalwar
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • G. Burt
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • G. Burt
    Lancaster University, Lancaster, United Kingdom
 
  An ongoing programme of development superconducting thin film coating for SRF cavities requires a facility for a quick sample evaluation at the RF conditions. One of the key specifications is a simplicity of the testing procedure, allowing an easy installation and quick turnover of the testing samples. Choked test cavities operating at 7.8 GHz with three RF chokes have been designed and tested at DL in a LHe cryostat verifying that the system could perform as required. Having a sample and a cavity physically separate reduces the complexity involved in changing samples (major causes of low throughput rate and high running costs for other test cavities) and also allows direct measurement of the RF power dissipated in the sample via power calorimetry. However, changing a sample and preparation for a test requires about two-week effort per sample. In order to simplify the measurements and achieve a faster turnaround, a new cryostat cooled with a closed-cycle refrigerator has been designed, built and tested. Changing a sample, cooling down and testing can be reduced to 2-3 days per sample. Detailed design and results of testing of this facility will be reported at the conference.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP070  
About • paper received ※ 21 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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TUP072 The Development of Niobium Sputtering on Copper Cavities at IHEP cavity, niobium, vacuum, photon 613
 
  • J. Dai, P. He, Z.Q. Li, Y. Ma, F.Y. Yang, P. Zhang
    IHEP, Beijing, People’s Republic of China
 
  A R&D program focusing on niobium sputtering on copper cavities started at IHEP in 2017. Single-cell 1.3 GHz elliptical cavity shape has been initially chosen as sputtering substrate. A magnetron sputtering system have been developed in 2018. In addition, a surface treatment facility to polish the copper substrate before sputtering has been developed and commissioned. This paper will present the Nb/Cu coating activities at IHEP.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP072  
About • paper received ※ 19 June 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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TUP073 Superconducting Thin Films Characterization at HZB with the Quadrupole Resonator cavity, quadrupole, niobium, FEL 616
 
  • D.B. Tikhonov, S. Keckert, J. Knobloch, O. Kugeler, Y. Tamashevich
    HZB, Berlin, Germany
  • A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
 
  Funding: EASITrain - European Advanced Superconductivity Innovation and Training. This Marie Sklodowska-Curie Action Innovative Training Networks founded by H2020 under Grant Agreement no. 764879
Superconducting thin films have great potential as post-Nb material for use in SRF applications in future accelerators and industry. To test the RF-performance of such films in practice, would require the building and coating of a full RF cavity. Deposition of thin films on such scales in test facilities are challenging, in particular when curved surfaces have to be coated. This greatly complicates their systematic research. In this contribution we report on the method we use to characterize small and flat thin film samples (Deposited onto both Nb and Cu substrates) in an actual cavity named the Quadrupole Resonator (QPR). We also summarize the latest measurement results of NbTiN thin films. The Quadrupole Resonator at HZB is a tool that is able to perform SRF characterizations at frequencies ~415, 847, 1300 MHz with RF fields using an RF-DC power compensation technique.
 
poster icon Poster TUP073 [2.318 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP073  
About • paper received ※ 23 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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TUP075 New Progress for Nb Sputtered 325 MHz QWR Cavities in IMP cavity, target, experiment, niobium 621
 
  • F. Pan, H. Guo, Y. He, T.C. Jiang, C.L. Li, M. Lu, T. Tan
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Comparing with bulk niobium cavities, the Nb/Cu cavities feature a much better stability at 4.5 K. Last year, two 325 MHz QWR copper cavities coated with biased DC diode sputterred Nb for CiADS has been accomplished at IMP. But vertical tests showed the cavities had low Q0 at 4 K. To solve the issue, a new coating system was designed and built. The sputtering target was redesigned and manufactured. The coating parameters were selected again and auxiliary heating was used to control the coating temperature in the process of sputtering. The power and Ar pressure during coating were also carefully selected. The paper covers resulting film characters, vertical tests with the evolution of the sputtering process, and improvements we made since last year.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP075  
About • paper received ※ 22 June 2019       paper accepted ※ 14 August 2019       issue date ※ 14 August 2019  
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TUP076 Electrochemical Deposition of Nb3Sn on the Surface of Cu Substrates niobium, cavity, site, controls 624
 
  • M. Lu, Q.W. Chu, Y. He, Z.Q. Lin, F. Pan, T. Tan, Z.Q. Yang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Coating superconducting Nb3Sn thin film on the inner surface of a superconducting RF cavity is one of the most promising approaches to improve the performance of the accelerating cavity. Compared with traditional evaporation and sputtering, electrochemical coating has the advantages on process simplicity, low cost and mass production. However, the conventional electroplating, because of its low growth temperature and aqueous reaction environment, tends to produce porous, loosely bonded, and often contaminated film. All these properties result in excessive pinning center and deteriorate the superconducting radio frequency cavities performance. In this paper, a new method including multi-layer electroplating and heat treatment is used to deposit Nb3Sn thin film on top of copper substrates. Important growth parameters, e.g. electrical current density, layer thickness ratio, and annealing temperature are studied. The morphology of the film surfaces was observed by scanning electron microscope (SEM) and the structure of the film was analyzed by X-ray diffraction (XRD). The results showed that a flat and uniform Nb3Sn layer on copper can be obtained, and the thickness is about 7 micron.  
poster icon Poster TUP076 [0.716 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP076  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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TUP077 Nb3Sn Thin Film Coating Method for Superconducting Multilayered Structure site, cavity, target, experiment 628
 
  • R. Ito, T. Nagata
    ULVAC, Inc, Chiba, Japan
  • H. Hayano, R. Katayama, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto, Japan
 
  S-I-S (superconductor-insulator-superconductor) multilayered structure has been proposed in order to increase the maximum acceleration gradient of SRF cavities. Nb3Sn is the material most expected as a superconducting layer of the S-I-S multilayered structure because it offers both a large critical temperature and large predicted Hsh. Most important in fabricating Nb3Sn thin films is the stoichiometry of the material produced, and the lack of tin leads to performance degradation. We have launched a new in-house DC magnetron sputtering apparatus for Nb3Sn deposition. Nb and Sn layers were alternately and repeatedly deposited on Si wafer while adjusting the film thickness of each layer, so we successfully obtained Nb-Sn films having appropriate composition ratio. The as-deposited films were annealed under the temperature of 600 degree C for 1 hour to generate the Nb3Sn phase. The characteristics of Nb-Sn films evaluated by XRD, XRF, FE-SEM, and so on. We also measured critical temperature of the annealed films. In this paper, the detail of the Nb3Sn coating method and the measurement result of the Nb-Sn films will be reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP077  
About • paper received ※ 02 July 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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TUP078 Lower Critical Field Measurement of NbN Multilayer Thin Film Superconductor at KEK solenoid, cavity, shielding, radio-frequency 632
 
  • H. Ito
    Sokendai, Ibaraki, Japan
  • C.Z. Antoine
    CEA-IRFU, Gif-sur-Yvette, France
  • H. Hayano, R. Katayama, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • R. Ito, T. Nagata
    ULVAC, Inc, Chiba, Japan
  • Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
 
  Funding: The work is supported by Japan Society for the Promotion of Science Grant-in-Aid for Young Scientist (A) No.17H04839.
The multilayer thin film structure of the superconductor has been proposed by A. Gurevich to enhance the maximum gradient of SRF cavities. The lower critical field Hc1 at which the vortex start penetrating the superconducting material will be improved by coating Nb with thin film superconductor such as NbN. It is expected that the enhancement of Hc1 depends on the thickness of each layer. In order to determine the optimum thickness of each layer and to compare the measurement results with the theoretical prediction proposed by T. Kubo, we developed the Hc1 measurement system using the third harmonic response of the applied AC magnetic field at KEK. For the Hc1 measurement without the influence of the edge or the shape effects, the AC magnetic field can be applied locally by the solenoid coil of 5mm diameter in our measurement system. ULVAC made the NbN-SiO2 multilayer thin film samples of various NbN thicknesses. In this report, the measurement result of the bulk Nb sample and NbN-SiO2 multilayer thin film samples of different thickness of NbN layer will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP078  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP079 Deposition of Nb3Sn Films by Multilayer Sequential Sputtering for SRF Cavity Application cavity, site, FEL, niobium 637
 
  • Md.N. Sayeed, H. Elsayed-Ali
    ODU, Norfolk, Virginia, USA
  • M.C. Burton, G.V. Eremeev, C.E. Reece, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
  • U. Pudasaini
    The College of William and Mary, Williamsburg, Virginia, USA
 
  Nb3Sn is considered as an alternative of Nb for SRF accelerator cavity application due to its potential to obtain higher quality factors and higher accelerating gradients at a higher operating temperature. Magnetron sputtering is one of the effective techniques that can be used to fabricate Nb3Sn on SRF cavity surface. We report on the surface properties of Nb3Sn films fabricated by sputtering multiple layers of Nb and Sn on sapphire and niobium substrates followed by annealing at 950°C for 3 h. The crystal structure, film microstructure, composition and surface roughness were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). The RF performance of the Nb3Sn coated Nb substrates were measured by a surface impedance characterization system. We also report on the design of a multilayer sputter deposition system to coat a single-cell SRF cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP079  
About • paper received ※ 22 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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TUP080 Tuner Design and Test for 166.6 MHz SRF Cavity of HEPS cavity, simulation, high-voltage, LLRF 642
 
  • Z.H. Mi, Z.Q. Li, H.Y. Lin, W.M. Pan, Q.Y. Wang, P. Zhang, X.Y. Zhang, H.J. Zheng
    IHEP, Beijing, People’s Republic of China
 
  The 166.6 MHz superconducting RF cavities have been proposed for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale light source. The cavity is of quarter-wave type made of bulk niobium with ’=1. Each cavity will be operated at 4.2 K providing 1.2 MV accelerating. To compensate the frequency change due to manufacturing uncertainty, Lorentz force, beam loading, He pressure and microphonics the plunger tuner and gap tuner are chosen as options. Now the plunger tuner and low temperature gap tuner have been test with cavity, while the warm gap tuner is being designed. Details of the design and summary of the test results of the two type tuners with cavity are presented in this paper.  
poster icon Poster TUP080 [1.141 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP080  
About • paper received ※ 22 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP081 Status of the HL-LHC Crab Cavity Tuner cavity, cryomodule, GUI, vacuum 646
 
  • K. Artoos, L. Arnaudon, R. Calaga, E. Cano-Pleite, O. Capatina, T. Capelli, D.F. Cartaxo dos Santos, M. Garlasché, D.C. Glenat, A. Krawczyk, R. Leuxe, P. Minginette, J.S. Swieszek
    CERN, Geneva, Switzerland
  • T.J. Jones
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • A. Krawczyk, B. Prochal
    IFJ-PAN, Kraków, Poland
  • J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
  • S. Verdú-Andrés
    BNL, Upton, New York, USA
 
  Funding: Research supported by the HL-LHC project
The resonance frequency of the HL-LHC Double Quarter Wave (DQW) and Radio Frequency Dipole (RFD) crab cavities is set to the operating frequency of 400.79 MHz by deforming the cavities. For both types of cavities, the tuning principle foresees a symmetric mechanical deformation of parts of the cavities in vertical direction, with the tuner motor placed outside on top of the vacuum vessel. The tuner design was successfully tested on the DQW prototype cryomodule with two cavities in 2018 in the SPS at CERN. This paper describes the design of DQW and RFD crab tuners. The experience and results of assembly and cold testing is given together with some required improvements. Finally, the final series crab tuners preparation is reported.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP081  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP083 Performance of the 650 MHz SRF Cavity Tuner for PIP II Project cavity, cryomodule, interface, resonance 652
 
  • Y.M. Pischalnikov, S.K. Chandrasekaran, S. Cheban, I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev, J.C. Yun
    Fermilab, Batavia, Illinois, USA
  • C. Contreras-Martinez
    FRIB, East Lansing, Michigan, USA
 
  The PIP-II linac will include fifty seven 650MHz SRF cavities. Each cavity will be equipped with tuner for coarse and fine frequency tuning. Design and operations parameters will be discussed. Results from room temperature tests with prototype tuner installed on a 650MHz ’G=0.90 elliptical cavity will be presented.  
poster icon Poster TUP083 [1.567 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP083  
About • paper received ※ 23 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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TUP084 Testing of the Piezo-actuators at High Dynamic Rate Operational Conditions cavity, operation, vacuum, linac 656
 
  • Y.M. Pischalnikov, J.C. Yun
    Fermilab, Batavia, Illinois, USA
  • C. Contreras-Martinez
    FRIB, East Lansing, Michigan, USA
 
  Reliability of the piezo-actuators that deployed into SRF cavity tuner and operated at high dynamic rate operational conditions made significant impact on the overall performance of the SRF linacs. We tested at FNAL piezo-actuators P-P-844K075 that were developed at Physik Instrumente for LCLS II project. Even these actuators were developed for CW linac we tested them at high dynamic rate inside cryogenic/insulated vacuum environment. Results of the tests will be presented. Different modes of the piezo-actuators failure will be discussed.  
poster icon Poster TUP084 [3.168 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP084  
About • paper received ※ 23 June 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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TUP085 Operation of an SRF Cavity Tuner Submerged into Liquid He cavity, experiment, resonance, operation 660
 
  • Y.M. Pischalnikov, D.J. Bice, A. Grassellino, T.N. Khabiboulline, O.S. Melnychuk, R.V. Pilipenko, S. Posen, O.V. Pronitchev, A.S. Romanenko
    Fermilab, Batavia, Illinois, USA
 
  To precisely control the resonance of 1.3 GHz SRF cavities during testing at the FNAL’s Vertical Test Facility, we install for the first time a double lever tuner and operate it when submerged into the liquid He bath. Both active components of the tuner: electromechanical actuator (stepper motor) and piezo-actuators are operated inside superfluid helium. Accuracy in controlling the SRF cavity resonance frequency will be presented. Specifics of the tuner operation when submerged into liquid He will be discussed.  
poster icon Poster TUP085 [2.164 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP085  
About • paper received ※ 23 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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TUP086 Frequency Tuning System Based on Mobile Plungers For Superconductive Coaxial Half Wave Resonators cavity, simulation, linac, vacuum 664
 
  • D. Bychanok, S. Huseu, S.A. Maksimenko
    INP BSU, Minsk, Belarus
  • A.V. Butenko, E. Syresin
    JINR, Dubna, Moscow Region, Russia
  • E.A. Gurnevich
    Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk, Belarus
  • M. Gusarova, M.V. Lalayan, S.M. Polozov
    MEPhI, Moscow, Russia
 
  The design of a prototype of the frequency tuning system (FTS) for superconductive coaxial half wave cavities (HWR) [1] developed for the Nuclotron-based Ion Collider fAcility (NICA) injector is presented. The proposed system is based on mobile plungers placed in the technological holes in the end caps of the resonator. The FTS allows controlling the penetration depth of plungers, which is monotonically related to the resonant frequency shift of the cavity. The developed FTS includes slow/fast tuner parts and is more compact and simple in comparison to traditional mechanical systems, which deform reversibly the HWR by applying an effort on the beam ports [2]. The similar plunger-based tuner design was considered for QWR cavities in [3]. The results of numerical simulations of the resonant frequency for a wide range of plunger parameters are presented and discussed. The most important parameters for effective frequency shift are estimated.
[1] S. Matsievskiy et al., RuPAC’18. doi:10.18429/JACoW-RUPAC2018-WEPSB48
[2] N. Misiara et al., LINAC’16. doi:10.18429/JACoW-LINAC2016-MOPRC026
[3] D. Longuevergne et al., ‘‘A cold tuner system with mobile plunger’’, in Proc. SRF2013, paper THIOD04.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP086  
About • paper received ※ 22 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP092 Experiences of Superconducting Radio Frequency Coldmass Production for the FRIB Linear Accelerator cavity, cryomodule, vacuum, solenoid 675
 
  • K. Elliott, B.W. Barker, C. Donald, E.S. Metzgar, L. Popielarski, D.R. Victory, J.D. Whaley, M.S. Wilbur
    FRIB, East Lansing, Michigan, USA
 
  Funding: *Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 and the National Science Foundation under Cooperative Agreement PHY-1102511.
The superconducting radio frequency (SRF) portion of the Facility for Rare Isotope Beams (FRIB) linear accelerator consists of 46 cryomodules of 6 different types. Each cryomodule contains a coldmass consisting of a string of SRF resonators. There are four different types of resonators; a β=0.041 quarter wavelength resonator (QWR), a β=0.085 QWR, a β=0.29 half wavelength resonator (HWR), and a β=0.53 HWR. In total there are 324 SRF resonators in the FRIB linear accelerator. This paper provides a summary of experiences from the assembly of all FRIB coldmass types in a clean room environment.
 
poster icon Poster TUP092 [1.481 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP092  
About • paper received ※ 23 June 2019       paper accepted ※ 14 August 2019       issue date ※ 14 August 2019  
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TUP093 Summary of FRIB Cavity Processing in the SRF Coldmass Processing Facility and Lessons Learned cavity, niobium, linac, controls 680
 
  • E.S. Metzgar, B.W. Barker, K. Elliott, W. Hartung, L. Popielarski, G.V. Simpson, D.R. Victory, J.D. Whaley
    FRIB, East Lansing, Michigan, USA
 
  Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 and the National Science Foundation under Cooperative Agreement PHY-1102511.
Baseline coldmass production for the linear particle accelerator at the Facility for Rare Isotope Beams (FRIB) is nearing completion. This paper will review the processing of cavities through the FRIB superconducting radio frequency (SRF) coldmass production facility focusing on chemical processing and high-pressure rinsing. Key processing data will be compiled and correlations between processing variables and cavity RF testing results will be examined.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP093  
About • paper received ※ 22 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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TUP094 Improvements to LCLS-II Cryomodule Transportation cavity, cryomodule, vacuum, ISOL 684
 
  • N.A. Huque, E. Daly, P.D. Owen
    JLab, Newport News, Virginia, USA
  • B.D. Hartsell, J.P. Holzbauer
    Fermilab, Batavia, Illinois, USA
 
  The Linear Coherent Light Source (LCLS-II) is currently being constructed at the SLAC National Laboratory. A total of 35 cryomodules will be fabricated at Jefferson Lab (JLab) in Virginia and Fermi National Laboratory (FNAL) in Illinois and transported via road to SLAC. A shipping frame with an inner bed isolated by springs was designed to protect the CMs from shocks and vibrations during shipments. Successful road testing of the JLab prototype paved the way for production CM shipments. The initial production shipments lead to several catastrophic failures in beamline vacuum in the cryomodules. The failures were determined to be due to fatigue in Fundamental Power Coupler (FPC) bellows due to excessive motion during shipment. A series of instrumented CM shipping tests and component tests were undertaken to develop a solution. A modified spring layout was tested and implemented, which reduced shocks on the CMs. FPC coupler bellows restraints were tested on a shaker table and on a CM during shipping; they were able to reduce bellows motion by a factor of three. The updated shipping system is currently in use and has successfully delivered six cryomodules to SLAC from JLab and FNAL.  
poster icon Poster TUP094 [0.958 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP094  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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TUP095 Lessons Learned Assembling the SSR1 Cavities String for PIP-II cavity, vacuum, solenoid, cryomodule 690
 
  • D. Passarelli, D.J. Bice, M. Parise, T.J. Ring, G. Wu
    Fermilab, Batavia, Illinois, USA
  • S. Berry
    CEA-DRF-IRFU, France
 
  The string assembly of the prototype Single Spoke Resonator type 1 (SSR1) cryomodule for PIP-II at Fermilab was successfully completed. Lessons learned from the preparation, assembly and the quality control activities of the final fully integrated assembly will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP095  
About • paper received ※ 28 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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TUP099 Particulate Sampling and Analysis During Refurbishment of Prototype European XFEL Cryomodule cavity, FEL, cryomodule, superconductivity 701
 
  • N. Krupka, C. Bate, D. Reschke, S. Saegebarth, M. Schalwat, P. Schilling, S. Sievers
    DESY, Hamburg, Germany
 
  Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Tech-nologies (MT) Program.
The cryomodule PXFEL31 is one of three prototype cryomodules for the European XFEL. In preparation of the series module assembly it was used for the qualification of infrastructure and personnel at CEA Saclay. After transport and tests at DESY the cryomodule was stored for several years. Last year we decided to refurbish this module with new cavities for the installation in the FLASH accelerator. During the disassembly of the cavity string in the clean room at DESY we took several particulate samples for analysis. Optical and laser optical microscopy give us an insight on the quantity and type of the particulates. We expect to get hints where the particulates come from and how they are transported through the cavity string during transport and operation.
 
poster icon Poster TUP099 [2.599 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP099  
About • paper received ※ 23 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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TUP100 Thermal Load Studies on the Photocathode Insert with Exchangeable Plug for the BERLinPro SRF-Photoinjector cathode, experiment, gun, cavity 705
 
  • J. Kühn, N. Al-Saokal, M. Bürger, M. Dirsat, A. Frahm, A. Jankowiak, T. Kamps, G. Klemz, S. Mistry, A. Neumann, H. Plötz
    HZB, Berlin, Germany
 
  For the operation of an SRF photoinjector a well-functioning and efficient cooling system of the photocathode is necessary. A test experiment was set up of the photocathode cooling system based on the original components, which we call thermal contact experiment (TCX). We present the results of our thermal load studies on the photocathode insert with exchangeable photocathode plug. The goal was to test all components before they are installed in the cold string of the BERLinPro SRF-Photoinjector to ensure the operation of very sensitive semiconductor photocathodes. The tests include the investigation of the cooling performance, the thermal load management and the mechanical stability of the photocathode insert.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP100  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP103 Pansophy Data as Used to Develop Metrics and Evaluate Trends Across SRF Projects and Facilities to Further Quality Improvement Initiatives cryomodule, database, status, cavity 718
 
  • M.G. McDonald, V.D. Bookwalter, M. Dickey, E.A. McEwen
    JLab, Newport News, Virginia, USA
 
  Pansophy, a JLAB SRF engineering data management system (EDMS), is composed of a collection of technolo-gies that together provide for the collection, management and analysis of data for the production and testing of cavities and cryomodules. From its inception in 2000, when data collection was a priority for such projects as SNS, CEBAF 12GeV upgrade, LCLS-II, and in the future the SNS-PPU, the focus has turned to data analysis and reporting on quality metrics and key performance indica-tors (KPIs). Reporting enhancements include monthly quality metrics, project specific KPIs, and trending across projects. With the use of Pareto Charts to help analyze vendor quality and non-conformance, timelines of pro-ject and facility metrics, project managers and subject matter experts (SME) are able to look for trends and pre-pare further quality improvement initiatives for their projects.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP103  
About • paper received ※ 20 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP104 Improvement of a Clean Assembly Work for Superconducting RF Cryomodule and Its Application to the KEK-STF Cryomodule cryomodule, cavity, vacuum, controls 721
 
  • H. Sakai, E. Kako, T. Konomi, K. Umemori, Y. Yamamoto
    KEK, Ibaraki, Japan
  • T. Ebisawa, A. Kasugai
    QST, Aomori, Japan
 
  We usually encountered the degradation of the superconducting RF cavities on the cryomodule test even though the performance of these cavities was good on the vertical test. In reality, the degradation of Q-values of two cavities of cERL main-linac were observed after cryomodule assembly in KEK [1] and STF cryomodule also met the degradation after the cryomodule assembly [2]. Some dusts and invisible particles might enter the cavity and generate field emission during the assembly work. Field emission is the most important cause of this degradation. In this paper, first we introduce some trials for the improved clean assembly work to SRF cavity by re-examining our clean assembly work and vacuum work. For example, slow pumping system with vacuum particle monitor was developed to know and control the particle movement during slow pumping and venting. Next we show the application of this improved work to the STF re-assemble cryomodule work in KEK.
[1} H. Sakai et al., SRF’13, Paris, France, p.855, 2013.
[2] Y. Yamamoto et al., IPAC’16, Busan, Korea, p.2158, 2016.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP104  
About • paper received ※ 20 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP105 Preparation of the Cryomodule Assembly for the Linear IFMIF Prototype Accelerator (LIPAc) in Rokkasho cryomodule, vacuum, cavity, operation 726
 
  • T. Ebisawa, A. Kasugai, K. Kondo, S. Maebara, K. Sakamoto
    QST, Aomori, Japan
  • N. Bazin, S. Berry
    CEA-DRF-IRFU, France
  • P. Cara
    IFMIF/EVEDA, Rokkasho, Japan
  • H. Dzitko, G. Phillips
    F4E, Germany
  • E. Kako, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
 
  The staged installation and commissioning of LIPAc is ongoing at Rokkasho Fusion Institute of QST, Japan for validating the low energy section of the IFMIF deuteron accelerator up to 9 MeV. The LIPAc Superconducting Radio Frequency accelerator (SRF) cryomodule is assembled under the responsibility of the EU Home Team, and the assembly work recently started at Rokkasho in March 2019. To fulfil the cleanliness requirements for the assembly process, QST took the responsibility to prepare the infrastructure of a cleanroom and associated devices. In this present paper, the details of the preparation work for the cryomodule assembly made by QST will be presented.  
poster icon Poster TUP105 [2.116 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP105  
About • paper received ※ 17 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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WETEA3 Status of the IFMIF/EVEDA Superconducting Linac cavity, solenoid, cryomodule, linac 735
 
  • N. Bazin, G. Devanz, H. Jenhani, O. Piquet
    CEA-DRF-IRFU, France
  • S. Chel
    CEA-IRFU, Gif-sur-Yvette, France
  • T. Ebisawa
    QST, Aomori, Japan
  • G. Phillips
    F4E, Germany
  • D. Regidor, F. Toral
    CIEMAT, Madrid, Spain
 
  The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy neutron flux to test samples as possible candidate materials to a full lifetime of fusion energy reactors. A prototype of the low energy part of the accelerator (LIPAc) is under construction at Rokkasho Fusion Institute in Japan. It includes one cryomodule containing 8 half-wave resonators (HWR) operating at 175 MHz and eight focusing solenoids. The talk will cover the progress of developments in the IFMIF/EVEDA cryomodule: the qualification of 8 cavities, the RF conditioning results of 8 high-power couplers, the manufacturing and test of the 8 superconducting solenoids and the equivalent operational equivalent tests performed at Saclay. The assembling status of the cryomodule at Rokkasho site will also be presented.  
slides icon Slides WETEA3 [11.091 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-WETEA3  
About • paper received ※ 20 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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WETEB1 Development of Superconducting Quarter-Wave Resonator and Cryomodule for Low-Beta Ion Accelerators at RIKEN Radioactive Isotope Beam Factory cavity, cryomodule, linac, vacuum 750
 
  • N. Sakamoto, T. Dantsuka, M. Fujimaki, H. Imao, O. Kamigaito, K. Kusaka, H. Okuno, K. Ozeki, K. Suda, A. Uchiyama, T. Watanabe, Y. Watanabe, K. Yamada
    RIKEN Nishina Center, Wako, Japan
  • H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa
    MHI-MS, Kobe, Japan
  • E. Kako, H. Nakai, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
 
  A prototype cryomodule with a superconducting quarter- wave resonator (SC QWR) has been developed at RIKEN Radioactive Isotope Beam Factory (RIBF). During the last SRF conference, we presented the performance of our first SC QWR and the first cool-down test of its cryomodule. Since then, we have continued our efforts to improve cavity performance and succeeded in recovering deteriorated Q0. In this paper, we report what we constructed and learned from the prototype, including design issues with the cavity and its cryomodule. Design issues related to the new SC QWRs and their cryomodules for the SC linac booster of the RIKEN Heavy-Ion Linac (RILAC) are described as well.  
slides icon Slides WETEB1 [120.252 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-WETEB1  
About • paper received ※ 24 June 2019       paper accepted ※ 05 July 2019       issue date ※ 14 August 2019  
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WETEB2 Identifying Specific Cryomodule and Cleanroom Particulate Contamination: Understanding Legacy Issues and Providing New Feedback Standards cavity, cryomodule, GUI, feedback 758
 
  • C.E. Reece, J.K. Spradlin, O. Trofimova, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
While the techniques used to provide "UHV clean" and "particle-free" beamline components, including SRF cavities, continue to evolve, "real-world" operating machines must deal with actual accumulated and latent contamination issues that produce non-trivial cryogenic heatload, radiation, activation, and degradation via field emission. We have developed a standardized and automated particulate contamination assay method for use in characterizing particulates found on beamline components and in cleanroom assembly environments. We present results from using this system to analyze samples taken from reworked cryomodules from CEBAF. Particle sizes are much larger than anticipated. Utility for feedback on sources to enable improved source reduction is explored.
 
slides icon Slides WETEB2 [13.320 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-WETEB2  
About • paper received ※ 23 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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WETEB4 Virtual SRF Cavity: Testing SRF Cavity Support Systems Without the Hassle of Liquid Helium and Klystrons cavity, controls, LLRF, FPGA 770
 
  • P. Echevarria, J. Knobloch, A. Neumann, A. Ushakov
    HZB, Berlin, Germany
  • E. Aldekoa, J. Jugo
    University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
 
  Setting up and debugging SRF support systems, such as LLRF control, quench detection, microphonics and Lorentz-force detuning control, etc., often requires extensive time spent operating the cavities. This results in time consuming and costly operation. Early into the development stages the actual cavity system may not even be available. It is therefore highly desirable to pre-evaluate these systems under realistic conditions prior to final testing with the SRF cavities. We devised an FPGA-based "virtual cavity" that takes a regular low-level RF input and generates the signals for RF-power reflection, transmission and detuning that mimic the response of a real cavity system. As far as the user is concerned, the response is the same as for a real cavity. This "black-box" model includes mechanical modes, Lorentz force detuning, a field depended quality factor, quenches and variable input coupling and is currently being expanded. We present the model and show some applications for operating the quench detection, LLRF and microphonics control for 1.3 GHz BERLinPro cavities. The same system can be used for other cavity types, including normal conducting cavities.  
slides icon Slides WETEB4 [9.784 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-WETEB4  
About • paper received ※ 23 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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WETEB6 Active Suppression of Microphonics Detuning in High QL Cavities cavity, controls, linac, resonance 776
 
  • N. Banerjee, G.H. Hoffstaetter, M. Liepe, P. Quigley
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was performed through the support of New York State Energy Research and Development Agency (NYSERDA). SRF 2019 provided travel support in the form of a student grant.
Accelerators operating with low beam loading such as Energy Recovery Linacs (ERL) greatly benefit from using SRF cavities operated at high loaded quality factors, since it leads to lower RF power requirements. However, large microphonics detuning several times the operating bandwidth of the cavities severely limit the maximum accelerating fields which can be sustained in a stable manner. In this talk, I will describe an active microphonics control technique based on the narrow band Active noise Control (ANC) algorithm which we have used in CBETA, a multi-turn SRF ERL being commissioned at Cornell University. I will describe its stability and performance during beam operations of CBETA with consistent reduction of peak detuning by almost a factor of 2 on multiple cavities.
 
slides icon Slides WETEB6 [10.296 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-WETEB6  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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THFUA1 RF Characterization of an S-I-S’ Multilayer Sample niobium, quadrupole, ECR, cavity 800
 
  • S. Keckert, J. Knobloch, O. Kugeler, D.B. Tikhonov
    HZB, Berlin, Germany
  • A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
 
  S-I-S’ multilayers promise to boost the performance of bulk superconductors in terms of maximum field and surface resistance. At HZB, RF-surface resistance measurements were performed with a Quadrupole Resonator (QPR) and an S-I-S’ sample (75 nm NbTiN on 15 nm AlN insulator on bulk Nb) prepared at JLab. Measurements were performed at 414, 845, and 1286 MHz at sample temperatures from 2 K up to well above the transition temperature of NbTiN of ~17.3 K. The Rs exhibits an unexpected temperature dependence: Rather than rising monotonically, as expected from BCS theory, a local maximum is observed. There is a temperature range where Rs decreases with increasing temperature. Such behavior indicates that an additional interaction between the superconducting layers may have to be included in the surface resistance model. Measurements of the baseline Nb sample prior to coating exhibited no such behavior; hence systematic measurement errors can be excluded as the explanation. The maximum field was limited by a hard magnetic quench near 20 mT, close to Hc1 of NbTiN, suggesting that the sample is limited by early flux penetration.  
slides icon Slides THFUA1 [1.004 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THFUA1  
About • paper received ※ 22 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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THFUA6 Nb3Sn Films for SRF Cavities: Genesis and RF Properties cavity, niobium, interface, experiment 810
 
  • U. Pudasaini, M.J. Kelley
    The College of William and Mary, Williamsburg, Virginia, USA
  • J.W. Angle, M.J. Kelley, J. Tuggle
    Virginia Polytechnic Institute and State University, Blacksburg, USA
  • G.V. Eremeev, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
 
  Funding: Partially authored by Jefferson Science Associates under contract no. DE¬AC05¬06OR23177. Supported by Office of High Energy Physics under grants DE-SC-0014475 to the College of William and DE-SC-0018918 to Virginia Tech.
Understanding of Nb3Sn nucleation and growth is essential to the progress with Nb3Sn vapor diffusion coatings of SRF cavities. Samples representing different stages of Nb3Sn formation have been produced and examined to elucidate the effects of nucleation, growth, process conditions, and impurities. Nb3Sn films from few hundreds of nm up to ~15 µm were grown and characterized using AFM, SEM/EDS, XPS, EBSD, SIMS, and SAM. Microscopic examinations of samples suggest the mechanisms behind Nb3Sn thin film nucleation and growth. RF measurements of coated cavities were combined with material characterization of witness samples to adapt the coating process in "Siemens" coating configuration. Understanding obtained from sample studies, applied to cavities, resulted in Nb3Sn cavity with quality factor 2 ×1010 at 15 MV/m accelerating gradient at 4 K, without "Wuppertal" Q-slope. We discuss the genesis of the Nb3Sn thin film in a typical tin vapor diffusion process, and its consequences to the coating of SRF cavities.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THFUA6  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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THFUB1 Nb3Sn at Fermilab: Exploring Performance cavity, multipactoring, niobium, superconductivity 818
 
  • S. Posen, J. Lee, O.S. Melnychuk, Y.M. Pischalnikov, D.A. Sergatskov, B. Tennis
    Fermilab, Batavia, Illinois, USA
  • J. Lee, D.N. Seidman
    NU, Evanston, Illinois, USA
 
  Fermilab’s Nb3Sn coating program produced its first 1.3 GHz single cell cavities in early 2017 and since then has explored the performance of Nb3Sn on a wide variety of cavity substrates and performed microscopic studies down to atomic resolution. Results to present in this talk include a study of frequency dependence from 650 MHz to 1.3 GHz of BCS resistance, residual resistance, and magnetic flux sensitivity. We show microscopic studies performed in collaboration with Northwestern University’s Materials Science and Engineering Department of limitation mechanisms in Nb3Sn, including thin film regions and tin segregation at grain boundaries, discussing correlations with RF performance and mechanisms for the formation of these features during growth. Finally, we present results of the first 1.3 GHz 9-cell cavity coated with Nb3Sn.  
slides icon Slides THFUB1 [27.194 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THFUB1  
About • paper received ※ 29 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THFUB2 Progress with Nb Hipims Films on 1.3 GHz Cu Cavities cavity, lattice, cathode, superconductivity 823
 
  • M.C. Burton, A.D. Palczewski, C.E. Reece, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In recent years, efforts have been invested to leverage the different processes involved in energetic condensation to tailor Nb film growth in sequential steps. The resulting Nb/Cu films display high quality material properties and show promise of high RF performance. The lessons learned are now applied to 1.3 GHz Nb on Cu cavity deposition via high power impulse magnetron sputtering (HiPIMS). RF performance is measured at different temperatures. Particular attention is given to the effect of cooldown and sensitivity to external applied magnetic fields. The results are evaluated in light of the Nb film material and superconducting properties measured with various microscopy and magnetometry techniques in order to better understand the contributing factors to the residual and flux induced surface resistances. This contribution presents the insights gained in exploiting energetic condensation as a path towards RF Q-slope mitigation for Nb/Cu films, correlating film material characteristics with RF performance.
 
slides icon Slides THFUB2 [7.869 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THFUB2  
About • paper received ※ 02 July 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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THP002 Metallographic Polishing Pathway to the Future of Large Scale SRF Facilities cavity, niobium, embedded, cryogenics 828
 
  • O. Hryhorenko, M. Chabot, D. Longuevergne
    IPN, Orsay, France
  • C.Z. Antoine
    CEA-IRFU, Gif-sur-Yvette, France
 
  Funding: The financial support from the European Nuclear Science and Applications Research 2 (ENSAR 2) under grant agreeement N°654002.
Optimization of SRF cavities mainly focuses on pushing the limits of bulk Niobium, cost reduction of cavity fabrication and development of new SRF materials for future accelerators (ILC, FCC). Nowadays chemical etching is the only surface treatment used to prepare SRF surface made of Nb. However the operational cost of chemical facilities is high and these present a very bad ecological footprint. The search of an alternative technique could make the construction of these future large scale facilities possible. Metallographic polishing (MP) is a candidate not only for bulk Nb treatment, but could also provide the mirror-finished substrate for alternative SRF thin films deposition. Recent R&D studies, conducted at IPNO & IRFU, focused on the development of 2-steps MP procedure of Nb flat samples. Roughness of polished surface has been proven better than standard EP treatment and less polluted than CBP. MP provides on flat surfaces a high removal rate (above 1 µm/min) and high reproducibility. The paper will describe the optimized method and present all the surface analysis performed. The first RF characterization of a polished disk will be presented.
 
poster icon Poster THP002 [2.902 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP002  
About • paper received ※ 20 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP003 Results on Bulk Niobium Surface Resistance Measurement With Pillbox Cavity on TE011 and TE012 Modes cavity, niobium, coupling, experiment 833
 
  • G. Martinet
    IPN, Orsay, France
 
  Surface measurement of superconducting samples is required to characterize processes of bulk niobium preparation for SRF resonators. In order to reduce characterization cost and improve measurement performances, a pill-box cavity has been developed at IPN Orsay. Using TE011 and TE012 modes, we describe the latest results based on calorimetric method.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP003  
About • paper received ※ 23 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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THP004 Design and Fabrication of a Quadrupole-Resonator for Sample R&D quadrupole, cavity, simulation, niobium 838
 
  • R. Monroy-Villa, D. Reschke, M. Wenskat
    DESY, Hamburg, Germany
  • W. Hillert, R. Monroy-Villa, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Keckert, O. Kugeler, D.B. Tikhonov
    HZB, Berlin, Germany
  • P. Putek, S.G. Zadeh, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • U. van Rienen
    University of Rostock, Rostock, Germany
 
  Being able to obtain BCS and material properties from the same surface is necessary to gain a fundamental understanding of the evolution of SRF surfaces. A test resonator which will allow to obtain BCS properties from samples is currently under development at the University of Hamburg and DESY and is based on the Quadrupole Resonators developed and operated at CERN and HZB. The current status of the necessary infrastructure, the procurement process and design considerations are shown. In addition, an outline of the planed R&D project with the Quadrupole Resonator will be presented and first RF measurements and surface analysis results of samples will be shown  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP004  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP008 The Technical Study of Nb3Sn Film Deposition on Copper by HiPIMS niobium, cavity, electron, superconductivity 846
 
  • L. Xiao, X.Y. Lu, W.W. Tan, D. Xie, Y. Yang, L. Zhu
    PKU, Beijing, People’s Republic of China
 
  Our work is mainly focused on the deposition methods of Nb3Sn films on Cu substrates and film‘s properties. The superconducting transition temperature(Tc) of Nb3Sn film is 12K. There are diffraction peaks of Nb3Sn in the X-ray diffraction patterns in which without diffraction peaks of copper compounds. Scanning electron micro-structures of Nb3Sn film reflect its nice compactness and binding force between film and substrate.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP008  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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THP011 Niobium Semiproducts for the Superconducting Strands and SRF Cavities in Russia niobium, ECR, cavity, target 857
 
  • M.V. Alekseev, I.M. Abdyukhanov, V.A. Drobyshev, M.V. Kravtsova, M.V. Krylova, P.A. Lykianov, K.A. Mareev, V.I. Pantsyrny, M.V. Polikarpova, M.M. Potapenko, A.G. Silaev, A.S. Tsapleva
    SC A A Bochvar High-Technology Research Institute of Inorganic Materials, Moscow, Russia
  • M.Y. Shlyakhov, S.M. Zernov
    JSC - TVEL, Moscow, Russia
 
  The melting regimes of the niobium ingots with high chemical purity and low hardness for the Nb3Sn, NbTi and other superconducting materials manufacture have been developed at SC "VNIINM". Using this niobium material and by the SC "VNIINM" manufacture regimes at the SC "Chepetsky Mechanical Plant" 220 tons of Nb3Sn and NbTi strands for ITER and 12 km of Nb3Sn strands for HL-LHC (CERN) with the required characteristics have been successfully produced. The review of the characteristics of the different semiproducts (sheets, tubes, rods), made in Russia from the special grade niobium, and of the superconducting strands, manufactured with the use of them, is presented in the paper. The ways of the further improvement of the niobium ingots melting regimes and niobium sheets deformation and annealing regimes with the target of achieving RRR > 300 for the SRF cavities application are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP011  
About • paper received ※ 23 June 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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THP014 First Direct Imaging and Profiling TOF-SIMS Studies on Cutouts from Cavities Prepared by State-of-the-Art Treatments cavity, niobium, GUI, superconductivity 866
 
  • A.S. Romanenko, A. Grassellino, M. Martinello, Y. Trenikhina
    Fermilab, Batavia, Illinois, USA
  • D. Bafia
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  Funding: This work has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Small amounts of interstitial impurities in the penetra-tion depth of superconducting radio frequency (SRF) cavities have a dramatic effect on the quality factors and maximum accelerating gradients. Here we report the first TOF-SIMS studies of cutouts from cavities prepared by all modern surface treatments, which allow a direct corre-lation of the impurity distribution with the observed cavity performance. Imaging capability of our instrument allows to avoid the possible issues associated with the ‘‘ghost’’ depth profiles appearing as a consequence of particulate surface contamination, which likely caused the inconclusive SIMS results on e.g. oxygen diffusion in the past.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP014  
About • paper received ※ 02 July 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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THP017 Crystallographic Characterization of Nb3Sn Coatings and N-Doped Niobium via EBSD and SIMS niobium, interface, electron, cavity 871
 
  • J.W. Angle, M.J. Kelley, J. Tuggle
    Virginia Polytechnic Institute and State University, Blacksburg, USA
  • G.V. Eremeev, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
  • M.J. Kelley, U. Pudasaini
    The College of William and Mary, Williamsburg, Virginia, USA
 
  Historically, niobium has been used as the superconducting material in SRF cavities. Due the high operational costs, other materials are currently being considered. Nb3Sn coatings have been investigated over the past several decades, motivated by potentially higher operating temperatures. More recently niobium has been doped with nitrogen to improve the quality factor (Q). Currently, a need for better understanding still exists for both mechanisms. EBSD has been shown to be a viable technique to determine the crystallographic orientation and the size of the Nb3Sn grains. The EBSD maps obtained show a bimodal distribution of grain sizes with smaller Nb3Sn grains found present near the Nb3Sn/Nb interface. In addition to the Nb3Sn coatings, N-doped niobium coupons were analyzed by EBSD and found that the coupon had preferred surface orientation. The EBSD analysis was found to be vital as specific grains could be targeted in SIMS to better understand the diffusion of nitrogen with respect to crystal orientation.  
poster icon Poster THP017 [2.571 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP017  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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THP020 Study of Dislocation Content Near Grain Boundaries using Electron Channeling Contrast Imaging and its Effect on Superconducting Properties of Niobium cavity, electron, niobium, superconductivity 876
 
  • M. Wang, T.R. Bieler
    Michigan State University, East Lansing, Michigan, USA
  • S. Balachandran, S. Chetri, P.J. Lee
    NHMFL, Tallahassee, Florida, USA
  • S. Chetri, A. Polyanskii
    ASC, Tallahassee, Florida, USA
  • C. Compton, C. Compton
    FRIB, East Lansing, Michigan, USA
  • C. Compton
    NSCL, East Lansing, Michigan, USA
 
  Funding: U.S. Department of Energy. National Science Foundation Cooperative Agreement No. DMR-1157490 (-2017) DMR-1644779 (2018-) and the State of Florida
Trapped micro-Tesla levels of magnetic flux degrade the performance of Nb superconducting radio frequency (SRF) accelerators. Recent studies have revisited the role of small deformation (dislocation substructure influence) on cavity performance. However, the link between microstructural defects and mechanisms leading to poor performance is still unresolved. To examine the mechanism of flux pinning by dislocations and grain boundaries, systematic studies on bi-crystal Nb tensile samples were designed with strategically chosen orientation relationships between neighboring crystals with respect to the grain boundaries. Laue X-ray diffraction and electron backscatter diffraction analysis was used to measure crystal orientations of a large-grain Nb slice, from which the bi-crystals were extracted. Dislocation structures near the grain boundaries were characterized before and after 5% tensile deformation using electron channeling contrast imaging (ECCI), after which the magnetic flux behavior was observed using cryogenic magneto-optical imaging (MOI). We discuss the conditions under which we observe increased flux pinning in regions of high dislocation density.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP020  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP027 Cryogenics Performance of the Vertical Cryostat for Qualifying ESS-SRF High Beta Cavities cavity, cryogenics, operation, MMI 895
 
  • S.M. Pattalwar, R.K. Buckley, P.C. Hornickel, K.J. Middleman, M.D. Pendleton, P. Pizzol, P.A. Smith, T.M. Weston, A.E. Wheelhouse, S. Wilde
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • A.J. May, A. Oates, J.T.G. Wilson
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
 
  An innovative vertical cryostat has been developed and commissioned at STFC Daresbury Laboratory for qualifying the high-beta SRF cavities for the ESS (European Spallation Source). The cryostat is designed to test 3 dressed cavities in horizontal configuration in one cold run at 2K. The cavities are cooled to 2K with superfluid liquid helium filled into individual helium jackets of the cavities. This reduces the liquid helium consumption by more than 70% in comparison with the conventional vertical tests. The paper describes the cryogenic system and its performance with detail discussions on the initial results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP027  
About • paper received ※ 22 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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THP032 SRF Gun and SRF Linac Driven THz at ELBE Successfully in User Operation gun, radiation, electron, linac 915
 
  • R. Xiang, A. Arnold, P.E. Evtushenko, S. Kovalev, U. Lehnert, P.N. Lu, S. Ma, P. Michel, P. Murcek, A.A. Ryzhov, J. Schaber, Ch. Schneider, J. Teichert
    HZDR, Dresden, Germany
  • H. Vennekate
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  • I. Will
    MBI, Berlin, Germany
 
  Funding: The work was partly supported by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1 and Deutsche Forschungsgemeinschaft (DFG) project (XI 106/2-1).
The first all-SRF accelerator driven THz source has been operated as a user facility since 2018 at ELBE radiation center. The CW electron beam is extracted from SRF gun II, accelerated to relativistic energies and compressed to sub-ps length in the ELBE SRF linac with a chicane. THz pulses are produced by pass-ing the short electron bunches through a diffraction radiator (CDR) and an undulator. The coherent THz power increases quadratically with bunch charge. The pulse energy up to 10 µJ at 0.3 THz with 100 kHz has been generated.
 
poster icon Poster THP032 [1.207 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP032  
About • paper received ※ 02 July 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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THP041 Impact of the Cu Substrate Surface Preparation on the Morphological, Superconductive and RF Properties of the Nb Superconductive Coatings laser, cavity, radiation, niobium 935
 
  • C. Pira, E. Chyhyrynets
    INFN/LNL, Legnaro (PD), Italy
  • C.Z. Antoine
    CEA-IRFU, Gif-sur-Yvette, France
  • X. Jiang, S.B. Leith, M. Vogel
    University Siegen, Siegen, Germany
  • A. Katasevs, J. Kaupužs, A. Medvids, P. Onufrijevs
    Riga Technical University, Riga, Latvia
  • O. Kugeler
    HZB, Berlin, Germany
  • O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R. Ries, E. Seiler
    Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic
  • A. Sublet
    CERN, Meyrin, Switzerland
 
  Funding: This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871.
Nowadays, one of the main issues of the superconducting thin film resonant cavities is the Cu surface preparation. A better understanding of the impact of copper surface preparation on the morphological, superconductive (SC) and RF properties of the coating, is mandatory in order to improve the performances of superconducting cavities by coating techniques. ARIES H2020 collaboration includes a specific work package (WP15) to study the influence of Cu surface polishing on the SRF performances of Nb coatings that involves a team of 8 research groups from 7 different countries. In the present work, a comparison of 4 different polishing processes for Cu (Tumbling, EP, SUBU, EP+SUBU) is presented through the evaluation of the SC and morphological properties of Nb thin film coated on Cu planar samples and QPR samples, polished with different procedures. Effects of laser annealing on Nb thin films have also been studied. Different surface characterizations have been applied: roughness measurements, SEM, EDS, XRD, AFM, and thermal and photo-stimulated exoelectrons measurements. SC properties were evaluated with PPMS, and QPR measurements will be carry out at HZB in the beginning of 2019.
 
poster icon Poster THP041 [3.196 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP041  
About • paper received ※ 23 June 2019       paper accepted ※ 05 July 2019       issue date ※ 14 August 2019  
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THP042 Initial Results from Investigations into Different Surface Peparation Techniques of OFHC Copper for SRF Applications site, cavity, experiment, ECR 941
 
  • S.B. Leith, X. Jiang, Z. Khalil, A.S.H. Mohamed, M. Vogel
    University Siegen, Siegen, Germany
 
  Funding: This work forms part of the EASITrain research programme. This Marie Sklodowska-Curie Action (MSCA) Innovative Training Networks (ITN) has received funding from the European Union’s H2020 Framework Programme under Grant Agreement no. 764879
As part of efforts to improve the performance of thin film coated accelerating cavities, improvement of the topography of the surface of copper is being pursued. This is known to strongly affect the properties of the deposited superconducting thin film. This study focuses on determining the optimal procedure to enhance homogeneity and smoothness of the copper surface. OFHC copper substrates have been processed using mechanical polishing (MP), chemical polishing (CP) and electropolishing (EP) procedures as well as a combina-tion thereof. The parameters of each of the procedures have been tested and optimised to produce the smoothest surface possible. The resulting samples have been analysed using a scanning electron microscope, a laser profilometer and a confocal microscope. Results indicate the superior per-formance of electrochemical polishing over chemical polishing in terms of planarization efficiency, while a combination of mechanical polishing followed by electropolishing provides the most homogeneous and smooth surface when utilising the critical current density of the electrolyte.
 
poster icon Poster THP042 [1.190 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP042  
About • paper received ※ 22 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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THP044 RF Characterization of Novel Superconducting Materials and Multilayers cavity, niobium, site, plasma 950
 
  • T.E. Oseroff, M. Liepe, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • B. Moeckly
    STI, Santa Barbara, California, USA
  • M.J. Sowa
    Veeco-CNT, Medford, USA
 
  Cutting edge SRF technology is likely approaching the fundamental limitations of niobium cavities operating in the Meissner state. This combined with the obvious advantages of using higher critical temperature superconductors and thin film depositions leads to interest in the RF characterization of such materials. A TE mode niobium sample host cavity was used to characterize the RF performance of 5" (12.7 cm) diameter sample plates as a function of field and temperature at 4 GHz. Materials studied include MgB2 and thin film atomic layer deposition (ALD) NbN and NbTiN on Nb substrates. These higher critical temperature superconductors all having coherence lengths on the order of a few nm. It is therefore likely that defects on the order of the coherence lengths will cause early flux penetration well before the theorized superheating field of an ideal superconducting surface. Superconductor-insulator-superconductor (SIS) multilayers have been proposed as a mechanism of arresting these early penetration flux avalanches and are therefore studied here as well, using the same NbN and NbTiN films, but over thin layers of insulating AlN on Nb substrates.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP044  
About • paper received ※ 02 July 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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THP045 Improvements to the Cornell Sample Host System cavity, niobium, coupling, quadrupole 956
 
  • T.E. Oseroff, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  RF characterization of arbitrary superconducting samples has been of interest for many years but, due to the experimental complexities, has never been achieved to its full potential. A TE mode niobium sample host cavity has been used at Cornell to characterize the RF performance of 5" (12.7 cm) diameter sample plates. It was designed and built in 2012 – 2013 and since then has encountered a range of problems. The focus of this work is to highlight these and to present solutions to assist future researchers hoping to design novel RF characterization instruments. Topics covered include coupler design, cryostat support structure, sample preparation, and a discussion of potential systematic errors introduced by the data extraction and calibration methods applied to this device.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP045  
About • paper received ※ 01 July 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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THP046 Magnetic Field Mapping System for Cornell Sample Host Cavity cavity, monitoring, cryomodule, radio-frequency 961
 
  • S.N. Lobo, M. Liepe, T.E. Oseroff
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: Cornell Laboratory for Accelerator-Based Sciences and Education
Dissipation due to flux trapping is a persistent problem experienced in SRF cavity testing and cryomodule operation. This work addresses accurately and cheaply measuring magnetic fields in a cryostat without using delicate and expensive fluxgate magnetometers. Anisotropic Magnetoresistive (AMR) magnetic field sensors were investigated for the detection of small fields in a cryogenic environment. Initial development of instrumentation using 16 AMR sensors is presented for the purpose of measuring magnetic fields perpendicular the normal of a 5" diameter sample plate on the Cornell sample host cavity.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP046  
About • paper received ※ 29 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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THP047 Progress of TRIUMF Beta-SRF Facility for Novel SRF Materials cavity, optics, niobium, radio-frequency 964
 
  • E. Thoeng
    UBC & TRIUMF, Vancouver, British Columbia, Canada
  • R.A. Baartman, P. Kolb, R.E. Laxdal, B. Matheson, G. Morris, N. Muller, S. Saminathan
    TRIUMF, Vancouver, Canada
  • T. Junginger
    UVIC, Victoria, Canada
 
  Funding: NSERC (Natural Sciences and Engineering Research Council of Canada)
SRF cavities made with bulk Nb have been the backbone of high-power modern linear accelerators. Demands for higher energy and more efficient linear accelerators, however, have strained the capabilities of bulk Nb close to its fundamental limit. Several routes have been proposed using thin film novel superconductors (e.g. Nb3Sn), SIS multilayer, and N-doping. Beta-NMR techniques are more suitable for the characterization of Meissner state in these materials, due to the capability of soft-landing radioactive ions on the nanometer scale of London penetration depth, as compared to micrometer probe of the muSR technique. Upgrade of the existing beta-NQR beamline, combined with the capability of high parallel magnetic field (200 mT) are the scope of the beta-SRF facility which has been fully funded. All hardware required for the upgrade has also been procured. The status of the commissioning, which is currently in phase I, is reported here, together with the future schedule of phase II with the fully installed beta-SRF beamline. Finally, the detail layout of the completed beamline and sample requirements will be included in this paper which might be of interest of future users.
 
poster icon Poster THP047 [1.372 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP047  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP048 Characterization of Flat Multilayer Thin Film Superconductors dipole, superconducting-magnet, experiment, site 968
 
  • D. Turner, A.J. May
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • G. Burt, L. Gurran
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • K.D. Dumbell, N. Pattalwar, S.M. Pattalwar
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • T. Junginger, O.B. Malyshev
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  The maximum accelerating gradient of SRF cavities can be increased by raising the field of initial flux penetration, Hvp. Thin alternating layers of superconductors and insulators (SIS) can potentially increase Hvp. Magnetometry is commercially available but consists of limitations, such as SQUID measurements apply a field over both superconducting layers, so Hvp through the sample cannot be measured. If SIS structures are to be investigated a magnetic field must be applied locally, from one plane of the sample, with no magnetic field on the opposing side to allow Hvp to be measured. A magnetic field penetration experiment has been developed at Daresbury laboratory, where a VTI has been created for a cryostat where Hvp of a sample can be measured. The VTI has been designed to allow flat samples to be measured to reduce limitations such as edge effects by creating a DC magnetic field smaller than the sample. A small, parallel magnetic field is produced on the sample by the use of a ferrite yoke. The field is increased to determine Hvp by using 2 hall probes either side of the sample.  
poster icon Poster THP048 [0.327 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP048  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP050 Measurement of the Magnetic Field Penetration into Superconducting Thin Films experiment, solenoid, cavity, FEL 978
 
  • I.H. Senevirathne, G. Ciovati, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • G. Ciovati, J.R. Delayen
    JLab, Newport News, Virginia, USA
 
  The magnetic field at which first flux penetrates is a fundamental parameter characterizing superconducting materials for SRF cavities. Therefore, an accurate technique is needed to measure the penetration of the magnetic field directly. The conventional magnetometers are inconvenient for thin superconducting film measurements because these measurements are strongly influenced by orientation, edge and shape effects. In order to measure the onset of field penetration in bulk, thin films and multi-layered superconductors, we have designed, built and calibrated a system combining a small superconducting solenoid capable of generating surface magnetic field higher than 500 mT and Hall probe to detect the first entry of vortices. This setup can be used to study various promising alternative materials to Nb, especially SIS multilayer coatings on Nb that have been recently proposed to delay the vortex penetration in Nb surface. In this paper, the system will be described and calibration will be presented.  
poster icon Poster THP050 [1.201 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP050  
About • paper received ※ 20 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP053 Analysis of the Results of the Tests of IFMIF Accelerating Units cavity, cryomodule, vacuum, linac 992
 
  • N. Bazin, S. Chel, M. Desmons, G. Devanz, H. Jenhani, O. Piquet
    CEA-DRF-IRFU, France
 
  The prototype IFMIF-EVEDA cryomodule encloses eight superconducting 175 MHz β=0.09 Half-Wave Resonators (HWR). They are designed together with the power coupler to accelerate a high intensity deuteron beam (125 mA) from to 5 to 9 MeV. Two cavity packages, complete with tuning system and power couplers, have been tested in a dedicated horizontal test cryostat - SaTHoRI (Satellite de Tests HOrizontal des Résonateurs IFMIF). The successful operational equivalent tests and tuning of the SRF accelerating units is reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP053  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP054 Cryogenic Installations for Module Tests at Mainz cryogenics, cryomodule, operation, cavity 997
 
  • F. Hug, K. Aulenbacher, E. Schilling, D. Simon, T. Stengler, S.D.W. Thomas
    KPH, Mainz, Germany
  • K. Aulenbacher, T. Kürzeder
    HIM, Mainz, Germany
  • A. Skora
    IKP, Mainz, Germany
 
  Funding: This work is supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA+" EXC 2118/2019
At Helmholtz Institute Mainz a cryomodule test bunker has been set up for testing dressed modules at 2 K. In a first measurement campaign the high power rf tests of two 1.3 GHz cryomodules for the future MESA accelerator have been performed. We will report on the performance of the test setup, the present and upcom-ing cryogenic installations at the Institute for Nuclear Physics at Mainz, and in particular on the Helium re-frigeration and transport system comprising of a 220 m transport line for liquified gases.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP054  
About • paper received ※ 29 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP055 Magnetic Field Induced by Thermo Electric Current in LCLS-II Cryomodules cavity, cryomodule, niobium, vacuum 1003
 
  • G. Wu, S.K. Chandrasekaran
    Fermilab, Batavia, Illinois, USA
 
  Funding: The work is supported by Fermilab which is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Seebeck effect of metals play an important role in cryomodule design. As cryomodule cools down from room temperature down to nominal cavity operating temperature, components in a cryomodule experiences different temperatures. Some components such as power couplers cross from room temperature to 2 K. Thermo electric current forms loops circulating through and around cavities. Such current loops will generate additional magnetic field that could be trapped into cavity wall during superconducting transition as well as during cavity quench. These trapped field can degrade cavity quality factor and increase heat load. Simple circuit model is proposed and compared to calculated trapped field during cryomodule tests.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP055  
About • paper received ※ 26 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP060 Experience With LCLS-II Cryomodule Testing at Fermilab cryomodule, cavity, operation, detector 1018
 
  • E.R. Harms, E. Cullerton, C.M. Ginsburg, B.J. Hansen, B.D. Hartsell, J.P. Holzbauer, J. Hurd, V.S. Kashikhin, M.J. Kucera, F.L. Lewis, A. Lunin, D.L. Newhart, D.J. Nicklaus, P.S. Prieto, O.V. Prokofiev, J. Reid, N. Solyak, R.P. Stanek, M.A. Tartaglia, G. Wu
    Fermilab, Batavia, Illinois, USA
  • C. Contreras-Martinez
    FRIB, East Lansing, Michigan, USA
  • J. Einstein-Curtis
    Private Address, Naperville, USA
 
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The Cryomodule Test Stand (CMTS1) at Fermilab has been engaged with testing 8-cavity 1.3 GHz cryomodules designed and assembled for the LCLS-II project at SLAC National Accelerator Laboratory since 2016. Over these three years twenty cryomodules have been cooled to 2K and power tested in continuous wave mode on a roughly once per month cycle. Test stand layout and testing procedures are presented together with results from the cryomodules tested to date. Lessons learned and future plans will also be shared.
 
poster icon Poster THP060 [2.774 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP060  
About • paper received ※ 22 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP061 Performance of FRIB Production Quarter-Wave and Half-Wave Resonators in Dewar Certification Tests cavity, cryomodule, linac, MMI 1023
 
  • W. Hartung, S.H. Kim, D. Norton, J.T. Popielarski, K. Saito, J.F. Schwartz, C. Wei, T. Xu, C. Zhang
    FRIB, East Lansing, Michigan, USA
 
  The Facility for Rare Isotope Beams (FRIB) is under construction at Michigan State University (MSU). The FRIB superconducting driver linac will accelerate ion beams to 200 MeV per nucleon. The driver linac requires 104 quarter-wave resonators (QWRs, β = 0.041 and 0.085) and 220 half-wave resonators (HWRs, β = 0.29 and 0.54). The jacketed resonators are Dewar tested at MSU before installation into cryomodules. The cryomodules for β = 0.041, 0.085, and 0.29 have been completed and certified; 88% of the β = 0.54 HWRs have been certified (as of March 2019). Beam commissioning of the QWR cryomodules is in progress. The Dewar certification tests have provided valuable statistics on the performance of production QWRs and HWRs at 4.3 K and 2 K and on performance limits. Results will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP061  
About • paper received ※ 12 July 2019       paper accepted ※ 13 August 2019       issue date ※ 14 August 2019  
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THP062 Progress in FRIB Cryomodule Bunker Tests cavity, cryomodule, solenoid, operation 1029
 
  • W. Chang, S. Caton, A. Ganshyn, W. Hartung, S.H. Kim, B. Laumer, H. Maniar, J.T. Popielarski, K. Saito, M. Xu, T. Xu, C. Zhang, S. Zhao
    FRIB, East Lansing, Michigan, USA
 
  Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Facility for Rare Isotope Beams (FRIB) is under construction at Michigan State University (MSU). The FRIB superconducting driver linac will accelerate ion beams to 200 MeV per nucleon. The driver linac requires 104 quarter-wave resonators (QWRs, β = 0.041 and 0.085) and 220 half-wave resonators (HWRs, β = 0.29 and 0.54). The jacketed resonators are Dewar tested at MSU before installation into cryomodules. The cryomodules for β = 0.041, 0.085, and 0.29 have been completed and certified; 32 out of 49 cryomodules are certified via bunker test (as of March 2019). FRIB cryomodule needs 74 solenoid packages: 8-25 cm packages for 0.041 QWR CMs, 36-50 cm for 0.085 CMs, 12-50 cm for 0.29 CMs, and 18-50 cm for 0.53 CMs. The bunker certification completed 58 packages. All the magnets energized at FRIB goal (90 A/8 T for solenoid and 19 A/0.064 Tm for dipoles), all cavities tested at or above specified operating gradient. In this paper, we report the bunker test result.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP062  
About • paper received ※ 23 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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THP064 The Cryostat Results of Carbon Contamination and Plasma Cleaning for the Field Emission on the SRF Cavity cavity, plasma, experiment, cryogenics 1038
 
  • A.D. Wu, Q.W. Chu, H. Guo, Y. He, S.C. Huang, C.L. Li, F. Pan, Y.K. Song, T. Tan, P.R. Xiong, W.M. Yue, S.H. Zhang, H.W. Zhao
    IMP/CAS, Lanzhou, People’s Republic of China
 
  The field emission effect is the mainly limitation for the operating of SRF cavities in higher gradient with stability. In this paper, the experiments were performed to evaluate the impact of the carbon contaminants and plasma cleaning on the performance of SRF cavity. Contamination mechanism was classified into cryogenic adsorption with weak strength and chemical deposition with strong strength. For the weak strength condition, the methane was injected into the SRF cavity during vertical test to make a cryogenic adsorption layer on the inner surface of the cavity. The results revealed that the performance of SRF cavity degraded by methane physical adsorption, but the performance can be recovered by thermal cycle the cavity to 300K and pump methane out. For the strong strength condition, the chemical deposited dirty layer of carbon contamination was produced by using of Ar/CH4 mixed PECVD method, and the SRF cavity performance was deteriorated by the severe field emission. Finally, carbon deposited cavity was treated by the Ar/O2 plasma, and its results revealed that the field emission removed greatly and the gradient was increased.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP064  
About • paper received ※ 20 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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THP068 Evaluation of Low Heat Conductivity RF Cables vacuum, cavity, insertion, cryogenics 1045
 
  • G. Cheng, G. Ciovati, M.L. Morrone
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
New potential applications of superconducting radio-frequency can be envisioned with conduction cooling of the cavities using cryocoolers. In this case, the total heat load to the cryocoolers have to be carefully managed to assure sufficient margin to operate the cavity at an acceptable accelerating gradient. The static and dynamic heat load from rf cables connected to the cavity can be a significant contribution to the total heat load. In this contribution we report the results from measurements of the temperature profile at 1.3 GHz for two low heat conductivity rf cables, as a function of the rf power and with one end of the cable in thermal contact with a liquid helium bath at 4.3 K. A parametric model of the two cables was developed with ANSYS to match the temperature profiles and calculate the heat load at the cold end of the cable.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP068  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP070 CEPC HOM Coupler R&D HOM, cavity, collider, cryomodule 1050
 
  • H.J. Zheng, F. Meng, P. Sha, J.Y. Zhai
    IHEP, Beijing, People’s Republic of China
 
  The conceptual design report (CDR) for the Circular Electron Positron Collider (CEPC) has been published in September 2018. In this talk, the CDR design and prototyping of the HOM coupler for the CEPC Collider ring cavity will be given. Each cavity has two detachable coaxial HOM couplers mounted on the cavity beam pipe with HOM power handling capacity of 1 kW. A double notch coupler is chosen due to its wide bandwidth for the fundamental mode. A prototype of this HOM coupler and a coaxial line test bench have been fabricated and tested under low power. The low power test results agree well with the simulation results. The high power test was also carried out in room temperature.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP070  
About • paper received ※ 19 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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THP072 Development of HOM Absorbers for CW Superconducting Cavities in Energy Recovery Linac HOM, cavity, superconducting-cavity, linac 1060
 
  • T. Ota, S. Nakamura, K. Sato, M. Takasaki
    Toshiba Energy Systems & Solutions Corporation, Keihin Product Operations, Yokohama, Japan
  • E. Kako, T. Konomi, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • A. Miyamoto
    Toshiba, Yokohama, Japan
 
  Higher Order Modes (HOM) absorbers for superconducting cavities have been developing at TOSHIBA in collaboration with High Energy Accelerator Research Organization (KEK) since 2015. A new prototype HOM absorber for 1.3 GHz 9-cell superconducting cavity was fabricated. An AlN lossy dielectrics cylinder was brazed with a thin copper plate, and the cool-down tests by nitrogen gas was carried out. The copper plate and a copper cylinder were joined by electron beam welding. SUS flanges were electron beam welded to both ends of the copper cylinder to fabricate a whole prototype HOM absorber. Fabrication process of the prototype HOM absorber will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP072  
About • paper received ※ 21 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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THP074 Microphonics Noise Suppression with Observer Based Feedback cavity, controls, resonance, linac 1068
 
  • M. Keikha, K. Fong
    TRIUMF, Vancouver, Canada
  • M. Moallem
    SFU, Surrey, Canada
 
  Funding: TRIUMF
Detuning of superconducting radio frequency (SRF) cavities is mainly caused by the Lorentz force, which is the radiation pressure induced by a high radio frequency (RF) field, and environmental mechanical vibrations that induce undesirable interference signals referred to as microphonics. Both of these influences can be described by a second order differential equation of the mechanical vibration modes of the cavity. In this paper we consider three dominant mechanical modes of the system and develop a control scheme based on input-output linearization. It is shown through simulation studies that the proposed control technique can successfully the suppress microphonic noise due to the SRF cavity’s dynamics.
 
poster icon Poster THP074 [0.610 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP074  
About • paper received ※ 22 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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THP080 Status of the All Superconducting Gun Cavity at DESY cavity, cathode, gun, niobium 1087
 
  • E. Vogel, S. Barbanotti, A. Brinkmann, Th. Buettner, J.I. Iversen, K. Jensch, D. Klinke, D. Kostin, W.-D. Möller, A. Muhs, J. Schaffran, M. Schmökel, J.K. Sekutowicz, S. Sievers, L. Steder, N. Steinhau-Kühl, A. Sulimov, J.H. Thie, H. Weise, M. Wenskat, M. Wiencek, L. Winkelmann, B. van der Horst
    DESY, Hamburg, Germany
 
  At DESY, the development of a 1.6-cell, 1.3 GHz all superconducting gun cavity with a lead cathode attached to its back wall is ongoing. The special features of the structure like the back wall of the half-cell and cathode hole require adaptations of the procedures used for the treatment of nine-cell TESLA cavities. Unsatisfactory test results of two prototype cavities motivated us to re-consider the back-wall design and production steps. In this contribution we present the status of the modified cavity design including accessories causing accelerating field asymmetries, like a pick up antenna located at the back wall and fundamental power- and HOM couplers. Additionally, we discuss preliminary considerations for the compensation of kicks caused by these components.  
poster icon Poster THP080 [7.365 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP080  
About • paper received ※ 20 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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THP082 Geometry Dependent Beam Dynamics of a 3.5-cell SRF Gun Cavity at ELBE cavity, gun, emittance, electron 1095
 
  • K. Zhou
    CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
  • A. Arnold, S. Ma, J. Schaber, J. Teichert, R. Xiang
    HZDR, Dresden, Germany
 
  In order to optimize the next generation SRF gun at HZDR ELBE radiation source, the impact on beam dynamics from the SRF cavity geometry needs to be investigated. This paper presents an analysis on the electromagnetic fields and output electron beam qualities, by changing the geometry parameters of a 3.5-cell SRF gun cavity. The simulation results show the higher electric field ratio in the first half cell to the TESLA like cell, the better beam parameters we can obtain, which, however, will also lead to a higher Emax/E0 and Bmax/E0.  
poster icon Poster THP082 [1.935 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP082  
About • paper received ※ 22 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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THP086 Preliminary Design of Superconducting Cavity Test Platform in CSNS Campus cavity, superconducting-cavity, cryomodule, controls 1104
 
  • S.H. Liu, X. Li, W. Long, H. Sun, S. Wang, C.L. Zhang, J.Y. Zhu
    IHEP, People’s Republic of China
  • S.Y. Chen, Y. Liu, C. Shi
    DNSC, Dongguan, People’s Republic of China
  • P.C. Wang, B. Wu
    IHEP CSNS, Guangdong Province, People’s Republic of China
 
  For the beam power upgrade of CSNS (China Spallation Neutron Source) and the construction of the high performance photon source in South China in the near future, the superconducting cavity test platform which includes vertical test stand, single cavity horizontal test stand, cryomodule horizontal test stand and coupler test stand will be built. This paper will generally introduce the preliminary design of the test platform and corresponding test parameters.  
poster icon Poster THP086 [0.171 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP086  
About • paper received ※ 21 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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THP087 2 K SUPERFLUID HELIUM CRYOGENIC VERTICAL TEST STAND OF PAPS cavity, cryogenics, vacuum, superconducting-cavity 1107
 
  • L.R. Sun, R. Ge, R. Han, Y.C. Jiang, S.P. Li, C.C. Ma, M.J. Sang, M.F. Xu, R. Ye, J.H. Zhang, X.Z. Zhang, Z.Z. Zhang, T.X. Zhao
    IHEP, Beijing, People’s Republic of China
 
  Platform of Advanced Photon Source Technology R&D (PAPS) in the Institute of High Energy Physics (IHEP) is an ongoing project, which aimed to provide a comprehensive research and testing platform for the particle accelerator, X-ray detection and optics. As one of the important parts of the platform, cryogenic vertical test stand for the superconducting cavities is composed of three big vertical test cryostats with 2 different inner diameters, which can provide 4.5K liquid helium, 2K superfluid helium and the lowest 1.5K environments according to the cavities test requirements. The cryogen-ic vertical test stands also focus on current international ’hot spot’ fast cool down to the superconducting cavi-ties, maximum liquid helium mass flow rate can be reached to 80g/s. Because of the big size of the cryostats and certain scale, the finished cryogenic vertical test stand can meet several different type cavities test, such as 1.3GHz 9cell, Spoke, elliptical, etc. And also can provide the cavities’ mass vertical testing for the large scale superconducting accelerators.  
poster icon Poster THP087 [1.182 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP087  
About • paper received ※ 20 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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THP089 Development of Superconducting RF Double Spoke Cavity at IHEP cavity, coupling, niobium, linac 1114
 
  • Q. Zhou, F.S. He, W.M. Pan
    IHEP, Beijing, People’s Republic of China
 
  The China Spallation Neutron Source (CSNS) is de-signed to produce spallation neutrons. CSNS upgrade is planned to increase beam power by inserting a SRF linac after drift tube linac (DTL). IHEP is developing a 325MHz double spoke cavity at ’0 of 0.5 for the CSNS SRF linac. The cavity shape was optimized to minimize Ep/Ea while keeping Bp/Ep reasonably low. Meanwhile, mechanical design was applied to check stress, Lorentz force detuning and microphonic effects, and to minimize pressure sensitivity. A new RF coupling scheme was pro-posed to avoid electrons hitting directly on ceramic win-dow. After fabrication and post processing of cavity, the cavity reached Bp of 120mT at Eacc = 13.8MV/m and Q0 = 1.72·1010 under vertical test at 2K.  
poster icon Poster THP089 [2.176 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP089  
About • paper received ※ 22 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP096 ESS Prototype Cavities Developed at CEA Saclay cavity, niobium, HOM, linac 1143
 
  • E. Cenni
    CEA-IRFU, Gif-sur-Yvette, France
  • M. Baudrier, P. Carbonnier, G. Devanz, X. Hanus, L. Maurice, J. Plouin, D. Roudier, P. Sahuquet
    CEA-DRF-IRFU, France
 
  The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV up to the final energy at 2 GeV. The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. CEA Saclay is in charge of the cavity prototypes that is designing, manufacturing, testing and integrating them into demonstrator cryomodules. We have manufactured 6 medium beta and 5 high beta cavities and we present here the latest results concerning these activities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP096  
About • paper received ※ 22 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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THP099 The ESS Database for Elliptical Cavities cavity, database, HOM, cryomodule 1152
 
  • P. Pierini, C.G. Maiano
    ESS, Lund, Sweden
  • A. Bosotti, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • E. Cenni
    CEA-IRFU, Gif-sur-Yvette, France
  • M. Wang
    IHEP, Beijing, People’s Republic of China
 
  The large inkind scope of the elliptical superconducting RF linac of the ESS facility implies the handling of handover conditions between the cavities fabrication and testing phases performed at INFN and STFC, to the assembly of cryomodules at CEA and later to ESS in Lund. The performance qualification at the module test stand, and later the commissioning and operation phases require the availability of the cavity performance and frequency data under all environmental conditions during preparation (e.g. temperature, vacuum in beam line/He vessel/vacuum vessel, tuner state). Availability of the data needs to be guaranteed for the long term maintainability of the accelerator. For these reasons a cavity database has been set up at ESS, integrating the data contained in the handover documentation from the inkind partners and extending it during the activities at ESS after receiving the modules. The database has been used to analyze the preparation steps of the prototype demonstrator cryomodule for the tests at ESS, by benchmarking with the data collected during the tests at CEA, and is currently used during the series cavities handover phases.  
poster icon Poster THP099 [10.434 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP099  
About • paper received ※ 03 July 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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THP100 Insight into DESY’s Test Laboratory for Niobium Raw Material and Semi-finished Products cavity, niobium, FEL, controls 1157
 
  • J.I. Iversen, A. Brinkmann, A. Ermakov, A. Muhs, J. Ziegler
    DESY, Hamburg, Germany
 
  DESY has started setting up a test laboratory for niobium more than 20 years ago. The initial application was to assure required surface quality of niobium sheets before its forming to half cells for the 1.3 GHz SRF Tesla shape cavities. As a first test equipment DESY developed a basic eddy current test device which was refined continuously. Since that time the laboratory grew with the requirements on R&D activities for niobium raw material and its semi-finished products. To be able to assure the Quality of niobium products needed for the European XFEL series cavity production, the Lab’s infrastructure was updated significantly. Now the capabilities of the test laboratory cover the investigation of the fundamental physical properties of various materials including for example mechanical properties, surface, microstructure and chemical composition analysis. The Quality Assurance for the European XFEL was performed successfully on an outstanding level and in the meantime the laboratory was used for several other projects like LCLS-II and ESS. We present DESY’s test infrastructure as well as applied methods for the Quality Assurance and R&D activities and we report about experiences.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP100  
About • paper received ※ 25 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP101 Commissioning of a Cleanroom for SRF Activities at the Helmholtz Institute Mainz cavity, vacuum, operation, heavy-ion 1162
 
  • T. Kürzeder, K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, R.G. Heine, S. Lauber, J. List, M. Miski-Oglu
    HIM, Mainz, Germany
  • K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, S. Lauber, J. List, M. Miski-Oglu, S. Yaramyshev
    GSI, Darmstadt, Germany
  • K. Aulenbacher, F.D. Dziuba, S. Lauber
    IKP, Mainz, Germany
  • J. Conrad
    TU Darmstadt, Darmstadt, Germany
  • R.G. Heine, F. Hug, J. List, T. Stengler
    KPH, Mainz, Germany
 
  A newly built cleanroom is under commissioning at the Helmholtz-Institute Mainz (HIM). In its ISO-class 6 area vacuum components and cavities can be cleaned in different ultrasonic baths and in a dedicated conductance rinsing bath. In the ISO-class 4 area a large vacuum oven offers the possibility for comprehensive drying. A high pressure rinsing cabinet (HPR) has been installed between the two cleanroom areas to be loaded and unloaded from both sides. Complete cold-strings have to be mounted in the ISO-class 4 area and to be rolled out of the cleanroom on a rail system installed on the floor. All installations and tools have been integrated to treat and assemble superconducting 217 MHz multigap crossbar cavities for the Helmholtz Linear Accelerator (HELIAC), which is under development by HIM and GSI. Those crossbar cavities have a diameter of 650 mm and a weight of up to 100 kg. The cleanroom will be also used for the Mainz Energy-Recovering Superconducting Accelerator (MESA) project, processing the TESLA/XFEL type 9-cell cavities and other beamline components. This paper reports on the commissioning of the cleanroom and shows the features of the different installations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP101  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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THP102 Uncertainty Quantification of a Quadrupole-Resonator for Radio Frequency Characterization of Superconductors quadrupole, cavity, HOM, radio-frequency 1168
 
  • P. Putek, S. Gorgi Zadeh, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • W. Hillert
    ELSA, Bonn, Germany
  • W. Hillert, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • M. Wenskat
    DESY, Hamburg, Germany
  • U. van Rienen
    University of Rostock, Rostock, Germany
 
  Funding: This work has been supported by the German Federal Ministry for Research and Education BMBF under contract 05H18HRRB1.
To explore the fundamental properties of superconducting materials used in modern particle accelerators, high precision surface resistance measurements in a dedicated testing equipment is of key importance. The quadrupole resonator, originally developed at CERN, and then successfully modified at the Helmholtz-Zentrum Berlin, is ideally suited for characterization of samples at temperatures of 1.8 K to > 20 K, RF fields of up to 120 mT and frequencies of 433 MHz, 866 MHz and 1.3 GHz. In the past years, this set-up has been subject of intensive research on both its capabilities and limitations. Yet, one of the main challenges is the accuracy of the surface resistance measurement, which is determined by both the uncertainty in the RF measurement and manufacturing imperfections related to the production tolerances such as quenching and chemical polishing processes, etc. In this contribution, we focus on the influence of key geometrical parameters on operating the quadrupole resonator at the third mode, since the surface resistance measurement shows some unexpected behavior for this frequency.
* Design and Fabrication of a Quadrupole-Resonator for Sample R&D by M. Wenskat, W. Hillert, et al.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP102  
About • paper received ※ 25 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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THP105 Thermal Mapping of SRF Cavities by Second Sound Detection With Transition Edge Sensors and Oscillating Superleak Transducers cavity, diagnostics, experiment, luminosity 1182
 
  • G. Vandoni, T. Koettig, A. Macpherson, K. Turaj, L. Vega Cid
    CERN, Meyrin, Switzerland
  • H. Furci
    EPFL, Lausanne, Switzerland
 
  The SRF cavity testing facilities at CERN include four vertical cryostat stations in SM18 and a cryostat for small cavities in the Cryolab. A large range of structures are tested, from Nb thin film cavities for HIE-Isolde and LHC, to bulk Nb crab cavities for HiLumi or 704 MHz 5-cell high-gradient cavities. To cope with different shapes and small series tests, thermal mapping diagnostics is deployed by sensing second sound in superfluid helium. A new type of Transition Edge Sensors (TES) has been developed in the last 2 years. These are miniature resistors of thin-film superconducting alloys, micro-produced on insulating wafers. An extensive campaign of optimization of design, fabrication process and composition was accompanied by qualification in a calibration cryostat. Reproducibility, stability, then intensity, distance and angular dependence of the response were assessed and compared to Oscillating Superleak Transducers (OST). The TES were then installed in a vertical cryostat for tests of a prototype crab cavity for HiLumi. TES are now applied to quench localization on high gradient cavities, for which the most recent results will be presented, together with the OST results.  
poster icon Poster THP105 [2.186 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP105  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP106 An SRF Test Stand in High Intensity and High Energy Proton Beams cavity, cryogenics, cryomodule, vacuum 1187
 
  • G. Vandoni, K. Artoos, V. Baglin, K. Brodzinski, R. Calaga, O. Capatina, S.D. Claudet, L.P. Delprat, S. Mehanneche, E. Montesinos, C. Pasquino, J.S. Swieszek
    CERN, Meyrin, Switzerland
 
  In the framework of HL-LHC, a new infrastructure was installed in 2018, to test SRF structures in the proton beams of the SPS. Scope of the test stand is to study the operational performance of crab cavities for HL-LHC – more generally, SRF cavities – through a wide range of proton beam parameters up to high energy and current, under safe conditions for equipment and personnel. The SPS beam instrumentation is used to monitor orbit centering, RF phase scans, bunch rotation. To minimize impact on beam time, infrastructure and services allow for full remote control. Critical aperture restrictions is overcome by placing the test structure and its ancillaries on a motorized table for lateral translation in- and out of beam. Two articulated Y-shaped vacuum chambers connect the test cryomodule on a beam by-pass. A new cryogenic refrigerator is installed in a split scheme, with an underground cold box fed from a surface compressor. The two Inductive Output Tubes (IOT) power amplifiers deliver up to 60 kW cw via coaxial transmission lines to the two cavities and charges and circulators, the latter installed on the translation table. Interlocks and safety equipment complete the test stand.  
poster icon Poster THP106 [3.982 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP106  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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FRCAA3 Industrial Cavity Production: Lessons Learned to Push the Boundaries of Nitrogen-Doping cavity, niobium, cryomodule, linac 1199
 
  • D. Gonnella, S. Aderhold, A. Burrill, M.C. Ross
    SLAC, Menlo Park, California, USA
  • E. Daly, G.K. Davis, F. Marhauser, A.D. Palczewski, K.M. Wilson
    JLab, Newport News, Virginia, USA
  • A. Grassellino, C.J. Grimm, T.N. Khabiboulline, O.S. Melnychuk, S. Posen, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
 
  Funding: Work supported by US DOE Contract DE-AC02-76SF00515.
Nitrogen doping has been proven now in several labs to enhance Q0 values of 1.3 GHz cavities in the gradient domain favored by CW operation. The choice of doping for the LCLS-II project has given the community a wealth of statistics and experience on the challenge of transferring the doping technology to industry. Overall, industry-produced nitrogen-doped cavities have shown excellent performance, however some technical issues have arisen. This talk focuses on lessons learned from the production of over 300 nitrogen-doped cavities for LCLS-II and how issues were mitigated to further improve performance. Finally, I will discuss pushing the boundaries of nitrogen-doping further by exploring different doping regimes in order to maintain excellent Q0 performance, while reaching higher quench fields.
 
slides icon Slides FRCAA3 [16.880 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAA3  
About • paper received ※ 02 July 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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FRCAA6 Investigation on 1, 3 and 9-Cell SRF Elliptical Cavities made of Large Grain Niobium cavity, niobium, cryomodule, radio-frequency 1213
 
  • T. Dohmae, H. Inoue, T. Kubo, H. Shimizu, K. Umemori, Y. Watanabe, M. Yamanaka
    KEK, Ibaraki, Japan
 
  Large grain (LG) niobium is directly sliced from niobium ingot. LG niobium sheet has larger crystal size than that of fine grain (FG) niobium which is forged and rolled, and normally used as the SRF cavity materials. It is expected that higher Q-value can be achieved using LG niobium sheet. And, effective reduction in material cost can be also achieved by LG niobium since forge and rolling process are skipped. On the other hand, there are some difficulties in fabrication since it has large deformation due to strong anisotropy. Cavity fabrication facility in KEK has been fabricated 1, 3 and 9-cell elliptical cavities made by LG niobium and RF tested in vertical cryostat. In this talk, the fabrication process and test results from these cavities will be presented.  
slides icon Slides FRCAA6 [5.819 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAA6  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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FRCAB3 The Design of an Automated High-Pressure Rinsing System for SRF Cavity and the Outlook for Future Automated Cleanroom on Strings Assembly cavity, controls, linac, alignment 1216
 
  • H. Guo, Q.W. Chu, Y. He, C.L. Li, Y.K. Song, T. Tan, Z.M. You
    IMP/CAS, Lanzhou, People’s Republic of China
 
  High-pressure rinsing (HPR) and cavity assembly are two critical steps in cavity post-processing. Traditionally, high-pressure rinsing processing is based on ultra pure water system, pump, rinsing wand and simple-functional control system; cavity assembly processing is based on simple fixtures, wrenches, bolts and nuts. Beside the equipments, at least two operators are required in either of these two processing. Operators and their actions could bring mistakes and cause extra airborne particle contamination in cleanroom. To avoid the risk from labors, a robot has been introduced in IMP cleanroom for HPR assisting and assembly assisting. Labor cost and cavity RF test results are compared between the circumstances with and without robot assisting. In this work, an automated HPR system that has been designed and will be installed in IMP cleanroom will be presented. In addition, a future automated cleanroom on strings assembly will be discussed as well.  
slides icon Slides FRCAB3 [6.203 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB3  
About • paper received ※ 03 July 2019       paper accepted ※ 12 July 2019       issue date ※ 14 August 2019  
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FRCAB4 Development of High Intensity, High Brightness, CW SRF Gun with Bi-Alkali Photocathode cathode, gun, cavity, target 1219
 
  • T. Konomi, Y. Honda, E. Kako, Y. Kobayashi, S. Michizono, T. Miyajima, H. Sakai, K. Umemori, S. Yamaguchi
    KEK, Ibaraki, Japan
 
  Superconducting conduction electron guns can realize high acceleration voltage and high beam repetition. KEK has been developing the 1.3 GHz elliptical type 1.5 cell superconducting RF gun to investigate fundamental performance. The surface cleaning methods and tools were developed by using KEK SRF gun cavity #1 and surface peak electric field reached to 75 MV/m without field emission. We will apply this technique to the SRF gun cavity #2 for beam operation. The gun cavity #2 equips the helium jacket, frequency tuner cathode position adjuster to operate the electron beam. The RF structure was designed based on the gun cavity #1. The cathode rod is made of Nb. The photocathode deposited on the cathode rod will be cool down to 2K to minimize thermal emittance. The fabrication of the gun cavity #2 and helium jacket were completed. 4 times vertical tests were carried out. We will report the vertical test results and preparation of the horizontal test.  
slides icon Slides FRCAB4 [10.826 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB4  
About • paper received ※ 23 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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FRCAB5 Performance of 112 MHz SRF Gun at BNL gun, cathode, electron, cavity 1223
 
  • T. Xin, I. Ben-Zvi, J.C. Brutus, C. Folz, T. Hayes, P. Inacker, Y.C. Jing, D. Kayran, V. Litvinenko, J. Ma, G.J. Mahler, M. Mapes, K. Mernick, T.A. Miller, G. Narayan, P. Orfin, I. Pinayev, S. Polizzo, T. Rao, F. Severino, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, G. Wang, Q. Wu, B.P. Xiao, W. Xu, A. Zaltsman
    BNL, Upton, New York, USA
  • S.A. Belomestnykh
    Fermilab, Batavia, Illinois, USA
  • C.H. Boulware, T.L. Grimm
    Niowave, Inc., Lansing, Michigan, USA
  • K. Mihara
    Stony Brook University, Stony Brook, USA
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
  • K. Shih
    SBU, Stony Brook, New York, USA
 
  Funding: This work is funded by the DOE FOA (No. DE-FOA-0000632) and National Science Foundation (Award No. PHY-1415252).
A 112 MHz SRF electron photoinjector (gun) was developed at Brookhaven National Laboratory to produce high-brightness and high-bunch-charge bunches for the coherent electron cooling proof-of-principle experiment. The gun is designed to deliver electrons with a kinetic energy of up to 2 MeV. Electrons are generated by illuminating a high quantum efficiency (QE) K2CsSb photoemission layer with a green laser operating at a wavelength of 532 nm. The gun was able to generating 3 nC bunches at 1.7 MeV. The design goals, fabrication, performance and operational experience are reported here.
 
slides icon Slides FRCAB5 [3.984 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB5  
About • paper received ※ 22 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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FRCAB6 The Effect of Helium Processing and Plasma Cleaning for Low Beta HWR Cavity cavity, plasma, experiment, ion-effects 1228
 
  • S.C. Huang, Q.W. Chu, Y. He, C.L. Li, A.D. Wu, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  The commissioning of the 25 MeV high power and high intensity proton Linac demo for CiADS showed that the performance of the SRF cavities was mainly limited by field emission inside the cavities. Therefore, the techniques of helium processing and reactive oxygen plasma cleaning have been developed to mitigate field emission issues. We performed an experiment with a low beta HWR cavity exposed to air directly and processed by helium and reactive oxygen. In this paper, the details of the experiment will be described, the efficiency of helium processing and plasma cleaning will be compared and discussed  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB6  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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