Keyword: electron
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MOFAA2 Operation of the European XFEL Towards the Maximum Energy FEL, cavity, operation, MMI 9
 
  • M. Omet, V. Ayvazyan, J. Branlard, S. Choroba, W. Decking, V.V. Katalev, D. Kostin, L. Lilje, P. Morozov, Y. Nachtigal, H. Schlarb, V. Vogel, N. Walker, B. Yildirim
    DESY, Hamburg, Germany
 
  After the initial commissioning of the available 25 radio frequency (RF) stations of the European XFEL (RF gun, A1, AH1 and stations A2 through A23) a maximum electron beam energy of 14.5 GeV was achieved, 3 GeV short of the design energy of 17.5 GeV. In order to tackle this problem, the Maximum Gradient Task Force (MGTF) was formed. In the scope of the work of the MGTF, RF stations A6 through A25 (linac L3) were systematically investigated and voltage-limiting factors of the SRF accelerating modules and their RF distribution system were identified and improved. As a result, the design electron beam energy was exceeded at 17.6 GeV on the 18.7.2018. Beside this an overview over the regular RF operation at the European XFEL is given.  
slides icon Slides MOFAA2 [5.695 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOFAA2  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP004 Preparation of Pb-Photocathodes at National Centre for Nuclear Research in Poland – State of the Art cathode, plasma, laser, gun 25
 
  • J. Lorkiewicz, I. Cieślik, P.J. Czuma, A.M. Kosińska, R. Nietubyć
    NCBJ, Świerk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
 
  Funding: We are currently using a financial support within "PolFEL - Polish Free Electron Laser" cofounded by the European Regional Development Fund.
R&D activities related to preparation of the superconducting Pb photocathode layer on niobium substrate are ongoing at the National Centre for Nuclear Research (NCBJ) in cooperation with DESY, HZDR, HZB, BNL and other research institutes. The activities are part of the R&D program at DESY for the cw-upgrade of E-XFEL and for the newly approved free electron laser facility PolFEL to be built and operated at NCBJ. The optimization results obtained for the lead deposition on niobium and smoothing of the coated layers are reported. The photocathodes samples were tested for their surface morphology, microstructure and quantum efficiency in terms of the impact on the operation of all-superconducting RF electron injector, proposed for both facilities.
 
poster icon Poster MOP004 [1.446 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP004  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 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, SRF 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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MOP014 Electroplating of Sn Film on Nb Substrate for Generating Nb3Sn Thin Films and Post Laser Annealing laser, cavity, radio-frequency, HOM 51
 
  • Z. Sun, M. Liepe, T.E. Oseroff, R.D. Porter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T. Arias, A.B. Connolly, J.M. Scholtz, N. Sitaraman, M.O. Thompson
    Cornell University, Ithaca, New York, USA
  • X. Deng
    University of Virginia, Charlottesville, Virginia, USA
  • K.D. Dobson
    University of Delaware, Newark, Delaware, USA
 
  Controlling film quality of Nb3Sn is critical to its SRF cavity performance. The state-of-the-art vapor diffusion approach for Nb3Sn deposition observed surface roughness, thin grain regions, and misfit dislocations which negatively affect the RF performance. The Sn deficiency and non-uniformity at the nucleation stage of vapor deposition is believed to be the fundamental reason to cause these roughness and defects issues. Thus, we propose to pre-deposit a uniform Sn film on the Nb substrate, which is able to provide sufficient Sn source during the following heat treatment for Nb3Sn nucleation and growth. Here, we demonstrated successful electrodeposition of a low-roughness, dendrite-free, excellent-adhesion Sn film on the Nb substrate. More importantly, we further achieved a uniform, low-roughness (Ra = 66 nm), pure-stoichiometric Nb3Sn film through thermal treatment of this electroplated Sn film in the furnace. Additionally, we provide preliminary results of laser annealing as a post treatment for epitaxial grain growth and roughness reduction.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP014  
About • paper received ※ 22 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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MOP024 Vacancy-Hydrogen Dynamics in Samples During Low Temperature Baking positron, niobium, cavity, lattice 83
 
  • M. Wenskat, C. Bate, D. Reschke, H. Weise
    DESY, Hamburg, Germany
  • C. Bate
    University of Hamburg, Hamburg, Germany
  • M. Butterling, E. Hirschmann, M.O. Liedke, A. Wagner
    HZDR, Dresden, Germany
  • J. Cizek
    Charles University, Prague, Czech Republic
 
  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.
The recent discovery of a modified low temperature baking process lead to a reduction of surface losses and an increase of the accelerating gradient of TESLA shape cavities. The hypothesis linking the accelerator performance and the treatment is the suppression of lossy nanohydrides via defect trapping, with vacancy-hydrogen complexes forming at the lower temperatures. Utilizing Doppler broadening Positron Annihilation Spectroscopy and Positron Annihilation Lifetime Spectroscopy samples made from European XFEL niobium sheets and cavity cut-outs were investigated. The evolution of vacancies, hydrogen and their interaction at different temperature levels have been studied during in-situ annealing. Measurements of niobium samples and a correlation between RF, material properties, and V-H distribution in cavity cut-outs has been done.
 
poster icon Poster MOP024 [1.087 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP024  
About • paper received ※ 20 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, SRF, 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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MOP031 Investigation of Frequency Behavior Near Tc of Niobium Superconducting Radio-Frequency Cavities cavity, SRF, niobium, 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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MOP041 Comparison of the Lattice Thermal Conductivity of Superconducting Tantalum and Niobium scattering, lattice, simulation, niobium 148
 
  • P. Xu, N.T. Wright
    MSU, East Lansing, Michigan, USA
  • T.R. Bieler
    Michigan State University, East Lansing, Michigan, USA
 
  Funding: This work is supported by the U.S. Department of Energy, Office of High Energy Physics through Grant No. DE-FG02-13ER41974.
The thermal conductivity k of superconducting Ta behaves similarly to that of superconducting Nb, albeit at colder temperatures. This shift is due to the superconducting transition temperature of Ta being 4.3 K, versus 9.25 K for Nb. For example, the temperature of the phonon peak of properly treated Ta is about 1 K as opposed to a phonon peak at about 2 K for Nb. The typical value of k of Ta is smaller than Nb with the value at the phonon peak for Ta being O(10) W/ m/ K. Like Nb, k is dominated by phonons at these temperatures. This lattice k can be modeled by the Boltzmann transport equation, solved here by a Monte Carlo method using the relaxation time approximation. Individual scattering mechanisms due to boundaries, dislocations, and residual normal electrons are examined, and the phonon dispersion relation is included. Differences in the thermal response of deformed Ta, as compared with Nb, may be attributed to differences in dislocation densities of the two metals following similar levels of deformation. Boundary scattering dominates at the coldest temperatures. The phonon peak decreases and shifts to warmer temperatures with deformation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP041  
About • paper received ※ 19 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, SRF, cavity, 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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MOP064 Performance of First Prototype Multi-Cell Low-Surface-Field Shape Cavity cavity, SRF, 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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MOP077 Ceramic Study on RF Windows for Power Coupler, Waveguide, and Klystron in Particle Accelerator GUI, klystron, operation, multipactoring 255
 
  • Y. Yamamoto, S. Michizono
    KEK, Ibaraki, Japan
 
  R&Ds on different types of ceramic used in power coupler, waveguide, and klystron for particle accelerators are under progress in Center of Innovation (COI) at KEK, and at some outside companies. There are five important parameters on the properties of ceramics; that is, relative permittivity, dielectric loss tangent, surface and volume resistivity, and secondary electron emission coefficient. For measurements of these parameters, eight kinds of ceramic samples supplied from five vendors have been measured using three different measurement systems since 2017. In this report, the recent results for these studies will be presented in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP077  
About • paper received ※ 22 June 2019       paper accepted ※ 01 July 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 SRF, experiment, target, 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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MOP086 Conditioning of the First Mass Production Power Couplers for the ESS Elliptical Cavities vacuum, pick-up, cavity, Windows 288
 
  • C. Arcambal, M. Baudrier, P. Bosland, G. Devanz, T. Hamelin, C. Marchand, M. Oublaid, G. Perreu, S. Regnaud, C. Servouin, C. Simon
    CEA-DRF-IRFU, France
  • G. Monnereau
    CEA-IRFU, Gif-sur-Yvette, France
 
  In the framework of the European Spallation Source (ESS), CEA Paris-Saclay is in charge of the delivery of 9 medium beta (β = 0.67) and 21 high beta (β = 0.86) cryomodules. Each cryomodule is composed of 4 cavities equipped with RF (Radio Frequency) power couplers (704.42 MHz, 1.1 MW maximum peak power, repetition rate=14 Hz, RF pulse width > 3.1 ms). Ten prototype power couplers have been manufactured to validate the design and the performance. Currently the mass production of the 120 couplers started and the six first pre-series medium beta couplers have been successfully conditioned. The achievement of this milestone allowed us to launch the production of the remaining 30 medium beta couplers. This paper presents the conditioning of the pre-series couplers.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP086  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 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, SRF, niobium, 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, SRF, 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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TUP005 Cavity Designs for the CH3 to CH11 of the Superconducting Heavy Ion Accelerator HELIAC cavity, linac, heavy-ion, resonance 396
 
  • T. Conrad, M. Basten, M. Busch, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
  • K. Aulenbacher, W.A. Barth, F.D. Dziuba, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu
    HIM, Mainz, Germany
  • K. Aulenbacher
    KPH, Mainz, Germany
  • W.A. Barth, M. Heilmann, A. Rubin, A. Schnase, S. Yaramyshev
    GSI, Darmstadt, Germany
 
  In collaboration of GSI, HIM and Goethe University Frankfurt new designs for the CH-DTL cavities of the proposed Helmholtz Linear Accelerator (HELIAC) are developed. The cw-mode operated linac with a final energy of 7.3 MeV/u is intended for various experiments, especially with heavy ions at energies near the coulomb barrier. Currently twelve superconducting CH-cavities are considered which will be split into four different cryostats. Each cavity will be equipped with dynamic bellow tuners. After successful beam tests with CH0 as well as last surface preparations and ongoing rf tests with CH1 and CH2, CH3 to CH11 will be designed. Based on the successful test results, individual optimizations are carried out on the cavity design. Attention was paid to reduce production costs, for example by keeping the cavity diameter in each cryostat constant despite varying particle velocities and gap numbers. In addition to reaching the resonance frequency of 216.816 MHz and the influence of the bellow tuners on the frequency, the mechanical stability of the bellow tuners, the thermal effects on the cavity and the measures to mitigate secondary electron emission are investigated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP005  
About • paper received ※ 19 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP014 Mechanical Design and Fabrication Aspects of Prototype SSR2 Jacketed Cavities cavity, SRF, interface, cryomodule 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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TUP030 Automation of Particulate Characterization controls, cavity, software, SRF 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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TUP043 Ab-initio Study of Atomic Scale Interaction Among Nb, Sn, Cl, and O niobium, cavity, SRF, 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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TUP045 Ab Initio Calculations on Impurity Doped Niobium and Niobium Surfaces niobium, scattering, experiment, lattice 523
 
  • N. Sitaraman, T. Arias
    Cornell University, Ithaca, New York, USA
  • R.G. Farber, S.J. Sibener, R.D. Veit
    The University of Chicago, Chicago, Illinois, USA
  • M. Liepe, J.T. Maniscalco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was funded by the Center for Bright Beams
We develop and apply new tools to understand Nb surface chemistry and fundamental electronic processes using theoretical ab initio methods. We study the thermodynamics of impurities and hydrides in the near-surface region as well as their effect on the surface band gap. This makes it possible for experimentalists to relate changes in STM dI/dV measurements resulting from different preparations to changes in subsurface structure. We also calculate matrix elements for electron-impurity scattering in Nb for common impurities O, N, C, and H. By transforming these matrix elements into a Wannier function basis, we calculate lifetimes for a dense set of states on the Fermi surface and determine the mean free path as a function of impurity density. This technique can be generalized to calculate other scattering amplitudes and timescales relevant to SRF theory.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP045  
About • paper received ※ 02 July 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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TUP055 Nonlinear Dynamics and Dissipation of Vortex Lines Driven by Strong RF Fields cavity, ECR, radio-frequency, niobium 560
 
  • M.R.P. Walive Pathiranage, A.V. Gurevich
    ODU, Norfolk, Virginia, USA
 
  Trapped vortices can contribute significantly to a residual surface resistance of superconducting radio frequency (SRF) cavities but the nonlinear dynamics of flexible vortex lines driven by strong rf currents has not been well understood. Here we report extensive numerical simulations of large-amplitude oscillations of a trapped vortex line under the strong rf magnetic field. The rf power dissipated by an oscillating vortex segment driven by the rf Meissner currents was calculated by taking into account the nonlinear vortex line tension, vortex mass and a nonlinear Larkin-Ovchinnikov and overheating viscous drag force. We calculated the field dependence of the surface resistance Rs and showed that at low frequencies Rs(H) increases with H but as the frequency increases, Rs(H) becomes a non-monotonic function of H which decreases with H at higher fields. These results suggest that trapped vortices can contribute to the extended Q(H) rise observed on the SRF cavities.  
poster icon Poster TUP055 [1.744 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP055  
About • paper received ※ 23 June 2019       paper accepted ※ 05 July 2019       issue date ※ 14 August 2019  
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TUP056 A First-Principles Study on Magnetic Flux Trapping at Niobium Grain Boundaries niobium, cavity, simulation, radio-frequency 565
 
  • P. Garg, K.N. Solanki
    Arizona State University, Tempe, USA
  • T.R. Bieler
    Michigan State University, East Lansing, Michigan, USA
  • L.D. Cooley
    NHMFL, Tallahassee, Florida, USA
 
  Niobium is basis for all superconducting radio frequency cavities, a technology that accelerates charged particle beams to energy levels not possible by other means. When cavities are pushed to limits, significant heating appears at extended material defects, like grain boundaries. Therefore, it is crucial to understand how grain boundary (GB) structure and associated properties lead to trapping of magnetic field, and whether GB itself has any unusual magnetic behavior. Using first-principles calculations, external magnetic field along the GB plane was simulated within an all-electron full-potential linearized augmented plane-wave framework. A ground state with non-zero flux, indicative of flux trapping, was obtained at some grain boundaries, this outcome being influenced strongly by GB local structure. Furthermore, electronic density of states and charge-transfer calculations suggested non-zero spin polarization at grain boundaries, which may be consistent with recent observations of unusual paramagnetic magnetization as a function of specimen surface area for cavity-grade niobium.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP056  
About • paper received ※ 23 June 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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TUP064 Flashover on RF Window of HWR SRF Cavity cavity, pick-up, SRF, 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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THP008 The Technical Study of Nb3Sn Film Deposition on Copper by HiPIMS SRF, niobium, cavity, 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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THP017 Crystallographic Characterization of Nb3Sn Coatings and N-Doped Niobium via EBSD and SIMS niobium, interface, SRF, 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, SRF, 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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THP028 Superconducting RF Modules of TARLA cryomodule, rf-amplifier, cavity, MMI 900
 
  • Ç. Kaya, Ö. Karslı, İ.B. Koç
    Ankara University, Accelerator Technologies Institute, Golbasi, Turkey
  • A. Aksoy, O.F. Elçim
    Ankara University Institute of Accelerator Technologies, Golbasi, Turkey
 
  The Turkish Accelerator and Radiation Laboratory (TARLA) is proposed as an accelerator-based radiation source facility to provide a research instrument for researchers from both Turkey and region. The facility is located at the Ankara University Institute of Accelerator Technologies and proposed as the first accelerator based research infrastructure in Turkey. The superconducting accelerator of TARLA is currently under commissioning and will drive two Free Electron Laser (FEL) lines in the mid- and far-infrared ranges and a high flux Bremsstrahlung radiation to 40 MeV electron beam in Continuous Wave (CW) mode. The SRF cryomodules have been delivered by industry in 2017. In this paper, we present the achieved vertical test results of the SRF cavities, the results of the high power RF test of the fundamental power couplers and the first test results of the integrated piezo tuner. After the successful commissioning of the cryogenic plant operating at 1.8 K with ±0.2 mbar pressure stability, the commissioning of the SRF cryomodules is now ongoing and the current status and results achieved so far are explained.  
poster icon Poster THP028 [1.996 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP028  
About • paper received ※ 28 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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THP029 Towards Real-time Data Processing using FPGA Technology for High-speed Data Acquisition System at MHz Repetition Rates FPGA, detector, experiment, laser 905
 
  • M. Bawatna, A. Arnold, J.-C. Deinert, B.W. Green, S. Kovalev
    HZDR, Dresden, Germany
 
  Accelerator-based light sources, in particular, those based on linear accelerators, are intrinsically less stable than lasers or other more conventional light sources because of their large scale. In order to achieve optimal data quality, the properties of each light pulse need to be detected and implemented into the analysis of each experiment. Such schemes are of particular advantage in 4th generation light sources based on superconducting radiofrequency (SRF) technology, since here the combination of pulse-resolved detection schemes with high-repetition-rate is particularly fruitful. Implementation of several different purpose-built CMOS linear array detector will enable to perform arrival-time measurements at MHz repetition rates. An architecture based on FPGA technology will allow an online analysis of the measured data at MHz repetition rate and will decrease the amount of data throughput and disk capacity for storing the data by orders of magnitude. In this contribution, we will outline how the pulse-resolved data acquisition scheme of the TELBE user facility shall be upgraded to allow operation at MHz repetition rates and sub-femtosecond timing precision.  
poster icon Poster THP029 [1.616 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP029  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 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, SRF, radiation, 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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THP067 Cavity Tilt Measurement in a 1.3 GHz Superconducting Cryo-Module at FLASH cavity, dipole, polarization, HOM 1041
 
  • J.H. Wei
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  • N. Baboi
    DESY, Hamburg, Germany
  • T. Hellert
    LBNL, Berkeley, California, USA
 
  TESLA superconducting (SC) cavities are used for the acceleration of electron bunches at FLASH. The Higher Order Modes (HOMs) excited by the beam in these cavities may cause emittance growth. The misalignment of the cavities in a cryo-module is one of the essential factors which enhance the coupling of the HOMs to the beam. The cavity offset and tilt are the two most relevant misalignments. These can be measured by help of dipole modes, based on their linear dependence on the beam offset. The cavity offset has been measured before in several modules at FLASH. However, the cavity tilt has so far proved to be difficult to be measured, because the angular dependence of the dipole mode is much weaker. By carefully targeting the beam through the middle of a cavity, the strong offset contribution to the dipole fields could be reduced. Careful data analysis based on a fitting method enabled us then to extract the information on the cavity tilt. This measurement has been implemented in the cavities in one cryo-module at FLASH. First results of the ongoing measurements from several cavities are presented in this paper. It is for the first time that the cavity tilt in several cavities has been measured.  
poster icon Poster THP067 [1.392 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP067  
About • paper received ※ 23 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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THP073 Advanced LLRF System Setup Tool for RF Field Regulation of SRF Cavities controls, cavity, feedback, FEL 1063
 
  • S. Pfeiffer, J. Branlard, M. Hoffmann, Ch. Schmidt
    DESY, Hamburg, Germany
 
  Feedback operation at the European XFEL ensures an amplitude and phase stability of 0.01% and 0.01 deg, respectively. To reach such high RF field stability, model-based approaches for RF field system characterization and RF field controller design are in use. High demand on this system modelling is set especially to the characterization of additional passband modes for small bandwidth SRF cavities operated in pulsed mode and vector-sum regulation. This contribution discusses the developed "Advanced system setup tool" using a graphical user implementation in Matlab® for the RF field system characterization and the multiple-input-multiple-output feedback controller setup. Examples and current limitations will be presented.  
poster icon Poster THP073 [0.873 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP073  
About • paper received ※ 19 June 2019       paper accepted ※ 30 June 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 SRF, cavity, gun, emittance 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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THP083 Quadrupole Scan Transverse Emittance Measurements at HZDR ELBE quadrupole, emittance, focusing, experiment 1100
 
  • S. Ma, A. Arnold, A.A. Ryzhov, J. Schaber, J. Teichert, R. Xiang, K. Zhou
    HZDR, Dresden, Germany
 
  Two quadrupoles and one screen are used for beam transverse emittance measurements at HZDR ELBE. In this paper, the emittance calculated with two different methods, one with thin-lens approximation and the other one without this approximation, are compared and analized. To analyze the measurement error, quadrupole calibration is need. Two aspects about quadrupole analysis are made. The first one is quadrupole’s effective length and strength and the second one is quadrupole’s converged or diverged ability in reality.  
poster icon Poster THP083 [1.726 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP083  
About • paper received ※ 25 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
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THP093 Upgrade on the Experimental Activities for ESS at the LASA Vertical Test Facility cavity, radiation, diagnostics, detector 1133
 
  • M. Bertucci, A. Bosotti, A. D’Ambros, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
 
  The LASA vertical test facility is equipped for the cold test of ESS medium-beta 704.42 MHz cavities, with and without He tank, and is integrated with several diagnostic tools allowing a careful analysis of cavity performance limitations. This paper reports the latest tests on ESS cavities - both prototypes and series - and a discussion on the experimental results. The recent instrumental upgrades implemented in the facility - and the ones foreseen for the future in view of a further improvement of cavity performances - are also pointed out.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP093  
About • paper received ※ 24 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP097 Field Emission Studies on ESS Elliptical Prototype Cavities at CEA Saclay cavity, cryomodule, radiation, detector 1147
 
  • E. Cenni, M. Baudrier, G. Devanz, L. Maurice, O. Piquet, D. Roudier
    CEA-DRF-IRFU, France
 
  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. As part of these activities we are interested in field emission as one of the limiting factors for cavity performances. We are currently collecting data from cavities operated in vertical cryostat and inside cryomodules. Analysis are carried out by means of particle tracking simulation and comparison with radiation dose monitor and scintillators.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP097  
About • paper received ※ 27 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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FRCAB5 Performance of 112 MHz SRF Gun at BNL gun, cathode, SRF, 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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