Keyword: coupling
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MOP019 Surface Preparation and Optimization of SC CH Cavities cavity, operation, linac, ECR 71
 
  • P. Müller, M. Basten, M. Busch, T. Conrad, H. Podlech
    IAP, Frankfurt am Main, Germany
  • K. Aulenbacher, F.D. Dziuba, M. Miski-Oglu
    HIM, Mainz, Germany
  • W.A. Barth
    GSI, Darmstadt, Germany
 
  The Institute of Applied Physics (IAP) introduced the superconducting multi-gap CH-structure, which is mainly designed for low beta hadron acceleration. In 2017, a 217 MHz sc CH-structure was successfully tested with beam at GSI and multiple CH-structures are currently under development for the GSI cw linac. RF performance of all sc cavities are limited by the surface properties of the used material. Therefore, sufficient surface preparation and optimization is necessary to achieve optimal performance. Presently as standard procedure BCP and HPR is used for CH-cavities. Several surface treatments will be applied to the very first CH-prototype, a 360 MHz, 19-cell cavity. Prior to the first treatment, the status of the cavity was examined, including leak tests and performance tests at 4 and 2 K. This paper presents the performance development of a sc CH cavity depending on different preparation methods.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP019  
About • paper received ※ 23 June 2019       paper accepted ※ 05 July 2019       issue date ※ 14 August 2019  
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MOP062 Fabrication of SRF Cavity vacuum, cavity, SRF, 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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MOP074 External Q Measurement for Quarter Wave Resonators in RISP pick-up, cavity, cryomodule, simulation 245
 
  • S. Lee, B.H. Choi, M.O. Hyun, Y. Jung, J.W. Kim, Y. Kim, J. Lee, K.T. Seol
    IBS, Daejeon, Republic of Korea
 
  A heavy-ion accelerator facility is under construction for Rare Isotope Science Project(RISP) in Korea. The super conducting cavity, quarter wave resonator(QWR) which consists of driver and post linear accelerator system, is now in the mass production phase. In order to develop the QWR cavity and cryomodule, the RF couplers are fabriacated and tested. In this paper, the study of external Q for QWR coupler will be described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP074  
About • paper received ※ 21 June 2019       paper accepted ※ 29 June 2019       issue date ※ 14 August 2019  
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MOP078 Adjustable Power Coupler for NICA HWR Cavities cavity, vacuum, simulation, collider 260
 
  • S.V. Matsievskiy, M.V. Lalayan
    MEPhI, Moscow, Russia
  • D. Bychanok
    INP BSU, Minsk, Belarus
  • M. Gusarova
    JINR, Dubna, Moscow Region, Russia
 
  Current results on input power coupler development for Half-Wave superconducting accelerating cavity proposed for Nuclotron-based Ion Collider fAcility (NICA) collider injector upgrade are discussed. Two coupler designs are considered, first one is a low-power coupler for cavity tests and the second one is a high-power operational coupler. Both devices are of coaxial type with capacitive coupling; high-power coupler utilizes single ceramic vacuum window. NICA is designed to accelerate different types of ions. Due to the variable intensity of ion sources, beam current will vary in wide range. In order to ensure efficient acceleration, power coupler must be highly adjustable in terms of coupling coefficient. This introduces excessive mechanical stress in the ceramic RF window due to the bellows deformation. In order to mitigate this effect bellows were substituted with sliding contacts. This paper discusses new coupler design and its electrical, mechanical and thermal properties.  
poster icon Poster MOP078 [1.296 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP078  
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, SRF, cryogenics, 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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MOP085 The Destructive Effects to the RF Coupler by the Plasma Discharge plasma, cavity, experiment, vacuum 285
 
  • A.D. Wu, Q.W. Chu, H. Guo, Y. He, S.C. Huang, T.C. Jiang, C.L. Li, Z.Q. Lin, F. Pan, Y.K. Song, T. Tan, W.M. Yue, S.H. Zhang, H.W. Zhao
    IMP/CAS, Lanzhou, People’s Republic of China
 
  The low temperature RF plasma was proved an effec-tive method to clean the niobium surface and relieve the field emission effect for the SRF cavities. In the case of half-wave resonators, these cavities were usually powered via the fundamental coupler with the electric coupling. Thus, coupler antennas were fixed in the intense electric field region, and this region was where the plasma rou-tinely ignited. Therefore, the ceramic window of coupler taken the risk of breakdown under the sputtering of ions and heating loads that may be caused by the plasma drift and diffusion from the electric field region. In this paper, the plasma ignition for surface cleaning on the HWR cavity and its coupler was investigated, and the power transmission, temperature raising and vacuum degradation were tested to characterize the adverse impacts on the ceramic window. Finally, the solution was proposed to figure these issues.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP085  
About • paper received ※ 22 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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WETEB9 Design Development for the 1.5 GHz Couplers for BESSY VSR operation, cavity, diagnostics, GUI 795
 
  • E. Sharples, M. Dirsat, J. Knobloch, Z. Muza, A.V. Vélez
    HZB, Berlin, Germany
 
  The Variable pulse length Storage Ring (BESSY VSR) is a superconducting radio frequency (SRF) upgrade to the existing BESSY II storage ring at Helmholtz-Zentrum Berlin (HZB). BESSY VSR uses the RF beating of superconducting cavities at 1.5 GHz and 1.75 GHz to produce simultaneously long and short bunches. Higher power couplers capable of handling 13 kW peak power at standing wave operation, are required to provide an average power of 1.5 kW for both the 1.5 GHz and 1.75 GHz cavities. These couplers must also provide variable coupling with a range of Qext from 6x106 to 6x107 to allow flexibility to adjust to operating conditions of BESSY VSR. Here the full design development process for the 1.5 GHZ BESSY VSR coupler is presented including the design for a diagnostic prototype to ensure comprehensive monitoring of critical components during testing and cool-down.  
slides icon Slides WETEB9 [8.085 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-WETEB9  
About • paper received ※ 23 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, SRF, 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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THP035 Design of LHC Crab Cavities Based on DQW Cryomodule Test Experience cavity, pick-up, HOM, controls 925
 
  • S. Verdú-Andrés
    BNL, Upton, New York, USA
  • R. Calaga, E. Cano-Pleite, R. Leuxe
    CERN, Geneva, Switzerland
  • J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
 
  Funding: Work supported by US DOE through Brookhaven Science Associates LLC under contract No. DE-SC0012704, contract No. DE-FOA-0001848 and by the European Union HL-LHC Project.
A cryomodule with two Double-Quarter Wave (DQW) cavities was designed, built and tested with the SPS beam in 2018. Each cavity was equipped with an rf pickup antenna to monitor field amplitude and phase. The pickup antenna also included a section expressly designed to couple and extract one of the Higher-Order Modes (HOM) at 1.754 GHz. The SPS beam tests evidenced direct coupling of the beam to this pickup antenna, in a similar way that a beam position monitor pickup couples to the passing beam. This undesired coupling had an impact on the RF feedback system responsible to regulate the cavity field and frequency. The present paper proposes a new DQW cavity design with improved antennae which provides adequate fundamental mode extraction while providing a reduction of both direct coupling to the beam and heat dissipation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP035  
About • paper received ※ 23 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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THP036 An Insight on the Thermal and Mechanical Numerical Evaluations for the High-Luminosity LHC Crab Cavities cavity, pick-up, electromagnetic-fields, experiment 929
 
  • E. Cano-Pleite, A. Amorim Carvalho, K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, M. Garlasché, R. Leuxe, E. Montesinos
    CERN, Geneva, Switzerland
  • J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
  • S. Verdú-Andrés
    BNL, Upton, New York, USA
 
  Funding: Research supported by the HL-LHC project
One of the key devices of the HL-LHC project are SRF crab cavities. A cryomodule with two Double Quarter Wave (DQW) crab cavities has been successfully fabricat-ed and tested with beam at CERN whereas the Radio Frequency Dipole (RFD) crab cavities are currently on its fabrication process. The paper provides an insight on the multiple calculations carried out to evaluate the thermal and mechanical performance of the DQW and RFD cavi-ties and its components. In some cases, the presence of RF fields inside the cavity volume requires the use of mul-tiphysics numerical models capable of coupling these fields with the thermal and mechanical domains. In fact, the RF field presents a strong dependency on the cavity shape, whereas the mechanical, thermal and electrical properties of the materials may substantially vary as a function of temperature, which in turn depends on the RF field. The results presented in this paper, using both cou-pled and uncoupled models, allowed elucidating the importance of physics coupling on the numerical evalua-tion of RF cavities and its components. Analyses were also of great support for the design evaluation and im-provement of future prototypes.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP036  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP045 Improvements to the Cornell Sample Host System cavity, niobium, SRF, 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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THP089 Development of Superconducting RF Double Spoke Cavity at IHEP cavity, SRF, 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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THP095 Direct Measurement of Thermoelectric Currents During Cool Down cavity, simulation, experiment, niobium 1139
 
  • A.E. Ivanov, F. Gerigk, A. Macpherson
    CERN, Geneva, Switzerland
 
  In recent years there has been much discussion on thermoelectric effects and their role in flux expulsion during cool down of SRF cavities. Magnetic field is often measured to asses both flux expulsion as the cavity undergoes superconducting transition, and thermoelectric currents due to spatial thermal gradients. As a complementary view, in this paper we show direct measurement of the thermoelectric current independent from the expulsion measurement of the magnetic field. In our setup the azimuthally symmetric cavity is vertically installed and the thermal gradient is along the symmetry axis allowing to describe the cool down behavior of the thermoelectric current using simple coupled simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP095  
About • paper received ※ 21 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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