Keyword: HOM
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MOPO006 Crosstalk Effect in the LEReC Booster Cavity cavity, resonance, booster, cathode 47
 
  • B. P. Xiao, K. Mernick, F. Severino, K.S. Smith, T. Xin, W. Xu, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Linac of Low Energy RHIC electron Cooler (LEReC) is designed to deliver a 1.6 MeV to 2.6 MeV electron beam, with peak-to-peak dp/p less than 7·10-4. The booster cavity is the major accelerating component in LEReC, which is a 0.4 cell cavity operating at 2 K, with a maximum energy gain of 2.2 MeV. It is modified from the Energy Recovery Linac (ERL) photocathode gun, with fundamental power coupler, pickup coupler and HOM coupler close to each other. Crosstalk effect in this cavity is simulated and measured. Correction method is proposed to meet the energy spread requirement.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO006  
About • paper received ※ 14 September 2018      issue date ※ 18 January 2019  
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MOPO088 Study on a 325 MHz HOM Drift Tube Linac DTL, cavity, linac, impedance 187
 
  • L. Lu, T. He, W. Ma, C.C. Xing, L. Yang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Normally, drift tube linacs (DTL) are used following RFQ linacs for beam acceleration in middle and high beam energy region. but acceleration efficiency of DTLs is decreasing with beam energy increasing. Using resonated higher order mode (HOM) of cavity, DTL can get higher effective shunt impedance. we proposed a 325MHz DTL with TE115 mode. In this paper, the dynamics calculation and electromagnetic design of the HOM-DTL will be reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO088  
About • paper received ※ 13 September 2018      issue date ※ 18 January 2019  
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TUPO023 Preserving Micron Tolerances Through the Assembly Process of an X-band Accelerating Structure cavity, damping, linac, simulation 377
 
  • J. Sauza-Bedolla, N. Catalán Lasheras, A. Grudiev, S. Lebet, E. Rodriguez-Castro, P. Sobrino-Mompean, A. Solodko, K. T. Szypula
    CERN, Geneva, Switzerland
  • H. Bursali
    IZTECH, Izmir, Turkey
 
  The CLIC structures are designed for operating at X-Band, 2π/3 traveling wave mode with a loaded 100 MV/m gradient. Mechanical tolerances, at the submicron level, are required to satisfy the RF design constraints and beam dynamics and are reachable using ultra-precision diamond machining. However, inherent to the manufacturing process, there is a deviation from the nominal specifications and as a result; incorrect cavity dimensions produce a less efficient linac. Moreover, the assembly process increase the difference from the original geometry. As part of a cost and manufacturability optimization of the structures for mass production, this study aims to identify a correlation between frequency deviations and geometrical errors of the individual discs of the accelerating structures caused by the production process. A sensitivity analysis has been carried out to determine the most critical parameters. Cell frequency deviations have been monitored by bead pull measurements before and after bonding. Several accelerating structure prototypes have been tested to determine our assumptions and to assess if the assembly process preserves the tight tolerances achieved by machining.  
poster icon Poster TUPO023 [1.443 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO023  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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TUPO032 First Test Results of Superconducting Twin Axis Cavity for ERL Applications cavity, SRF, linac, niobium 398
 
  • H. Park, S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • A. Hutton, F. Marhauser, H. Park
    JLab, Newport News, Virginia, USA
 
  Superconducting cavities with two beam pipes had been proposed in the past for energy recovery linac applications. The relatively complex geometry of those cavities presented a serious challenge for fabrication and surface processing. Main concerns have now been overcome with the production and successful RF testing of a new elliptical twin-axis cavity proposed by Jefferson Lab and optimized by the Center for Accelerator Science at Old Dominion University in the frame of a DoE accelerator stewardship program. The cavity design provides uniform accelerating or decelerating fields for both beams. This paper describes the cavity design, fabrication experience, and the first cold RF test results and explores potential applications especially for Jefferson Lab s EIC (JLEIC).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO032  
About • paper received ※ 20 September 2018      issue date ※ 18 January 2019  
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TUPO033 Cryogenic Test Results of the SPS Prototype RF-dipole Crabbing Cavity with Higher Order Mode Couplers cavity, dipole, luminosity, multipactoring 402
 
  • S.U. De Silva, J.R. Delayen, H. Park
    ODU, Norfolk, Virginia, USA
  • Z. Li
    SLAC, Menlo Park, California, USA
  • H. Park
    JLab, Newport News, Virginia, USA
 
  The rf-dipole crabbing cavity planned for the LHC High Luminosity Upgrade is designed to deliver a transverse kick of 3.34 MV; crabbing the proton beam in the horizontal plane. The proton beams of the LHC machine operating at 7 TeV each sets high impedance thresholds on the crabbing cavity systems. The rf-dipole crabbing cavity is designed with a two higher order mode couplers to suppress those HOMs. The first prototype of the HOM couplers are fabricated at Jefferson Lab. This paper reports the cryogenic test results of the HOM couplers with the SPS prototype rf-dipole cavity.  
slides icon Slides TUPO033 [0.859 MB]  
poster icon Poster TUPO033 [1.838 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO033  
About • paper received ※ 17 September 2018      issue date ※ 18 January 2019  
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TUPO038 Several Experimental Phenomena of Sn Nucleation on Nb Surface Observed at IMP cavity, experiment, SRF, niobium 412
 
  • Z.Q. Yang, Y. He, F. Pan
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Nucleation process is an important step that affects the quality of Nb3Sn films coated by vapor diffusion method. A uniform distribution of nucleation centers is essential to the uniformity of Nb3Sn films. In this paper we report several experimental phenomena on the Sn nucleation on Nb surface. Better nucleation in the downstream of the pumping direction was observed. Influence of SnCl2 partial pressure inhomogeneity was studied. Samples with higher SnCl2 partial pressure have denser nucleation, which means homogeneous SnCl2 pressure is a critical factor to the uniform nucleation. Less-nuclear zones, mainly distributed at cracks, grain boundaries and even some whole grain surfaces, were found on the surfaces of all samples. The less-nuclear zones may result in the low tin regions of the Nb3Sn cavities. The specific solution to the less-nuclear problem was proposed. These studies help to better understanding of the mechanism underlying the nucleation process and will be useful foundation for the follow-up Nb3Sn/Nb project at IMP.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO038  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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TUPO041 LCLS-II Cavity Higher Order Modes Coupler Tuning Optimization and Challenges at Jefferson Lab cavity, cryomodule, vacuum, target 423
 
  • A.D. Solopova, D. Forehand, A.D. Palczewski
    JLab, Newport News, Virginia, USA
  • T.N. Khabiboulline
    Fermilab, Batavia, Illinois, USA
 
  LCLS-II is a new XFEL linac based on 1.3GHz SRF linac. Half of the LCLS-II cryomodules are being produced at Jefferson Lab. This paper summarizes the Higher Order Mode filter tuning challenges at Jefferson Lab and describes optimization of the procedure for a 9-cell Tesla type cavity and its integration into a cryomodule production line.  
poster icon Poster TUPO041 [0.719 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO041  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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TUPO045 Optimization of Dual Axis Asymmetric Cavity for Energy Recovery Linac cavity, linac, acceleration, coupling 435
 
  • Ya.V. Shashkov, A.M. Bulygin, M. Gusarova
    MEPhI, Moscow, Russia
  • I.V. Konoplev
    JAI, Oxford, United Kingdom
  • F. Marhauser
    JLab, Newport News, Virginia, USA
  • A. Seryi
    SLAC, Menlo Park, California, USA
 
  Funding: The reported study was funded by RFBR according to the research project № 18-302-00990
Optimization of the dual axis asymmetric cavity was performed to minimize the ratio of the peak magnetic and electric fields values to the accelerating voltage, to increase the distance between operating and neighbouring modes as well as to reduce the manufacturing cost of the cavity. To reach the goals several solutions have been suggested bringing the ratios to the acceptable values and leading to simplification of the manufacturing of the structure.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO045  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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THPO006 Status of 650 MHz SRF Cavity for eRHIC SRF Linac cavity, SRF, linac, collider 688
 
  • W. Xu, I. Ben-Zvi, Y. Gao, D. Holmes, P. Kolb, G.T. McIntyre, R. Porqueddu, K.S. Smith, F.J. Willeke, Q. Wu, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
A 5-cell 650 MHz SRF cavity was designed for eRHIC SRF linac. One Cu cavity was fabricated for HOM damping study, and one Nb cavity was fabricated for SRF studies. Through various post-processing recipes and vertical tests, the SRF study includes high Q-value study for ERL SRF linac and high gradient study for recirculating linac. This paper reports the HOM damping measurement on the Cu cavity and preliminary vertical test results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO006  
About • paper received ※ 22 August 2018      issue date ※ 18 January 2019  
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THPO113 Design of 4 Ampere S-Band Linac Using Slotted Iris Structure for Hom Damping linac, damping, beam-loading, target 934
 
  • J. Pang, S. Chen, X. He
    CAEP/IFP, Mainyang, Sichuan, People’s Republic of China
  • S. Pei, H. Shi, J.R. Zhang
    IHEP, Beijing, People’s Republic of China
 
  An S-band LINAC with the operating frequency of 2856 MHz and beam current of 4 A was designed for flash X-ray radiography for hydrodynamic test. The optimization of the parameters of the LINAC was processed to obtain the minimum beam radius and the maximum energy efficiency. For the purpose of reducing the beam orbits offset at the exit of LINAC, a slotted iris accelerating structure would be employed to suppress the transverse Higher Order Modes (HOMs) by cutting four radial slots in the iris to couple the HOMs to SiC loads. In this paper, we present the design of the LINAC and the results of beam dynamic analysis.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO113  
About • paper received ※ 10 September 2018      issue date ※ 18 January 2019  
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