Keyword: higher-order-mode
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TUP060 New HOM Coupler Design for High Current SRF Cavity HOM, cavity, linac, coupling 925
 
  • W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn, E.C. Johnson
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Damping higher order modes (HOMs) significantly to avoid beam instability is a challenge for the high current Energy Recovery Linac-based eRHIC at BNL. To avoid the overheating effect and high tuning sensitivity, current, a new band-stop HOM coupler is being designed at BNL. The new HOM coupler has a bandwidth of tens of MHz to reject the fundamental mode, which will avoid overheating due to fundamental frequency shifting because of cooling down. In addition, the S21 parameter of the band-pass filter is nearly flat from first higher order mode to 5 times the fundamental frequency. The simulation results showed that the new couplers effectively damp HOMs for the eRHIC cavity with enlarged beam tube diameter and two 120° HOM couplers at each side of cavity. This paper presents the design of HOM coupler, HOM damping capacity for eRHIC cavity and prototype test results.
 
 
TUP064 Designing Multiple Cavity Classes for the Main Linac of Cornell's ERL cavity, HOM, linac, dipole 937
 
  • N.R.A. Valles, M. Liepe
    CLASSE, Ithaca, New York, USA
 
  Funding: Work supported by NSF Grant No. PHY-0131508, and NSF/NIH-NIGMS Grant No. DMR-0937466
Cornell is currently developing a high current Energy Recovery Linac. The baseline 7-cell cavity design for the main linac has already been completed, and prototyping has begun, as of Fall 2010. Previous work showed that increasing the relative cavity-to-cavity frequency spread increases the beam break-up current through the linac. Simulations show that expected machining variations will introduce a relative HOM frequency spread of 0.5·10-3, corresponding to 150 mA of threshold current. The key idea of this work is to increase the relative cavity-to-cavity frequency spread by designing several classes of 7-cell cavities obtained by making small changes to the baseline center cell shape. This allows a threshold current in excess of 450 mA, which is well above the 100 mA goal for the Cornell Energy Recovery Linac.
 
 
TUP071 High Power Tests of Dressed Superconducting 1.3 GHz RF Cavities cavity, cryomodule, resonance, shielding 949
 
  • A. Hocker, E.R. Harms, A. Lunin, A.I. Sukhanov
    Fermilab, Batavia, USA
 
  Funding: U.S. Department of Energy, Contract No. DE-AC02-07CH11359
A single-cavity test cryostat is used to conduct pulsed high power RF tests of superconducting 1.3 GHz RF cavities at 2 K. The cavities under test are welded inside individual helium vessels and are outfitted (“dressed”) with a fundamental power coupler, higher-order mode couplers, magnetic shielding, a blade tuner, and piezoelectric tuners. The cavity performance is evaluated in terms of accelerating gradient, unloaded quality factor, and field emission, and the functionality of the auxiliary components is verified. Test results from the first set of dressed cavities are presented here.
 
 
TUP099 Design of Superconducting Parallel-bar Deflecting/Crabbing Cavities with Improved Properties cavity, HOM, damping, superconductivity 1021
 
  • J.R. Delayen, S.U. De Silva
    ODU, Norfolk, Virginia, USA
  • J.R. Delayen
    JLAB, Newport News, Virginia, USA
 
  The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties, compared to other conventional designs, that is being considered for a number of applications. All designs to-date have been based on straight loading elements and rectangular outer conductors. We present new designs of parallel-bar cavities using curved loading elements and circular or elliptical outer conductors, with significantly improved properties such as reduced surface fields and wider higher-order mode separation.  
 
TUP100 Design of Superconducting Spoke Cavities for High-velocity Applications cavity, HOM, superconductivity, linac 1024
 
  • J.R. Delayen, S.U. De Silva, C.S. Hopper
    ODU, Norfolk, Virginia, USA
  • J.R. Delayen
    JLAB, Newport News, Virginia, USA
 
  Superconducting single- and multi-spoke cavities have been designed to-date for particle velocities from β~0.15 to β~0.65. Superconducting spoke cavities may also be of interest for higher-velocity, low-frequency applications, either for hadrons or electrons. We present the design of spoke cavities optimized for β=0.8 and β=1.