Author: Carwardine, J.
Paper Title Page
THPB072 Higher Order Mode Damping in a Higher Harmonic Cavity for the Advanced Photon Source Upgrade 1293
 
  • S.H. Kim, J. Carwardine, Z.A. Conway, G. Decker, M.P. Kelly, B. Mustapha, P.N. Ostroumov, G.J. Waldschmidt
    ANL, Argonne, Illinois, USA
 
  Funding: Results in this report are derived from work performed at Argonne National Laboratory. Argonne is operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357.
A superconducting higher-harmonic cavity (HHC) is under development for the Advanced Photon Source Upgrade based on a Multi-Bend Achromat lattice. This cavity will be used to improve the Touschek lifetime and the single bunch current limit by lengthening the beam. A single-cell 1.4 GHz (the 4th harmonic of the main RF) cavity is designed based on the TESLA shape. Two adjustable fundamental mode power couplers are included. The harmonic cavity voltage of 0.84 MV will be driven by the 200 mA beam with a bunch length of >50 ps RMS. Higher-order modes (HOM) must be extracted and damped. This will be done with two silicon carbide beamline HOM absorbers to minimize heating of RF structures such as the superconducting cavity and/or couplers and suppress possible beam instabilities. The HHC system is designed such that 1) most monopole and dipole HOMs are extracted along the beam pipes and damped in the ‘beamline’ silicon carbide absorbers and 2) a few HOMs, resulting from introduction of the couplers, are extracted through the coupler and dissipated in a room temperature water-cooled load. We will present time and frequency domain simulation results and discuss damping of HOMs.
 
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THPB073
Beamline Silicon Carbide Higher Order Mode Damper for the Advanced Photon Source Upgrade Harmonic Cavity  
 
  • S.H. Kim, J. Carwardine, Z.A. Conway, G. Decker, R.L. Fischer, M.P. Kelly, P.N. Ostroumov, T. Reid, K.W. Shepard
    ANL, Argonne, Illinois, USA
 
  Funding: Results in this report are derived from work performed at Argonne National Laboratory. Argonne is operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357.
A superconducting higher harmonic cavity (HHC) is under development for Advanced Photon Source Upgrade based on a Multi-Bend Achromat lattice. The HHC improves the Touschek lifetime and the single bunch current limit by lengthening the bunch. A TESLA-shaped single-cell 1.4 GHz (4th harmonic of the main RF) cavity will be used. Monopole and dipole higher order modes (HOMs) will be extracted primarily along the beam pipes and damped in a pair of ‘beamline’ silicon carbide (SiC) HOM dampers. These water-cooled SiC dampers will be placed just outside of the cryomodule. Maximum power dissipation in both SiC HOM dampers is estimated to be 1.7 kW at the beam current of 200 mA total and 4.2 mA max/bunch with the bunch length of RMS >50 ps. The SiC cylinder is cooled by a precision fit copper sleeve with water cooling channels. The thermal contact conductance at the interface between SiC and copper has been experimentally measured. In this paper, we will present design details of the SiC HOM dampers and experimental results of the thermal contact conductance at the interface.
 
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