The design of the fundamental mode damper and the HOM dampers for the 56 MHz SRF cavity

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A 56 MHz Superconducting RF cavity is under development for the Relativistic Heavy Ion Collider (RHIC) aiming at luminosity enhancement The 56 MHz SRF cavity can adiabatically rebucket the beam from the 28 MHz accelerating cavities, provide shorter bunches and significantly enhance the luminosity. The 56 MHz SRF cavity will be turned on at store, therefore, the fundamental mode should be damped while the beam is injected and accelerated. The feature requires a fundamental mode damper (FD). The mechanical design of the FD is challenging since the fundamental mode damper has to be physically withdrawn while the cavity is turned ... continued below

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Choi,E.M.; Hahn, H.; Bellavia, S. & Ben-Zvi, I. May 4, 2009.

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A 56 MHz Superconducting RF cavity is under development for the Relativistic Heavy Ion Collider (RHIC) aiming at luminosity enhancement The 56 MHz SRF cavity can adiabatically rebucket the beam from the 28 MHz accelerating cavities, provide shorter bunches and significantly enhance the luminosity. The 56 MHz SRF cavity will be turned on at store, therefore, the fundamental mode should be damped while the beam is injected and accelerated. The feature requires a fundamental mode damper (FD). The mechanical design of the FD is challenging since the fundamental mode damper has to be physically withdrawn while the cavity is turned on. This motion introduces a frequency change of the cavity. Since for stability the cavity frequency must be kept below the beam frequency in this phase, we chose a judicious axial placement of the FD to minimize the frequency shift. Various studies of the FD were done with prototype cavity tests and numerical simulations. The engineering issues were addressed. Higher-order mode (HOM) dampers are necessary for stable operation of RHIC with the 56 MHz SRF cavity. The physics study of the HOM dampers will be presented in the paper. Based on the stability criteria of the cavity, the HOMs are properly damped by having two HOM dampers. The fundamental mode is filtered out by a 5 element high pass filter. The HOMs were identified and the external Q factors were obtained from tests of the prototype cavity and compared to simulations with the CST Microwave Studio{reg_sign} program.

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  • Particle Accelerator Conference; Vancouver, B.C., Canada; 20090504 through 20090508

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  • Report No.: BNL--81807-2009-CP
  • Grant Number: DE-AC02-98CH10886
  • Office of Scientific & Technical Information Report Number: 952536
  • Archival Resource Key: ark:/67531/metadc934546

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  • May 4, 2009

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  • Nov. 13, 2016, 7:26 p.m.

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  • Dec. 12, 2016, 8:31 p.m.

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Choi,E.M.; Hahn, H.; Bellavia, S. & Ben-Zvi, I. The design of the fundamental mode damper and the HOM dampers for the 56 MHz SRF cavity, article, May 4, 2009; United States. (digital.library.unt.edu/ark:/67531/metadc934546/: accessed August 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.