Optimization of Higher Order Mode Dampers in the 56MHz SRF Cavity for RHIC

Conference · Sun May 23 04:00:00 EDT 2010

OSTI ID:1013484

Wu, Q; Ben-Zvi, I

A 56 MHz superconducting RF cavity was designed for a luminosity upgrade of the Relativistic Heavy Ion Collider (RHIC), including requirements for Higher Order Mode (HOM) damping. In this paper, we describe our optimization of the damper's performance, and modifications made to its original design. We also show the effects of the damper geometry on the cavity's HOM impedance. To reduce the likelihood of magnetic breakdown, we lowered the magnetic field enhancement at the ports to a value less than the highest field in the cavity. We simulated all monopole and dipole HOMs up to 1GHz with their frequencies, mode configurations, R/Qs, and shunt impedances, verifying that all modes are well-damped with the optimized design and configuration. The 56 MHz superconducting RF cavity is a quarterwave resonator designed to have a gap voltage of 2.5 MV. Our plans are to place this beam-driven resonator at a common section of RHIC to provide a storage RF potential for both rings. The large bucket of the cavity will reduce spill due to Intra-Beam Scattering (IBS), and thus increase the luminosity for the detectors. It is very important to damp all the cavity's Higher Order Modes (HOMs) to avoid beam instabilities. The design chosen for the HOM damper is a magnetically coupled loop located at the rear end of the cavity. The loop and its port geometry must be optimized to assure sufficient damping, avoid a large enhancement of the local magnetic field. A high-pass filter is included in the circuit to reduce the power extraction from the fundamental mode. The number of HOM dampers used and their configuration also are important factors for the damping and cooling system. A small loop area will couple out less power from the cavity's fundamental mode, thus reducing the voltage and power dissipation in the damper's filter circuit; however, it might not be sufficient for HOM damping. This problem is resolved by increasing the number of the HOM dampers and carefully choosing their location. Details of the high-pass filter will be discussed in another paper.

• Research Organization: Brookhaven National Laboratory (BNL) Relativistic Heavy Ion Collider
• Sponsoring Organization: DOE - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1013484
• Report Number(s): BNL--90769-2010-CP; KB0202011
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ACCELERATORS
BREAKDOWN
BYPASSES
CONFIGURATION
COOLING SYSTEMS
DAMPING
DESIGN
DIPOLES
GEOMETRY
HEAVY IONS
IMPEDANCE
LUMINOSITY
MAGNETIC FIELDS
MODIFICATIONS
MONOPOLES
OPTIMIZATION
PERFORMANCE
RESONATORS
SCATTERING
STORAGE
relativistic heavy ion collider