IBS and expected luminosity performance for RHIC beams at top energy with 56 MHz SRF cavity

Fedotov,A.

关键词: FOCUSING;    HARMONICS;    LUMINOSITY;    PERFORMANCE;    PROTONS;    RF SYSTEMS;    ROTATION;    SCATTERING;    SIMULATION;    STORAGE;   

DOI  :  10.2172/944958
RP-ID  :  BNL--81722-2008-IR
PID  :  OSTI ID: 944958
Others  :  R&D Project: 18054
Others  :  Other: KB0202011
Others  :  TRN: US0900803

学科分类：物理（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

The purpose of RF system in RHIC is to capture injected bunches, accelerate them to the top energy, and store bunches at the top energy for many hours. The accelerating RF system operates at harmonic number h=360 of the particle revolution frequency f=78.196 kHz, which corresponds to 28.15MHz. The storage RF system accepts the shortened bunches at top energy and provides longitudinal focusing to keep these bunches short during the store time (collision mode). The storage system operates at harmonic number h=7x360=2520, which corresponds to an RF frequency of 197.05 MHz [1]. Recently, an upgrade of storage RF system with a superconducting 56 MHz cavity was proposed [2]. This upgrade will provide significant increase in the acceptance of storage RF bucket. Presently, the short bunch length for collisions is obtained via RF gymnastics with bunch rotation (called re-bucketing), because the length of 197MHz bucket of 5 nsec is too short to accommodate long bunches otherwise. However, due to bucket non-linearity and hardware complications some increase in the longitudinal emittance occurs during re-bucketing. The 56MHz cavity will produce sufficiently short bunches which would allow one to operate without re-bucketing procedure. This Note summarizes simulation of beam evolution due to Intra-beam scattering (IBS) for beam parameters expected with the 56 MHz SRF cavity upgrade. Expected luminosity improvement is shown both for Au ions at 100 GeV/nucleon and for protons at 250 GeV.