Experience with multibunch beam stability at PEP-II
- SLAC
In this report the authors discuss high-current, multibunch issues at the PEP-II B factory. To achieve the required beam currents, new techniques are used to help stabilize multibunch beams. In the longitudinal planes of both the low energy (LER) positron ring and the high energy (HER) electron ring, residual phase oscillations are damped with higher-order mode (HOM) absorbers on the accelerating cavities, direct and comb rf loops, low-frequency woofer link to correct multibunch modes supported by the cavity, and longitudinal bunch-by-bunch feedback. In the LER residual transverse motion has been successfully damped using transverse multibunch feedback up to the maximum current attained so far of 1.7 A. In the HER however a transverse instability has been observed at unexpectedly low beam currents. In this report the authors describe diagnostics used and summarize current thresholds and compare these with expectation. Next the authors present measurements made in the HER to better understand the apparently low threshold. The authors also show selected data using short bunch trains. Practical issues associated with very high beam currents are discussed including gap transients and the stabilizing influence of the beam-beam interaction on multibunch beam stability.
- Research Organization:
- Stanford Linear Accelerator Center, Menlo Park, CA (US)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- AC03-76SF00515;
- OSTI ID:
- 753293
- Report Number(s):
- SLAC-PUB-8363
- Country of Publication:
- United States
- Language:
- English
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