Commissioning experience from PEP-II HER longitudinal feedback
- Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States)
The DSP-based bunch-by-bunch feedback system installed in the PEP-II high-energy ring (HER) has been used to damp instabilities induced by unwanted higher-order modes (HOMs) at beam currents up to 605 mA during commissioning. Beam pseudospectra calculated from feedback system data indicate the presence of coupled-bunch modes that coincide with a previously observed cavity mode (0-M-2). Bunch current and synchronous phase measurements are also extracted from the data. These measurements reveal the impedance seen by the beam at revolution harmonics. The impedance peak at 3xf{sub rev} indicates incorrect parking of the idle cavities, and explains the observed instability of mode 3. Bunch synchrotron tunes are calculated from lorentzian fits to the data. Bunch-to-bunch tune variation due to the cavity transient is shown to be large enough to result in Landau damping of coupled-bunch modes.
- OSTI ID:
- 21202412
- Journal Information:
- AIP Conference Proceedings, Vol. 451, Issue 1; Conference: 8. beam instrumentation workshop, Stanford, CA (United States), 4-7 May 1998; Other Information: DOI: 10.1063/1.57037; (c) 1998 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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Commissioning experience from PEP-II HER longitudinal feedback
Multi-Bunch Longitudinal Dynamics and Diagnostics via a Digital Feedback System at PEP-II, DAFNE, ALS and SPEAR