Analysis of Coupled Bunch Instabilities in the NSLS-II Storage Ring with a 7-cell PETRA-III RF Structure
- Brookhaven National Lab. (BNL), Upton, NY (United States). Photon Sciences Directorate
We studied the coupled-bunch instability driven by a 7-cell PETRA-III cavity structure, which is considered to be installed in the commissioning Phase 1 in the NSLS-II storage ring at an average current of 25mA. For instability threshold calculations we used the parameters of the bare lattice (no DW’s and Landau cavities). The transverse and longitudinal coupled-bunch instabilities can be driven by the higher order modes (HOM’s) of the 7-cell PETRA-III cavity structure. In the case of uniform filling the beam is longitudinally stable, and transversely unstable at zero chromaticity. To increase the transverse instability threshold we studied the stabilizing effect of the slow head-tail instability at positive chromaticity. We assume the slow head tail effect is driven by a broadband resonator impedance. In the case of all RF buckets filled (M=1320 bunches, N=3.1x108 particles per bunch) the beam is unstable for values of the chromaticity in the range [0 2]. To increase the damping provided by the slow head-tail effect, we discuss fillings with a larger number of particles per bunch. We analyze uniform filling configurations with M=132 (N=3.1x109) and M=66 (N=6.2x109). We also discussed HOM’s frequencies detuning based upon temperature change as a cure of the coupled-bunch instabilities, and proposed working points to make the 7-cell PETRA-III cavity structure stable under coupled-bunch interaction.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- DOE Contract Number:
- SC0012704
- OSTI ID:
- 1505122
- Report Number(s):
- NSLSII-ASD-TN-126; BNL-211122-2019-TECH
- Country of Publication:
- United States
- Language:
- English
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