Proton Beam Emittance Growth due to Centroid Fluctuations in Strongly Disrupted Electron Bunches in the Linac-Ring eRHIC
- Brookhaven National Lab. (BNL), Upton, NY (United States)
In the energy recovery linac (ERL) based eRHIC design, the electron beam, accelerated in a superconducting ERL, collides with the proton beam circulating in the RHIC ring ones, undergoing a very strong beam-beam interaction with the protons, which warrants careful examination. Following the analysis of the transverse disruption and linear mismatch effects in the electron beam caused by beam-beam collision discussed in [2], we adopt the beam parameters listed in Table I for the eRHIC linac-ring design. After a review of the electron disruption process, we perform long term strong-strong beam-beam simulations with a modification of K. Ohmi’s strong-strong beam-beam code BBSS, with the modification consisting of the regeneration of the electron beam after every collision with the proton beam. With the parameters listed in Table I, a kink instability is observed in the proton beam. By reducing the proton bunch length, thus decreasing the electron disruption parameter, the kink instability is observed to disappear for a proton bunch length σz,p < 10 cm, or electron disruption parameter de < 1.5. The effect of random offsets in the electron bunch centroids on the long term stability of the proton beam is studied next, with a proton bunch length σz,p = 6.3 cm (de = 0.9), thus below the kink instability threshold. The random offsets of the electron bunch centroids are assumed to be Gaussian distributed, with standard deviation offs, and "delta-correlated" in time (white noise). Studies to take into account finite time-correlation effects and random offsets generated by non-Gaussian random processes will be considered in the future. The effect from fluctuations in the electron bunch population has been studied analytically and will be discussed numerically in a companion paper.
- 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:
- 1569252
- Report Number(s):
- BNL-211544-2019-TECH; NSLSII-ASD-TN-300; TRN: US2000160
- Country of Publication:
- United States
- Language:
- English
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