Electron lenses for head-on beam-beam compensation in RHIC

Abstract

Two electron lenses (e-lenses) have been in operation during the 2015 RHIC physics run as part of a head-on beam-beam compensation scheme. While the RHIC lattice was chosen to reduce the beam-beaminduced resonance-driving terms, the electron lenses reduced the beam-beam-induced tune spread. This has been demonstrated for the first time. The beam-beam compensation scheme allows for higher beam-beam parameters and therefore higher intensities and luminosity. In this paper, we detail the design considerations and verification of the electron beam parameters of the RHIC e-lenses. Longitudinal and transverse alignments with ion beams and the transverse beam transfer function measurement with head-on electronproton beam are presented.

Halo removal experiments with hollow electron lens in the BNL Relativistic Heavy Ion Collider

“…More studies have followed, such as the calculation of the transverse kicks from the hollow electron-lens bends [20], the beam diocotron instability control [21], and the hollow electron gun characterization [22], as well as experimental and numerical studies for a hollow electron-lens system [23][24][25][26][27][28]. The above studies, as well as the existing electron-lens experience from Tevatron and RHIC [29][30][31][32][33][34], provide information for the design of a hollow electron-lens system that meets the halo removal requirements for the HL-LHC, as well as the future applications of beam collimation in the FCC-hh [35] at CERN or Super Proton-Proton Collider (SPPC) [36] in China.…”

“…The RHIC consists of two rings on a common horizontal plane: the blue ring for clockwise and the yellow ring for counterclockwise beams. The two RHIC electron lenses (e-lenses) with Gaussian transverse profiles, both located near the interaction point (IP) IP10, were designed to compensate for the beam-beam effects from the protonproton interactions at the two interaction points IP6 and IP8 [29][30][31][32][33][34].…”

“…VI. Figure 1 is a schematic horizontal sectional view of one of the two RHIC electron lenses [33]. Each RHIC electron lens includes an electron gun and a collector [38] as the electron beam source and dump.…”

“…There is instrumentation [41][42] for the beam diagnostic and the alignment of the electron and ion beams. [33].…”

Beam-beam amplitude detuning with forced oscillations

“…Experimental studies are ongoing at the LHC [21,22]. These would allow verifying and optimizing beam-beam correction schemes [23][24][25][26][27]. For all the above reasons it is important to gain understanding in the beam dynamics of forced oscillations.…”