Long-Range Beam-Beam Compensation in RHIC

We review wire-based beam-beam compensation experiments in the SPS, prospects of wire-compensation studies at RHIC, exploratory ideas for future pulsed wire devices, simulations of LHC wire compensation, and requirements for LHC crab cavities.

The performance of the Large Hadron Collider (LHC) and its minimum crossing angle are limited by long-range beam-beam collisions. Wire compensators can mitigate part of the long-range effects and may allow for smaller crossing angles, smaller β*, or higher beam intensity. A prototype long-range wire compensator should be installed in the LHC by 2014/15. We report simulation studies examining and comparing the efficiency of the wire compensation, in terms of tune footprint or dynamic aperture, at various candidate locations, with different wire shapes, and for varying transverse distance from the beam.

2012

The performance of the Large Hadron Collider (LHC) and its minimum crossing angle are limited by long-range beam-beam collisions. Wire compensators can mitigate part of the long-range effects and may allow for smaller crossing angles, smaller β∗, or higher beam intensity. A prototype long-range wire compensator should be installed in the LHC by 2014/15. We report simulation studies examining and comparing the efficiency of the wire compensation, in terms of tune footprint or dynamic aperture, at various candidate locations, with different wire shapes, and for varying transverse distance from the beam.

2008

Charged particle beams in high energy, high luminosity particle colliders are accompanied by strong and highly nonlinear electromagnetic fields. When two counterrotating beams pass each other these fields give rise to so called ``beam-beam interactions'' with a wide spectrum of negative consequences for the beam dynamics resulting e.g. in particle loss and emittance blow up. In the Large Hadron Collider (LHC) such crossings will occur each turn four times ``head-on'' (once at each interaction point, IP) and fifteen times ``long-range'' on each side of each IP with a small transverse offset. In order to correct for the resulting perturbations a wire compensator is foreseen. In the framework of this thesis the tracking code ``BBTrack'' has been developed and employed to investigate long-range beam-beam interaction and its wire compensation in the CERN LHC (nominal and upgraded). Complementary experimental studies at RHIC at BNL and the CERN SPS ...

Beam-beam interactions are one of the dominant sources of emittance growth and luminosity lifetime deterioration. A current carrying wire has been proposed to compensate long-range beam-beam effects in the LHC and the effect of a DC wire on the beam is now also studied in RHIC. Tune shift, beam transfer function, and beam loss rates are measured in dedicated experiments. In this paper, we do simulations to study the effect of a wire compensator based on diffusive apertures, beam loss rates, and beam transfer function using a parallel weak-strong beam simulation code (bbsimc) without parasitic collisions. The simulation results are compared with measurements.

2017

Long-range beam-beam (LRBB) interactions can be a source of emittance growth and beam losses in the LHC during physics and will become even more relevant with the smaller β* and higher bunch intensities foreseen for the High Luminosity LHC upgrade (HL-LHC), in particular if operated without crab cavities. Both beam losses and emittance growth could be mitigated by compensating the non-linear LRBB kick with a correctly placed current carrying wire. Such a compensation scheme is currently being studied in the LHC through a demonstration test using current-bearing wires embedded into collimator jaws, installed either side of the high luminosity interaction regions. For HL-LHC two options are considered, a current-bearing wire as for the demonstrator, or electron lenses, as the ideal distance between the particle beam and compensating current may be too small to allow the use of solid materials. This paper reports on the ongoing activities for both options, covering the progress of the wire-in-jaw collimators, the foreseen LRBB experiments at the LHC, and first considerations for the design of the electron lenses to ultimately replace material wires for HL-LHC.

2007 IEEE Particle Accelerator Conference (PAC), 2007

Long-range beam-beam interactions can cause significant degradation of beam quality and lifetime in high energy ring colliders. In this paper, we report on numerical simulation of the long-range beam-beam interactions at RHIC using a parallel strong-strong particle-in-cell code, BeamBeam3D. The simulation includes nonlinearities from both the beam-beam interactions and the arc sextupoles. Scan studies in tune space show strong emittance growth islands around 7th and 11th order resonances. The large emittance growth inside the resonance island is driven by the dynamic tune modulation together with the nonlinear forces from beam-beam interactions and sextupole magnet. The emittance growth decreases quickly as the beam-beam separation increases from four to six sigmas.

2007

1993

Compensation of the beam-beam effect in high-energy proton-proton colliders using a low-energy electron beam is proposed. It is concluded that such compensation looks feasible.

2013

To reduce the beam-beam resonance driving terms with half head-on beam-beam compensation in the RHIC polarized-proton operations, the betatron phase advances between the interaction point IP8 and the center of the electron lenses located around IP10 should be kπ ,w herek is an integer. Realistic beam-beam compensation lattices meeting the phase advance requirements were developed and used in the beginning of 2013 polarized proton run, although head-on beam-beam compensation was not implemented yet. In this article, with these lattices and a 6D weak-strong beam-beam simulation model, we calculate the proton dynamic apertures with and without beam-beam compensation. Preliminary results with second order chromaticity correction are also presented.