RF WIRE COMPENSATOR OF LONG-RANGE BEAM-BEAM EFFECTS

The dynamic aperture of the proton beam circulating in the Large Hadron Collider (LHC) is expected to be lim- ited by up to 120 long-range beam-beam encounters. In order to perfectly compensate the LHC long-range beam- beam effect for nominal as well as for so-called 'PAC- MAN' bunches, i.e. bunches at the start or end of a bunch train, the strength of a wire compensator should be adjusted for each bunch individually. Here an RF-based compensator is proposed as a practi- cal solution for the PACMAN compensation. We show that this approach also allows relaxing the power and precision requirements compared with those of a pulsed DC device, to a level within the state-of-the-art of RF technology. Fur- thermore it permits the use of a passive circulator in the tunnel close to the beam and thus a significant reduction of the transmission line length and of the associated multiple reflections. Simulations of dynamic aperture and emittance growth, issues related to RF phase noise, and first experi- mental results from laboratory models are presented.