Long-Range Beam-Beam 2018

A recurrent issue of the LHC operation, observed both during Run1 and Run2 is the asymmetric behaviour of the two beams in terms of particle losses. The fact that Beam 1 shows higher losses when compared to Beam 2 is not intuitive, especially when compared to the symmetric design of the two rings. The beam-beam effects induced by the interaction of the two beams in the experimental inserts, as well as noise sources contribute to the degradation of the beam lifetime, possibly asymmetrically between the two beams. In this Machine Development study, several machine and beam configurations are considered to identify or discard some of the possible sources of this behaviour. The impact of the active filters of the main bends in the beam spectrum is tested at injection energy as a possible source of 50 Hz harmonics. A variation in the beam-beam separation induced by a crossing angle bias, and the impact of the optics choice of different phase advances between the two high-luminosity interaction points are scrutinized as source of lifetime asymmetry. Finally, the wire beam-beam compensator is tested for the first time with full beam in a sub-optimal configuration and its impact is assessed.