Hysteresis effects of MCBX magnets on the LHC operation in collision

Abstract

The Large Hadron Collider beams are brought into collision by superconducting orbit corrector magnets which generate the parallel separation and crossing angles at the interaction points during the different cycle phases. Unfortunately, the magnetic field errors that result from hysteresis effects in the operation region of these magnets lead to unwanted orbit perturbations. In a previous paper, it has been shown that these effects are within the perturbations coming from beam-beam interactions for the MCBC and the MCBY magnets but are significant in the case of the MCBX magnets. This paper presents a refined model of their field in the frame of the Field Description for the LHC (FiDeL); the results obtained from new magnetic measurements in cold conditions to test the model; the powering mechanism employed to maximize their field reproducibility; and the impact the modelling error is predicted to have on the LHC orbit in phase 1.