Estimation of the Influence on the LHC Beam of Parasitic Magnetic Fields Resulting from Magnet Interconnections

The Large Hadron Collider (LHC) is equipped with 1232 main superconducting dipole magnets, 474 superconducting quadrupole magnets and more than 7400 superconducting corrector magnets that are distributed around the eight sectors of the accelerator. Each of the magnets is powered via superconducting power cables, the so-called main busbars for the main magnets and auxiliary busbars for the corrector magnets. Within the main magnets, the field produced by the superconducting busbars is shielded by the magnet's iron yoke. However, in the numerous magnet interconnections, the busbars are magnetically unshielded with respect to the beam pipes and produce parasitic fields that can affect the beam. Extensive analyses have been carried out in the past to assess the field quality of the individual magnets and its influence on the two counter-rotating beams. However, no detailed evaluation of the influence of the parasitic fields of the main and auxiliary busbars and their effect on beam optics had been performed so far. In this report, the integrated field perturbation resulting from parasitic fields is calculated and effects on some beam dynamics parameters are estimated.