Cold Test Results of the Inner Triplet Orbit Correctors for the LHC

Abstract

The inner triplet orbit correctors for the LHC, MCBX and MCBXA, underwent acceptance tests at superfluid helium temperature at CERN, before shipping to FNAL for integration in the cold masses. A total of 27 MCBX (Horizontal-Vertical Dipole Correctors), of which 9 MCBXA (with nested Sextupole-Dodecapole insert), are needed for the LHC, including spares. The paper discusses the test protocols for series magnets, and reports the results of quench performance and cold magnetic measurements. The peculiarities of combined training and the hysteresis effects in the nested windings are presented, together with the search of the optimum setting procedure to minimize the persistent current effects on the beam dynamics.

Screening current induced magnetic field and stress in ultra-high-field magnets using REBCO coated conductors

“…Another similar method, often referred to as the 'degaussing procedure' or the 'demagnetization cycle', was previously developed for LTS accelerator magnets. Repeated current sweep cycles with decreasing overshooting amplitudes around the target current can establish a current distribution with alternating patterns in a filament, which can substantially suppress the field error and temporal drift caused by a combination of flux creep and current redistribution in LTS conducors [52][53][54]. For insulated REBCO coils, however, a similar procedure designed by Yanagisawa et al indicated that the full suppression of the SCF and its relaxation would require an overly large overshoot that is undesirable in practice [16].…”