Speaker
Description
KEK have so far tested four series beam separation dipoles, a.k.a. D1 (MBXF) magnets, for the High Luminosity LHC upgrade (HL-LHC). The magnet is wound on Nb-Ti Rutherford cables and designed to operate at 1.9 K generating a central field of 5.6 T with a magnetic length of 6.3 m, which corresponds to a field integral of 35 Tm. All the series magnets were subjected to a quench training campaign in the KEK-owned vertical cryostat, and were energized successfully up to an ultimate current of 13.23 kA. The magnetic field error of these magnets was also evaluated with a rotating coil system developed in-house, and was confirmed to meet the acceptance criteria.
Statistics of the test results have been accumulated so far with four series magnets. We have observed that each magnet showed various training trends. Particularly MBXF2 and MBXF3, which are the 3rd and 4th series magnet respectively, showed a slow training rate; more than 10 quenches were required to reach the ultimate current. We have also confirmed that there is a correlation between the individual coil size and unallowed multipoles, which were investigated through finite element (FEM) analyses. In this paper we first report the recent result of the MBXF3 test obtained during the period of Dec. 2024-Jan. 2025. Then we introduce the training trend and magnetic field quality of the MBXF series obtained so far. We also give our insight on the field quality using the FEM analysis and the mechanical data obtained during fabrication process.
