Improvement in Training Performance by Enhancing Coil Mechanical Support in the Beam Separation Dipole Model Magnet for the HL-LHC Upgrade

Nb-Ti based large-aperture beam separation dipoles (MBXFs) will be installed on both sides of two interaction points, ATLAS and CMS, for the high-luminosity LHC upgrade. The most important requirements for MBXF is a coil aperture of 150 mm and the field integral of 35 T·m. Nominal dipole field is 5.6 T at 12 kA and 1.9 K. KEK is in charge of developing MBXF within a framework of CERN-KEK collaboration. This study reports training performance of three 2-m long model magnets (MBXFS1-3) assembled under different mechanical support conditions. Azimuthal pre-stress both in the straight section and at coil end, and axial pre-load were controlled to counteract Lorentz force. In MBXFS2 and 3, wet-winding was also applied but solely to the coil end. Quench start locations for the model magnets are compared to validate the effectiveness of each support method.