Mechanical analysis of the Nb$_3$Sn dipole magnet HD1

The Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL) has recently fabricated and tested HD1, a Nb$_3$Sn dipole magnet. The magnet reached a 16 T field, and exhibited training quenches in the end regions and in the straight section. After the test, HD1 was disassembled and inspected, and a detailed 3D finite element mechanical analysis was done to investigate for possible quench triggers. The study led to minor modifications to mechanical structure and assembly procedure, which were verified in a second test (HD1b). This paper presents the results of the mechanical analysis, including strain gauge measurements and coil visual inspection. The adjustments implemented in the magnet structure are reported and their effect on magnet training discussed.