Electromagnetic and Mechanical Analysis of the Coil Structure for the CLAS12 Torus for 12 GeV Upgrade

The torus magnet for the CLAS12 spectrometer is a 3.6-T superconducting magnet being designed and built as part of the Jefferson Lab 12-GeV upgrade. The magnet consists of six coil case (enclosed in a vacuum-impregnated coil pack) assemblies mounted to a cold central hub. The coil pack consists of a 117-turn double-pancake winding wrapped with two layers of 0.635-mm-thick copper cooling sheets. The coil case assembly is cooled by supercritical helium at 4.6 K. This presents the electromagnetic and structural analysis of the coil case assembly and the assessment of the coil pack stresses. For the normal operation of the torus magnet, the coil case assembly was analyzed for cool down to 4.6 K and the Lorentz forces at normal operating current. In addition to the normal operating configuration, the coil case assembly was analyzed for Lorentz forces arising from coil misalignment and current imbalances. Primary stresses were limited to the lesser of 2/3 times the yield strength or 1/3 times the ultimate tensile strength. Primary plus secondary stresses were limited to 3 times the primary stress allowable. The analysis was performed using ANSYS Maxwell and ANSYS Mechanical to calculate the magnetostatic loads and calculate the stresses.