Detailed evaluation of insulation stresses in the KSTAR central solenoid

The insulation system of the Korea Superconducting Tokamak Advanced Research (KSTAR) device plays a role of the structural element by binding the conductor jackets as well as breaking the current. The KSTAR Central Solenoid (CS) coils are stacked with four pairs of coils with up-down symmetry. The insulation of the CS coils experiences various stress states, such as tensile, normal compressive, and shear stresses due to applied preload at room temperature, thermal contraction difference during cool-down, and magnetic forces during operation. In particular, the normal tension and shear of the insulation has been a critical issue for magnet design. In this paper, a more detailed model in addition to electromagnetic and global structural analysis will be constructed and analyzed to evaluate the insulation stress. The results may suggest appropriate allowable stress criteria for insulation systems at cryogenic temperature.