Evaluation of Temperature Rise Caused by AC Loss Due to Plasma Disruption in Joint of JT-60SA Poloidal Field Coil

Two kinds of joints (the lap and butt joints) for JT-60SA poloidal field coil are evaluated. We measured and analyzed AC losses of the joints for JT-60SA under a time-varying magnetic field, and based on the analytical AC loss, the temperature rise of the joints is estimated at the plasma disruption by using the FEM simulation software COMSOL Multiphysics. As a result, the maximum temperature of the lap joint is constant, on the other hand, the maximum temperature of the butt joint strongly depends on the mass flow of the supercritical helium. When the mass flow of the supercritical helium is 4 g/s and more in all the initial temperatures (4.2-7.0 K), the butt joint has a sufficient temperature margin at the plasma disruption. The obtained results become fundamental data to estimate the temperature margin of the coil.