ITER CENTRAL SOLENOID COIL INSULATION QUALIFICATION

An insulation system for ITER Central Solenoid must have sufficiently high electrical and structural strength.Design efforts to bring stresses in the turn and layer insulation within allowables failed.It turned out to be impossible to eliminate high local tensile stresses in the winding pack.When high local stresses can not be designed out, the qualification procedure requires verification of the acceptable structural and electrical strength by testing.We built two 4x4 arrays of the conductor jacket with two options of the CS insulation and subjected the arrays to 1.2 million compressive cycles at 60 MPa and at 76 K.Such conditions simulated stresses in the CS insulation.We performed voltage withstand tests and after end of cycling we measured the breakdown voltages between in the arrays.After that we dissectioned the arrays and studied micro cracks in the insulation.We report details of the specimens' preparation, test procedures and test results.