Development of Paschen-Tight Insulation Repair for Complex Geometries for the ITER CS Modules

The US ITER Domestic Agency is responsible for supplying seven Central Solenoid Modules (CSM) to the ITER organization. The modules are fabricated by General Atomics (GA). As part of the fabrication process, all CSMs undergo factory acceptance testing (FAT) prior to shipment to the IO. The FAT includes Paschen testing the CSMs up to 15 kV between 1e-3 and 100 mbar, and up to 30 kV at ambient conditions. During post-cooldown Paschen testing of CSM6, there was a fault on one of the terminal breakout locations which required a repair. This location of the fault consisted of complex geometry that required development of advanced insulation repair methods to return the module to Paschen-tight condition. Successful insulation repairs typically require sufficient compression to achieve a Paschen-tight seal of the applied insulation to the underlying surfaces. Typically for circumferential shapes, compression is achieved utilizing shrink tape or silicone tape wrapped around the perimeter. The complex geometry of CSM6 terminal required research into other compression methods including vacuum bagging, expanding foam, and externally pressurized bladders of complex shapes. Multiple test articles were created to replicate the shape of the fault area and repair methods were developed and Paschen tested to 30 kV, from 1e-3 to 1000 mbar. This paper will discuss the development of the qualified repair process for the complex geometry of the CSM6 terminal, and present to the magnet community the lessons learned from that development.