High Shear-Strength Electrical Insulations for Plasma Confinement Magnets

Nuclear fusion is being developed as a source of abundant, renewable energy. Fusion energy production utilizes large, superconducting magnets to confine and shape burning plasmas, and fusion reactions have been demonstrated and studied at several facilities. While the science is well-understood, several challenges must be overcome to construct reactors for power generation. Most notably, superconducting magnet systems that can operate reliably for long periods of time under ever increasing loads and radiation fluences must be developed. A particular challenge for magnet designers in these applications involves developing electrical insulation that is able to withstand the combined loads of extreme temperatures (both cryogenic and elevated temperatures), large shear stresses, cyclic fatigue, high operating voltages, and high levels of incident irradiation. Composite technology development (CTD) has investigated a series of toughened insulations with the objectives of enhancing fatigue and shear strength, radiation tolerance, and dielectric strength. Significant shear fatigue resistance improvements were achieved for two cases. CTD-425 saw a 250% improvement in cycles to failure, while the improved CTD-101K laminate did not fail under cyclic loading (180 000 cycles) when using treated fibers. Radiation resistance was improved as much as 45% at four times the ITER design fluence.