Insulation systems for superconducting fusion magnets based on cyanate ester blends

Advanced epoxy-based glass fiber reinforced plastics are commercially used as insulating materials in fusion magnet technology. However, their mechanical strength drops dramatically upon irradiation to a fast neutron fluence of 1 × 1022 m−2 (E > 0.1 MeV), i.e. the ITER design fluence. The recent results demonstrated that cyanate ester (CE)/epoxy blends were not affected at this fluence level. In this work, various magnet insulation systems containing boron-free R-glass fiber reinforcements embedded in CE/epoxy blends are investigated. The mechanical properties were assessed at 77 K in tension as well as in the interlaminar shear mode prior to and after reactor irradiation at ambient temperature (∼340 K) to neutron fluences of up to 4 × 1022 m−2 (E > 0.1 MeV) under static and dynamic load conditions. The results show only a small reduction of the mechanical properties at twice the ITER design fluence. At the highest irradiation level the interlaminar shear strength of blends with at least 40% CE is only reduced by 20–30%.