Influence of irradiation temperature on REBCO tape degradation

Abstract

Commercial rare earth barium copper oxide (REBCO) coated conductor tapes were irradiated at temperatures ranging from 20 to 300 K with 1.2 MeV protons up to fluences of 10 21 m −2 . With in situ transport current measurements, we found that self-field critical currents ( I c ) and transition temperature ( T c ) degrade in cold (20–200 K) irradiations by a factor of 1.6 faster than in 300 K irradiations. This warrants caution when basing the development of REBCO fusion magnets, which are operated at 20 K, on results from room-temperature irradiations. The degradation of I c , n-value and T c for irradiations in the range 20–200 K closely matched each other. However, small annealing effects can already be observed at 80 K, which is a lower threshold than previously thought. The observed I c recovery increases with annealing temperature and is at 300 K four times higher than at 200 K. And finally, we compared the experimental data from this study with the calculated decrease of superfluid density, and find a surprisingly good correlation, supporting the Eisterer hypothesis for I c degradation.