The effect of fast neutron irradiation on the superconducting properties of REBCO coated conductors with and without artificial pinning centers

Abstract

Superconductors are essential components of future fusion power plants. The magnet coilsresponsible for producing thefieldrequiredforconfining the fusion plasma are exposed toconsiderable neutron radiation. This makes irradiation studies necessary for understanding theradiation response of the superconductor. High temperature superconductors are promisingcandidates as magnet coil materials. YBCO and GdBCO tapes of several manufacturers wereirradiated to fast neutronfluences of up to 3.9×1022m−2in the research reactor at the Atominstitut.Low energy neutrons contribute to thefission reactor spectrum but not to the expected spectrum atthe fusion magnets. Low energy neutrons have to be shielded in irradiation experiments to avoid theirsubstantial effect on the superconducting properties of tapes containing gadolinium. The criticalcurrent(Ic)of the tapes in this study was examined atfields of up to 15 T and down to a temperatureof 30 K.Icfirst increases upon irradiation and reaches a maximum at a certainfluence, whichdepends highly on temperature, being highest at low temperature.Icdeclines at highfluences andeventually degrades with respect to its initial value. Tapes with artificial pinning centers(APCs)degrade at lowerfluences than tapes without them. Then-values decrease in all types of tapes afterirradiation even when the critical currents are increased. Thefield dependence of the volume pinningforce differs in pristine tapes with and without APCs but shows the same behavior after irradiation.