The effects of high-fluence neutron irradiation on the superconducting properties of magnetron sputtered NbN films

Abstract
Neutron irradiation experiments on sputtered NbN films up to a fluence of 1023 m2 (E>0.1 MeV) are reported. Both the transition temperatures Tc and the normal state resistivities change only slightly with neutron fluence. While the critical current densities degrade (up to 30%) in an intermediate field range (6–14 T), the high field data show virtually no change of Jc due to the radiation‐induced increase of Bc2 and the occurrence of peak effects near the upper critical field. It is therefore proven experimentally that NbN is an extremely radiation‐hard high field superconductor.