Fast-neutron irradiation of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathrm{x}}$

We have studied the effects of fast neutron (E>0.1 MeV) irradiation on the superconducting properties of polycrystalline ${\mathrm{YBa}}_2$ ${\mathrm{CU}}_3$ ${\mathrm{O}}_{\mathrm{x}}$ with x=7±0.1. For fluences less than ${1\times 10}^{18}$ n/${\mathrm{cm}}^2$, the superconducting transition temperature $T_c$ decreases at a linear rate of about 3.0 K/${10}^{18}$ n/${\mathrm{cm}}^2$. Measurements of the critical magnetization current density $J_c$ at 7 K and zero field show an increase by a factor of three to 4.4×${10}^4$ A/${\mathrm{cm}}^2$ at 1×${10}^{18}$ n/${\mathrm{cm}}^2$ fluence and larger relative increases at high fields. At 75 K, $J_c$ is also enhanced with neutron irradiation, although the absolute values of $J_c$ are nearly two orders of magnitude smaller than at 7 K.