DEFECT SIZE DEPENDENCE OF CRITICAL CURRENT-DENSITY ENHANCEMENT FOR IRRADIATED YBA2CU3O7-DELTA

The effects of 100 MeV electron (to 3.6 x 10(18) cm-2) and fast neutron irradiation (to 4.0 x 10(18) cm-2) on the superconducting properties of melt-textured YBa2Cu3O7-delta is studied experimentally. By comparing the critical current enhancement effects normalized to the total atomic displacement damage, it is found that the enhancement depends heavily on the type and energy of radiation and on the beam direction with respect to the crystal. Fast neutron irradiation is more effective than 100 MeV electron irradiation (along the c-axis) in enhancing the critical current, and electron irradiation along the c-axis is more effective than electron irradiation along the a, b-plane. A model based on defect size is proposed to interpret the effects.