IRRADIATION EFFECTS ON FLUX PINNING AND JC IN HIGH-TEMPERATURE SUPERCONDUCTORS

We have introduced neutron and electron irradiation defects in bulk YBCO melt-textured materials. The defects and their effect on the critical current density (J(c)) have been examined. The enhancement of J(c) is found to be heavily dependent on the type and energy of the beam as well as on the direction of the beam with respect to the crystal. Two types of defects have been identified in neutron irradiated YBCO by positron annihilation experments. The large defects (approximately 20 angstrom) correlate with the enhancement of J(c) and are 10(3) times more effective in flux pinning than point defects.