The study on enhancing the critical current density Jc of the MTG YBCO and GdBCO superconductors by thermal neutron irradiation

The effect of the thermal neutron irradiation on critical current density Jc of Melt-Textured Growth (MTG) YBa2Cu3O7-y and GdBa2Cu3O7-y superconductors are studied systematically within a horizontal beam hole of the Heavy Water Research Reactor (HWRR). Neutron irradiation experiments include eight samples of YBCO with thermal neutron fluences from 3.7 x 1011 to 1.4 x 1017 cm-2 and six samples of GdBCO with thermal neutron fluences from 5.2 x 1013 to 4.7 x 1017 cm-2. For all MTG superconductive samples, the critical current density Jc, which is determined by the hysteresis loops measured by a moving sample magnetometer, is compared before and after irradiation. The results of YBCO show that the Jc values of irradiated samples with thermal neutron fluence of 1017 cm-2 are twice as high as that of unirradiated samples, and the results of GdBCO also show that the Jc value are enhanced significantly. It is found that the increments of the Jc of irradiated samples are increasing with the augmentation of the thermal neutron fluence and the increment of the Jc in higher magnetic field is larger than that in lower magnetic field. This phenomenon seems to be explained as follows. With the augmentation of the thermal neutron fluence, the increase of the crystal defects as flux pinning centers is increasing, namely the density of flux pinning centers is increasing and the distance between pinning centers is shortened, so as to be advantageous to the pinning function at higher magnetic field