The nature of the granular structure determines the role of γ-rays in silver-sheathed (Bi,Pb)2223 tapes

We have investigated the role of the granular structure on the effect of γ-irradiation of a dose of 100 MR on the behavior of the critical current density, Jc in silver-sheathed Bi1.6Pb0.4Sr2Ca2Cu3O10 and Bi1.8Pb0.4Sr2Ca2Cu3O10 superconducting tapes. This study was conducted under several values of applied magnetic field, B and at 80 K using I-V measurements. The samples were irradiated at room temperature by a 60Co γ-ray source at a dose rate of 0.5 MR/h. The behavior of Jc as the applied field is increased was found to be different in the two samples. Although Jc values in both samples were found to be significantly enhanced at all applied fields, after γ-irradiation, the enhancement was not the same in both samples. These results are discussed in terms of the role of the regions of grain boundaries on the effect of γ-rays on the superconducting properties.