EFFECT OF INTERNAL FISSION-FRAGMENT IRRADIATION ON CRITICAL CURRENTS AND FLUX-CREEP IN BI-SR-CA-CU-O SUPERCONDUCTORS DOPED WITH UO2

Fission fragment damage was introduced into samples of Bi2Sr2CaCu2Ox a nd Bi1.7Pb0.3Sr2Ca2Cu3Oy, doped with various levels of UO2, by irradia tion with thermal neutrons. The critical temperatures were unchanged. Concurrent with an increase in intragranular J(c) previously reported, a decrease in flux creep was observed. The apparent pinning potential for creep at 10 K and 0.8 T increased on irradiation by about two to three times for both the 2212 and 2223 compounds. This increased appar ent pinning potential is attributed to the strong pinning introduced b y the damage caused by the travel of the fission fragments through the crystal. Pinning potential after irradiation increased with an increa se in the amount Of UO2 in the sample. The increase in bulk pinning po tential on irradiation was proportional to the increase in intragranul ar critical currents on irradiation, qualitatively as expected theoret ically.