Development of Robust HTS-SQUID for Non-destructive Inspection System in Unshielded Environment

摘要

Cross-shaped YBa_2Cu_3O_(7-x) (YBCO) film was overlapped on directly-coupled multi-pickup-coil HTS-dc-SQUID magnetometer in flip-chip configuration as a superconducting shield, and the characterestics of the SQUID were examined in DC and AC magnetic fields. We created slots in the YBCO film and pickup-coil of HTS-SQUID magnetometer for suppression of flux trapping. In low magnetic field environment, we measured the characteristics of the SQUID without and with HTS film. The most of the parameters were same with and without the HTS films, while S_ф~(1/2) with the HTS film was a bit smaller than that of the bare SQUID. In the DC field, I_c of the HTS-SQUID covered with the HTS film did not change until a DC field over 140 μT was applied to the SQUID, while the bare SQUID's I_c decreased with the increase of the applied DC field. In the AC fields at 10 MHz, the SQUID with the HTS film showed degradation of the parameters such as V_(pp) and S_ф~(1/2) at lower field amplitude than the bare SQUID.