Mobile HTS-SQUID Magnetometer in an Unshielded Environment

– Application to a Robot-based Non-destructive Evaluation System –

Abstract

Here, we developed a robust HTS-SQUID magnetometer based on a bicrystal SrTiO₃ substrate and single-layer YBa₂Cu₃O_7-x film, aiming for a mobile magnetometer in an unshielded environment. The robustness in the unshielded environment was achieved by coverage of the SQUID magnetometer with another HTS cross-shaped film in a flip-chip configuration, and introduction of a mesh structure in both the magnetometer and the HTS film. The SQUID parameters in DC and AC fields, such as critical current 2I_c, resistance R_n/2, modulation depth V_pp and flux noise S_∅^1/2, were studied. The SQUID was rotated and moved in the environment using a robot-arm, resulting in stable operation during the motion at 20 mm/s with active magnetic shielding.