Robot-Based NDE System Using Movable HTS-SQUID Magnetometer Covered With HTS Film for Use in Unshielded Environment

We developed a robust HTS-SQUID magnetometer utilizing bicrystal SrTiO₃ substrates, single-layer YBa₂Cu₃O_7-x films and flip-chip technique, aiming for movable robot-based NDE system in unshielded environment. Robustness in the unshielded environment was achieved by coverage of the SQUID magnetometer with another cross-shaped HTS film in flip-chip configuration, and introduction of mesh structure in both the magnetometer and the HTS film. SQUID parameters, such as critical current 2I_c, resistance R_n/2, modulation voltage depth V_pp, and flux noise S_Φ^1/2, were measured in DC and AC fields. The SQUID magnetometer was rotated in unshielded environment, and moved by a robot arm, resulting in stable operation during the motion at 20 mm/s with active magnetic shielding technique.