Robot-Based NDE System Using 3D-Mobile HTS-SQUID

A novel HTS-SQUID gradiometer with ramp-edge Josephson junctions (JJs) composed of SmBa<sub>2</sub>Cu<sub>3</sub>O<sub>y</sub> base-electrode and La<sub>01</sub>Er<sub>0.95</sub>Ba<sub>1.95</sub>Cu<sub>3</sub>O<sub>y</sub> counter-electrode was developed. The robustness of the gradiometer in AC field perpendicular to the device plane was investigated. In an AC field of less than 2.8 mT<sub>pp</sub> at 100 Hz, flux-trapping, jumping and increase in noise did not happen in the gradiometer, while a traditional HTS-SQUID gradiometer with YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> thin film and bicrystal JJs with the same dimension as the novel gradiometer could not be operated properly in an AC field of about several tens nT<sub>pp</sub>. A robot-based NDE system utilizing the novel HTS-SQUID gradiometer was developed. The system could move the gradiometer three-dimensionally (3D) in an unshielded environment without magnetic shielding or compensation technique. Eddy-current-based detection of a through hole in magnetized stainless steel board was demonstrated by the robot-based HTS-SQUID NDE system.