An eddy current probe utilizing a cooled normal pickup coil and a high-Tc superconducting quantum interference device (SQUID) picovoltmeter was developed. The pickup coil could be moved in an unshielded environment, during which the signal voltage across the pickup coil was transferred to the SQUID picovoltmeter, which was fixed in a cylindrical magnetic shield. By moving the pickup coil, we successfully detected a small crack on the back surface of a Cu plate in the unshielded environment. The dependences of the detected signal on the excitation frequency and thickness of the Cu plate were clarified. The frequency dependence could be used to estimate the depth of the crack from the surface of the Cu plate.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)