Eddy-current nondestructive measurements using SQUIDs: Preliminary results

Eddy-current nondestructive testing based on superconducting devices is an emerging technique well suited for detection of second and third layer cracks and corrosion which result from the machining process or ageing of electrically conductive structures. The high field sensitivity at very low frequency of superconducting magnetometers allows measurements of deep embedded flaws even in magnetically unshielded environments. We present here a prototype for nondestructive evaluation based on high-temperature SQUID gradiometry. Comparison of results on detection of mm scale anomalies obtained by conventional fluxgate technology and this innovative technique in NDE applications are shown. Noise characterization and preliminary results of nondestructive testing on aluminum alloy plates performed by both probes are presented, further indicating the superior performance of SQUID.