Nondestructive evaluation of various materials using a SQUID-based eddy-current system

We have investigated the applicability of SQUIDs for nondestructive evaluation of various materials from industrial production. For this purpose, we tested production samples and compared the results with other NDE methods such as conventional eddy-current or ultrasonic testing. The materials investigated included niobium sheets for superconducting resonators and indium-tin-oxide sputtering targets for solar panels. Especially for the case of thick, highly conductive or ferromagnetic materials, as well as sintered materials, we found that the SQUID-based systems show a much higher sensitivity compared to conventional eddy-current NDE and ultrasonic testing. In addition, the SQUID systems have the advantage that the sample does not need to be immersed in water (which is necessary for ultrasonic testing), which can lead to serious degradation of sample quality.