Electronic axial HTS dc SQUID gradiometer cooled by pulse-tube cooler

An electronic axial high-T/sub c/ dc SQUID gradiometer cooled by pulse-tube cooler was developed. In order to extend the operating times, a method of temperature control was used to stabilize the operating temperature of the SQUID. We used the SQUID gradiometer cooled by pulse-tube cooler to perform eddy-current nondestructive evaluation and corrosion signal detection in an unshielded environment.