Design and preliminary results from a high temperature superconducting SQUID milliscope used for non-destructive evaluation

We present the design and preliminary results from a SQUID 'milliscope'. Th e device was designed for non-destructive evaluation (NDE) as part of the E nhanced Surveillance Program at Los Alamos National Laboratory. A high temp erature superconducting (HTS) SQUID sensor is used to map magnetic fields i nduced in the sample. Eddy currents are induced in the conducting sample by a wire coil designed to produce minimal magnetic field at the SQUID when n o sample is present. The features of interest are characterized by anomalie s in the induced magnetic field. The goal of the instrument is sensitivity to small features generally buried under several intervening layers (simila r to 1-20 mm) of conducting and/or non-conducting materials and robustness of design (i.e. the ability to operate in a noisy, unshielded environment). The device has primarily focussed on specific NDE problems such as the abi lity to detect buried "seams" in conducting materials and quantify the widt h of these seams. We present the design of the instrument, and some data to demonstrate its capabilities.