Ma. Espy et al., Design and preliminary results from a high temperature superconducting SQUID milliscope used for non-destructive evaluation, IEEE APPL S, 9(2), 1999, pp. 3692-3695
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.