A low-noise and compact SQUID-NDE system cooled by acryocooler has been developed for practical NDE of carbon-fibercomposites. In order to suppress the magnetic noise due to a cryocooler, aplanar high-Tc SQUID gradiometer, coaxial pulse tube cryocooler, andSQUID stage separated from the cold head of the cryocooler wereintroduced. There was no increase of magnetic flux noise due to thecryocooler compared to noise by liquid-nitrogen cooling with the sameSQUID. The temperature at the SQUID stage was controlled at 75K±0.05Kfor several hours by heaters. The field generator with ferrite cores wasemployed for relatively lower electric conductive composites. Detectionsof deep-lying hidden slots in stacked carbon-fiber composite specimenswere demonstrated to show the effectiveness of the system.
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