Low-noise Cryocooler-cooled Compact SQUID-NDE System for Carbon-Fiber Composites
نویسندگان
چکیده
A low-noise and compact SQUID-NDE system cooled by a cryocooler has been developed for practical NDE of carbon-fiber composites. In order to suppress the magnetic noise due to a cryocooler, a planar high-Tc SQUID gradiometer, coaxial pulse tube cryocooler, and SQUID stage separated from the cold head of the cryocooler were introduced. There was no increase of magnetic flux noise due to the cryocooler compared to noise by liquid-nitrogen cooling with the same SQUID. The temperature at the SQUID stage was controlled at 75K±0.05K for several hours by heaters. The field generator with ferrite cores was employed for relatively lower electric conductive composites. Detections of deep-lying hidden slots in stacked carbon-fiber composite specimens were demonstrated to show the effectiveness of the system.
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