Development of High-T c SQUID System for Nondestructive Evaluation |
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Authors: | Hong-sheng Ding Zhong-sheng Jiang Li-jun Lu |
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Affiliation: | (1) Department of Physics, University of Science and Technology Beijing, Beijing, 100083, China |
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Abstract: | Nondestructive evaluation (NDE) system with high spatial resolution power based on high-T c superconducting quantum interference device (SQUID) has been developed. The SQUID is fabricated by YBCO thin film and mounted in vacuum at the end of a cold finger fixed at the inner wall bottom of the dewar, which is filled with liquid nitrogen (77 K) to cool the SQUID sensor. The sensor faces a thin flat sapphire window on the outer wall of the dewar and is thermally isolated from it by a vacuum space at a distance of less than 1 mm. The magnetic field sensitivity of SQUID is about 40 pT/ Hz in magnetically unshielded environment. This NDE system was used to detect the flaws buried into materials. The remnant magnetic field inducted by the local damages in a stainless steel sample was measured. Incorporated a gradiometric double-D excitation coil, the eddy current NDE was carried out. Small cracks in the aluminum below the surface can be detected effectively in unshielded environment. |
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Keywords: | SQUID Magnetic field measurement Eddy current Nondestructive evaluation (NDE) |
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