High Tc SQUID Detector for Magnetic Metallic Particles in Products

Saburo TANAKA  Tomonori AKAI  Yoshimi HATSUKADE  Shuichi SUZUKI 

Publication
IEICE TRANSACTIONS on Electronics  Vol.E92-C  No.3  pp.323-326
Publication Date: 2009/03/01
Online ISSN: 1745-1353
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Superconducting Analog Devices and Their Applications)
Category: INVITED
Keyword: 
SQUID,  superconductor,  detection,  inspection,  metallic contaminant, 

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Summary: 
High-Tc superconducting quantum interference device (SQUID) is an ultra-sensitive magnetic sensor. After the discovery of the high-Tc superconducting materials, the performance of the high-Tc SQUID has been improved and stabilized. One strong candidate for application is a detection system of magnetic foreign matters in industrial products. There is a possibility that ultra-small metallic foreign matter has been accidentally mixed with industrial products such as lithium ion batteries. If this happens, the manufacturer of the product suffers a great loss recalling products. The outer dimension of metallic particles less than 100 micron cannot be detected using X-ray imaging, which is commonly used for the inspection. Therefore a highly sensitive system for small foreign matters is required. We developed detection systems based on high-Tc SQUID for industrial products. We could successfully detect small iron particles of less than 50 micron on a belt conveyer. These detection levels were hard to be achieved using conventional X-ray detection or other methods.