A high-T_cSQUID micro-detector with a high performance magnetic shield for contaminant detection in industrial products

Abstract

A high-Tc superconducting quantum interference device (SQUID) system for the detection of magnetic foreign matter in industrial products was developed. There is a possibility that ultra-small metallic foreign matter has been accidentally mixed with industrial products such as lithium ion batteries. Metallic particles with outer dimensions less than 100 µm cannot be detected by conventional x-ray imaging. Therefore we developed a detection system based on a high-Tc SQUID microscope with a high performance magnetic shield. The use of SQUID microscopes with a 0.5 mm thick vacuum window was proposed. This design enables the SQUID to approach the object to be measured as close as 1 mm and enhances the sensitivity. A new magnetic shield with sleeves was carefully designed and built. As a result, we could successfully measure small particles sized 100 µm. This detection level was hard to achieve using a conventional x-ray detection method.

Prototype of Multi-Channel High-Tc SQUID Metallic Contaminant Detector for Large Sized Packaged Food

“…Thus, if the SNR of 4.0 at a maximum point can be realized, the SNR more than 3.0 can be obtained in the range of 300 mm width. The magnetic shield covering the sensors is a crucial part of the system for practical use [7]. A three-layer structure was used with the following dimensions of the outer shield: (W × D × H) 862 mm × 729 mm × 972 mm.…”

Vector sensor for scanning SQUID microscopy

“…It was invented by Jaklevic et al of Ford Research Labs [1] after theoretical prediction of the effect in 1962 by Josephson [2]. The SQUID devices are useful in various fields such as magnetics, electronics, biology, spintronics, security analysis, agriculture, information technology, communication, material science, and physics [3][4][5][6][7][8][9]. In those applications, the DC SQUID is very sensitive to the magnetic field because it utilizes an interference effect of two JJs [10,11].…”

Metallic contaminant detection system using multi-channel high Tc SQUIDs

“…Some SQUID detection systems for detecting contaminants in food have been developed [1][2][3][4]. One of these systems is commonly available now [5]. However, in most cases, the matrix of industrial products is magnetized, and the magnetic signal from the matrix is sometimes sufficiently large to mask the signals from the contaminants.…”