Detection of fine iron particles in high speed scrolled wire by high-T-c SQUID

High-T-c SQUID was applied to the detection of magnetized fine particle moving at high speed. Two types of SQUIDs were used. One was a large washer type and the other was a flux transformer type. Their Josephson junctions were step edge type. The iron particle was attached on a nylon wire and scanned under the SQUID. High-T-c SQUID detected an iron particle of 50 mu m diameter running at 800 m/min. It was shown that the magnetic field measured by the SQUID was proportional to the volumer of the particle and is inversely proportional to the distance between the SQUID and the particle. This technique using high-T-c SQUID is hopeful not only to wire production line but also for the processing of food and medicine, etc.