NDT of high speed fine particles by high Tc SQUID

Abstract

We detected moving magnetized fine particles with high Tc SQUIDs. The output signals of SQUIDs were investigated with various particle speeds. It was found that the signal decreases less than 20% with an increase of particle speed from 10 to 500 m/min. An iron particle of 50 /spl mu/m diameter could be detected by the SQUID. The high Tc SQUID had a trilayered 15-turn flux transformer. It has a magnetic field resolution of 48 fT Hz/sup -1/2/ at white noise level and a magnetic field capture area of 2.7 mm/sup 2/.