Trapped field of YBCO single-domain samples using pulse magnetization from 77K to 20K

Abstract

ReBCO single-domain bulk superconductors have been shown to trap significant magnetic field at 77K and below. They can advantageously replace permanent magnets in cryogenic motors; more power in a smaller volume can be achieved. But practically, their magnetization has to be performed in situ. Usually it implies the use of pulse magnetization which is severe for the samples. This technique generates heat and stress on the superconductors. The magnetic-flux-trapping capabilities of YBCO single-domain samples were explored using the pulse-field facilities at the LNCMP (National Pulsed Magnetic Field Laboratory) at Toulouse, France. The flux dynamic was monitored during magnetic pulses by measuring the surface induction with a Hall probe on top of the samples at different temperatures from 77K to 20K. The samples were 16 mm in diameter and about 10 mm in height. The best one trapped 400 mT at 77K and 2.5T at 20K. The trapped field increases almost linearly down to 40K. The magnetic pulse is seen to generate heat. The temperature rise increases with decreasing temperature dwell because of lower heat capacity. The achieved trapped field is a compromise between the temperature rise and the applied field, and depends greatly of the magnetization history. © 2008 IOP Publishing Ltd.