100 T magnet developed in Osaka

Abstract

A non-destructive pulsed magnet for 100 T has been developed to carry out precise magnetic measurements at extremely low temperatures and under high pressures. Our record magnet has generated 80.3 T in a 10 mm bore with 7 ms pulse duration and then is called a 80 T magnet. The 80 T magnet consists of inner and outer coils, both of these are made by winding with Cu–Ag wire and reinforced by maraging steel. The inner coil is a single-layer coil backed up with a thin maraging pipe and the outer coil is made with nine layers reinforced by a thick maraging ring. Magnetization and magnetoresistance measurements at 1.3 K have been carried out up to 70 T in the 80 T magnet. The outer coil of the 80 T magnet has an 18 mm bore and can generate 71.3 T as a record and then is called a 70 T magnet. The 18 mm bore of the 70 T magnet is a useful space for introducing an extremely low temperature into high magnetic field; this was used to carry out both magnetization and magnetoresistance measurements at 80 mK up to 60 T. We have examined the lifetime of the 70 T magnet at various maximum fields in ordinary use. The results show that about 100 shots can be made with 60 T and 500 shots at 55 T. We have developed another 70 T magnet with longer pulse duration of about 20 ms for magnetization measurements under high pressure up to 10 kbar. The 70 T magnet for high-pressure experiments has an 18 mm bore and an inductance of about 3 mH. The magnet consists of an inner five-layer coil backed up with a thick maraging steel pipe and the outer has 11 layers and a maraging ring. As the pressure cell used for the measurement is made of Be–Cu, a longer pulse is necessary to allow penetration of the pulsed field into the cell. Magnetization measurements under high pressure have been carried out successfully up to 55 T although the pulse duration is not long enough to keep the temperatures very low. A new pulsed magnet with higher field and longer pulse duration is proposed.