Advances in the First Cryogen-Free Hybrid Magnet

Abstract

In order to solve problems of a large amount of liquid helium supply for a wide bore superconducting magnet of a hybrid magnet, we intended to construct the first cryogen-free 23 T hybrid magnet, consisting of an outer wide bore cryogen-free superconducting magnet and an inner water-cooled resistive magnet. Up to now, the wide bore cryogen-free superconducting magnet was tested to generate a total central field 6.0 T in a 360 mm room temperature bore. The world's first cryogen-free hybrid magnet achieved 21.5 T in a 52 mm room temperature bore, combining with 15.5 T water-cooled Bitter magnet. As the result, the cryogen-free hybrid magnet no longer needs a troublesome handling time for liquid helium transfer, and the machine time is extremely enlarged. The improvement of the maximum magnetic field generation toward our design value of 23 T is being carried out continuously. Furthermore, we have started a new construction project of a cryogen-free 30 T hybrid magnet. Since the magnetic force field BdB/dz of 2274 T/sup 2//m is obtained at 21.5 T, the cryogen-free hybrid magnet can provide a large magnetic force field enough to levitate diamagnetic materials. For new processing of materials development, a YAG laser furnace was installed into the cryogen-free 23 T hybrid magnet. A container-less melting for paraffin was examined by controlling a thermocapillary convection. We succeeded in fabricating a magnetic field oriented ball in magnetic levitation.