Competition for the development of compact superconducting SR equipment that could be installed in semiconductor factories began during the latter half of the 1980s. Thereafter, 5 SR units were developed, 4 in Japan and 1 in England. These units are easy to operate and are in practical use. This paper describes the compact superconducting SR unit which authors have developed. Also this paper summarizes and compares the 5 compact superconducting SR units which have been developed and describes the main parameters of the superconducting magnets used therein.
The hybrid magnet, which is a large system composed of an inner water-cooled magnet and an outer superconducting magnet, is well known to be the most suitable for generating steady high-magnetic fields. Thirty T-class hybrid magnets are being operated at several high-magnetic field laboratories, The world's highest steady field at present is 35.2T. Projects to enhance the steady fields up to 40-45T are progressing now at the National Research Institute for Metal, Japan, and the National High Magnetic Field Laboratory, USA. In particular, the NRIM project is just now nearing the final stage. In this article, I review in detail the hybrid magnet technology including those of superconducting magnet and water-cooled magnet, the present status of hybrid magnet systems in operation, and the developing projects at NRIM.
Applicability of resistance butt welding to (Nb, Ti)3Sn multifilamentary superconducting wires was studied in both single-and seven-strand conductors, and the dominant factors for the contact resistance of those joints were investigated. Superconducting joint characteristics were partially attained in the case of welding after reaction (react & weld) and that of reaction after welding (weld & react). For react & weld joints, damaging effects on the superconducting filaments in the welding process were dominant, while for weld & react joints the degree of filament-to-filament alignment was found to be the dominant factor. In the seven-strand conductor joint case, the degree of strand-to-strand alignment at the bonding interface was found to become the dominant factor.
Electrical insulation is one of the important factors needed to realize superconducting power apparatuses. Some of the apparatuses have no magnetic field shielding due to the requirement of their construction, where the electrical insulation is exposed to high magnetic fields and/or high mechanical stress as well as cryogenic temperatures. However, electrical characteristics of the composite insulation system of coolant and polymeric film under magnetic field have not been reported even though it is a promising electrical insulation system for superconducting cables. This paper focuses on the effect of magnetic fields on partial discharge breakdown of a composite electrical insulation system of liquid nitrogen and polyethylene film. The experimental results show that the life-time of the film to electrical breakdown becomes shorter as the magnetic field increases up to 1 Tesla. This may be attributed to the change of partial discharge activities caused by the magnetic field.