Electrical insulation technology for superconducting devices in Japan

The abnormal voltage induced in a superconducting magnet is examined, and the need to utilize insulating materials that do not degrade electrically or mechanically at a very low temperature is demonstrated. Breakdown of the liquid helium in which most superconducting magnets are immersed is discussed. Different types of superconducting magnets are briefly described. Research activities in Japan on electrical insulation technology at cryogenic temperatures and several practical examples of electrical insulation for superconducting devices are reviewed.>