Magnetic field generator, a persistent current switch assembly for such a magnetic field generator, and the method of controlling such magnetic field generator

摘要

A magnetic field generator has a superconductive coil immersed in a coolant material. When power is supplied to the superconductive coil from a suitable power source, the superconductive coil is energized to generate the magnetic field. The ends of the superconductive coil may then be shorted through a persistent current switch, to maintain the magnetic field without the need for further power. The persistent current switch has a superconductive connection connected across the ends of the superconductive coil and a heater. These components are enclosed in a casing with a gap between these components and the casing. Apertures in the casing permit coolant material to enter the gap. When the heater is energized, it heats the coolant material in the gap until it vaporizes. There is then a significant decrease in the thermal conductivity through the gap and hence the superconductive connection is heated rapidly to its critical temperature. Only low power is needed. When the heater stops being energized, liquid coolant material fills the gap thereby rapidly cooling the superconductive connector to below its critical temperature.