Superconducting Magnet Producing a Cusp Type Magnetic Field for High Temperature Plasma Trapping

The equipment producing a cusp type magnetic field, which is used to trap high temperature plasma, by a pair of superconducting magnets, was constructed. The working space of a cusp field is 20mm between the two magnets and 10mm in the inner diameter of each magnet. The rated magnetic field at the center of each coil is 40kG. The maximum tested field is 55kG. Each superconducting coil is sealed in a liquid helium vessel, to which liquid helium is supplied from a liquid helium supplying vessel. The capacity of the liquid helium supplying vessel is about 5l, and the average helium loss is about 1.8l/h at 40kG of the field strength.