Development of supercritical helium circulation system for cooling tests of superconducting magnet

IHI has manufactured a supercritical helium (SHe) circulation system for National Institute for Fusion Science. The system will be used for cooling and charging tests of the superconducting poloidal coil of the Large Helical Device (LHD) that is now under construction. The SHe circulation system is the forced-flow cooling type to maintain the magnet in the superconducting state at a temperature of 4.5 K. The system consists of a SHe cryogenic circulation pump, a liquid helium tank, and a heat exchanger which are contained in a vacuum vessel with a liquid nitrogen thermal shield. This system features compactness, wide operation range, and easy thermal control using a plate-fin heat exchanger and efficient centrifugal pump, as compared with the conventional system. (author)