Determination of critical parameters in the EAST subcooled helium system

The cryogenic system at the Experimental Advanced Superconducting Tokamak (EAST) is designed for a capacity of 1050 W/3.5 K + 200 W/4.5 K + 13 g/s liquid helium+ 13 kW/80 K. The 3.5 K subcooled helium is obtained from an oil ring pump. The cryogenic system is now being upgraded with a centrifugal cold compressor that should reduce the helium-tank pressure and temperature. This article discusses the determination of critical parameters for the cold compressor, including the efficiency of heat exchange, the location of the thermal anchor, and the length of the tip clearance between the impeller and shroud. Developing the centrifugal cold compressor is a significant aspect of the EAST cryogenic system upgrades, and the preliminary tests reported herein demonstrate the promise of the retrofit project.