A cryostat coupled with helium refrigerator has been constructed and tested in order to establish an on-board refrigeration system of superconducting magnets for magnetically levitated high speed trains.
The cryostat (1975mm in length×745mm in hight×185mm in width, and 320kg in weight) is composed of a liquid helium vessel in which a coil and a liquid helium condenser are mounted, two layers of radiation shields and an outer vessel.
A modified Sumitomo's 4l/h helium liquefier is used as a refrigerator which provides its helium coolant to two radiation shields and to the liquid helium condenser, simultaneously.
The helium mist coolant in the condenser suppresses an increase of gas phase pressure inside the liquid helium vessel. This clearly indicates the condensation of evaporated helium gas in the vessel.
All the system showed smooth, stable operation throughout the experiments. A series of tests provide us useful design data for the on-board refrigeration system.
