Dynamic simulation of the helium refrigerator for LHD

A dynamic simulation model of a helium refrigerator has been developed. This model was applied to the first cool-down of superconducting magnets of LHD( Large Helical Device) at NIFS. During the cool-down several switch-over operations are needed and in order to conduct effective and efficient cool-down with satisfying limitations, the dynamic behavior of the helium refrigerator must be studied and confirmed in advance by the dynamic simulation. This paper describes the outline of the model and shows the comparison between the calculation results and the actual operation data at the first cool-down from February to June in 1998.