Construction Report of 10 kW Class Helium Refrigerator for LHD

Publisher Summary The Large Helical Device (LHD) is a heliotron fusion experimental device in which magnetic fields are controlled exclusively by superconducting magnets: a pair of helical coils and three pairs of poloidal coils. A 10 kW class helium refrigerator has been constructed for LHD at National Institute for Fusion Science. During the last twelve months between 1995 and 1996, the refrigerator has been put to the training operations without connecting to any of the superconducting magnets of LHD. As one of its series report, this chapter reviews the paper on significant events and major observations experienced during that period and makes a brief discussion about several interesting topics on preliminary base. The observations revealed that there are two insufficient control system designs that forced the operator to pull the shut-down button. One is the external intervention to the engineering workstation through the integrated services digital network (ISDN) line between the manufacturer and the operator. The other is due to the insufficient computer program proof inspection before loading on the VME.