Process analysis and control flow design of the 1kW @ 4.5K helium refrigerator for NNBI

Abstract A helium cryogenic system with a cooling capacity of 1kW@4.5K was designed in order to support the NNBI(Negative ion based Neutral Beam Injection system) test facility, cryopumping test facility and beam source test facility, which consists of a helium compressor with its storage and recovery system, 1kW@4.5K helium refrigerator, a cryogenic distribution valve box, cryogenic transfer lines and a helium Dewar, etc. Based on the SIMATIC S7-1500H PLC, the cryogenic control system can realize seven major operational modes, including the independent refrigeration mode and independent liquefaction mode, etc. On the basis of process analysis, the control flow of the NNBI helium cryogenic system in each operational modes was designed and will be presented in this paper. It will direct the control system to realize automatic control in multiple operational modes.