| Neutral beam injection (NBI) heating is one of the main auxiliary heating methods in controllable nuclear fusion experiment. Stabilizing vacuum of NBI system quickly is the key issue that many countries are concerning and researching actively. The working principle of liquid helium cryocondensation pump is strong absorptive force between 4.2K cryogenic surface and gas molecules. The pump has great advantage in large instant pumping speed under high gas load, large working pressure range, high & neat ultimate vacuum. It can meet the requirements of NBI for vacuum.The fundament of NBI system used on the HT-7 device of ASIPP and its requirement for vacuum is introduced in the thesis. Studies on the determining of the performance of 4.0 l05L/S(for H2) liquid helium cryocondensation pump are developed in detail. The principle of physical absorption is analyzed. The design of liquid helium cryocondensation pump, heat and mass transfer, performance testing are also researched.The paper mainly consider the followings: the performance parameter determination of cryopump, heat load determination and heat transfer of large cryopanel, reasonable distribution of heat load, the condition for construct steady flow in small vertical circle pipeline, balance condition for gas and liquid two-phase flow in the connection pipe between cryopanel and dewar, the safety of cryopump. The key performance parameters are gotten through treating and analyzing the data getting from the cryopump cool-down test.To research in the area of liquid helium cryopump used in NBI system is meaningful for obtaining better beam transportation efficiency. Physical parameters and experience are obtained that are very useful in developing cryopumps. The primary experiment shows that the prospective objects of the design are obtained.
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