On The Character Of Large Cryocondensation Pump For Neutral Beam Injector

Liquid helium cryopump is based on the principle of strong adhesive force between condensation surface and gas molecules. Liquid helium cryocondensation pump has great advantages in large pumping speed, working pressure range and high ultimate pressure, etc. It's more excellent than any other vacuum pump. It can meet the vacuum requirement of NBI and can improve the transportation efficiency. The development of Neutral Beam Injection (NBI) system in the world, the structure of NBI system used on the HT-7 device of ASIPP was introduced in the thesis. The theoretical analysis of large cryocondensation pump for NBI was mainly concerned. This paper emphasized on analyzing and calculating the heat load of cryocondensation pump, simulating thermal transmission coefficient and molecule transmission coefficient of radiation baffle according to Monte Carlo method, analyzing the process on cryo-surface and the factor of affecting pumping speed and hydrogen layer thickness of influencing cryo-parameter,etc. Finally by verifying the pumping speed on large cryocondensation pump for Neutral Beam Injection system, the pumping speed of 4.0x105L/S (for H2) was proven to be reasonable.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 were obtained which is very useful in developing even larger cryopump.