Pumping Performance Of Cryoadsorption At Interzone Temperature Of Liquid Helium

Neutral beam injector (NBI) is an equipment that is used to inject high energetic particle beam into the fusion device and heat plasma availably. The research of injecting neutral particle beam is always an important issue in the fusion research. As the improvement of beam power, the vacuum system need to provide104-106L/s of the hydrogen pump capacity. The performance of the vacuum system of Neutral beam injector relates to the merits of the high and low beam transmission efficiency and affects the life and the use of safety of other internal components in the entire bundle. Based on the theory of cryoadsorption and the research of characteristics of cyrocondensation in the interzone temperature of liquid helium, the characteristics of cryoadsorption pumping were studied. The method of adding activate carbon was proposed and the high and stable capacity of pumping to hydrogen and its isotope gas was enhanced. The requirements of NBI's steady run of can be achieved.Analysis of the structure and properties of various adsorbents were researched. Based on the method of BET and mode of HK aperture analysis, the characteristics of four active carbons were tested. The C2 active carbon had the surface area of 837.17cm2/g, the pore volume of 0.4396 cm3/g and the pore size distribution less than 7.63 angstrom which was more than 80% by numerical methods and data fitting.According to the system of NBI cryoadsorption, it needed high and stable capacity of pumping at 10-3Pa magnitude. The experiment of cryoadsorption of C2 active carbon in the interzone temperature of liquid helium was carried out by using the developed testing system. The affections of background gas, flow size of input gas, adsorbate gas to the capability of cryoadsorption were analyzed. The data was processed and calculated, the result displayed that the system of cryoadsorption pumping which surface was bonded by C2 activated carbon had the pumping speed of 4.5L/s·cm2 to hydrogen at 10-3Pa magnitude. The requirements of pumping speed of NBI at steady state can be achieved at stable vacuum pressure and the desired research objective was reached. It provided a theoretical basis for further research about the cryoadsorption in the interzone temperature of liquid helium and designing and developing a cryopump used in NBI.