Investigation of nitrogen and helium cryosorption on molecular sieves

Abstract The helium-containing plasma exhaust gases of Tokamaks can be pumped by cryopumps using cryosorption panels coated with solid porous materials. The best pumping characteristics are achieved with activated charcoal and molecular sieves at temperatures below 10 K. In order to select the most suitable material with respect to cryosorption properties and reactivation behaviour, comparative tests on various molecular sieve types differing in cavity structure, pore size and polarity were carried out. Nitrogen and helium adsorption isotherms were determined at LN 2 temperature and at 14.5 K, respectively, expecting that an extrapolation mechanism between the adsorption properties of both …