Modified cryogenic diffusion pump

摘要

A pumping device is provided which is suitable for pumping mixtures of gases at cryogenic temperatures which is a combination of a cryogenic diffusion pump and a thermal gradient barrier diffusion pump. Specifically the pumping device comprises an elongate body (1) of material capable of withstanding cryogenic temperatures and of sustaining an axial temperature gradient in use, said body having an inlet for the gas mixture and an outlet (3) for one or more gases to be pumped wherein the outlet is fitted with a porous barrier (4) through which gases must pass to exit the device, said porous body having a heating means (5) disposed at its outlet side. The pumping device is designed for use in pumping waste gas mixtures from a fusion reactor containing helium. In such a use the outer surfaces of the body (1) and the outlet tube (3) are cooled to a temperature which causes hydrogen isotopes and impurities thereon, allowing pumping of the helium alone.