Cryosorption Pumping of Helium at 4.2 °K Available to Purchase

The cryosorption pumping of helium gas by means of Molecular Sieve 5A cryosorption panels has been studied at 4.2 °K and in the pressure range from $10−7$ to $10−8$ Torr. The sticking coefficient of the gas was found to vary from about 0.70 to 0.91 at these pressures, respectively, corresponding to the high pumping speeds of 20000 to 27000 $liter/sec/ft2$ of panel. The absorptive capacity for helium was also high down to $10−8$ Torr, but the pumping speed decreased with increasing surface coverage. It is concluded that helium can be pumped effectively in the high-vacuum region with cryosorption panels refrigerated to 4.2 °K.