Cryosorption Pumping of Hydrogen at 20 °K II. Development and Performance of Cryosorption Panels Available to Purchase

The development of cryosorption panels consisting of Molecular Sieve adsorbents bonded to refrigerated aluminum plates is described. The sticking coefficient of hydrogen on a cryosorption panel refrigerated with liquid hydrogen was found to be 0.16 in the high-vacuum range, corresponding to a pumping speed of $6600 liter/sec per ft2$ of panel. A higher sticking coefficient, near unity, can be obtained with a more efficient shielding of the adsorbent surface against thermal radiation. The pumping speed decreases markedly when the surface is contaminated with more condensable gases, such as nitrogen. Therefore, the cryosorption panels must also be shielded from condensable contaminants. The panels can be mounted directly inside vacuum chambers, and can be scaled up without difficulty.