Development and Application of Cryosorption Pumping of Hydrogen at 20 K by Molecular Sieve Adsorbent Panels

Abstract

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Cryosorption

“…As a consequence of these factors, from consideration of Oatley's (12) treatment of conductance through baffles in series, the parameter 9 for cryopumping can be defined by: 1 r 1 1 111 »-U + s + --'id + «--" (12) As mentioned above, auxiliary pumping techniques are necessary to supplement cryopumping for ultrahigh vacuum service and diffusion and/or ion pumps have been successfully used for this function. Recent work (2,5,8) with cryosorption pumping of hydrogen and helium has demonstrated the practicability of this mechanism as an alternate to diffusion or ion pumping for ultrahigh vacuum service.…”

“…In addition, the ultimate pressure, Pm can be reduced to very low levels by proper sizing of the adsorbent mass, since Pu is defined by the equilibrium loading-of the panel. For dynamic cryosorption pumping, the effective equilibrium loading will be less than the capacity determined from an isotherm since diffusion through the panel bed is rate limiting (5).…”

“…Recently, effort (2,5,(7)(8)(9)(10)(11)13) has been directed toward development of cryogenic pumping techniques to evacuate the noncondensable species, with particular interest expressed in the mechanisms of cryotrapping and cryosorption. Results with the latter approach have been most promising (2,5,8).…”