A demountable electron tube for high-vacuum applications : A. Matthewson, Vacuum, 13 (10), Oct. 1963, 425

Abstract

The advantages of cryopumping, e.g. high pumping speed, flexibility, cleanliness and wide pressure range of operation, have long been recognised. Nevertheless, industrial application of this method has been rejected so far. This paper describes the vacuum performance of a cryopump equipped with a recently introduced cryogenerator. The machine offers a cold production of approximately 50 W at 80 K and 10 W at 20 K simultaneously, thus eliminating the need for a liquid helium and (or) nitrogen supply. Data presented show that industrial applications of cryopumping at 20 K impose special requirements on the design of the cryopanels and the cold capacity of the cryogenerator. It is shown that a 10 W cold capacity will offer long term operation of the pump, particularly in industrial thin film coaters, if (a) hydrogen gas is distributed uniformly over an adsorbent glued on a 20 K panel, (b) the grain size of the adsorbent is about one millimetre, and (c) contamination of the adsorbent by gases more easily condensable than hydrogen is avoided.