CALCULATION OF CAPTURE COEFFICIENTS FOR A CYLINDRICAL CRYOPUMP

Abstract

A new efficient method has been developed for calculating the pumping efficiency of a cryopump for different types of gases, which uses the geometric view factors between the surface elements of a cryopump. This method is as accurate as the Monte Carlo method, but much faster and more efficient when a systematic change in the system parameters is investigated. The method is applied for investigating the effect of cryopanel geometry on the pumping characteristics of cryopump arrays for different types of gases. One major result from such calculation is that the diameter of the cryopanel should be about 0.6 times that of the pumpbody diameter in order to give maximum pumping of He and H2 by the cryosorption element attached on the reverse side of the panel.