Outgassing measurement of various activated carbon sorbents for application in prototype cryopump

Abstract

The ultimate pressure in any Ultra High Vacuum (UHV) system is related to the magnitude of the gas load; therefore, the measures taken to reduce outgassing are critical for the production of UHV. An OutGassing Measurement System (OGMS) has been established to measure the outgassing rate of different materials to be used in the cryopump in vacuum condition [1]. The outgassing rate measurement in OGMS is based on throughput method and has the base outgassing rate of < 5 x 10-12 mbar-liter/sec-cm2.For standard materials, Outgassing data are available in literature. It is not available for the specific materials in use of particular application. Micro porous activated carbonaceous compounds are the best sorbents and suitable for adsorbing gases to cater the cryopumping [2]. Coconut shell charcoal (of various granular size), activated carbon spheres (ACS), carbon cloth (woven and nonwoven fabric) are some of the examples of sorbents serving the said purpose.This paper shows the results of the Outgassing measurements of various activated charcoal sorbents coated on stainless steel samples having physical dimensions of 10 cm (L) x 5 cm (W) x 0.15 cm (thick) for each sample and the surface area is about 104 cm2.