Water vapour sorption characteristics of a non-evaporable getter pump

Abstract

Non-evaporable getter pumps are widely used in applications in the uhv range where hydrogen and carbon monoxide are the dominant gases, but they can find equally satisfactory use in poorly baked systems where water vapour is not a negligible part of the residual atmosphere. While literature data generally refer to basic kinetics and mechanisms of water sorption on getter materials, lack of data exist about the overall sorption characteristics of complex structures like a getter cartridge. An experimental system has been set up in which the factors possibly affecting a sorption test for water vapour have been minimized. Water vapour sorption curves have been determined on a NEG pump in a pressure range below 10 −4 mbar and are presented to show pumping speed vs sorbed quantity at different temperatures. A comparison with the sorption curves for other gases (CO, H 2) is also discussed.