Pumping Characteristics of Zr-V-Fe Nonevaporable Getter in Mixture of H sub 2 and Carbon Monoxide Gases

The effect of impure gases on the vacuum performance of a Zr-V-Fe nonevaporable getter (NEG) module were investigated using a gas mixture composed of 80% H sub 2 and 20% carbon monoxide to simulate a practical vacuum environment. Pumping speeds for H sub 2 and CO in the mixture were measured simultaneously and continuously with two quadrupole mass analyzers in a standard test dome. The pumping speed for H sub 2 was strongly influenced by CO molecules absorbed on the surface of the NEG, while that of CO was nearly independent of H sub 2 absorbed in the NEG. The H sub 2 pumping speed in the mixture with CO with changed very steeply, similarly to that of CO. It is expected that the results of the mixed gas experiment will be utilized to devise a proper operation schedules of the NEG pumps installed in the SPring-8 storage ring.