Nonevaporable getter investigation at the National Synchrotron Light Source

We report H2, CO, and CO2 pumping speed measurements on a linear pump using NEG strip St 707 (Saes Getters Inc.) as a function of both adsorbed gases and number of activations. To simulate the conditions of an operating storage ring a gas mixture of 50% H2, 35% CO, and 15% CO2 is used in all measurements. Initial measured pumping speeds of ≫450 l m^-1 s^-1 decrease to 200 and 100 l m^-1 s^-1 for H2 and CO, respectively, after 70 air exposures. A further drop to 50 l m^-1 s^-1 for CO occurs at CO loading of 1×10^-2 Torr l m^-1. CO2 and CO pumping speeds are about the same. The photon stimulated desorption for both baked and activated strips is an order of magnitude lower than that for stainless steel.