Cesium gettering by graphite-improvement in the gettering efficiency

摘要

Results of experimental investigations of the cesium (Cs) gettering properties of graphite at various temperatures are reported. Possible reasons for this behavior are discussed. A model based on the grain boundary and surface diffusion of Cs in graphite is used to explain the results. Using this model, the activation energy for surface/grain boundary diffusion of Cs into polycrystalline graphite is estimated to be approximately 14 kcal/mole. The initial motivation was to examine the performance of graphite getters used in the cesium beam tube frequency standards. New results are presented regarding the dramatic improvement in the Cs gettering efficiency of graphite when heated to and maintained at elevated temperatures (100-130 degrees C) over the room-temperature efficiency.