Sensitivity variations in Bayard-Alpert gauges caused by Auger emission at the collector

Abstract

Positive ions strike the collector of a BAG at energies of the order of 100 eV where almost all secondary electrons result from Auger electron emission, thus a change in Auger yield causes a change in the apparent gauge sensitivity. The Auger yield is strongly affected by the presence of chemisorbed gas layers on the surface. Experiments are reported that show the change in gauge sensitivity for rare gases caused by the adsorption of CO, O2, N2, or H2 on the collector. At the high pressure used for most absolute gauge calibration the collector may be rapidly cleaned by sputtering, resulting in a different sensitivity than in normal gauge use. Experiments confirm that errors in absolute sensitivity measurements of several percent can result unless care is taken to minimize sputtering of the collector. Investigations of various collector materials to reduce this effect are reported.