Influence of envelope geometry on the sensitivity of ''nude'' ionization gauges

This article presents the results of some measurements of the influence of envelope size and shape on the N-2 sensitivity of two nominally identical ''nude'' extractor ionization gauges, and three common ''nude'' versions of the Bayard-Alpert ionization gauge. Measurements were made over the pressure range 10(-7)-10(-1) Pa, using typical gauge operating parameters and with vacuum chamber and gauge envelope at ground potential. Sensitivity values corresponding to the three different envelopes used in this work differed by as much as a factor of 2 (comparing maximum value to minimum value for each gauge) for the Bayard-Alpert gauges. For the extractor gauges, the differences were as large as 7%.