Plots of gauge constant vs pressure for analyzing cold-cathode gauge calibration data

Abstract

Gauge current vs pressure calibrations of inverted magnetron cold-cathode ionization gauges were made over the pressure range 10 −10 to 10 −4 torr. For pressures greater than 10 −6 torr a spinning rotor gauge (SRG) was used as the pressure reference. At lower pressures the reference was an extractor gauge which had been calibrated against the SRG in the overlap region. In addition to the usual log-log plots of current vs pressure used to fit the cold-cathode gauge equation I ga = K' P rmn , it was found useful to make plots of the gauge constant, K', vs P. Such plots are more sensitive to scatter in the data due to poor measurement techniques or to discontinuities in the gauge characteristic curve. Examples of K' vs P plots are given for two inverted magnetron cold-cathode gauges. The value of K' for two grouped nitrogen calibrations of a prototype gauge with a 2.2 kG magnetic field was constant within ±4.5% from 10 −8 to 10 −4 torr.