High Pressure Ionization Gauge for Calibration in the 10-7 to 10-1 Torr Range

Abstract

A new concept in high pressure gauge (JHP) has been studied for use as a reference-transfer of an absolute interferometric differential manometer (MDI). Electron current I- of the JHP is divided into three components, one of which is regulated to maintain the linearity from 2.10-7 to 7.10-2 Torr for I-=5.10-5 A. The small value of the residual current, mainly due to electron impact desorption, is achieved by shielding the ion collector from the electron impact surface. JHP calibration has been made by the adjustable conductance method used with a monitor gauge acting as an additional control. Sensitivity for argon is ≃3.3/Torr with an experimental accuracy Eexp of ±2% and a reference pressure error (MDI) of ±1.5%. Absolute calibration for various gases leads to determination of the sensitivity ratios taking argon as reference: 0.82 for N2, 0.36 for H2 and 0.16 for He. These values are compared to the yields deduced from the classical values of total ionization cross-sections. Using the same calibration system for BA gauges, the JHP allows one to determine sensitivity with an Eexp of 2% and also to check their linearity, the upper limit of which is accurately measured.