Buried Collector Gauge for Measurements in the 10−11 Torr Pressure Range

Abstract

A nude ionization gauge is described in which a shielded collector is used to lower the x-ray current. Pressures as low as 4×10−12 Torr have been indicated with an estimated x-ray current corresponding to a pressure below 2.6×10−12 Torr. Calibration of the gauge on an orifice flow-rate system in the pressure range between 10−6 and 10−9 Torr with 4-mA emission and a collector to filament voltage of −300 V, yielded a gauge constant of 20 Torr−1. For pressure below 10−9 Torr the buried collector gauge was compared to the bent-beam Helmer gauge. Data from tests performed on the bent beam Helmer gauge are also given. These include a calibration and a plot of gauge constant as a function of emission current in the range between 0.1 and 10 mA.