Residual currents in several commercial ultrahigh vacuum Bayard–Alpert gauges

Abstract

Residual currents have been determined for several commercial UHV Bayard–Alpert gauges, including two modulated gauges, by comparison against an extractor gauge. Residual currents in the modulated gauges were also determined by the modulation method (Redhead mode I) and these results are compared with those of the first method. Residual current modulation factors were estimated by combining the results of these two methods. A significant residual current modulation factor (1.33) was found for one of the modulated Bayard–Alpert gauges. One notable aspect of this work is the finding that residual current values can differ by more than a factor of 10 among nominally identical gauges. Another interesting and somewhat surprising feature of these measurements, which were performed in H2 at pressures in the range 4×10−9 to 4×10−5 Pa, is that no hysteresis was detected in the gauges’ response to large, rapid decreases in the H2 pressure.