Residual currents detected with a correcting electrode in a modified Bayard–Alpert hot-cathode-ionization gauge

Abstract

A nude-type hot-cathode-ionization-gauge head with correcting electrode and shield tube, succeeded in reducing practical pressure-measurement errors caused by an influx of photoelectrons in a synchrotron radiation environment. In the development of this modified Bayard-Alpert hot-cathode-ionization gauge, experimental results showed that a basic ion current generated around the correcting electrode by emission from the gauge filament, was proportional to an emission current (less than 10% of the normal emission current) detected with a grid of correcting electrode, and that differences between estimated and measured basic ion currents in a pressure range of higher than 10(-8) Pa order meant pressure-independent residual currents detected with the correcting electrode. By using calculated forward x-ray currents, these results also showed that the estimated residual currents with the correcting electrode were mainly caused by x rays from the grid of the hot-cathode-ionization-gauge head and the grid of correcting electrode, and that the x-ray currents with the correcting electrode only caused by x rays from the grid of the hot-cathode-ionization-gauge head were about 11% of the nominal x-ray current of the ionization-gauge head. Furthermore, they may suggest that an expected residual current with the collector can be calculated by using the estimated residual current with the correcting electrode, and that this ionization gauge has an additional function to reduce pressure-measurement errors caused by residual currents, though it is necessary to test the ionization gauge in an extremely high-vacuum environment under the x-ray limit of the gauge.

Precise method of compensating radiation-induced errors in a hot-cathode-ionization gauge with correcting electrode

“…3(a), the pressure from the BA-S4 was about 30 % higher than the reference pressure from the NIG-2F, due to degassing from the inner surface of the sleeve in Ref. 10. As the result, electrons from the externalelectron source scarcely flowed into the BA-S4, because the sleeve prevented the electrons from flowing into the vacuum-gauge head, different from the strong reflected light of the synchrotron radiation environment.…”

“…10, CE is the proportionality constant for radiation-induced current between the correcting electrode cable and its reference cable, I CErr (A) is the detected current in the reference cable, C is the proportionality constant for radiation-induced current between the collector cable and its reference cable, and I Crr (A) is the detected current in the reference cable, S CE (1/Pa) is the sensitivity of the correcting electrode, shown in Ref. 5.…”

“…But it has a performance to reduce x-ray currents shown in Ref. 10. We would like to test the removal performance in an extremely high-vacuum environment less than 10 -9 Pa under an x-ray limit of the vacuum gauge.…”

Thermionic Emitters

“…14.7, measurements of the current due to externally-produced electrons are made at the correcting electrode in an auxilliary gauge which does not contain a thermionic emitter filament, and these measurements, applied to the current measurement from the normal gauge, can be used to make corrections to the measured ion current and calculated pressure. The details of this are dealt with in a recent paper [28], and background information will be found in earlier papers [29][30][31][32][33][34][35]. Figure 14.7 shows the side view of the gauge design and its logic.…”

A Cylindrical Triode Ultrahigh Vacuum Ionization Gauge with a Carbon Nanotube Cathode

“…In recent years, ultrahigh and extremely high vacuum pressure measurements have become widely demanded in many science and engineering fields [ 1 , 2 , 3 ], including space exploration, surface science, particle accelerator, storage ring, etc. To date, hot cathode and cold cathode ionization gauges are the only practically available electronic vacuum sensors in this pressure region [ 4 , 5 ].…”