Electric Discharge Vacuum Gauges

Authored by: Igor Bello

Vacuum and Ultravacuum

Print publication date:  November  2017
Online publication date:  November  2017

Print ISBN: 9781498782043
eBook ISBN: 9781315155364
Adobe ISBN:

10.1201/9781315155364-24

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Abstract

With the assistance of magnetic and strong electric fields, we can induce electrical discharges over a very wide range of pressures from atmosphere down to UHV. The induced electrical current depends on the ionization processes that are related to the reduced electric field, geometrical electrode configuration, magnetic field, molecular density, and thus pressure. The reduced electric field is the ratio of electric field and pressure (E/p). The electric current is the result of ionization processes in sufficiently high electric fields. The electric current is constituted by ionized particles and electrons drifting to corresponding electrodes. At a smaller electric field, electric discharge can be triggered and maintained only with auxiliary agents such as thermionic electrons, alpha particles, energetic photons, or gamma radiation. Since there is a proportionality between the electric current and pressure, the magnitude of electric current is the measure of pressure. However, along the ionization and excitation processes, there are also recombination processes and some of them can be radiative. The rate of excitation and recombination is again related to the molecular density and pressure. Thus, it is anticipated that the intensity of radiation from electric discharges is related to pressure as well.

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