Pressure measurement#Ionization gauge

An ionization gauge is a pressure gauge for pressure determination in high and ultra high vacuum range, ie up to about mbar. The principle is based on an indirect pressure measurement by means of electrical quantities, which are proportional to the residual gas particles with the particle number density. For this purpose, the residual gas must be ionized, for which there are different implementation options:

  • Cold cathode ionization gauge
  • Thermionic ionization

Cold cathode ionization gauge

Between the anode and the cathode is connected to a DC voltage of about 2 kV. Existing electrons are accelerated in this field and ionize residual gas by impact ionization. It forms a pressure-dependent discharge current is measured. Mbar above the ion current changes into a glow discharge, which is independent of the pressure ( upper range limit ).

End date ions remain either adhere to the cathode and are neutralized there, or they beat out material ( cathode ). The material is deposited on the walls of the measuring rooms. Through this process, the cathode is consumed slowly and is therefore usually designed interchangeable.

On the Restgasionisation by cold cathode based on:

  • Penning vacuum meter
  • Magnetron systems

Thermionic ionization

This system is based on the emission of electrons from a heated cathode material. Between the hot cathode and the anode, a voltage (), which accelerates the emitted electrons (). These electrons can (with ionization ) ionize the residual gas from the condition. The positively charged gas ions are attracted to a further cathode whose potential is more negative than that of the thermionic cathode. Neutralization of ions results in a measurable (electron ) current, which is based on the ion current and, therefore, dependent on the particle density in the residual gas.

On the Restgasionisation means of thermionic cathodes are based:

  • Bayard -Alpert vacuum gauge
  • Extractor ionization gauge
  • Orbitron system with extra long electron paths
  • Magnetron vacuum gauge etc.
Ionization energy
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