Ionization vacuum gauges

Penning vacuum gauge probe open

An ionization vacuum gauge is a pressure measuring device for determining pressure in the high and ultra-high vacuum region , so as to mbar. The principle is based on an indirect pressure measurement using electrical quantities that are proportional to the residual gas particles with the particle number density. For this, the residual gas must be ionized, for which there are different implementation options: ${\displaystyle 10^{-3}}$ ${\displaystyle 10^{-12}}$

• Cold cathode ionization vacuum gauges
• Hot cathode ionization vacuum gauges

Cold cathode ionization vacuum gauges

A DC voltage of around 2 kV is applied between the anode and cathode . Existing electrons are accelerated in this field and ionize residual gas particles through impact ionization . A pressure-dependent discharge current is formed which is measured. Above mbar, the ion current changes into a glow discharge that is independent of pressure (upper measuring range limit). ${\displaystyle 10^{-2}}$

Ions that impact either stick to the cathode and are neutralized there, or they knock out material (cathode sputtering). The material is deposited on the walls of the measuring rooms. This process slowly consumes the cathode and is therefore usually designed to be replaceable.

Based on residual gas ionization using cold cathodes:

• Penning vacuum gauges
• Magnetron systems

Hot cathode ionization vacuum gauges

Bayard-Alpert hot cathode

This system is based on the emission of electrons from the heated cathode material. A voltage ( ) is applied between the hot cathode and the anode , which accelerates the emitted electrons ( ). These electrons can ionize the residual gas particles under the condition (where ionization energy ). The positively charged gas ions are attracted to another cathode, the potential of which is more negative than that of the hot cathode. The neutralization of the ions leads to a measurable (electron) current which is based on the ion current and therefore depends on the particle number density in the residual gas. ${\displaystyle U}$ ${\displaystyle e}$ ${\displaystyle e\cdot U\geq E_{I}}$ ${\displaystyle E_{I}=}$

Based on residual gas ionization using hot cathodes:

• Bayard-Alpert vacuum meter (invented by Robert T. Bayard in 1950 and developed and described by Daniel Alpert )
• Extractor ionization vacuum gauge
• Orbitron system with particularly long electron paths
• Magnetron vacuum gauges etc.

literature

• Wutz, Adam, Walcher: Theory and Practice of Vacuum Technology, Vieweg-Verlag.

See also

• Pressure gauge
• Flow measurement technology

Individual evidence

1. ↑ Patent US2605431 : Ionization vacuum gauge. Applied March 30, 1950 , published June 29, 1952 , applicant: Westinghouse Electric Corp, inventor: Robert T. Bayard. ‌
2. ^ Robert T. Bayard, Daniel Alpert: Extension of the Low Pressure Range of the Ionization Gauge . In: Review of Scientific Instruments . tape 21 , no. 6 , June 1950, p. 571-572 , doi : 10.1063 / 1.1745653 .
3. ^ Daniel Alpert: New Developments in the Production and Measurement of Ultra High Vacuum . In: Journal of Applied Physics . tape 24 , no. 7 July 1953, p. 860 , doi : 10.1063 / 1.1721395 .