Ionization vacuum gauges

The formation of ions is a consequence of either a discharge at a high electric field strength (so-called cold-cathode or Penning discharge, see 

1) or the impact of electrons that are emitted from a hot cathode (see 

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Example If the pressure of a gas essentially consisting of pump fluid molecules is measured with an ionization vacuum gauge, then the pressure reading (applying to air or Nj), as shown in Table 3.2, is too high by a factor of about 10. 

Cold-cathode ionization vacuum gauges (Penning vacuum gauges)... 

Fig. 3.13 Schematic diagram and potentiai curve in a hot-cathode ionization vacuum gauge...

Fig. 3.14 Apparent iow pressure iimit due to X-ray effect in a normai ionization vacuum gauge...

In addition to the conventional ionization gauge, whose electrode structure resembles that of a common triode, there are various ionization vacuum gauge systems (Bayard-Alpert system, Bayard-Alpert system with modulator, extractor system) which more or less suppress the two effects, depending on the design, and are therefore used for measurement in the high and ultrahigh vacuum range. Today the Bayard-Alpert system is usually the standard system. 

When the sputter-ion pumps are installed one should ensure that the magnetic fields will not interfere with the operation of other devices (ionization vacuum gauges, partial pressure measurement units, etc.). Mounting devices for the sputter-ion pumps may not short circuit the inductance flow and thus weaken the air gap inductance and pumping speed. 

In all those measurement instruments which use the ionization of gas molecules as the measurement principle (cold-cathode and hot-cathode ionization vacuum gauges), strong magnetic leakage fields or electrical potentials can have a major influence on the pressure indication. At low pressures it is also possible for wall potentials which deviate from the cathode potential to influence the ion trap current. 

Penning ionization vacuum gauge Magnetroij gauge... 

Triode ionization vacuum gauge for high vacuum... 

Bayard-Alpert ionization vacuum gauge with modulator... 

Liu H, Nakahara H. et al.. Ionization vacuum gauge with a carbon nanotube field electron emitter combined with a shield electrode. Vacuum, 2009. 84(5) 713-717. 

Dong CK, Myneni GR, Carbon nanotube electron source based ionization vacuum gauge. Applied Physics Letters, 2004. 84(26) 5443-5445. 

Penning vacuum gauge (vacuum technology) An ionization vacuum gauge in which the electric and magnetic fields are approximately parallel. Also called the Phillips ionization gauge. See also Vacuum gauge. 

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