Cold cathode ionization vacuum gauge

COLDION<sup>®</sup>In a cold cathode ionization gauge, electrons are emitted and accelerated by an applied high voltage of several 1000 volts.
By the existing crossed electric and magnetic fields, the electrons are forced onto spiral paths. This increases the probability that the accelerated electron strikes a neutral gas particles and ionizes it due to the energy gained in the electric field.
The ionized gas particles are accelerated in the electric field in the direction of the grounded cathodes. They are neutralized when hitting them. The current required for neutralization is dependent on the number of ions that need to be neutralized during each time unit. Thus, the current is a measure of the prevailing pressure in the sensor. Since the ionization probability depends on the predominant gas in the measuring volume, the pressure measurement is gas type dependent.

Cold cathode ionization gauges of the Penning type are characterized by cathode sheets (at ground potential) and a typically ring-shaped anode (several 1000 volts). Due to the cold emission there are no heat sources are present in the vacuum such as they can be found in hot cathode ionization gauges. On atmosphere side, these cold cathode ionization gauges are equipped with two magnets and an iron yoke. These components are necessary for igniting and sustaining the gas discharge.
The stray magnetic field should be taken into account in the selection of cold cathode ionization gauges, for example if applications are to be operated with electron beams etc.

Other types of cold cathode ionization gauges are the magnetron and the inverted magnetron, which operate on the same basic principle.

Further Information

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