An orbitron type ionisation gauge with external electron injection

An orbitron type ionisation gauge with external electron injection R K Fitch, Birmingham

Physics 4

Department,

University

of Aston

in Birmingham,

Gosta

Green,

An orbifron type ionization gauge has been constructed which is based on fhe original idea of Gabor’ for an elecfro-static ion pump. Electrons are injected info the radial elecfro-static field from a simple electron gun. If is shown that the ion current varies smoothly with changes of voltage on the gun anode, and does not exhibit any instabilities which are frequently reported with the orbitron. Gauge sensifivifies in the region of lo4 forr-’ have been obtained for volfages of 500 V on the central anode. Resistance paper analogue techniques have been used to show the field disforfion produced at the outer collector by the external gun. A rubber model analogue has also been consfrucfed to simulate the electron trajectories and has shown that certain orientations of fhe gun and gun apertures of small diameter, are necessary for high gauge sensitivities.

Reference 1 D Gabor,

British

Paled

887,251, 1962.

Note: A paper by W J Thatcher on ‘The Twinwire Oscillator Mr Thatcher spoke at the conference on this subject.

Gauge’

is to be published

shortly.

393