The Poisoning of Thoriated Tungsten Cathodes

Journal Article · Mon Jan 01 04:00:00 EST 1962 · Journal of Electronics and Control

DOI:https://doi.org/10.1080/00207216208937351· OSTI ID:4842558

JENKINS, R. O.; TRODDEN, W. G.

An experimental study was made of the poisoning of the thermionic emission from thoriated tungsten cathodes by oxidizing gases. It is shown that rapid poisoning takes place when a critical partial pressure is exceeded. For a fully carburized cathode this critical partial pressure measured, using an omegatron mass spectrometer, is as follows: O₂ 10⁻⁵ torr, CO₂ 2.5 x 10⁻⁵ torr, and water vapor 6 x 10⁻⁶ torr. The total pressures measured by ion gage were considerably higher due to the formation of CO at the cathode surface. The resistance to poisoning depends almost entirely on the presence of carbon on the surface, and any decarburization lowers the critical pressure. For a truly uncarburized cathode the critical pressures are less than 10⁻⁹ torr, only the arrival of fresh thoriura at the surface counteracting the adsorption of the poisoning gas. It appears probable that in the past so- called uncarburized cathodes must have had a small amount of carbon in the surface. (auth)

• Research Organization: General Electric Co. Ltd., Wembley, Eng.
• Sponsoring Organization: USDOE
• NSA Number: NSA-16-017845
• OSTI ID: 4842558
• Journal Information: Journal of Electronics and Control, Journal Name: Journal of Electronics and Control Journal Issue: 1 Vol. 12; ISSN 0368-1947
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

CARBIDES
CARBON
CARBON OXIDES
CATHODES
EFFICIENCY
EMISSION
ENGINEERING AND EQUIPMENT
GASES
IONS
MASS SPECTROMETERS
OXIDATION
OXYGEN
PERFORMANCE
PRESSURE
THERMIONICS
THORIUM
TUNGSTEN
VAPORS
WATER
WIRES