Degradation of coated impregnated cathode's surface coating

The author investigates the quantitative temperature dependence on the surface coating degradation of M-type impregnated cathodes. Osmium-ruthenium coated M-type cathodes were continuously heated at four different temperatures for 2000-20000 h in vacuum apparatus with an Auger electron spectrometer...

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Bibliographic Details
Published in:IEEE transactions on electron devices 1991-11, Vol.38 (11), p.2554-2557
Main Author: Mita, N.
Format: Article
Language:English
Subjects:
Applied sciences
Boundary conditions
Cathodes
Coatings
Degradation
Electronics
Electrons
Equations
Exact sciences and technology
Insulation
Spectroscopy
Temperature dependence
Testing, measurement, noise and reliability
Tungsten
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Summary:The author investigates the quantitative temperature dependence on the surface coating degradation of M-type impregnated cathodes. Osmium-ruthenium coated M-type cathodes were continuously heated at four different temperatures for 2000-20000 h in vacuum apparatus with an Auger electron spectrometer (AES). The cathode surface concentration of tungsten increases with time by diffusion from tungsten base metal. The diffusion equation is solved with the boundary condition of the insulated surface and a theoretical equation is derived which represents the tungsten surface concentration. The data calculated from this equation are in very good agreement with the measured data. The activation energy obtained for a tungsten diffusion coefficient in the surface coating (osmium-ruthenium-tungsten) is 8.4 eV. It was found that the surface coating was stable during over 100000 h at cathode temperature of 1050 degrees C/sub B/.< >
ISSN:0018-9383
1557-9646
DOI:10.1109/16.97422