Degradation of coated impregnated cathode´s surface coating

Author

Mita, Nagahisa

Author_Institution

NTT Radio Commun. Syst. Labs., Kanagawa, Japan

Volume

38

Issue

11

fYear

1991

fDate

11/1/1991 12:00:00 AM

Firstpage

2554

Lastpage

2557

Abstract

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°C_B

Keywords

Auger effect; cathodes; coatings; diffusion in solids; temperature; travelling-wave-tubes; 100000 hr; 1050 degC; AES; Auger electron spectrometer; M-type; Os-Ru alloy; Os-Ru-W alloy; TWT electrode; W surface concentration; activation energy; diffusion equation; impregnated cathodes; surface coating degradation; temperature dependence; Boundary conditions; Cathodes; Coatings; Degradation; Electrons; Equations; Insulation; Spectroscopy; Temperature dependence; Tungsten;

fLanguage

English

Journal_Title

Electron Devices, IEEE Transactions on

Publisher

ieee

ISSN

0018-9383

Type

jour

DOI

10.1109/16.97422

Filename

97422