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Surface studies of thermionic cathodes and the mechanism of operation of an impregnated tungsten cathode

Technical Report ·
OSTI ID:7116525
The surface properties of conventional impregnated cathodes were investigated by the use of Auger spectroscopy and work function measurements, and these were compared with a synthesized barium- or barium oxide coated tungsten surface. The barium- and barium oxide coated surfaces were prepared by evaporating barium onto a tungsten surface that can be heated to elevated temperatures. Multilayer or monolayer coverages can be investigated using this technique. The results of this study show that the surface of an impregnated tungsten cathode is identical to that observed for a synthesized monolayer or partial monolayer of barium on partially oxidized tungsten, using the criteria of identical Auger patterns and work functions. Desorption measurements of barium from a tungsten surface were also made. These results in conjunction with Auger and work function data were interpreted to show that throughout most of its life an impregnated cathode operating in the range of 1100 C has a partial monolayer rather than a monolayer of barium on its surface. (auth)
Research Organization:
National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
OSTI ID:
7116525
Report Number(s):
N-76-31415; NASA-TN-D-8295; E-8515
Country of Publication:
United States
Language:
English

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Related Subjects

30 DIRECT ENERGY CONVERSION
300403 -- Thermionic Converters-- Materials
Components
& Auxiliaries
36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
ALKALINE EARTH METAL COMPOUNDS
ALKALINE EARTH METALS
AUGER EFFECT
BARIUM
BARIUM COMPOUNDS
BARIUM OXIDES
CATHODES
CHALCOGENIDES
COATINGS
ELECTRODES
ELEMENTS
EVAPORATION
METALS
NESDPS Office of Nuclear Energy Space and Defense Power Systems
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
REFRACTORY METALS
SURFACE PROPERTIES
THERMIONIC EMITTERS
TRANSITION ELEMENTS
TUNGSTEN
VERY HIGH TEMPERATURE
WORK FUNCTIONS