Close-spaced high-temperature Knudsen flow. Annual report, May 16, 1984-May 15, 1985

Technical Report · Sat Jun 15 04:00:00 EDT 1985

OSTI ID:6493654

McVey, J B

This work continued to investigate thermionic energy conversion in the Knudsen (collisionless) operating mode. A SAVTEC-type converter with an interelectrode spacing of 18-22 microns was tested over a range of emitter temperatures up to about 1700 K. Maximum performance followed the predictions of vacuum-mode analysis for emitter temperatures below 1580 K. Above that temperature the converter operated in the unignited mode, with partial space-charge neutralization by surface ionization of cesium. It was found that collisionless and diffusion mode theories could be extended into the regime of maximum output power for the unignited mode (spacing and electron mean-free path about equal) to give good agreement with the experimental data. The Knudsen-mode thermionic converter with a structured emitter was also investigated. Analysis has shown that associative ionization between barium and cesium is unlikely to be the cause of the current enhancement observed in previously published work. An analysis which considered the trapping of positive ions in the emitter slots has given good qualitative agreement with published data. Work is continuing on this analysis. Parts for a structured emitter variable spacing converter have been constructed and are being assembled.

• Research Organization: Rasor Associates, Inc., Sunnyvale, CA (USA)
• OSTI ID: 6493654
• Report Number(s): AD-A-158280/8/XAB; NSR-22-3
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
300402* -- Thermionic Converters-- Performance & Testing
ALKALI METALS
ALKALINE EARTH METALS
BARIUM
CATIONS
CESIUM
CHARGED PARTICLES
DIRECT ENERGY CONVERTERS
ELEMENTS
FLUID FLOW
GAS FLOW
IONIZATION
IONS
KNUDSEN FLOW
METALS
NESDPS Office of Nuclear Energy Space and Defense Power Systems
PERFORMANCE
SPACE CHARGE
SURFACE PROPERTIES
THERMIONIC CONVERTERS
THERMIONIC EMITTERS
VERY HIGH TEMPERATURE