Close-spaced high-temperature Knudsen flow. Annual report, 1 February 1983-15 May 1984

Technical Report · Fri Jun 15 04:00:00 EDT 1984

OSTI ID:5968370

McVey, J B

This work is a study of discharge processes in Knudsen mode (collisionless), thermionic energy converters. Areas of research involve mechanisms for reducing the effects of electron space charge in such devices. Such mechanisms are essential for thermionic converters to produce useful current and power densities. The mechanisms chosen to study are: reduction of space charge through a very close interelectrode gap (less than 10 microns); transport and retention of positive cesium ions generated by surface ionization; transport of positive cesium ions generated in an arc external to the electrodes; and the mechanism for enhanced current output due to a structured emitter in a mixed barium-cesium vapor. This last process may involve the production of barium-cesium dimer ions. The experimental work used SAVTEC (Self-Adjusting, Versatile Thermionic Energy Converter) diode structures, which were tested in a chamber containing 0.1-1.0 torr of cesium vapor. Comparison of measured volt-ampere curves with theory gave excellent agreement and indicated an interelectrode gap of 6.5 microns at an emitter temperature of 1250 K. A theoretical model of the collisionless thermionic diode was developed which included surface ionization, auxiliary ions from an external source, and trapping of charged particles in potential wells due to infrequent collisions. Studies show that trapping of positive ions leads to a large, beneficial increase in current density.

• Research Organization: Rasor Associates, Inc., Sunnyvale, CA (USA)
• OSTI ID: 5968370
• Report Number(s): AD-A-148477/3/XAB
• 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
CHEMICAL REACTIONS
CONVERSION
DIMERS
DIRECT ENERGY CONVERTERS
ELECTRODES
ELEMENTS
ENERGY CONVERSION
FLUID FLOW
FLUIDS
GAS FLOW
GASES
HIGH TEMPERATURE
IONIZATION
IONS
KNUDSEN FLOW
METALS
NESDPS Office of Nuclear Energy Space and Defense Power Systems
REDUCTION
SPACE CHARGE
SURFACE PROPERTIES
THERMIONIC CONVERTERS
VAPORS