Close-spaced high-temperature Knudsen flow. Annual report, 1 February 1983-15 May 1984
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
Similar Records
Close-spaced high-temperature Knudsen flow. Annual report, May 16, 1984-May 15, 1985
SOURCES OF POSITIVE IONS FOR SPACE CHARGE NEUTRALIZATION AT LOW TEMPERATURES
Related Subjects
KNUDSEN FLOW
THERMIONIC CONVERTERS
SPACE CHARGE
BARIUM
CATIONS
CESIUM
DIMERS
ELECTRODES
ENERGY CONVERSION
HIGH TEMPERATURE
IONIZATION
IONS
REDUCTION
SURFACE PROPERTIES
VAPORS
ALKALI METALS
ALKALINE EARTH METALS
CHARGED PARTICLES
CHEMICAL REACTIONS
CONVERSION
DIRECT ENERGY CONVERTERS
ELEMENTS
FLUID FLOW
FLUIDS
GAS FLOW
GASES
METALS
NESDPS Office of Nuclear Energy Space and Defense Power Systems
300402* - Thermionic Converters- Performance & Testing