THE TRANSITION TO THE ARC MODE AND ITS INFLUENCE ON THERMIONIC CONVERTER PERFORMANCE
Several investigators have reported that a thermionic converter with a given emitter temperature can operate in either a high current or a low current mode. In earlier published work, the high current mode was attributed correctly to volume ionization. At that time, the conclusion that volume ionization was occurring was based on the appearance of a alow in the space between emitter and collector as the voltage of the collector was made more positive. The discontinuity in the volt-ampere curve at this breakdown voltage is very definite. The phenomenon was studied irrespective of whether it occurred in the power quadrant or with a positive potential applied to the collector. A detailed analysis of this phenomenon now can be presented. At low emitter and low cesium control temperatures breakdown occurs when a potential drop near the collector is equal to the ionization potential of cesium. At the high emitter and high cesium control temperatures, the breakdown occurs at higher currents with potential drop as low as 2 v. This indicates that ionization of excited cesium atoms is occurring when the converter is operating in the power quadrant. The V-A curve in the arc mode is logarithmic, and the voltage at which maximum power occurs is equal to the voltage equivalent of the electron temperature. It will be shown that electron temperature increases with cesium pressure. The short-circuit current in the arc mode was measured and compared with a new theory of the condition which determines if a given converter is operating electron-rich or ion- rich. The current output in the volume ionization mode is surprisingly independent of emitter temperature. This fact is especially important where series operation will be required, since it will be difficult to maintain the same emitter temperatures in all diodes. The higher efficiency obtainable in the high current mode and the relative independence of emitter temperature may help to accelerate the development of thermionic systems. (auth)
- Research Organization:
- Boeing Co., Seattle
- NSA Number:
- NSA-17-020618
- OSTI ID:
- 4720198
- Journal Information:
- Advan. Energy Conversion, Vol. Vol: 2; Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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High-efficiency thermionic converter studies
EXPERIMENTAL OPTIMIZATION OF CESIUM VAPOR THERMIONIC CONVERTERS WITH METAL EMITTERS
Related Subjects
ATOMS
BREAKDOWN
CESIUM
CIRCUITS
CONVERSION
CURRENTS
DIODES
EFFICIENCY
ELECTRIC ARCS
ELECTRIC POTENTIAL
ELECTRON TEMPERATURE
ELECTRON TUBES
ELECTRONS
EMISSION
ENERGY
EXCITATION
GLOW DISCHARGES
IONIZATION
IONS
MEASURED VALUES
PERFORMANCE
POWER
PRESSURE
TEMPERATURE
THERMIONICS
TRANSIENTS
VELOCITY
VOLUME
NESDPS Office of Nuclear Energy Space and Defense Power Systems