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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Results obtained from studies of a (1) solar concentrator, (2) solar energy receiver - thermionic converter system, and (3) solar thermionic topping system are described. Peripheral subsystems, which are required for any solar energy conversion system, are also discussed.
Collision ionization and electron temperatures in cesium vapor thermionic converters
High temperature zero drop thyratron tube for thermionic converter generator
Randomization of electron energies in one- dimensional thermionic converter by computer methods
It is shown that thermionic converters at moderate emitter temperatures of about 1600 K can be designed for a radiatively coupled 100 kWe device. A nuclear reactor is a primary heat source, with heat pipes extracting heat from the reactor and distributing it over a large surface opposite an array of thermionic energy converters. The radiative heat transfer across the vacuum gap heats up the thermionic emitters, and excess heat from the converters is radiated from the collector electrodes to the vacuum of space; the heat transfer is controlled by the energy density to be transferred, and by the temperature differential between the heat source and the heat receiver. It is concluded that this system achieves isolation of power converter modules from the heat source, elimination of additional radiators, and reduction of converter dimensions.
High temperature power conditioning system for thermionic converter generator consisting of thyratrons, transformer, and associated circuits
Cesium fluoride and argon plasma additive effects in thermionic converters
Thermionic converter research - electrode materials evaluation and theory of vacuum double diode
Long term testing of cylindrical diodes and irradiation of fuel and insulators - thermionic converter development, thermal and irradiation testing of fuel clad emitters and alumina
Cesium vapor thermionic converters - use of argon with inert gas additives
Ion production rate in cesium thermionic converter related to Saha-Langmuir surface ionization equation
Fuel and solar cells, chemical batteries, Rankine and Brayton cycle power plants, thermoelectric generators, and thermionic converters for space power applications
Discrepancy between observed ion production rate in cesium thermionic converter and Saha-Langmuir equation prediction suggests locality of ion formation
A low cost cylindrical thermionic converter has been designed, fabricated, and tested for use in a NASA-JPL program to directly measure converter lead efficiencies using various electrode materials and surfaces. Efficiency measurements are made using input emitter heater power, output power at the leads, and calculated values of the parasitic losses that would not be present in the application configuration. This information can be used to predict the performance characteristics of the advanced converters currently under development. A series of five converters has been tested. Both structured and smooth molybdenum collectors have been used. Emitters included smooth molybdenum, smooth rhenium, and microstructured rhenium. Cesium pressure families of current-voltage curves are presented for emitter temperatures of 1600, 1700, and 1800 K, along with measured efficiencies as a function of converter current densities for each temperature.
Operational parameters for thermionic converter - cesium vapor diode formulation and computer method of analysis
Thermionic converter life testing, thermal and irradiation testing of fuel clad emitters, and irradiation of high purity alumina at vacuum temperature
Thermionic converter performance, electron emission and work functions of vapor-deposited rhenium samples, and electron emission microscope design and micrographs
The collector electrode of a thermionic converter requires a material having a low thermionic work function and chemical stability in a Cs atmosphere in the 800-K range. This letter reports that ZnO with an adsorbed Cs film meets these requirements. The work function is approximately 1.3 eV. Various methods of preparing the ZnO film are described as well as an experiment in which Cs was replaced by K.