Based on the extremely low output, the experiment must be carefully performed to exclude thermoelectric effects from different lead wire material junctions and thermal electric differences.
You don't need to run kilowatts into the kiln to heat the cathode, just heat the filament with it's rated current and you will get a current flow from cathode to anode.
I did this test some months back and recorded the current flow from cathode to anode in a triode with no applied plate voltage. If anyone is interested, attached is the spreadsheet I ran.
In vacuum tube design, formulations applied to the cathode enhance electron emission and some were radioactive.
Research thermionic generators, there are many designs and patents, the effect is well documented.
http://www.youtube.com/watch?v=K5GVrYcjBKsThermionic emission is a good area to do more research.
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Thermionic Conversion Papers and Research
Recent advances enable thermionic converters to achieve energy conversion efficiencies of up to 30%. Advanced Energy Technology will explore this technology for nuclear space power. High efficiency means that more power can be obtained with a smaller system radiator; this reduces spacecraft mass and increases manueverability, as well as improved packaging. Our converter is inherently survivable against laser and nuclear threats - in fact, it can continue to operate and produce power at elevated heat sink temperatures. Its modular for survivability against pellet threats. This device uses SAVTEC close-spaced thermionic converter technology and barium-cesium thermionic converter technology. High efficiency is achieved by an optimized two-stage configuration. Potential uses of the conversion technology with non-nuclear heat sources are more efficient terrestial commercial power plants and cogeneration of electricity in industry.
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High efficiency thermionic converter studies
Huffman, F. N.; Sommer, A. H.; Balestra, C. L.; Briere, D. P.; Oettinger, P. E.
Unknown
The objective is to improve thermionic converter performance by means of reduced interelectrode losses, greater emitter capabilities, and lower collector work functions until the converter performance level is suitable for out-of-core space reactors and radioisotope generators. Electrode screening experiments have identified several promising collector materials. Back emission work function measurements of a ZnO collector in a thermionic diode have given values less than 1.3 eV. Diode tests were conducted over the range of temperatures of interest for space power applications. Enhanced mode converter experiments have included triodes operated in both the surface ionization and plasmatron modes. Pulsed triodes were studied as a function of pulse length, pulse potential, inert gas fill pressure, cesium pressure, spacing, emitter temperature and collector temperature. Current amplifications (i.e., mean output current/mean grid current) of several hundred were observed up to output current densities of one amp/sq cm. These data correspond to an equivalent arc drop less than 0.1 eV.
Keywords: EFFICIENCY, THERMIONIC CONVERTERS, ELECTRODES, PLASMA JETS, WORK FUNCTIONS, ZINC OXIDES
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