This report was prepared on Air Force Contract AF 33(6l6)-7355 under Task Nr. 61098 of Project Nr. 3145 "Microwave Energy Conversion".


Plasma Diode. Operating conditions for the microwave absorber are set forth. A tapered coaxial load is proposed in which the outside of the load is also the cathode of the plasma diode which should operate at temperatures of 2000 - 2500° K, The load and cathode temperature must be raised from about 300°K to operating temperature by microwave power. A test set up is proposed for making the necessary measurements of conductivity, thermal and mechanical properties of the more promising absorber-cathode materials. Some of the test equipment is not yet available but tests at room temperature on conductivity at microwave frequencies are now in progress on carbon, zirconium carbide and silicon carbide. The thermodynamic problems of the microwave absorber- cathode are discussed. Direct Rectification by Semi-conductor Diodes. Test have been made on a considerable number of diodes at 60 cycles, 600 Mc, and 2500-3000 Mc, with resistance loads, with and without capacitance filters, and at power levels of 370 milliwatts at 600 Mc, and 200 milliwatts per diode at microwave frequencies. The best measured efficiencies obtained with resistance-capacitance loads were between 40 and 63% at microwave frequencies. When storage batteries were used as the load at microwave frequencies maximum efficiency with a two volt load was 72% and with a four volt load it was 65%. Higher efficiencies are anticipated with full-wave and bridge type rectifiers using a new higher power source. Conversion by Acceleration of Electron Beams Klystron Converter. A theoretical model is described and the equations presented. The computer results are not complete but it appears that for high power the klystron converter is not much better than the closed spaced diode which may reach actual efficiencies of 65 to 70%. Inverted Magnetron. Theoretical equations are presented, for a parallel plane type of magnetron, and some results have been obtained on a computer. At 3000 Mc. efficiencies of 25 - 35% were computed. The work is still in progress. Vacuum Diode. The vacuum diode has been investigated theoretically and the results presented in curve form. From the curve efficiencies for a close space diode of 65 - 70% "appear' to be feasible. Experimental results are described which would indicate reasonably high efficiencies at microwave frequencies.

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