The paper describes the present status of research and development on thermionic converters and thermionic reactors. The future trends of converter technology and possible applications for utilization of thermionic reactors are also discussed. A thermionic converter consists of two refractory metal electrodes facing closely each other, and it is such a device that converts heat energy into electrical energy directly by utilizing the thermionic emission of electrons. The electrical output characteristic of a cesium vapor converter shows two modes of operation, ignited mode and unignited mode, but a practical operation mode is analyzed as compared with the idealized mode. The theoretical analysis in the USSR of internal phenomena between the electrodes is briefly reviewed. Various methods for improving the converter performance are proposed by utilization of a new generation of electrode materials and structures. The energetic research and development work on the thermionic reactor-a reactor with a number of power-producing thermionic converters in the core-is being carried out in many advanced countries. The USSR provided the most significant demonstrations of thermionic thermal reactor technology (TOPAZ I and II) in 1971. The USSR is being concentrated on power sources for telecommunication satellites and terrestrial applications. The US is carrying out the research and development work on the thermionic fast reactor as a power source for electric propulsion of spacecrafts.
To investigate the feasibility of various materials as electrodes of a MHD generator, the electrical, physical and chemical characteristics of the metallic and ceramic electrodes made of Inconel, LaCrO3-ZrO2, AlSl-304 and other refractory alloys were investigated under simulated conditions using a 1.2 MW test rig and DC power source. The Inconel was selected as representative of metallic materials. Its electrical performances were improved remarkably above the temperature at which surface oxide was produced. As the electrode temperature increased the amount of weight loss by oxidation and chemical erosion increased, however the electrical erosion increased at the lower temperatures. The optimum temperature for performance was found to be from 800 to 1, 000°C. In this temperature region, the weight loss of the anode was less than that of the cathode, but this tendency was reversed below the temperature of 800°C.
A new type of ion plating system using a R. F. coil has been designed. The R. F. coil electrode, connected to a 13. 56 MHz (1.2kW) generator, was placed between the evaporator of the anode and the substrate holder of the cathode. A portion of the vapourized beam was ionized by the gas discharge and the R. F. oscillating field, and then accelerated toward the cathode. Ion plating depositions were carried out in the argon gas pressure of the order of 10-4 Torr. The appearance of glow discharge and the cathode circuit current density in this ion plating system were observed. The adherence of thin gold films ion plated onto glass ware measured by a pulling test. The porosity of gold films were observed by a scanning electron microscope. It appears that the R. F. method is superior to the D. C. method in forming films by ion plating.
Non-absorbing light scattering in polystyrene latex dispersion solution was computed using Hartel's treatment. Particles of five diameters ranging from 0.5 to 0.855μ were selected for computing the light scattering. Three kinds of concentration 1.0×10-4, 1.0×10-3, 1.0×10-2g/g, and three path lengths 220, 440, 880μ were examined using light of wavelength 0.5461μ. From these results we have obtained detailed informations of multiple light scattering which have not previously been calculated.
When measuring the variation of refractive index of plasmas by the conventional optical interferometry, the light intensity is found to vary with cos φ(t), where φ(t) is the phase shift. Moreover, when the refractive index changes intricately, thereby producing a complex fringe pattern, it is difficult to detect the change in refractive index exactly. An application of an interferometry, which is a modification of the two wavelengths laser interferometry, is introduced here for measuring the variation of the refractive index of a plasma behind a shock front directly from the pattern observed on the oscilloscope. A laser light is split into two components whose spectra are adjacent to each other in the longitudinal laser modes. After one of the light components passes through the medium whose refractive index varies with time, the split components are made to join each other. The beat frequency between the two light components is modulated, and the signal of the beat is integrated after frequency detection.