A short (without a positive column) Knudsen thermionic discharge initiated in barium and strontium vapor has been investigated. It has been shown that the behavior of these discharges and their formation mechanism, effective heating of the plasma electrons by a cathode electron beam, are, in general, similar to the discharge in cesium.

We report on the results of investigation of a plasma switch with complete grid control in a discharge with a cathode spot on the liquid-metal cesium cathode without grid diaphragming. The retention of the working area of the grid relative to the anode area leads to an order-of-magnitude increase in the switching anode current (up to 20 A/cm2 over the anode area) and a substantial (up to 100 V and higher) increase in the switching voltages. The use of the cathode jet makes it possible to reduce the working pressures of cesium vapor (down to 10–3 Torr). We discuss the results of analysis of peculiarities of grid discharge quenching in such a switch, which make it possible to determine possible reasons for limitation of the working parameters of the switch and the ways of their further increase.

Some peculiarities in the development of high-current pulse-periodic discharge in cesium vapor have been studied. It is established that, at a cesium vapor pressure of P Cs > ∼100 Torr, a difference between the electron temperature and that of the heavy plasma component almost does not influence the development of discharge. At P Cs ∼ 250 Torr, the character of discharge exhibits significant changes, which require further detailed investigations.

We report on the results of successful implementation of full grid control in a cesium discharge with a cathode spot. The discharge is quenched by a negative grid pulse for a discharge current density up to 75 A/cm2 in the grid plane for voltage switching up to 100 V in the pressure range 0.5–1.5 Pa for a voltage drop of 5–6 V in the discharge. It is shown that quenching is the break-off type. The discovered effect of “evacuation” of the heavy component (ions) from the grid-anode gap to the cathode region leads to an unusually long (hundreds of microseconds) time of stabilization of the steady state in the discharge under the experimental conditions.

Results of theoretical and experimental studies of the optical spectrum of a pulse-periodic high-pressure cesium discharge are presented. The results of calculations are in good agreement with experimental data. The possibility of creating an efficient light source based on recombination emission from the discharge plasma is demonstrated. The formation mechanisms of the continuous spectrum of discharge radiation are considered.

The first results of an investigation of the complete current switching (initiation and quenching) using a fine-mesh grid in discharge with a cathode spot on liquid cesium are reported. Experimental data show the possibility of using this method of control at current densities within 5–25 A/cm 2 in the grid plane.

Results of theoretical and experimental studies of the optical spectrum of a pulseperiodic high pressure cesium discharge are presented. The results of calculations are in good agreement with experimental data. The possibility of creating an efficient light source based on recombination emission from the discharge plasma is demonstrated. The formation mechanisms of the continuous spectrum of discharge radiation are considered.

The formation of a continuous emission spectrum of pulsed discharge in high-pressure cesium vapor ( P ≤ 1 bar) has been experimentally studied under conditions of increased power deposited in discharge. Experimental data well agree with the results of theoretical calculations. Physical mechanisms underlying the observed phenomenon are discussed. It is shown that, as the pumping current pulse amplitude is increased from 15 to 80 A, a discrete line spectrum transforms into the continuous spectrum. This is accompanied by an increase in the light yield (from 15 to 85 lm/W) and color-rendering index (from 86 to 98).

The feasibility of using a thermionic thermal-to-electrical energy converter as a rectifier of industrial-frequency alternating current is considered. The design of a rectifier module with a high-current converter the emitter of which is heated by a gas torch to 1400 K is described. The basic operating performance of the module is studied, and the prospects for using this module in electroplating are discussed.

The spectrum of pulse-periodic discharge in high-pressure cesium vapor has been studied by experimental and theoretical methods. Experiments confirmed a significant shift of the 6P and 5D recombination continuum thresholds toward longer wavelengths, which was theoretically predicted previously for the emission from discharge in a dense cesium plasma. The overlapping continua form an almost continuous spectrum of emission in the visible spectral range. The results of calculations well agree with the experimental data. It is established that the discharge under consideration is an effective, mercury-free source of light with a color rendering index of R a = 98 and a light yield of η = 81 lm/W.

The results of investigation of the ignition voltage for a low-voltage cesium arc and direct voltage drops in the discharge in cesium triodes with fine-mesh (∼0.2 mm) and coarse-mesh (∼2 mm) control grids are presented. It is shown that in a cesium vapor pressure range of 0.05–0.1 Torr and for discharge currents of 5–10 A/cm2, direct voltage drops can be reduced to 0.7–0.5 V even for a fine-mesh grid. For a coarse-mesh grid whose holdoff voltage is sufficient for rectifying low voltages (∼15–20 V), direct voltage drops are almost the same as for a diode even for currents of 1 A/cm2 and lower. The critical factor of holdoff voltage loss is the grid emission level (∼1 mA/cm2).

The characteristics of open atmospheric dc discharge between a liquid nonmetal cathode (tap water layer) and a metal anode have been studied. The effect of discharge on a layer of oil products (diesel fuel, lubricant oils) contaminating the liquid cathode surface was determined. The discharge current-voltage characteristics and the dependence of the cathode current density on the discharge current I were measured in the interval 20 mA ≤ I ≤ 300 mA for the discharge gap width varied within h = 2–10 mm. For h ≥ 4 mm and I ≥ 120 mA, the cathode current density and the interelectrode voltage are independent of the discharge current, which is characteristic of the normal glow discharge. Under the action of discharge, oil products in the contamination layer on the liquid cathode surface are partly decomposed and partly converted, after which the conversion products can be readily removed from the surface by mechanical methods. The efficiency of contaminant removal can reach 98%. Analysis of the conversion products showed that they are composed of polymer chains with variable length and structure involving oxygen-containing groups.

Measurements were made of the absorption of microwave power in a discharge plasma generated using tapwater electrodes in atmospheric-pressure air in order to determine the electron density. The high-voltage discharge burned in a bulk (diffuse) form with a lower current density than an arc discharge. This type of discharge with nonmetallic liquid electrodes is extremely promising for various technical applications. Regimes with I =50–60 mA and voltages U =2.9–3.1 kV were studied. The measurements were made at probe radiation frequencies F =29.6 and 35.2 GHz. A two-conductor transmission line was used to localize the microwave power in the plasma. An estimate was obtained for the average electron density in the central part of the discharge (4×10 11 )< n e <,(7×10 11 )cm −3 . This result shows good agreement with the results of earlier probe measurements.

For the goats of practical use of cesium switches (a nuclear powerplant for spacecraft with a thermoionic reactor and subsequent current conversion), the study of their performance in a biphase inverter mode is of much interest. Unlike a half-period mode for active load, which so far has received the primary attention, the work of each switch is determined tangibly by the state of its neighbor. The demands on the mutual arrangement of extinguishing and igniting purses are defined experimentally for either a symmetrical circuit or a nonsymmetrical one with the switches based on various extinguishing principles.

Results are presented from a systematic investigation of the conditions under which anomalously high rates of plasma generation are observed in the anode region of a low-voltage Knudsen arc in grid plasma switch elements. The phenomenon develops over a wide range of currents and switched voltages under conditions for which the plasma density in the cathode-grid region is noticeably higher than the density in the anode region. and its onset is characterized by a pronounced pressure threshold of ∼2×10−2 Torr. The results are analyzed from the standpoint of the possible mechanisms for anomalous plasma generation — collisional nonresonance diffusion of electrons in velocity space, leading to enrichment of the distribution function in fast particles, and the collapse of Langmuir waves in the gap at the high energies of the beam produced when the wires of the grid are bridged by the quenching pulse and and the current is blocked.