Experimental and theoretical investigations of Cs-Ba vapor tacitron inverter for power conditioning in space power systems

The operation characteristics of the Cs-Ba tacitron as a switch are investigated experimentally in three modes: (a) breakdown mode, (b) I-V mode, and (c) current modulation mode. The switching frequency, grid potentials for ignition and extinguishing of discharge, and the Cs pressure and emission conditions (Ba pressure and emitter temperature) for stable current modulation are determined. The experimental data is also used to determine the off-time required for successful ignition, and the effects of the aforementioned operation parameters on the ignition duty cycle threshold for stable modulation. Operation parameters measured include switching frequency up to 20 kHz, hold-off voltage up to 180 V, current densities in excess of 15 A/cm[sup 2], switch power density of 1 kW/cm[sup 2]. and a switching efficiency in excess of 90% at collector C: realer than 30 V. The voltage drop strongly depends on the Cs pressure and to a lesser extent on the emission conditions. Increasing the Cs pressure and/or the emission current lowers the voltage drop, however, for the same initial Cs pressure and emission conditions, the voltage drop in the I-V mode is usually lower than that during current modulation. As long as the discharge current is kept lower that the.emission current, the voltage drop during stable current modulation could be as low as 3 V

Experimental and theoretical investigations of Cs-Ba vapor tacitron inverter for power conditioning in space power systems. Annual report, April 15, 1992--April 14, 1993

The operation characteristics of the Cs-Ba tacitron as a switch are investigated experimentally in three modes: (a) breakdown mode, (b) I-V mode, and (c) current modulation mode. The switching frequency, grid potentials for ignition and extinguishing of discharge, and the Cs pressure and emission conditions (Ba pressure and emitter temperature) for stable current modulation are determined. The experimental data is also used to determine the off-time required for successful ignition, and the effects of the aforementioned operation parameters on the ignition duty cycle threshold for stable modulation. Operation parameters measured include switching frequency up to 20 kHz, hold-off voltage up to 180 V, current densities in excess of 15 A/cm{sup 2}, switch power density of 1 kW/cm{sup 2}. and a switching efficiency in excess of 90% at collector C: realer than 30 V. The voltage drop strongly depends on the Cs pressure and to a lesser extent on the emission conditions. Increasing the Cs pressure and/or the emission current lowers the voltage drop, however, for the same initial Cs pressure and emission conditions, the voltage drop in the I-V mode is usually lower than that during current modulation. As long as the discharge current is kept lower that the.emission current, the voltage drop during stable current modulation could be as low as 3 V

CW ultraviolet and visible laser action from ionized silver in an electron beam generated plasma

Includes bibliographical references (page 14).Continuous wave laser oscillation was obtained in the 318.1 nm and the 478.8 nm lines of AgII in a neon-silver vapor mixture excited by glow discharge electron beams. Laser output powers of 14 and 60 mW were obtained in the ultraviolet and blue transitions, respectively, using nonoptimized optical cavities

Cd recombination laser in a plasma generated by an electron beam

Includes bibliographical references (page 512).Laser action was obtained in the 1.40, 1.43, and 1.65 μm lines of CdI following electron-ion recombination in a plasma generated by an electron beam. Lasing does not occur during the excitation pulse due to the electron impact population of the laser lower levels. In this plasma, supercooling of the electrons is achieved under stationary conditions, and efficient CW recombination laser action might also be possible on lines in which the lower level is not significantly populated by electron collisions. Seven new infrared laser lines in CdII are also reported

CW silver ion laser with electron beam excitation

Includes bibliographical references (page 1556).A CW laser power of 140 mW was obtained in the 840.39 nm transition of Ag II by electron beam excitation. This electron beam excited metal vapor ion laser is capable of operating using metals with high vaporization temperatures and is of interest for generation of CW coherent radiation in the 220-260 nm spectral region

Recombination lasers in a flowing negative glow discharge

Includes bibliographical references (pages 1631-1632).A fast gas flow through a negative glow plasma creates an afterglow region where supercooled electrons are separated from energetic beam electrons to produce a population inversion by collisional recombination. We report spatially-resolved electron temperature measurements of the afterglow plasma showing electron temperatures in the range of 750-1100 K under steady-state conditions. A 4 cm long flowing hollow cathode discharge was used to obtain CW recombination laser oscillation in ArI. Collisional recombination of singly- and doubly-ionized metal vapor species in the same type of plasma has also produced pulsed laser action in infrared lines of PbI, ZnI, PbII, and SnII. The addition of H2 is demonstrated to significantly increase the laser output intensity

Generation of pulsed electron beams by simple cold cathode plasma guns

Includes bibliographical references (page 522).Electron-beam pulses of current up to 20 A have been generated using glow discharge electron guns of simple construction. Beam pulses of 1-20 μs long at energies between 2 and 15 keV have been created at helium pressures between 1 and 5 torr. Results obtained using 3-cm diameter aluminum cathodes of two different geometries are discussed. As an example of the use of these electron guns for laser excitation, we have excited an He-Zn metal vapor mixture. Three new infrared laser transitions in ZnII are reported

Engineering Spectral Control Using Front Surface Filters for Maximum TPV Energy Conversion System Performance

Energy conversion efficiencies of better than 23% have been demonstrated for small scale tests of a few thermophotovoltaic (TPV) cells using front surface, tandem filters [1,2]. The engineering challenge is to build this level of efficiency into arrays of cells that provide useful levels of energy. Variations in cell and filter performance will degrade TPV array performance. Repeated fabrication runs of several filters each provide an initial quantification of the fabrication variation for front surface, tandem filters for TPV spectral control. For three performance statistics, within-run variation was measured to be 0.7-1.4 percent, and run-to-run variation was measured to be 0.5-3.2 percent. Fabrication runs using a mask have been shown to reduce variation across interference filters from as high 8-10 percent to less than 1.5 percent. Finally, several system design and assembly approaches are described to further reduce variation