Abstract! The phototron is a photoelectric device that converts light to radio ■Frequency energy. It is a vacuum tube, free electron, device that is mechanically similar to a reflex klystron with the hot -Filament cathode replaced by a large area photocathode. The device can operate either with an external ATTACHMENT : voltage source used to accelerate the photoelectrons or with zero bias voltage; in which case the photokinetic energy o-F the electrons sustains the R.F. oscillations in the tuned R.F. circuit. To date, we have tested one basic design o-F the phototron. We have obtained -Frequencies as high as about 1 GHz and an overall efficiency of about 1% in the biased mode. In the unbiased mode, the frequencies of operation and efficiencies are considerably lower. Success with test model suggests that considerable improvements are possible through design refinements. One such design refinement is the reduction of the length of the electron flight path. Tests on such a reduced scale device are underway. Title: Radiation-driven MHD systems for space applications Source: Proceedings of the AFOSR Special Conference on Prime-Power for High Energy Space Systems, Norfolk, Virginia, USA, Feb. 22-25, 1982. (Paper No. VI-12) Authors: Lee, Ja H.; <Vanderbilt University> Jalufka, Nelson W.; <NASA Langley Research Center> Date: 02-22-82 Classification: u Keywords: space energy conversion, onboard power storage and distribution, transportation, lasers, Abstract: High-power radiation such as concentrated solar or high-power laser radiation is considered as a driver for magnetohydrodynamic (MHD) systems which could by developed for efficient power generation and propulsion in space. Eight different systems are conceivable since the MHD systems can be classified ATTACHMENT : in two: plasma and liquid-metal MHD's. Each of these systems is reviewed and solar— (or laser-) driven MHD thrusters are proposed. Title: Interaction between the SPS Solar Power Satellite solar array and the magnetoshperic plasma Source: Proceedings of the AFOSR Special Conference on Prime-Power for High Energy Space Systems, Norfolk, Virginia, USA, Feb. 22-25, 1982. (Paper No. VI-13) Authors: Freeman, John W. ; <Dept. of Space Physics and Astronomy, Rice University, Houston, TX 77251> Date: 02-22-82 Classification: u Keywords: solar cells, environmental effects, prototype? systems, Abstract: This paper summarizes the results of study to determine the effects of space plasmas on a large GaAs solar cell array using solar reflectors at a concentration ratio of 2 in Geostationary orbit. The configuration studied was an early Rockwell International SPS. It was concluded that the system could ATTACHMENT : function in the GEO environment if certain design changes were implemented. These included conductive coatings on the solar cells, changing the reflector material from Kapton to a higher conductivity material and oversizing the array to compensate for a 0.77. parasitic load due to losses from the ambient magnetospheric plasma. The study also looked at the operation of the solar powered Earth Orbit. Transfer Vehicle in LEO and concluded severe arcing would take place on all high voltage negative portions of the array. The parasitic load loss at LEO was estimated at 37.. Operation of a high voltage array at LEO represents a major problem. Charge exchange ion feedback from argon ion thrusters located near the EOTV solar array was also examined and all problems found were believed to be solvable by the placement of protective ground screens.
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