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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Improved thin film triodes of cadmium selenide and tellurium, metal based transistor junctions, and substrate evaluation
Thin film triode fabrication, metal base transistor, and circuit design for thin film personal communications and telemetry system
Guidance and control research on solid state triodes, evaporated thin film cadmium sulfide photodectors, and reduction of plasma maintenance voltage with magnetic field
Pumping speeds of diode and triode getter-ion pumps measured for hydrogen, helium, and nitrogen at low pressures
Saturation effects studied by pumping speed measurements of diode and triode type getter ion pumps for He, molecular hydrogen and nitrogen at low pressures as function of time
Developing evaporated gallium arsenide to determine electrical and structural transport properties for coplanar electrode, space charge limited triodes
Solid film lubricants deposited by DC triode sputtering on Ni, Ni-Cr and Nb surfaces friction tested under ultrahigh vacuum conditions
Fabrication processes for integrated vacuum circuits and life tests of dual triodes for low temperature thermionic emitters
A prototype all carbon triode ultrahigh vacuum gage was fabricated and tested. The gage exhibited a sensitivity of 3.7 per torr for nitrogen and an X-ray background approximately 0.1 as large as would be expected of a metal gage of the same design. The gage made from these materials, showed good sensitivity and durability. A practical technique was developed for bonding carbon components together without metal fasteners. The bond is made with a cross-linked phenolic resin which is converted to vitreous carbon by a careful pyrolysis procedure. The resulting bonds are strong, electrically conductive, and can withstand repeated excursions to 2500 K in vacuum. Measurements of adsorption and outgassing characteristics of four refractory carbons have confirmed that such materials are suitable for use in ultrahigh vacuum and that some are superior refractory metals in man respects.
Triode gauge with electron source, electron collector, and positive ion collector made from either graphite or carbon material extends low-pressure ranges of existing gauges by changing only materials used in construction. Advantages of graphite gauge stem from physical properties of graphite (or carbon).
A quantitative analysis of a large and representative sample of available data has been made to determine the best criteria for predicting the relative sensitivities of ionization-type vacuum gauges to different gases. The molecular property of the gas that correlates best with relative sensitivity is the ionization cross section (eV). For high-pressure ionization gauges, a cross section evaluated at 2/3 of the accelerating potential of the gauge is the best choice. For Bayard-Alpert and triode gauges, any of three choices are of approximately equal value. These are 100 eV cross section values, maximum cross section value for each gas, and a cross section evaluated at 2/3 of the accelerating potential for each gauge. For the Alphatron gauge, cross section values in the range 5000-10,000 eV provide the best correlation.
Bulk-sputtered OFHC Cu and Cu-0.15 Zr used as inner walls of advanced regeneratively cooled thrust chambers are evaluated as to microstructure, surface topography, and fractography. It is found that under conditions of low substrate temperature, crystallite size and openness of the structure increase with increasing deposition rate for both materials. At elevated temperatures, an equiaxed ductile structure of OFHC Cu is produced only at low deposition rates; at higher deposition rate, open structures are observed with recrystallized equiaxed grains within large poorly bonded crystallites. The Cu-0.15 Zr alloy sputtered from the hollow cathode using a diode discharge shows open-type structures for all conditions evaluated. The use of a triode discharge in generating a dense non-voided structure of Cu-0.15 Zr is discussed.
Computer-designed sensor, consisting of single-stage electrostatically-focused, triode image intensifier, provides high quality imaging characterized by exceptionally low geometric distortion, low shading, and high center-and-corner modulation transfer function.
Basic analytical and experimental exploration was conducted on several types of advanced thermionic energy converters, and preliminary analysis was performed on systems utilizing advanced converter performance. The Pt--Nb cylindrical diode which exhibited a suppressed arc drop, as described in the preceding report, was reassembled and the existence of the postulated hydrid mode of operation was tentatively confirmed. Initial data obtained on ignited and unignited triode operation in the demountable cesium vapor system essentially confirmed the design principles developed in earlier work, with a few exceptions. Three specific advanced converter concepts were selected as candidates for concentrated basic study and for practical evaluation in fixed-configuration converters. Test vehicles and test stands for these converters and a unique controlled-atmosphere station for converter assembly and processing were designed, and procurement was initiated.
Procedures for closing out coolant passages in regeneratively cooled thrust chambers by triode sputtering, using post and hollow Cu-0.15 percent Zr cathodes are described. The effects of aluminum composite filler materials, substrate preparation, sputter cleaning, substrate bias current density and system geometry on closeout layer bond strength and structure are evaluated. High strength closeout layers were sputtered over aluminum fillers. The tensile strength and microstructure of continuously sputtered Cu-0.15 percent Zr deposits were determined. These continuous sputtered deposits were as thick as 0.75 cm. Tensile strengths were consistently twice as great as the strength of the material in wrought form.
A theoretical model was used to study the effects of structured electrodes on converter I-V characteristics and results are given. An auxiliary-ion-source triode operated as a plasmatron was used for studying the enhancement distribution and magnetic effects, and results are reported. Design features of the high current-zero power (ZEPO) converter tests are given.
Recent progress at Thermo Electron in developing advanced thermionic converters is summarized with particular attention paid to the development of electrodes, diodes, and triodes. It is found that one class of materials (ZnO, BaO and SrO) provides interesting cesiated work functions (1.3-1.4 eV) without additional oxygen. The second class of materials studied (rare earth oxides and hexaborides) gives cesiated/oxygenated work functions of less than 1.2 eV. Five techniques of oxygen addition to thermionic converters are discussed. Vapor deposited tungsten oxide collector diodes and the reflux converter are considered.
Sputter deposited aluminum containing argon was melted to produce foam, both in the earth's gravitational field and in a zero-gravity space environment. Experiments leading to trapping of up to 270 ppm argon sputtering gas in pure aluminum during high-rate dc triode sputter deposition are discussed. Conduct of the melting experiments and design of the furnace used are described. Metallography; an analysis of bubble size, distribution, and morphology; and a preliminary description of the kinetics are also presented.