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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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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Surface hardening of steel by boriding in a cold rf plasma

Scanning electron spectroscopy, X-ray diffractometry, Auger electron spectroscopy, and microhardness measurements, are used to study the surfaces of 4340-steel samples that have been borided in a cold RF plasma which had been initiated in a gas mixture of 2.7 percent diborane in Ar. As a result of the dislocation of the diborane in the plasma, boron is deposited on the surface of the steel substrate and two crystalline phases, tetragonal Fe2B and orthorhombic FeB, are formed. The formation of boride phases then increases the surface microhardness from 2650 MPa to a maximum value of 7740 MPa.

Finberg, I.↗
NASA NTRS1986

RF characterization of monolithic microwave and mm-wave ICs

A number of fixturing techniques compatible with automatic network analysis are presented. The fixtures are capable of characterizing GaAs Monolithic Microwave Integrated Circuits (MMICs) at K and Ka band. Several different transitions are used to couple the RF test port to microstrip. Fixtures which provide chip level de-embedding are included. In addition, two advanced characterization techniques are assessed.

Romanofsky, R. R.↗
NASA NTRS1986

Life problems of dc and RF-excited low-power CW CO2 waveguide lasers

A number of different, RF-excited 3-W CW CO2 waveguide lasers have been built. Four of these lasers, after continuously working for 15,000-30,000 h, still yield about 70 percent of their original power output. The design variations cover N2and CO-bearing gas mixtures, as well as internal- and external-capacitively coupled excitation electrodes. A similar laser survived 50,000 5-min-ON/5-min-OFF cycles without significant mirror damage. It was not possible to find suitable cold cathodes that allow the building of longitudinally dc-excited CW CO2 waveguide lasers that work for such extended periods of time.

Hochuli, U. E.↗
NASA NTRS1986

Techniques for using emitting probes for potential measurement in RF plasmas

Investigations of the effects of RF on plasma potential measurements with electron emitting probes and methods for interpreting data are presented. Techniques correspond to the floating and inflection point methods of single-emitting and differential emitting probes, respectively. A simple method of measurement of plasma potential fluctuations is given which makes use of time-averaged emitting probe I-V characteristics.

Wang, E. Y.↗
NASA NTRS1988

RF Testing Of Microwave Integrated Circuits

Fixtures and techniques are undergoing development. Four test fixtures and two advanced techniques developed in continuing efforts to improve RF characterization of MMIC's. Finline/waveguide test fixture developed to test submodules of 30-GHz monolithic receiver. Universal commercially-manufactured coaxial test fixture modified to enable characterization of various microwave solid-state devices in frequency range of 26.5 to 40 GHz. Probe/waveguide fixture is compact, simple, and designed for non destructive testing of large number of MMIC's. Nondestructive-testing fixture includes cosine-tapered ridge, to match impedance wavequide to microstrip. Advanced technique is microwave-wafer probing. Second advanced technique is electro-optical sampling.

Romanofsky, R. R.↗
NASA NTRS1988

Growth of diamond by RF plasma-assisted chemical vapor deposition

A system has been designed and constructed to produce diamond particles by inductively coupled radio-frequency, plasma-assisted chemical vapor deposition. This is a low-pressure, low-temperature process used in an attempt to deposit diamond on substrates of glass, quartz, silicon, nickel, and boron nitride. Several deposition parameters have been varied including substrate temperature, gas concentration, gas pressure, total gas flow rate, RF input power, and deposition time. Analytical methods employed to determine composition and structure of the deposits include scanning electron microscopy, absorption spectroscopy, scanning Auger microprobe spectroscopy, and Raman spectroscopy. Analysis indicates that particles having a thin graphite surface, as well as diamond particles with no surface coatings, have been deposited. Deposits on quartz have exhibited optical bandgaps as high as 4.5 eV. Scanning electron microscopy analysis shows that particles are deposited on a pedestal which Auger spectroscopy indicates to be graphite. This is a phenomenon that has not been previously reported in the literature.

Meyer, Duane E.↗
NASA NTRS1988

Fine structure in RF spectra of lightning return stroke wave forms

The power spectra of the wide-band (10 Hz to 100 kHz) magnetic-field signals for a number of lightning return strokes measured during a thunderstorm which occurred in Lindau in August, 1984 have been calculated. The RF magnetic field data are obtained with the engineering unit of the Galileo Jupiter Probe lightning experiment. Each return stroke data stream is passed through an adaptive filter designed to whiten its spectrum. The spectra of the magnetic field data definitely show fine structure, with two or three distinct peaks in the spectra of many of the waveforms. A peak at f of about 60-70 kHz is often seen in the power spectra of the waveform time segments preceding and following the rise-to-peak amplitude of the return stroke.

Lanzerotti, L. J.↗
NASA NTRS1989

RF Modal Quantity Gaging

The primary objective is to provide a concept of a radio frequency (RF) modal resonance technique which is being investigated as a method for gaging the quantities of subcritical cryogenic propellants in metallic tanks. Of special interest are the potential applications of the technique to microgravity propellant gaging situations. The results of concept testing using cryogenic oxygen, hydrogen, and nitrogen, as well as paraffin simulations of microgravity fluid orientations, are reported. These test results were positive and showed that the gaging concept was viable.

Vanleuven, K.↗
NASA NTRS1990

The propagation of RF wave in a tandem mirror plasma propulsion device

The propagation of RF waves launched in the end and the central cell of the tandem mirror propulsion device has been investigated both theoretically and experimentally. It was found that the amplitude of the wave excited in the plasma peaked while approaching the resonance, but then damped out, indicating strong absorption of the wave by the plasma. The absorption took place near the axis and the midplane of the device. The experimental results confirmed the theoretical prediction of the resonance effect. A very important discovery of this experiment was the broadening of the ICRF Fourier spectrum in the presence of the plasma.

Yang, T. F.↗
NASA NTRS1990

High-temperature metal purification using a compact, portable rf heating and levitation system on the wake shield

The potential use of a compact, battery-operated rf levitator and heating system to purify high-temperature melting materials in space is described. The wake shield now being fabricated for the Space Vacuum Epitaxy Center will provide an Ultra-high vacuum (10(exp -14) Torr hydrogen, 10(exp -14) Torr helium, 10(exp -30) Torr oxygen). The use of the wake shield to purify Nb, Ti, W, Ir, and other metals to a purity level not achievable on earth is described.

Hahs, C. A.↗
NASA NTRS1990

High temperature metal purification using a compact portable rf heating and levitation system on the wake shield

The Wake Shield Facility (WSF) can provide an ideal vacuum environment for the purification of high temperature metals in space. The Modular Electromagnetic Levitator (MEL), will provide the opportunity to study undercooling of metals in space and allow to determine material properties in space. The battery powered rf levitation and heating system developed for the MEL demonstrated efficiency of 36 percent. This system is being considered to purify metals at temperatures below 3000 C.

Hahs, C. A.↗
NASA NTRS1991

Experiment and numerical simulation of RF heating in the Tandem Mirror plasma propulsion device

Recent results of experimental and theoretical studies of ICRF heating of the plasma in the Tendem Mirror rocket are presented. The radial and axial profile of the magnetic field of the wave have been measured, and the data agree with the results from numerical simulation. One very important new finding is that the wave damped when it approached the resonance plane. This is a strong indication of beach heating effect and that RF power is absorbed by the ions in the plasma as expected. This power absorption phenomenon was also further confirmed by the refined analytical study of the wave propagation in a slab model. The electron density in the central cell has been measured by a microwave interferometer. The existence of two types of discharge similar to those of H-alpha emission have also been observed from the density measurements. A preliminary design of a flight system for a 100-day Mars transit has been undertaken. The specific weight for a 10 MW rocket is only 0.04 kg/kW.

Yang, T. F.↗
NASA NTRS1991

A YBCO RF-squid variable temperature susceptometer and its applications

The Superconducting QUantum Interference Device (SQUID) susceptibility using a high-temperature radio-frequency (rf) SQUID and a normal metal pick-up coil is employed in testing weak magnetization of the sample. The magnetic moment resolution of the device is 1 x 10(exp -6) emu, and that of the susceptibility is 5 x 10(exp -6) emu/cu cm.

Zhou, Luwei↗
NASA NTRS1992

RF FEL for power beaming

The laser device components associated with operating a radio frequency-free electron laser (RF-FEL) for beaming power from Earth were designed and tested. Analysis of the power beaming system requirements reveals that the FEL, identified by NASA as the laser of choice, is the major subsystem requiring demonstration before proceeding further in proving the efficacy of laser power beaming. Rocketdyne has identified a series of low cost, low risk demonstrations which proceed sequentially, as follows: (1) a 1 kW proof-of-principle demonstration; (2) a 150 kW demonstration of beaming power to a satellite; and (3) a MW class demonstration of Earth to lunar surface power transmission. This sequence of events can be completed in 5.5 years at a cost of $188M, with key milestones each year.

Burke, Robert↗
NASA NTRS1991

Fiberoptic sensing technique employing RF modulated interferometry

A detection technique for intensity type fiberoptic sensors is described. It employs a multimode fiber interferometer, with the sensor in one arm, excited by an LED modulated at RF frequencies f(o) and 2f(o). Sensor induced changes in intensity result in corresponding changes in the ratio of the detected f(o) and 2f(o) signals, thus eliminating various common mode effects. Results obtained with a displacement sensor and preliminary results from a pressure sensor illustrate the capabilities of this technique.

Eustace, John G.↗
NASA NTRS1990

Integrated CMOS RF amplifier

This paper reports an integrated 2.0 micron CMOS RF amplifier designed for amplification in the 420-450 MHz frequency band. Design techniques are shown for the test amplifier configuration. Problems of decreased amplifier bandwidth, gain element instability, and low Q values for the inductors were encountered. Techniques used to overcome these problems are discussed. Layouts of the various elements are described and a summary of the simulation results are included. Test circuits have been submitted to MOSIS for fabrication.

Charity, C.↗
NASA NTRS1993

Direct digital RF synthesis and modulation for MSAT mobile applications

A practical method of performing direct digital RF synthesis using the Hilbert transform single sideband (SSB) technique is described. It is also shown that amplitude and phase modulation can be achieved directly at L-band with frequency stability and spurii performance exceeding stringent MSAT system requirements.

Crozier, Stewart↗