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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Charged particle measurements on a 30-CM diameter mercury ion engine thrust beam

Measurements of both thrust ions and charge exchange ions were made in the beam of a 30 centimeter diameter electron bombardment mercury ion thruster. A qualitative model is presented which describes magnitudes of charge exchange ion formation and motions of these ions in the weak electric field structure of the neutralized thrust beam plasma. Areas of agreement and discrepancy between observed and modeled charge exchange properties are discussed.

Sellen, J. M., Jr.↗
NASA NTRS1979

Measurements of particle emission from discharge sites in Teflon irradiated by high energy electron beams

Anomalous behavior of synchronous orbit satellites manifested by overall degradation of system performance and reduced operating life is associated with electrical discharges resulting from differential charging of the spacecraft surface by fluxes of high energy electrons. During a laboratory simulation silver-backed Teflon samples have been irradiated by electron beams having energies in the range 16-26 keV. Charged particles emitted from the resultant electrical discharges have been measured with a biased Faraday cup and retarding potential analyser. Measurements indicate the presence of two distinct fluxes of particles, the first being an early pulse (0-600ns) of high energy (about 7keV) electrons, while the second is a late pulse (1-5 microseconds) of low energy electrons (less than 1eV) and ions (70eV) leaving the discharge site as a quasi plasma. Calculations indicate an electrostatic field as the dominant accelerating mechanism for charged particles.

Hazelton, R. C.↗
NASA NTRS2002

Response of a tissue equivalent proportional counter to neutrons

The absorbed dose as a function of lineal energy was measured at the CERN-EC Reference-field Facility (CERF) using a 512-channel tissue equivalent proportional counter (TEPC), and neutron dose equivalent response evaluated. Although there are some differences, the measured dose equivalent is in agreement with that measured by the 16-channel HANDI tissue equivalent counter. Comparison of TEPC measurements with those made by a silicon solid-state detector for low linear energy transfer particles produced by the same beam, is presented. The measurements show that about 4% of dose equivalent is delivered by particles heavier than protons generated in the conducting tissue equivalent plastic. c2002 Elsevier Science Ltd. All rights reserved.

NASA Center JSC↗
NASA NTRS1994

Low-Flow-Rate Dry-Powder Feeder

Apparatus feeds small, precise flow of dry powder through laser beam of optical analyzer measuring patterns of light created by forward scattering (Fraunhofer diffraction) of laser beam from powder particles. From this optical measurement, statistical distribution of sizes of powder particles computed. Rates of flow optimized for measurement of particle-size distributions. Developed for analyzing particle-size distributions of solid-propellant powders. Also adapted to pharmaceutical industry, in manufacture of metal powder, and in other applications where particle-size distributions of materials used to control rates of chemical reactions and/or physical characteristics of processes.

Ramsey, Keith E.↗
NASA NTRS1972

Particle detection with intensified laser beam

Application of external and laser output mirrors to produce intensified light beam for measurement of light scattered by dispersed particles is described. Use of fiber optics bundles to collect light is discussed. Diagram of equipment and principles of operation are presented.

Knollenberg, R. G.↗
NASA NTRS1971

Hanle-effect mean-life measurements on aligned fast ions.

Mean lives of several levels of the first two ionized states of argon were obtained by Hanle-effect measurements on the fast-beam particles, following coherent alignment of the magnetic substates by beam-foil interaction. The g factors of the levels were obtained by observation of quantum beats. Mean lives are compared with results of the usual beam-foil mean-life measurement technique. We show that the Hanle effect can sometimes clarify beam-foil results.

Church, D. A.↗
NASA NTRS1974

Coherent optical instrumentation for measurements of particle parameters

The application of cross-beam Laser Doppler Velocimeter (LDV) for sizing small particles was investigated from September 1973 to August 1974. Theoretical results were obtained by analyzing the scattering characteristics of small particles in a cross-beam LDV system. Theoretical calculations based on scalar diffraction theory and Mie scattering theory were performed. Experimental results were also obtained to compare with theoretical predictions. It is concluded that the forward scattering characteristics of small particles in a cross-beam LDV system can be used for particle sizing.

Chu, W. P.↗
NASA NTRS1981

Space experiments with particle accelerators

The purpose of space experiments with particle accelerators (SEPAC) is to carry out active and interactive experiments on and in the Earth's ionosphere and magnetosphere. It is also intended to make an initial performance test for an overall program of Spacelab/SEPAC experiments. The instruments to be used are an electron beam accelerator, magnetoplasma dynamic arcjet, and associated diagnostic equipment. The accelerators are installed on the pallet, with monitoring and diagnostic observations being made by the gas plume release, beam-monitor TV, and particle-wave measuring instruments also mounted on the pallet. Command and display systems are installed in the module. Three major classes of investigations to be performed are vehicle charge neutralization, beam plasma physics, and beam atmosphere interactions. The first two are mainly onboard plasma physics experiments to measure the effect of phenomena in the vicinity of Spacelab. The last one is concerned with atmospheric modification and is supported by other Spacelab 1 investigations as well as by ground-based, remote sensing observations.

Obayashi, T.↗
NASA NTRS1999

Fragmentation of 200 and 244 MEV/u Carbon Beams in Thick Tissue-Like Absorbers

Stacks consisting of thin CR-39 sheets sandwiched between thick lucite and water absorbers were perpendicularly bombarded by C-12 ions at 200 and 244 MeV/u. Track radius distributions representing the charge composition of the fragmented beams were automatically measured by a particle track analysis system. After analysis of the nuclear charge distributions, the total charge removal cross-sections and elemental production cross-sections of fragments with atomic numbers from 5 to 3, were obtained down to the lower energies (approx. 50 and 100 MeV/u, respectively). It has been found that the measured total charge removal cross-section agrees with theoretical predictions within approx. 10% and very well with previous experiments in corresponding energy regions. Two model calculations for production of B fragment are in good agreement with our measured data while a third model overestimates it by approx. 12%. Theoretical cross-sections for Be and Li fragments differ strongly among the different models and from measured values.

Golovchenko, A. N.↗
NASA NTRS1999

Fragmentation of 200 and 244 MeV/u Carbon Beams in Thick Tissue-Like Absorbers

Stacks consisting of thin CR-39 sheets sandwiched between thick Lucite and water absorbers were perpendicularly bombarded by C-12 ions at 200 and 244 MeV/u. Track radius distributions representing the charge composition of the fragmented beams were automatically measured by a particle track analysis system. After analysis of the nuclear charge distributions, the total charge removal cross sections and elemental production cross sections of fragments with atomic numbers from 5 to 3, were obtained down to the lower energies (approximately 50 and 100 MeV/u, respectively). It has been found that the measured total charge removal cross section agrees with theoretical predictions within approximately 10% and very well with previous experiments in corresponding energy regions. Two model calculations for production of B fragment are in good agreement with our measured data while a third model overestimates it by approximately 12%. Theoretical cross sections for Be and Li fragments differ strongly among the different models and from measured values.

Golovchenko, A. N.↗
NASA NTRS1972

On charged particle tracks in cellulose nitrate and Lexan

Investigations were performed aimed at developing plastic nuclear track detectors into quantitative tools for recording and measuring multicharged, heavy particles. Accurate track etch rate measurements as a function of LET were performed for cellulose nitrate and Lexan plastic detectors. This was done using a variety of incident charged particle types and energies. The effect of aging of latent tracks in Lexan in different gaseous atmospheres was investigated. Range distributions of high energy N-14 particle bevatron beams in nuclear emulsion were measured. Investigation of charge resolution and Bragg peak measurements were carried out using plastic nuclear track detectors.

Benton, E. V.↗
NASA NTRS1986

Determination of cosmogenic Ca-41 in a meteorite with tandem accelerator mass spectrometry

The first use of tandem accelerator mass spectrometry (TAMS) to measure the content of Ca-41 in a natural sample, the iron Bogou meteorite, is reported. Ca in the samples was extracted by hydroxide precipitation and purified by means of a caution exchange resin (AG 50W-X8). After adding 4 percent ammonium oxide, the precipitate was ignited to CaO in a quartz vial at about 1100 C. The Ca-41/Ca ratios were determined following acceleration by alternate measurements of the Ca-40 beam current in an image Faraday cup. Ca-41 particles were also measured using a gas counter. The measured Ca-41/Ca ratio was 3.8 + or -0.6 x 10 to the 12th, which corresponds to a Ca-41 activity of 6.9 + or -1.1 d.p.m. per kg. Calculation of the half-life of Ca-41 in the Bogou meteorite yielded an age of 103,000 years.

Kubik, P. W.↗
NASA NTRS1979

Instrument for aerosol characterization

Differential pumping system that directs particles into beam moving at high speed measures size distribution and chemical composition of aerosols and is useful in study of atmospheric contamination, smog, stack gases, and chemical aerosols.

Varsi, G.↗
NASA NTRS1988

Protons and alpha particles in field-aligned beams upstream of the bow shock

Measurements of H(+) and He(2+) ions in field-aligned beams (about 10 keV/nuc) made with the AMPTE-CCE spacecraft are reported. The proton beam population has a density of less than about 1 percent of the solar wind density and a significant thermal anisotropy, in agreement with previous observations. The observed beam velocities are in reasonable agreement with the 'direct reflection' model, in which a portion of the solar wind is reflected and energized at the earth's bow shock, but are consistently larger than expected from magnetosheath leakage models. The He(2+) ions in the beams have approximately the same velocity as the H(+) ions, but the He(2+) to H(+) density ratio is dramatically smaller than that measured simultaneously in the solar wind. The present beam observations were obtained during several of the time intervals previously analyzed by other workers, using data from the same spacecraft, who attributed the streaming upstream ions to magnetospheric rather than bow shock origin.

Ipavich, F. M.↗
NASA NTRS1979

The total scattering cross sections for H2 + H2, D2 + D2, and HD + HD for relative collision energies below 10 meV

Relative total scattering cross sections for normal H2 + normal H2, para-H2 + para-H2, normal D2 + normal D2, ortho-D2 + ortho-D2, and HD + HD were measured at energy below 10 meV by colliding particles from two inclined nozzle beams. Cross sections for the H2 + H2 pairs were measured over a relative velocity range of 200-1450 m/s; the normal H2 + normal H2 results suggest a l = 3 orbiting resonance near 375 m/s while the para-H2 + para-H2 results have a l = 4 orbiting resonance near 585 m/s. This latter resonance has a peak energy of 1.79 meV and a FWHM of 1.05 meV. The D2 + D2 cross sections were measured over the velocity range of 190 to 1000 m/s and a minimum between the l = 4 and l = 5 orbiting resonances was observed. Some preliminary measurements on HD + HD over the range of 250-1250 m/s indicate a possible l = 4 orbiting resonance near 300 m/s. The experimental work compares favorably to cross sections calculated from a theoretical potential.

Johnson, D. L.↗