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Results for “PLASMA DIAGNOSTICS”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

The potential for plasma diagnostics from stellar extreme-ultraviolet observations

A description of the lines from the most abundant ions in the EUV spectrum in the range 50-500 A that have special diagnostic significance is presented. These lines are from plasmas in the temperature range from 10 exp 5 to 10 exp 7 K. Their utility for determining temperature, density, and abundances is demonstrated. An objective grating spectrometer, based on the Skylab slitless spectrograph, for making celestial observations in the EUV spectral region with high spectral resolution is also described. Such an instrument, if equipped with a multilayer grating, can achieve efficiencies over limited EUV wavelength ranges that rival much larger telescope-spectrometer instruments for the observation of stars and other celestial objects.

Feldman, U.↗
NASA NTRS1973

Application of cylindrical Langmuir probes to streaming plasma diagnostics.

The current-voltage characteristics of cylindrical probes in a high velocity collisionless plasma flow have been investigated experimentally and theoretically. The plasma was generated by a focused laser pulse incident on a metallic target in vacuum. An analysis, developed from a stationary plasma analog to the flowing case, demonstrated a failure of plasma shielding of probe potential in the electron attracting region. Modifications of relatively simple previous treatments were found to be valid for computing electron current to a probe. The electron characteristics derived from the present analysis agree well with experimental results. The ion and electron portions of the characteristics are consistent with each other and with independent diagnostic measurements.

Segall, S. B.↗
NASA NTRS2000

Demonstrating the Power of Chandra High Resolution Spectroscopy Plasma Diagnostics

The Chandra spectrometers can resolve spectroscopic features that can be used to diagnose the state of emitting plasma. Based on high resolution Chandra High Energy Transmission Grating (HETG) calibration observations of the active RS CVn-type Binary V711 Tau (HR1099), we determine for the first time the plasma density at a range of coronal temperatures for this type of object. The results are used to constrain coronal structural models and build a picture of the change in coronal structure from stars of solar-like activity to the most active RS CVn-type binaries.

Drake, Jeremy↗
NASA NTRS1980

A Recoverable Plasma Diagnostics Package (RPDP) for Spacelab

The RPDP is a fully instrumented, ejectable and recoverable unit with flight and ground support systems so that it can be utilized attached to the orbiter remote manipulator system, tethered from the orbiter, or as an orbiter subsatellite. Core instruments on the RPDP are flight proven hardware which provide diagnostics measurements of energetic particles, AC electromagnetic and electrostatic waves, vector magnetic field signatures of current systems, vector electric field signatures associated with plasma flow and particle acceleration, thermal plasma ion composition and density, thermal plasma electron density and temperature, and images of optical emissions regions in UV or visible wavelengths.

Shawhan, S. D.↗
NASA NTRS1985

Variable frequency VLF signals in the magnetosphere Associated phenomena and plasma diagnostics

Coherent variable-frequency signals (ramps) extending from 1 to 8 kHz, injected into the magnetosphere from Siple Station, Antarctica (L=4.3), exhibit upper and lower cutoffs when received at the conjugate station, Roberval, Quebec. Ramp group delay measurements and ionospheric sounding data are used to determine the cold plasma density and L shell of the propagation path. Relationships among f, df/dt, and the 'phase equator' for gyroresonance are calculated using second-order resonance equations generalized to relativistic electrons. The concept thereby introduced is used to develop a diagnostic technique which, for an assumed g(alpha)(v exp -n) electron distribution, provides an estimate of the energy dependence n. Additional aspects of the magnetospheric response to ramp injection, such as emission triggering, curvature due to dispersion, and amplitude saturation, are discussed.

Carlson, C. R.↗
NASA NTRS1988

Silane and germane plasma diagnostics for depositing photosensitive a-SiGe:H films

Highly photosensitive a-SiGe:H films with a light-to-dark conductivity ratio of 8 x 103 and an optical bandgap of 1.40 eV have been produced by RF glow discharge using hydrogen dilution of SiH4 and GeH4 mixed gas plasma. The critical role of hydrogen dilution in GeH4 containing plasmas is to suppress the gas-phase polymerization and promote the incorporation of Ge into the film. It is observed that inelastic laser light scattering of the RF plasma is a sensitive method for monitoring the onset of the gas-phase polymerization. In situ coherent anti-Stokes Raman spectroscopy measurements have shown that the dissociation rate of GeH4 is a factor of three larger than that of SiH4.

Shing, Y. H.↗
NASA NTRS1984

Physics of the inner heliosphere 1-10R sub O plasma diagnostics and models

The physics of solar wind flow in the acceleration region and impulsive phenomena in the solar corona is studied. The study of magnetohydrodynamic wave propagation in the corona and the solutions for steady state and time dependent solar wind equations gives insights concerning the physics of the solar wind acceleration region, plasma heating and plasma acceleration processes and the formation of shocks. Also studied is the development of techniques for placing constraints on the mechanisms responsible for coronal heating.

Withbroe, G. L.↗
NASA NTRS1982

EUV spectroscopic plasma diagnostics for the solar wind acceleration region

Possibilities are considered for probing physical conditions in the solar corona with strong EUV resonance lines from ions such as N V, O VI, Ne VIII, Mg X, and Si XII. Through measurements of the intensities and profiles of EUV spectral lines with coronagraphic instrumentation employing normal incidence reflecting optics, it is possible to acquire information on electron, proton, and ion temperatures and velocity distributions; electron, H I, and ion densities; mass flow and nonthermal velocities; and chemical abundances. This information will provide critical empirical constraints on physical processes responsible for plasma heating, solar wind acceleration, and transport of mass, momentum, and energy in the solar corona, as well as providing constraints on theoretical models for solar and stellar coronae and mass loss.

Kohl, J. L.↗
NASA NTRS1984

Measurements of electromagnetic interference on OV102 Columbia using the plasma diagnostics package

The third Space Shuttle mission's OSS-1 payload included 30 Hz-800 MHz and S-band receivers which assessed the intentional (transmitter) and unintentional (subsystem) EMI levels. It was noted that, at the pallet location, the UHF voice downlink transmitter field strengths did not exceed 0.1 V/m. At the remote manipulator system, the figure was 0.5 V/m. Below 300 kHz, the magnetic field noise was 30 dB pT + or - 20 dB, while the electric field noise was broadband and variable over at least 60 dB, depending on thruster firings and Orbiter attitude. This noise may have been generated by the Orbiter's interaction with the ambient plasma.

Shawhan, S. D.↗
NASA NTRS1976

Plasma diagnostic techniques in the ultraviolet - The C III density-sensitive lines in the sun

Spectra and spectroheliograms of the C III transitions at 977 and 1176 A are obtained with the Harvard extreme-ultraviolet spectrometer on Skylab. Analysis of the intensities of these lines, and of their density-sensitive ratio, indicates a wide range of temperature gradients and electron densities in the transition region of various solar features. From values of the observed ratio, we suggest necessary revisions to the excitation rates, and propose a relationship between the ratio and density. The significantly higher ratio found in active regions indicates a density increase of about a factor 2 relative to the network. In the quiet sun, there is no significant difference in density between network and cell interiors, but the uncertainty is as large as a factor 3. The very central 10% of the areas of cell interiors shows a significantly higher density than the mean value for cell interiors.

Dupree, A. K.↗
NASA NTRS1978

The importance of spectroscopy in the 80-800 A region for plasma diagnostics in the solar atmosphere

The importance of the spectral range from about 80 to 800 A for determining physical conditions in different regions of the solar atmosphere is discussed. Examples are given of line ratios that may be used to determine electron densities in quiet-sun regions, active regions, and flares. The possibility of determining electron temperatures from line ratios in the EUV is considered. It is shown that profiles, as well as intensities, of spectral lines must be obtained for a proper interpretation of the spectra. Approximate parameters are provided for a solar grazing-incidence spectrograph suitable for the study of the 80-800-A wavelength region.

Feldman, U.↗
NASA NTRS1983

Some spectral plasma diagnostics for prominences and structures in the middle chromosphere

The present investigation is concerned with the statistical equilibrium of the low-lying levels of Na, Sr(+), and Ba(+) under conditions appropriate to structures just above the solar surface. The solar and atomic data required for this objective are largely available with an adequate precision. However, the metastable (2)D term photoionization cross sections had to be calculated. In the calculations a variant of the scaled Thomas-Fermy method suggested by Kahler (1971) was used. The Na and Sr(+) resonance lines are readily measurable in ordinary prominences. The Ba(+) are weak. It is shown that the ratio of Na to Sr(+) resonance-line integrated intensities provides a useful and sensitive electron-density diagnostic for prominences, yielding values in the neighborhood of 10 to the 11th per cu cm. The statistical equilibrium solutions are applied to an analysis of data from the flash spectrum at eclipse.

Landman, D. A.↗
NASA NTRS1984

Plasma diagnostics for the outer solar corona - UV and XUV Fe XII lines

The formation of the UV and XUV spectral lines of Fe XII in the outer corona was investigated. The results indicate that these lines can be an important tool for probing the physical conditions in the coronal regions where the solar wind is generated. The Fe XII lines can be particularly useful for determining outflow velocities of heavy ions in the solar wind and for providing critical empirical constraints on energy transport and dissipation mechanisms in the solar wind acceleration region. Application of the theoretical calculations to existing UV, EUV, and XUV observations of the low corona provide evidence that: (1) the inclusion of the effects of resonances in the collision strengths for the low-lying levels of Fe XII is important, (2) that the contributions of resonances for these levels are even larger than the estimates given in the present paper, and (3) that the collision strengths used here yield populations for these levels which are accurate to a factor of 2. These results have implications concerning the accuracy of abundances and densities derived from observations of the Fe XII lines in the low corona.

Withbroe, G. L.↗
NASA NTRS1985

Potential of CCDs for UV and X-ray plasma diagnostics

A program is under way to develop charge-coupled device (CCD) sensors for space-based X-ray astronomy imaging spectrometers. To date, laboratory line-emission spectra have been acquired throughout the range of 277 to 8000 eV (carbon through copper K-alpha emission) and CCD sensitivity has been demonstrated throughout the range of 1.1 through 8000 eV. Image resolution is excellent, limited almost entirely by the 15 micron pixel size. These results are presented and specialized techniques are described which permit such low energy response, high spectral resolution, and efficient charge collection. Finally, analysis is presented of one particular CCD characteristic which currently limits UV and X-ray performance: charge diffusion.

Janesick, J. R.↗
NASA NTRS1986

Laser techniques for arc jet plasma diagnostics; continuation of a feasibility and design study

This study is concerned with the continuation of a feasibility and design study of laser-based diagnostic techniques for the non-instrusive measurement of species concentrations, temperatures, and velocity in the low density, high enthalpy flow through the arc-heated wind tunnel facility (ARMSEF) at NASA/JSC. Last summer several laser-induced radiation scattering methods were investigated and some preliminary measurements of the spectral distribution of radiation emitted by the arc-heated gas flow were made. Based upon those preliminary measurements and subsequent investigations, four laser-induced radiation scattering methods were selected for further detailed study, and preliminary design of a measurement system has been undertaken. Further measurements of the spectral distribution of radiation emitted from the arc-heated free stream and shock layer flows, using a redesigned measurement system, have been made for one axial position in the flow for a range of tunnel operating power levels. Further study of the literature for physical property data, theoretical models of processes, and applications of the diagnostic methods has been also carried out.

Wierum, F. A.↗
NASA NTRS1986

UV observations of transition-region plasmas in solar flares - Plasma diagnostics and relationships between UV and hard X-ray bursts

The impulsive and gradual phases of solar flares are investigated, comparing simultaneous SMM UVSP and HXRBS observations. Data for several 1980 flares are presented graphically and characterized in detail, with reference to the results of numerical simulations based on theoretical models. Consideration is given to the density and mass velocity in the transition region, the temporal and spatial relationships between the impulsive UV and X-ray bursts, and the relationships between the impulsive and gradual phases.

Cheng, Chung-Chich↗