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Results for “PLASMA FLUX MEASUREMENT”

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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Evaporative cooling of flare plasma

We investigate a one-dimensional loop model for the evaporative cooling of the coronal flare plasma. The important assumptions are that conductive losses dominate radiative cooling and that the evaporative velocities are small compared with the sound speed. We calculate the profile and evolution of the temperature and verify the accuracy of our assumptions for plasma parameters typical of flare regions. The model is in agreement with soft X-ray observations on the evolution of flare temperatures and emission measures. The effect of evaporation is to greatly reduce the conductive heat flux into the chromosphere and to enhance the EUV emission from the coronal flare plasma.

Antiochos, S. K.↗
DOE OSTI2024

Avalanche statistics of fluctuation-induced fluxes from the SLPM and the W7-AS stellarator

Measurements of fluctuating floating potentials and ion saturation currents at different radial locations in the Santander Linear Plasma Machine (Castellanos et al 2005 Plasma Phys. Control. Fusion47 2067) and at the edge of the W7-AS stellarator by means of radially movable Langmuir probes allow to infer the corresponding fluctuation-induced radial flux temporal series. Avalanche-like transport events are identified in the time series and statistically characterized in terms of avalanche size/duration/quiet-time distributions and size-duration scaling relations. Transport is diffusive in the inner and intermediate radial region of the SLPM r < r tr ≈ 2.6 cm, undergoing a transition at r tr , becoming non-diffusive in the outermost region of the device, r > r tr . Here, the results obtained at the edge of the W7-AS stellarator are similar to those found in SLPM for r > r tr , i.e. consistent with what would be expected for scale-free, self-similar plasma transport dynamics near a critical state.

Avalanches↗
NASA NTRS1985

Advanced missions to primitive bodies

Six interplanetary spacecraft, three earth orbital experiments, and one spacecraft orbiting Venus will observe comets Halley and Giacobini-Zinner in 1985-86. At comet Halley, attempts will be made to image the nucleus, remote sensing will be made by spectrometers in wavelength ranges from the IR to the UV, and in-situ observations will be made with neutral, ion and dust mass spectrometers. Plasma measurements will be made at both comets and at comet Halley the upstream solar wind flux will be simultaneously monitored by nearby spacecraft. In the post-Halley era, there are several missions being planned for the continued exploration of the solar system's most primitive bodies - comets and asteroids.

Yeomans, D. K.↗
NASA NTRS2004

Interplanetary Radiation and Internal Charging Environment Models for Solar Sails

A Solar Sail Radiation Environment (SSRE) model has been developed for characterizing the radiation dose and internal charging environments in the solar wind. The SSRE model defines the 0.01 keV to 1 MeV charged particle environment for use in testing the radiation dose vulnerability of candidate solar sail materials and for use in evaluating the internal charging effects in the interplanetary environment. Solar wind and energetic particle instruments aboard the Ulysses spacecraft provide the particle data used to derive the environments for the high inclination 0.5 AU Solar Polar Imager mission and the 1.0 AU L1 solar sail missions. Ulysses is the only spacecraft to sample high latitude solar wind environments far from the ecliptic plane and is therefore uniquely capable of providing the information necessary for defining radiation environments for the Solar Polar Imager spacecraft. Cold plasma moments are used to derive differential flux spectra based on Kappa distribution functions. Energetic particle flux measurements are used to constrain the high energy, non-thermal tails of the distribution functions providing a comprehensive electron, proton, and helium spectra from less than 0.01 keV to a few MeV.

Minow, Joseph I.↗
NASA NTRS2008

The Formation of Coronal Loops by Thermal Instability in Three Dimensions

Plasma loops in solar active regions have been observed in EUV and soft X-rays for decades. Their formation mechanism and properties, however, are still not fully understood. Predictions by early models, based on 1D hydrostatic equilibria with uniform plasma heating, are not consistent with high-resolution measurements. In this Letter, we demonstrate, via 3D simulations, that a class of heating models can lead to the dynamic formation of plasma loops provided the plasma is heated sufficiently to match SXT soft X-ray measurements. We show that individual flux tubes in a 3D magnetic structure tend to stand out against their neighbors. The loops have large aspect ratios and nearly uniform cross sections in the corona, similar to those observed by EIT and TRACE. The coronal EUV emission from these thermally unstable solutions is roughly consistent with EIT measurements. The solution oscillates in time through a large-amplitude, nonlinear cycle, leading to repeated brightening and fading of the loops.

Mok, Yung↗
NASA NTRS2017

Characterization of a 50kW Inductively Coupled Plasma Torch for Testing of Ablative Thermal Protection Materials

With the development of new manned spaceflight capabilities including NASA's Orion capsule and the Space-X Dragon capsule, there is a renewed importance of understanding the dynamics of ablative thermal protection systems. To this end, a new inductively coupled plasma torch facility is being developed at UT-Austin. The torch operates on argon and/or air at plasma powers up to 50 kW. In the present configuration the flow issues from a low-speed subsonic nozzle and the hot plume is characterized using slug calorimetry and emission spectroscopy. Preliminary measurements using emission spectroscopy have indicated that the torch is capable of producing an air plasma with a temperature between 6,000 K and 8,000 K depending on the power and flow settings and an argon plasma with a temperature of approximately 12,000 K. The operation envelope was measured, and heat flux measured for every point within the envelope using both a slug calorimeter and a Gardon gauge heat flux sensor. The torch was found to induce a stagnation point heat flux of between 90 and 225 W/sq cm.

Greene, Benton R.↗
NASA NTRS1974

Measurement of the X-ray emission of the solar atmosphere during a period of low activity

A large-area high-sensitivity X-ray spectrometer has been constructed and used to measure the 1.8- to 5.3-A X-ray emission of the sun under quiescent conditions. The instrument utilizes Bragg reflection from mosaic graphite crystals. The data indicate that the X-ray emission can best be accounted for by a multitemperature model of the solar atmosphere in which both the overall corona and active regions contribute to the X-ray spectrum. Theoretical calculations of the X-ray flux of a hot, optically thin plasma have been used to estimate the solar conditions at the time when the measurements were made.

Wolff, R. S.↗
NASA NTRS1979

Investigation of the magnetospheric boundary plasma and magnetic field data from Explorers 33, 43, and 50

Understanding of the plasma depletion process in the dayside magnetosheath, the nature of magnetotail boundary motion, and the geometry of the magnetospheric boundary layers was examined. A model of the dayside boundary layers, based on the hypothesis that merging occurs only for strictly anitparallel fields was developed which provides a qualitative solution to the problem of the half-wave rectifier response of the magnetosphere to the solar wind electric field. Regarding magnetotail boundary motion, consideration of the data led to the conclusion that at lunar distance, substorms are associated with very large amplitude compressional wave motion of the sausage type. A study of IMF orientation for depletion and nondepletion cases suggests that depletion is most likely to occur for angles between the IMF and the normal to the magnetopause at the measurement location near 90 deg, in agreement with predictions. Observations of the heat flux in the dayside magnetosheath plasma suggest that the energized plasma ions have their source along a given flux tube at that intersection with the bow shock where the magnetic field is most compressed.

Siscoe, G. L.↗
DOE OSTI2023

Ion concentration ratio measurements of ion beams generated by a commercial microwave electron cyclotron resonance plasma source

A commercially available electron cyclotron resonance (ECR) plasma source (GenII Plasma Source, tectra GmbH) is widely used for surface processing. This plasma source is compatible with ultrahigh vacuum systems, and its working pressure is relatively low, around 10 –6 –10 –4 Torr even without differential pumping. Here, we report ion flux concentration ratios for each ion species in an ion beam from this source, as measured by a mass/energy analyzer that is a combination of a quadrupole mass spectrometer, an electrostatic energy analyzer, and focusing ion optics. In this study, the examined beams were those arising from plasmas produced from feed gases of H 2 , D 2 , N 2 , O 2 , Ar, and dry air over a range of input power and working pressures. H 2 (D 2 ) plasmas are widely used for nuclear fusion applications and, hence, the ion concentration ratios of H + , H 2 + , and H 3 + reported here will be useful information for research that applies this plasma source to well-controlled plasma-material interaction studies. Ion energy distributions, stability of operation, and impurity concentrations were also assessed for each of the plasma species investigated.

47 OTHER INSTRUMENTATION↗
NASA NTRS1984

Reconnection at the earth's magnetopause - Magnetic field observations and flux transfer events

Theoretical models of plasma acceleration by magnetic-field-line reconnection at the earth magnetopause and the high-resolution three-dimensional plasma measurements obtained with the ISEE satellites are compared and illustrated with diagrams, graphs, drawings, and histograms. The history of reconnection theory and the results of early satellite observations are summarized; the thickness of the magnetopause current layer is discussed; problems in analyzing the polarization of current-layer rotation are considered; and the flux-transfer events responsible for periods of patchy reconnection are characterized in detail. The need for further observations and refinements of the theory to explain the initiation of reconnection and identify the mechanism determining whether it is patchy or steady-state is indicated.

Russell, C. T.↗
NASA NTRS2003

Plasmaspheric Mass Loss and Refilling as a Result of a Magnetic Storm

Using the sounding measurements from the radio plasma imager on IMAGE, and a plasma density inversion algorithm, we derive the plasma density profiles along the magnetic field in a few L-shells every 14 hours at magnetic local noon before, during, and after the March 31,2001 magnetic storm. An empirical model of the plasmaspheric plasma density distribution is derived as a reference using the measurements before the storm. During the storm, the equatorial plasma was substantially depleted in a range of L-shells. The flux tubes were refilled after the storm. The filling ratio, the equatorial plasma density normalized by its quiet-time value before the storm, is introduced to assess the time evolution of the depletion and refilling processes. The depletion, more than two thirds of the quiet time content, appeared to occur rather quickly after the storm onset, as determined by the limited temporal resolution of the measurements. The refilling proceeded, although more slowly than the depletion process, significantly faster than the theoretical prediction of a 3-day time scale. Dynamic structures are observed in situ and confirmed by the extreme ultraviolet imager (EUV) measurements.

Reinisch, B. W.↗
NASA NTRS1989

Case study of modeled and measured D-region plasma densities

Two of the many sounding rockets launched as part of the MAC/Epsilon campaign are particularly suited to test the validity or quality of D region models. The measurements covered atomic oxygen, neutral temperatures and fluxes of charged particles. With these parameters as inputs, one is thus in the position to assess their relevance for the measured parameters, i.e., ion composition, transition heights of clusters and negative ions and total plasma density. The two IOMAS payloads are believed to be the only night flights with associated measurements of atomic oxygen extending below the ledge at about 80 km.

Friedrich, M.↗
NASA NTRSDate not supplied

Measurement of Material Recession and Shock Standoff in Plasma Windtunnel using Neural Nets

Arcjets are plasma wind tunnels used to test the performance of heatshield materials for spacecraft atmospheric entry. These facilities present an extremely harsh flow environment with heat fluxes up to 109 W/m2 for up to 30 minutes. The plasma is low-temperature (∼1 eV) but high pressure (> 10 kPa) creating high-enthalpy supersonic flows similar to atmospheric entry conditions. Typically, material samples are measured before and after a test to characterize the total recession. However, this does not capture time-dependent effects such as material expansion and non-linear recession. This work will present new analysis of arcjet test videos which measure both the time-dependent 2D recession of the material samples and the shock standoff distance. The results show non-linear time-dependent effects are present for some conditions. The material and shock edges are extracted from the videos by training and applying a convolutional neural network. Due to the consistent camera settings, the machine learning model achieves high accuracy (± 2 px) relative to manually segmented images with only a small number of training frames (80).

Neural network↗
NASA NTRS2003

Coronal Heating, Spicules, and Solar-B

Falconer et al. investigated the heating of the quiet corona by measuring the increase of coronal luminosity with the amount of the magnetic flux in the underlying network at solar minimum when there were no active regions on the face of the Sun. The coronal luminosity was measured from Fe IX/X - Fe XII pairs of coronal images from SOHO/EIT, under the assumption that practically all of the coronal luminosity in these very quiet regions came from plasma in the temperature range 0.9 x 10(exp 6) K is less than or equal to T is less than or equal to 1.3 x 10(exp 6) K. The network magnetic flux content was measured from SOHO/MDI magnetograms. It was found that luminosity of the corona in these quiet regions increased roughly in proportion to the square root of the magnetic flux content of the network and roughly in proportion to the length of the perimeter of the network flux clumps. From 1) this result; 2) the observed occurrence of many fine-scale explosive events (e.g., spicules) at the edges of network flux clumps; and 3) a demonstration that it is energetically feasible for the heating of the corona in quiet regions to be driven by explosions of granule-sized sheared-core magnetic bipoles embedded in the edges of the network flux clumps, Falconer et al. infer that in quiet regions that are not influenced by active regions the corona is mainly heated by such magnetic activity in the edges of the network flux clumps. From their observational results together with their feasibility analysis, Falconer et al. predict that 1) At the edges of the network flux clumps there are many transient sheared core bipoles of the size and lifetime of granules and having transverse field strengths greater than approx. 100 G; 2) Approx. 30 of these bipoles are present per supergranule; and 3) Most spicules are produced by explosions of these bipoles. The photospheric vector magnetograms, chromospheric filtergrams, and EUV spectra from Solar-B are expected to have sufficient sensitivity, spatial resolution, and cadence to test these predictions. The Falconer et al. (2003) inferred mixed-polarity magnetic flux at the base of spicules is compatible with the observed magnetic structure of Ha macrospicules recently found by Yamuchi et al. (2003).

Moore, Ron↗
NASA NTRS1986

Models of the plasmaspheric thermal plasma distribution

Current understanding of the thermal plasma in the atmosphere and its coupling to the ionosphere is reviewed. Existing models appear adequate to explain the gross behavior of the cold thermal plasma, but there remain some vexing problems. Notably, (1) why does the density in flux tubes appear to saturate at lower values than are predicted theoretically, (2) what causes the sunset peak in measured Te, and (3) why does the equatorial plasmapause signature differ in latitude from the ionosphere signatures. The more difficult problem of what happens during the early stages of refilling after a magnetic storm, when the high altitude plasma is likely to be supersonic and collisionless, has received much attention, but the results are not definite. A number of papers have dealt with the interaction of supersonic counterstreaming fluxes and there are now models that can handle the transition from supersonic to subsonic flows although the transition from a collisionless to a collision-dominated plasma remains difficult to deal with.

Richards, P. G.↗
NASA NTRS1977

Composition of the hot plasma near geosynchronous altitude

Although there were no direct measurements of the composition of the hot (keV) plasma at geosynchronous altitudes, the combination of other observations leads to the conclusion that, at least during geomagnetically disturbed periods, there are significant fluxes of ions heavier than protons in this region. Ion composition measurements below 8000 km altitude show upward streaming fluxes of both O(+) and H(+) ions in the L-region of the geosynchronous orbit. These observations are consistent with the conclusion that at least a portion of the total ion fluxes observed at geosynchronous altitude to be highly peaked near the magnetic field lines are heavier than protons and originate in the ionosphere.

Johnson, R. G.↗
NASA NTRSDate not supplied

Measurement of material recession and shock standoff in plasma windtunnel using neural nets

Arcjets are plasma wind tunnels used to test the performance of heatshield materials for spacecraft atmospheric entry. These facilities present an extremely harsh flow environment with heat fluxes up to 10^9 W/m^2 for up to 30 minutes. The plasma is low-temperature (~1 eV) but high pressure (> 10 kPa) creating high-enthalpy supersonic flows similar to atmospheric entry conditions. Typically, material samples are measured before and after a test to characterize the total recession. However, this does not capture time-dependent effects such as material expansion and non-linear recession. This work will present new analysis of arcjet test videos which measure both the time-dependent 2D recession of the material samples and the shock standoff distance. New results showing non-linear material erosion rates will be highlighted. The material and shock edges are extracted from the videos by training and applying a convolutional neural network. Due to the consistent camera settings, the machine learning model achieves high accuracy (~99%) on new data with only a small number of training frames (~80). The new results will be discussed in the context of temperature dependent plasma-surface interaction.

Magnus A Haw↗
NASA NTRS2007

Plasma Propulsion Testing Capabilities at Arnold Engineering Development Center

This paper describes the results of a series of experiments aimed at quantifying the plasma propulsion testing capabilities of a 12-ft diameter vacuum facility (12V) at USAF-Arnold Engineering Development Center (AEDC). Vacuum is maintained in the 12V facility by cryogenic panels lining the interior of the chamber. The pumping capability of these panels was shown to be great enough to support plasma thrusters operating at input electrical power >20 kW. In addition, a series of plasma diagnostics inside the chamber allowed for measurement of plasma parameters at different spatial locations, providing information regarding the chamber's effect on the global plasma thruster flowfield. The plasma source used in this experiment was Hall thruster manufactured by Busek Co. The thruster was operated at up to 20 kW steady-state power in both a lower current and higher current mode. The vacuum level in the chamber never rose above 9 x 10(exp -6) torr during the course of testing. Langmuir probes, ion flux probes, and Faraday cups were used to quantify the plasma parameters in the chamber. We present the results of these measurements and estimates of pumping speed based on the background pressure level and thruster propellant mass flow rate.

Polzin, Kurt A.↗