Search NASA⌕ Search

SEARCH · Search NASA

Results for “Plasma measurements”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

A survey of the plasma electron environment of Jupiter - A view from Voyager

A survey of the plasma environment within Jupiter's bow shock is given in terms of the in situ calibrated electron plasma measurements made between 10 eV and 5.95 keV by the Voyager Plasma Science Experiment (PLS). The measurements are analyzed and corrected for spacecraft potential variations; the data are reduced to nearly model independent macroscopic parameters of the local electron density and temperature. The electron parameters are derived without reference to or internal calibration from the positive ion measurements made in the PLS experiment. Extensive statistical and direct comparisons with other determinations of the local plasma charge density indicate clearly that the analysis procedures have successfully and routinely discriminated between spacecraft sheath and ambient plasmas.

Scudder, J. D.↗
NASA NTRS1996

Ulysses OUt-of-ecleptic Observations of Interplanetary Shocks

Interplanetary shocks observed at the Ulysses spacecraft as it traveled from the ecliptic plane to the southern solar pole have been identified and analyzed using both magnetic field and plasma measurements.

Interplanetary shocks Ulysses magnetic field plasm↗
DOE OSTI2020

Preliminary design overview and performance assessment of the ITER low-field side reflectometer

The design of the ITER low-field side reflectometer (LFSR) has matured to a complete end-to-end preliminary design. LFSR will supply three key plasma measurements: (1) electron density profile, (2) electron density fluctuations, and (3) poloidal rotation. Simultaneous measurements of the three quantities are enabled by an array of six monostatic antennas which inject from an equatorial port on the outboard side of the ITER vessel. Low-loss transmission lines, consisting of corrugated, overmoded waveguide and miter bends, transmit the 30–165 GHz, O- and X-mode signals to and from the ITER plasma. Integrated transmission-line components serve a range of purposes, such as protection from high-power stray radiofrequency radiation, accommodation of transmission-line displacement, and simultaneous measurement of reference and plasma phases during the discharge. Broadband transmission signals are realized by full-band microwave transceivers combined with quasi-optical multiplexing. A field-programmable gate array (FPGA) processor demodulates the profile reflectometer signals, enabling real-time density profile measurements for plasma control system feedback. A full-scale transmission line test facility provides an integrated environment to assess the performance of critical LFSR components. Theoretical modeling together with insertion loss measurements provide the basis for a comprehensive power budget, which accounts for transmitted output power, transmission-line losses, antenna coupling, and plasma effects. Results indicate that high signal-to-noise ratios are achievable with the current design. A synthetic reflectometer model, using real design parameters and baseline ITER profiles, has been developed to estimate the return signal. With evolving microwave and data acquisition technologies, full-band, ultrafast sweeps (<1 μs) will be realizable for ITER.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1990

Ion composition measurement techniques for space plasmas

Plasmas found in space range from the solar wind with a typical temperature of 100,000-1,000,000 K, about 400 km/s bulk flow speed, and high ionization (charge states) of ions, to the hot, slowly moving plasmas in the outer magnetospheres of the giant planets, to the cold, corotating plasmas in inner magnetospheres. Space plasma instruments and techniques are reviewed, with an emphasis on hot plasma composition measurements. Starting with Faraday Cup detectors some 30 years ago, plasma instruments have evolved to the present time-of-flight systems with excellent mass resolution and three-dimensional viewing capabilities.

Gloeckler, George↗
NASA NTRS1979

Electron observations and ion flows from the Pioneer Venus Orbiter plasma analyzer experiment

Additional plasma measurements in the vicinity of Venus are presented. It is shown that (1) there are three distinct plasma electron populations - solar wind electrons, ionosheath electrons, and nightside ionosphere electrons; (2) the plasma ion flow pattern in the ionosheath is consistent with deflected flow around a blunt obstacle; (3) the plasma ion flow velocities near the downstream wake may, at times, be consistent with the deflection of plasma into the tail, closing the solar wind cavity downstream from Venus at a relatively close distance (within 5 Venus radii) to the planet; (4) there is a separation between the inner boundary of the downstream ionosheath and the upper boundary of the nightside ionosphere; and (5) during the first 4.5 months in orbit the measured solar wind plasma speed continued to vary, showing a number of high-speed, but generally nonrecurrent, streams.

Intriligator, D. S.↗
NASA NTRS1983

Measurement of macroscopic plasma parameters with a radio experiment: Interpretation of the quasi-thermal noise spectrum observed in the solar wind

The ISEE-3 SBH radio receiver has provided the first systematic observations of the quasi-thermal (plasma waves) noise in the solar wind plasma. The theoretical interpretation of that noise involves the particle distribution function so that electric noise measurements with long antennas provide a fast and independent method of measuring plasma parameters: densities and temperatures of a two component (core and halo) electron distribution function have been obtained in that way. The polarization of that noise is frequency dependent and sensitive to the drift velocity of the electron population. Below the plasma frequency, there is evidence of a weak noise spectrum with spectral index -1 which is not yet accounted for by the theory. The theoretical treatment of the noise associated with the low energy (thermal) proton population shows that the moving electrical antenna radiates in the surrounding plasma by Carenkov emission which becomes predominant at the low frequencies, below about 0.1 F sub P.

Couturier, P.↗
NASA NTRS1978

Deep space telecommunications and the solar cycle: A reappraisal

Observations of density enhancement in the near corona at solar cycle (sunspot) maximum have rather uncritically been interpreted to apply equally well to the extended corona, thus generating concern about the quality of outer planet navigational data at solar cycle maximum. Spacecraft have been deployed almost continuously during the recently completed solar cycle 20, providing two powerful new coronal investigatory data sources: (1) in-situ spacecraft plasma measurements at approximately 1 AU, and (2) plasma effects on monochromatic spacecraft signals at all signal closest approach points. A comprehensive review of these (solar cycle 20) data lead to the somewhat surprising conclusions that for the region of interest of navigational data, the highest levels of charged particle corruption of navigational data can be expected to occur at solar cycle minimum, rather than solar cycle maximum, as previously believed.

Berman, A. L.↗
NASA NTRS2004

Model of a Hollow Cathode Insert Plasma

A 2-D axisymmetric fluid model of the plasma in the insert region of a hollow cathode is presented. The level of sophistication included in the model is motivated in part by the need to determine quantitatively plasma fluxes to the emitter surface. The ultimate goal is to assess whether plasma effects can degrade the life of impregnated inserts beyond those documented throughout the 30-50 year history of vacuum cathode technologies. Results from simulations of a 1.2-cm diameter cathode operating at a discharge current of 25 A, and a gas flow rate of 5 sccm, suggest that approximately 10 A of electron current, and 3.5 A of ion current return to the emitter surface. The total emitted electron current computed by the model is about 35 A. Comparisons with plasma measurements suggest that anomalous heating of the plasma due to two-stream instabilities is possible near the orifice region. Solution to the heavy species energy equation, with classical transport and no viscous effects, predicts heavy species temperatures as high as 2640 K.

hollow cathodes↗
NASA NTRS1998

Magnetic Storms

One of the oldest mysteries in geomagnetism is the linkage between solar and geomagnetic activity. The 11-year cycles of both the numbers of sunspots and Earth geomagnetic storms were first noted by Sabine. A few years later, speculation on a causal relationship between flares and storms arose when Carrington reported that a large magnetic storm followed the great September 1859 solar flare. However, it was not until this century that a well-accepted statistical survey on large solar flares and geomagnetic storms was performed, and a significant correlation between flares and geomagnetic storms was noted. Although the two phenomena, one on the Sun and the other on the Earth, were statistically correlated, the exact physical linkage was still an unknown at this time. Various hypotheses were proposed, but it was not until interplanetary spacecraft measurements were available that a high-speed plasma stream rich in helium was associated with an intense solar flare. The velocity of the solar wind increased just prior to and during the helium passage, identifying the solar ejecta for the first time. Space plasma measurements and Skylab's coronagraph images of coronal mass elections (CMES) from the Sun firmly established the plasma link between the Sun and the Earth. One phenomenon associated with magnetic storms is brilliant "blood" red auroras, as shown.

Tsurutani, Bruce T.↗
NASA NTRS1991

Plasma contactor research, 1990

Emissive and Langmuir probes were used to measure plasma potential profiles, plasma densities, electron energy distributions, and plasma noise levels near a hollow cathode-based plasma contactor emitting electrons. The effects of electron emission current (100 to 1500 mA) and contactor flowrate (2 to 10 sccm (Xenon)) on these data are examined. Retarding potential analyzer (RPA) measurements showing that high energy ions generally stream from a contactor along with the electrons being emitted are also presented, and a mechanism by which this occurs is postulated. This mechanism, which involves a high rate of ionization induced between electrons and atoms flowing together from the hollow cathode orifice, results in a region of high positive space charge and high positive potential. Langmuir and RPA probe data suggests that both electrons and ions expand spherically from this potential hill region. In addition to experimental observations, a simple one-dimensional model which describes the electron emission process and predicts the phenomena just mentioned is presented and is shown to agree qualitatively with these observations. Experimental results of the first stage of bilateral cooperation with the Italian Institute of Interplanetary Space Physics (IFSI CNR) are presented. Sharp, well-defined double layers were observed downstream of a contactor collecting electrons from an ambient plasma created in the IFSI Facility. The voltage drop across these double layers was observed to increase with the current drawn from the ambient plasma. This observation, which was not as clear in previous IFSI tests conducted at higher neutral pressures, is in agreement with previous experimental observations made at both Colorado State University and NASA Lewis Research Center. Greater double layer voltage drops, multiple double layers, and higher noise levels in the region near the double layers were also observed when a magnetic field was imposed and oriented perpendicular to the line joining the contactor and simulator.

Williams, John D.↗
NASA NTRS2017

A Survey of Nanoflare Properties in Active Regions Observed with the Solar Dynamics Observatory

In this paper, we examine 15 different active regions (ARs) observed with the Solar Dynamics Observatory and analyze their nanoflare properties. We have recently developed a technique that systematically identifies and measures plasma temperature dynamics by computing time lags between light curves. The time lag method tests whether the plasma is maintained at a steady temperature, or if it is dynamic, undergoing heating and cooling cycles. An important aspect of our technique is that it analyzes both observationally distinct coronal loops as well as the much more prevalent diffuse emission between them. We find that the widespread cooling reported previously for NOAA AR 11082 is a generic property of all ARs. The results are consistent with impulsive nanoflare heating followed by slower cooling. Only occasionally, however, is there full cooling from above 7 megakelvins to well below 1 megakelvin. More often, the plasma cools to approximately 1-2 megakelvins before being reheated by another nanoflare. These same 15 ARs were first studied by Warren et al. We find that the degree of cooling is not well correlated with the reported slopes of the mission measure distribution. We also conclude that the Fe (sup XVIII)-emitting plasma that they measured is mostly in a state of cooling. These results support the idea that nanoflares have a distribution of energies and frequencies, with the average delay between successive events on an individual flux tube being comparable to the plasma cooling timescale.

Viall, Nicholeen M.↗
DOE OSTI2023

Shock physics and shadowgraphic measurements of laser-produced cerium plasmas

Shadowgraphic measurements are combined with theory on gas-dynamics to investigate the shock physics associated with nanosecond laser ablation of cerium metal targets. Time-resolved shadowgraphic imaging is performed to measure the propagation and attenuation of the laser-induced shockwave through air and argon atmospheres at various background pressures, where stronger shockwaves characterized by higher propagation velocities are observed for higher ablation laser irradiances and lower pressures. The Rankine-Hugoniot relations are also employed to estimate the pressure, temperature, density, and flow velocity of the shock-heated gas located immediately behind the shock front, predicting larger pressure ratios and higher temperatures for stronger laser-induced shockwaves.

42 ENGINEERING↗
NASA NTRS1995

Density fluctuations in solar wind flow types at 1 AU: Comparison to Doppler scintillation measurements

Density fluctuations with periods 10 minutes to 1 hour have been investigated in ISEE 3 plasma measurements of solar wind flows at l AU. Coronal hole, interstream, plasma sheet, coronal mass ejection, and interaction region flow types are considered. The ISEE 3 results support the interpretation of the large-scale variations in density fluctuations observed by Doppler scintillation measurement techniques inside 0.2 AU. The highest absolute and relative density fluctuations occur ahead of and within the plasma from coronal mass ejections, with the maximum values occurring between the associated interplanetary shocks and the driver gas. For the quasi-stationary solar wind, density and relative density fluctuations are highest around the heliospheric current sheet and lowest in the high-speed coronal flow. Superposed epoch analysis shows that the region of enhanced density fluctuations and its abrupt boundaries observed in the vicinity of the heliospheric current sheet near the Sun persists to l AU, providing further support for the filamentary nature of the extensions of coronal streamers. The results of this study confirm the advantages of using density fluctuations rather than density as a tracer of solar wind flows with differing origins at the Sun and as a detector of propagating interplanetary disturbances.

Huddleston, D. E.↗
DOE OSTI2024

Temporal evolution of the light emitted by a thin, laser-ionized plasma source

We present an experimental and simulation-based investigation of the temporal evolution of light emission from a thin, laser-ionized helium plasma source. We demonstrate an analytic model to calculate the approximate scaling of the time-integrated, on-axis light emission with the initial plasma density and temperature, supported by the experiment, which enhances the understanding of plasma light measurement for plasma wakefield accelerator (PWFA) plasma sources. Our model simulates the plasma density and temperature using a split-step Fourier code and a particle-in-cell code. A fluid simulation is then used to model the plasma and neutral density, and the electron temperature as a function of time and position. We then show the numerical results of the space-and-time-resolved light emission and that collisional excitation is the dominant source of light emission. We validate our model by measuring the light emitted by a laser-ionized plasma using a novel statistical method capable of resolving the nanosecond-scale temporal dynamics of the plasma light using a cost-effective camera with microsecond-scale timing jitter. This method is ideal for deployment in the high radiation environment of a particle accelerator that precludes the use of expensive nanosecond-gated cameras. Our results show that our models can effectively simulate the dynamics of a thin, laser-ionized plasma source. In addition, this work provides a detailed understanding of the plasma light measurement, which is one of the few diagnostic signals available for the direct measurement of PWFA plasma sources.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Chasing Fast Dynamos in the Plasma Lab

Self-generating magnetic field research is performed through the operation of the newly built Madison Plasma Dynamo Experiment (MPDX). MPDX is designed to explore a hitherto unexplored part of parameter space where dynamos operate in nature. Dynamos are systems which continuously transform kinetic energy from plasma flow into magnetic energy. Before this project, MPDX had demonstrated the ability to create steady-state, unmagnetized high conductivity, low viscosity plasmas in the lab and shown that sheared flows can be driven from the plasma boundary using an electrostatic stirring technique; the resulting Reynolds numbers and Alfvén Mach numbers easily match those required for our dynamo scenarios. The research activities included: (1) systematic undertaking of a set of plasma hydrodynamics experiments, exploring several different flow geometries, measuring plasma viscosity, how toroidal and poloidal flows self-consistently interact, observing the transition to turbulence and experimentally understanding the boundary conditions (on flow and magnetic field) that make this system unique, (2) searching for slow, laminar dynamos, and (3) searching for fast, turbulent dynamos. Discovering the conditions under which dynamos self-generate magnetic fields and then understanding how this field changes plasma dynamics is one of the most compelling questions in all of plasma astrophysics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗