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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Observations of xenon spectra on the EAST x-ray crystal spectrometer for high-temperature plasma diagnostics

The Xe 44+ 2.7203 Å line, which has been proposed as one of the diagnostic lines for the x-ray imaging crystal spectrometer on ITER, is observed on the EAST tokamak together with its several satellite lines. The observations are made under high electron temperature (T e ) conditions (core T e > 5 keV). Most of the observed xenon lines are identified by comparing the experiment results with the atomic simulation results. The first ion temperature measurements made by the xenon spectra on EAST are also reported in this article. These xenon spectra observations contribute to the justification for using xenon as the diagnostic impurity in x-ray crystal spectrometers in future reactor-scale high-temperature plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Analysis of coherent Thomson scattering from a low temperature plasma

In this work, the spectrum of coherent Thomson scattering (CTS) induced by a periodic ponderomotive perturbation in a low-density low temperature plasma is considered. The analysis is performed for the case when the period of the resulting optical lattice is less than the Debye screening length in the plasma by solving an electron Boltzmann equation, where the total force is the sum of the periodic force due to the optical lattice and the electrostatic force due to self-consistent electric field in the plasma. An analogy between the CTS spectra calculated here and coherent Rayleigh scattering spectra in a neutral gas is established. For relatively low intensity for the optical lattice, the calculated CTS spectra are nearly Gaussian with widths slightly wider than the incoherent Thomson widths. We demonstrate that at higher intensities the line shape narrows and saturates to a width approximately half of that found at low lattice intensities. The proportionality of the spectral width to the square root of the electron temperature allows one to extract the electron temperature from the saturated spectra. Possible application of CTS for remote measuring the electron temperature in plasma is discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

On the interaction between two fireballs in low-temperature plasma

We report experimental results and theoretical modeling showing the interaction between two fireballs excited on two positively biased electrodes immersed in a low-temperature plasma. This interaction leads to a synchronized dynamics of the two fireballs, its frequency depending on the plasma density, the voltages applied on the electrodes, and the distance between the two electrodes. By considering that the plasma particles (electrons, ions, neutrals) move on fractal curves, a theoretical model describing the interaction between the two fireballs is developed. The results of the theoretical model were found to be in good agreement with the experimental results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Scenarios of transition to chaos competition in low-temperature plasma

Dynamics of a fireball created in front of a positively biased electrode immersed into low-temperature plasma was experimentally investigated. By analyzing the time series of the oscillations of the current collected by the electrode, several successive scenarios of transitions to chaos were identified: by intermittencies, by cascade of sub-harmonic bifurcations and by quasi-periodicity (Ruelle-Takens scenario)

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Study of transport properties with relativistic ponderomotive effect in two-electron temperature plasma

In the present paper we make an analytical investigation to study transport properties with relativistic ponderomotive effect in two-electron temperature plasma. Using fluid model the two-electron temperature are introduced through relativistic ponderomotive force for the transportation of two species of electrons. Applying WKB and paraxial ray approximation the nonlinear dielectric constant and self-focusing equation is evaluated and analyzed with experimental relevance. Numerical calculations are made for different concentration of electron density (10{sup 19}−10{sup 21} per cm{sup 3}) at arbitrary values of laser intensity in the range 10{sup 18}−10{sup 21} W/cm{sup 2}. For a minimum radius depending on the initial conditions it is oscillating between a minimum and maximum value. The hot electrons leading to the increase of the on-axis transportation and favorable effect on relativistic self-focusing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

A scheme to produce high density and high temperature plasma for opacity measurement

The opacity of shock-compressed material is of general scientific interest for astrophysical plasmas and for inertial confinement fusion research. A proposal is suggested to produce high temperature plasma with density around 1 g/cm{sup −3}. Two types of opacity target (the sandwich target and the foam enhanced sandwich target) are investigated numerically. The foam enhanced sandwich target has structure of foam–solid-sample-solid-foam. The foam will increase laser absorption efficiency and the ablating pressure. Hydrodynamic simulations confirm that the laser can be fully absorbed by the under-critical-density foam and a faster shock is produced inside the CH layer. High intensity lasers heat opacity target from both sides. The CH layers must be thick enough to keep the laser away from the sample. The laser-driven shocks move inward and collide at the center. Part of their kinetic energy is converted into internal energy and high density and high temperature local thermodynamic equilibrium sample plasma is produced. The plasma produced by laser heating the foam enhanced sandwich target has higher sample temperature than by laser heating the sandwich target. It may be useful for measuring the opacity of shock compressed material in laboratory.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Characterization of a Low-Temperature Plasma (LTP) Ambient Ionization Source Using Temporally Resolved Monochromatic Imaging Spectrometry

The low-temperature plasma (LTP) probe is a common plasma-based source used for ambient desorption–ionization mass spectrometry (MS). While the LTP probe has been characterized in detail with MS, relatively few studies have used optical spectroscopy. In this paper, two-dimensional (2D) imaging at selected wavelengths is used to visualize important species in the LTP plasma jet. First, 2D steady-state images of the LTP plume for N 2 + (391.2 nm), He I (706.5 nm), and N 2 (337.1 nm) emissions were recorded under selected plasma conditions. Second, time-resolved 2D emission maps of radiative species in the LTP plasma jet were recorded through the use of a 200 ns detection gate and varying gate delays with respect to the LTP trigger pulse. Emission from He I, N 2 + , and N 2 in the plasma jet region was found to show a transient behavior (often referred to as plasma bullets) lasting only a few microseconds. The N 2 + and He I maps were highly correlated in spatial and temporal structure. Further, emission from N 2 showed two maxima in time, one before and one after the maximum emission for N 2 + and He I, due to an initial electronic excitation wave and ion–electron recombination, respectively. Third, the interaction of the LTP probe with a sample substrate and an electrically grounded metallic needle was studied. Emission from a fluorophore on the sample substrate showed an initial photon-induced excitation from plasma-generated photons followed by electronic excitation by other plasma species. The presence of a grounded needle near the plasma jet significantly extended the plasma jet lifetime and also generated a long-lived corona discharge on the needle. The effect of LTP operating parameters on emission spectra was correlated with mass-spectral results including reagent-ion signals. Lastly, five movies provide a side-by-side comparison of the temporal behavior of emitting species and insights into the interactions of the emission clouds with a sample surface as well as an external needle. Temporally and spatially resolved imaging provided insights into important processes in the LTP plasma jet, which will help improve analyte ion sampling in LTP–MS.

Chan, George C. -Y.↗
NASA NTRS1976

X-ray emission from high temperature plasmas

The physical processes occurring in plasma focus devices were studied. These devices produce dense high temperature plasmas, which emit X rays of hundreds of KeV energy and one to ten billion neutrons per pulse. The processes in the devices seem related to solar flare phenomena, and would also be of interest for controlled thermonuclear fusion applications. The high intensity, short duration bursts of X rays and neutrons could also possibly be used for pumping nuclear lasers.

Harries, W. L.↗
DOE OSTI2015

Comparison of plasma temperature and electron density on nanosecond laser ablation of Cu and nano-Cu

Laser-induced breakdown spectroscopy is performed through the collection of spectra by spectral detection equipment at different delay times and distances from targets composed of Cu and nano-Cu, which are ablated using a Nd:YAG laser (532 nm, 10 ns, 10 Hz) in our experiments. The measured wavelength range is from 475 nm to 525 nm. Using the local thermodynamic equilibrium model, we analyze the characteristics of the plasma temperature and the electron number density for different distances between the target surface and the lens. The results show that when compared with the nano-Cu plasma case, the temperature of the Cu plasma is higher, while its electron number density is lower.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Experimental evidence of the increased transport due to the wall bounded magnetic drift in low temperature plasma

This paper presents experimental results on plasma transport across the magnetic field (B) in magnetized low-temperature plasma sources. Due to the presence of chamber walls, this transport can be complex even in a non-turbulent regime. In particular, in configurations without cylindrical symmetry, the magnetic drifts tend to be bounded by the chamber walls, thereby inducing plasma asymmetry and reducing magnetic confinement. In this work, we measure electron and ion current densities at metal chamber walls bounding a rectangular magnetic filter and demonstrate that these current densities are asymmetrically nonuniform. We also provide an experimental confirmation of model predictions of increased cross-field electron transport in such filter configuration, scaling as 1/B rather than the classical 1/B{sup 2} scaling.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Collisional transport coefficients of dense high-temperature plasmas within the quantum Landau-Fokker-Planck framework

In this paper, we extend the long-established formulas for the transport coefficients of classical plasmas inside the dense plasma regime for temperatures and densities where the classical Landau equation breaks down but its quantum extension that includes quantum degeneracy effects is valid. To this end, the quantum Landau kinetic equation is solved by the Chapman-Enskog method. The mathematical derivation is done in full generality, i.e., for multicomponent systems and to all orders of the polynomials expansion used to approximate the distribution functions. We apply the general results to two important examples, the electron gas model and an electron-ion plasma model consisting of one type of ions of any charge. We discuss the combined effects of the Pauli exclusion principle, of the electron-electron, and of the electron-ion collisions on the transport coefficients and on the convergence of the Chapman-Enskog method. For the electron gas model, the effect of the Pauli exclusion principle on the transport coefficients rapidly becomes non-negligible outside the domain of validity of the classical Landau equation. For the electron-ion plasmas, the effect of the Pauli exclusion principle depends sensitively on the ion charge Z and varies non-monotonically with Θ. For instance, for ion charge Z = 1, the electrical conductivity is increased by up to ~30% compared to its classical value over the range of degeneracy parameters studied, the thermal conductivity is reduced by up to ~9%, and the shear viscosity coefficient is increased by up to ~13%. Finally, in the Lorentz gas ( Z → ∞ ) limit, the electrical conductivity is reduced by up to ~14% compared to its classical value over the range of degeneracy parameters studied, the thermal conductivity is reduced by up to ~39%, and the shear viscosity coefficient is not affected.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1980

Thermal bremsstrahlung from high-temperature plasmas

Analytic expressions are derived for the total bremsstrahlung energy-loss rate per unit volume and the spectral emission rate of a very hot (10 million K to 1 billion K) plasma. At these temperatures the principal contribution to emission can be computed from the nonrelativistic limit of electron-ion bremsstrahlung in the Born approximation. Modifications to this rate are evaluated from (1) relativistic corrections to the thermal-electron velocity distribution function, (2) relativistic and spin corrections to the nonrelativistic electron-ion bremsstrahlung cross section, (3) electron-electron bremsstrahlung, and (4) first-order Born approximation corrections to electron-ion bremsstrahlung.

Gould, R. J.↗
DOE OSTI2013

Simultaneous measurement of nitrogen and hydrogen dissociation from vacuum ultraviolet self-absorption spectroscopy in a developing low temperature plasma at atmospheric pressure

We demonstrate a method for determining the dissociation density of N and H atoms present in a developing low temperature plasma, based on the emission and self-absorption of vacuum ultraviolet radiation produced from the plasma. Spark plasmas are produced via pulsed discharge in N{sub 2}/H{sub 2} mixtures at atmospheric pressure, where information on the dissociated densities of the constituent gas molecules is desired without employing invasive diagnostic techniques. By analyzing the self-absorption line profile of 121.5 nm Lyman-{alpha} H radiation emitted within the first {approx}1.0 mm of plasma near the anode tip, a peak dissociated H atom concentration of 5.6 Multiplication-Sign 10{sup 17} cm{sup -3} was observed {approx}100 ns into spark formation, with an estimated electron density of 2.65 Multiplication-Sign 10{sup 18} cm{sup -3} determined from Stark broadening. Similarly, simultaneous line fitting of the N 120.0/124.3 nm emission profiles revealed a peak dissociated N atom concentration of 3.8 Multiplication-Sign 10{sup 17} cm{sup -3} during the same discharge period.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Electron kinetics in low-temperature plasmas

This work presents an overview of recent advances in the field of electron kinetics in low-temperature plasmas (LTPs). It also provides author's views on where the field is headed and suggests promising strategies for further development. The authors have selected several problems to illustrate multidisciplinary nature of the subject (space and laboratory plasma, collisionless and collisional plasmas, and low-pressure and high-pressure discharges) and to illustrate how cross-disciplinary research efforts could enable further progress. Nonlocal electron kinetics and nonlocal electrodynamics in low-pressure rf plasmas resemble collisionless effects in space plasma and hot plasma effects in fusion science, terahertz technology, and plasmonics. The formation of electron groups in dc and rf discharges has much in common with three groups of electrons (core, strahl, and halo) in solar wind. Runaway electrons in LTPs are responsible for a wide range of physical phenomena from nano- and picoscale breakdown of dielectrics to lightning initiation. Understanding electron kinetics of LTPs could promote scientific advances in a number of topics in plasma physics and accelerate modern plasma technologies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Advancing the Predictive Understanding of Low Temperature Plasmas

The purpose of this paper is to characterize the need for improved predictive capabilities in low-temperature plasma (LTP) science, and to identify possible means of accomplishing this. While these means may constitute an initiative of their own, we consider these ideas to have widespread importance to discovery plasma science. Therefore, it is our hope that these ideas are more generally incorporated in future work.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗