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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

SUMMA hot-ion plasma heating research at NASA Lewis Research Center

The SUMMA superconducting magnetic mirror facility and the associated hot-ion plasma research were described. SUMMA is characterized by intense magnetic fields and a large-diameter working bore (41 cm diameter) with room-temperature access. The goal of the plasma research program is to produce steady-state plasmas of fusion reactor densities and temperatures (but not confinement times). The program includes electrode development to produce a hot, dense, large-volume, steady-state plasma and diagnostics development to document the plasma properties. SUMMA and its hot-ion plasma are ideally suited to develop advanced plasma diagnostics methods. Two such methods whose requirements are well matched to SUMMA are: (1) heavy ion beam probing to measure plasma space potential; and (2) submillimeter wavelength laser Thomson scattering to measure local ion temperature.

Reinmann, J. J.↗
NASA NTRS1975

SUMMA hot-ion plasma heating research at NASA Lewis Research Center

This report describes the SUMMA superconducting magnetic mirror facility at the NASA Lewis Research Center and the hot-ion plasma research conducted therein. SUMMA is characterized by intense magnetic fields (designed for 8.6 T at the mirrors) and a large-diameter working bore (41 cm diameter) with room-temperature access. The goal of the plasma research program is to produce steady-state plasmas of fusion reactor densities and temperatures (but not confinement times). The program includes electrode development to produce a hot, dense, large-volume, steady-state plasma and diagnostics development to document the plasma properties. SUMMA and its hot-ion plasma are ideally suited to develop advanced plasma diagnostics methods. Two such methods whose requirements are well matched to SUMMA are: (1) heavy ion beam probing to measure plasma space potential, and (2) submillimeter wavelength laser Thomson scattering to measure local ion temperature. Two NASA University Grants were established to identify major requirements for developing these two diagnostic techniques in SUMMA.

Reinmann, J. J.↗
DOE OSTI2018

Calcium Isotope Separation in a Hot-Wall Plasma Centrifuge

We propose a method of calcium isotope sepration using a countercurrent plasma centrifuge with a hot wall, which separating the fractions by means of vapor deposition at the end faces of the device. The centrifugal force, providing the effect of radial separation, is excited due to acceleration of a weakly ionized calcium plasma by a rotating magnetic field, while the axial circulating flow, which increases the effect of radial separation, is created by a traveling magnetic field. The capabilities of the method are demonstrated by the example of calculation of the separation factor of the plasma centrifuge as a function of the parameter characterizing the circulation intensity.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2020

Effect of Electron Capture on Spectral Line Broadening in Hot Dense Plasmas

Accurate calculation of spectral line broadening is important for many hot, dense plasma applications. However, calculated line widths have significantly underestimated measured widths for Δn = 0 lines of Li-like ions, which is known as the isolated-line problem. In this Letter, scrutinization of the line-width derivation reveals that the commonly used expression neglects a potentially important contribution from electron-capture. Line-width calculations including this process are performed with two independent codes, both of which removed the discrepancies at temperatures below 10 eV. In conclusion, the revised calculations also suggest the remaining discrepancy scales more strongly with electron temperature than the atomic number as was previously suggested.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Three-dimensional reconstruction of inertial confinement fusion hot-spot plasma from x-ray and nuclear diagnostics on OMEGA

Multidimensional effects degrade the neutron yield and the compressed areal density of laser-direct-drive inertial confinement fusion implosions of layered deuterium–tritium cryogenic targets on the OMEGA Laser System with respect to 1D radiation-hydrodynamic simulation predictions. A comprehensive physics-informed 3D reconstruction effort is under way to infer hot-spot and shell conditions at stagnation from four x-ray and seven neutron detectors distributed around the OMEGA target chamber. Neutron diagnostics, providing measurements of the neutron yield, hot-spot flow velocity, and apparent ion-temperature distribution, are used to infer the mode-1 perturbation at stagnation. The x-ray imagers record the shape of the hot-spot plasma to diagnose mode-1 and mode-2 perturbations. A deep-learning convolutional neural network trained on an extensive set of 3D radiation-hydrodynamic simulations is used to interpret the x-ray and nuclear measurements to infer the 3D profiles of the hot-spot plasma conditions and the amount of laser energy coupled to the hot-spot plasma. A 3D simulation database shows that larger mode-1 asymmetries are correlated with higher hot-spot flow velocities and reduced laser-energy coupling and neutron yield. Three-dimensional hot-spot reconstructions from x-ray measurements indicate that higher amounts of residual kinetic energy are correlated with higher measured hot-spot flow velocities, consistent with 3D simulations.

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↗
NASA NTRS1978

Multi-harmonic electron cyclotron instabilities

The reported investigation constitutes an extension of studies conducted by Ashour-Abdalla and Kennel (1975, 1976, 1978) with respect to a basic plasma model of Young et al. (1973). The model involves a combination of a cold Maxwellian background plasma, a hot plasma, and a 'loss cone' type of free energy source. Previous results on the first cyclotron harmonic bands are extended to multiharmonics. The significance of the obtained relations is discussed and tentative conclusions are presented. Given that the spatial growth rates of the convective modes are comparable, and that simultaneous nonconvective instability (NCI) is possible, it is concluded that multiharmonic emissions ought to be a common feature of the magnetospheric electrostatic wave observations. Since the volume of parameter space for which the first harmonic is NCI, and the volume for which the convective first harmonic mode has significant spatial growth rates, exceed those for the higher harmonics, first harmonic waves should be the most commonly observed and the higher harmonics should usually be accompanied by the first harmonic.

Ashour-Abdalla, M.↗
NASA NTRS1974

Hot ion plasma heating experiments in SUMMA

Initial results are presented for the hot-ion plasma heating experiments conducted in the new SUMMA (superconducting magnetic mirror apparatus) at NASA Lewis Research Center. A discharge is formed by applying a radially inward dc electric field between cylindrical anodes and hallow cathodes located at the peak of the mirrors. Data were obtained at midplane magnetic field strengths from 1.0 to 3.5 tesla. Charge-exchange neutral particle energy analyzer data were reduced to ion temperatures using a plasma model that included a Maxwellian energy distribution superimposed on an azimuthal drift, finite ion orbits, and radial variations in density and electric field. The best ion temperatures in a helium plasma were 5 keV and in hydrogen the H2(+) and H(+) ions were 1.2 keV and 1 keV respectively. Optical spectroscopy line broadening measurements yielded ion temperatures about 50 percent higher than the charge-exchange neutral particle analyzer results. Spectroscopically obtained electron temperature ranged from 3 to 30 eV. Ion temperature was found to scale roughly linearly with the ratio of power input-to-magnetic field strength, P/B.

Reinmann, J. J.↗
DOE OSTI2018

Kinetic-j : A computational kernel for solving the linearized Vlasov equation applied to calculations of the kinetic, configuration space plasma current for time harmonic wave electric fields

We present the Kinetic-j code, a computational kernel for evaluating the linearized Vlasov equation withapplication to calculating the kinetic plasma response (current) to an applied time harmonic wave electricfield. This code addresses the need for a configuration space evaluation of the plasma current to enablekinetic full-wave solvers for waves in hot plasmas to move beyond the limitations of the traditional Fourierspectral methods. We benchmark the kernel via comparison with the standard k-space forms of the hotplasma conductivity tensor.

Green, David L.↗
NASA NTRS1994

Studies on equatorial shock formation during plasmaspheric refilling

Investigations based on small-scale simulations of microprocesses occurring when a magnetic flux tube refills with a cold plasma are summarized. Results of these investigations are reported in the following attached papers: (1) 'Numerical Simulation of Filling a Magnetic Flux Tube with a Cold Plasma: The Role of Ion Beam-Driven Instabilities'; and (2) 'Numerical Simulation of Filling a Magnetic Flux Tube with a Cold Plasma: Effects of Magnetically Trapped Hot Plasma'. Other papers included are: 'Interaction of Field-Aligned Cold Plasma Flows with an Equatorially-Trapped Hot Plasma: Electrostatic Shock Formation'; and 'Comparison of Hydrodynamic and Semikinetic Treatments for a Plasma Flow along Closed Field Lines'. A proposal for further research is included.

Singh, N.↗
NASA NTRS1975

Hot ion plasma heating experiments in SUMMA

Initial empirical results are presented for the hot-ion plasma heating experiments conducted in the new SUMMA (Superconducting Magnetic Mirror Apparatus) at NASA Lewis Research Center. A discharge was formed by applying a radially inward dc electric field near the mirror throats. Data were obtained at midplane magnetic flux densities from 1.0 to 3.5 tesla. Charge-exchange neutral particle energy analyzer data were reduced to ion temperatures using a plasma model that included a Maxwellian energy distribution superimposed on an azimuthal drift, finite ion orbits, and radial variations in density and electric field. Using this plasma model, the highest ion temperatures computed were 5 keV, 1.2 keV, and 1 keV for He(+), H2(+), and H(+), respectively. These were obtained at a midplane magnetic flux density of 1.6 T.-

Reinmann, J. J.↗
NASA NTRS1980

Energetic /approximately 100-keV/ tailward-directed ion beam outside the Jovian plasma boundary

The hot plasma instrument on the Voyager-2 spacecraft measured a nearly monoenergetic (100 keV) ion beam several hours after crossing the Jovian plasma boundary on the nightside of the planet. The beam, deduced to consist primarily of heavy ions, persisted for about four hours and originated from the general direction of Jupiter. The energy density of the beam was about several times the energy density of the magnetic field (beta greater than 1). This beam, a product of an as yet not understood Jovian plasma acceleration mechanism, provides a dramatic example of the energetic dynamics of Jupiter's magnetosphere.

Krimigis, S. M.↗
DOE OSTI2024

Full wave modeling of radio-frequency beams in tokamaks in the electron cyclotron frequency range

Simulation of full wave, without paraxial approximation, high-resolution solution of wave equations in frequency domain in the electron cyclotron resonance (ECR) frequency range for realistic Tokamak plasma parameters became possible by using recently formulated hybrid iterative algorithm [Svidzinski et al., Phys. Plasmas 25, 082509 (2018)] for numerically solving discretized wave equations. This approach combines time evolution and iterative relaxation techniques into iteration cycles. This algorithm is implemented in 2D code FullWave, solving wave equations in Tokamaks in cold and hot plasma models, and it has been tested in 3D full wave iterative RF beams simulation tool, which is presently being developed to model 3D ECRH RF beams in fusion devices using dynamic grid adaptation. The results of 2D full wave modeling, assuming specified toroidal mode number, of ECRH RF beams in DIII-D plasma, performed in the cold and hot plasma models for outboard and top launch scenarios using FullWave are presented. Nonlocal hot plasma response model, based on accurate numerical solution of linearized Vlasov equation, is used to model beam propagation and absorption in the 2nd electron cyclotron harmonic region. Demonstration of capability of the hybrid iterative algorithm to model ECRH RF beams in 3D is made by simulating a substantial part of realistic beam in DIII-D, launched from outboard side of the machine. All relevant physics of RF beam propagation, most of which is not captured in paraxial approximation, such as beam's divergence, interference between the X and O modes in the beam, X-O mode conversion, beam splitting into the X and O mode beams, transformation of beam's cross section, and absorption at the 2nd electron cyclotron harmonic, is captured in the simulations. A numerical technique to find an optimal beam polarization at the launcher to launch a nearly pure X or O mode beam in plasma is developed and tested.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Fast and Universal Kohn-Sham Density Functional Theory Algorithm for Warm Dense Matter to Hot Dense Plasma

Understanding many processes, e.g., fusion experiments, planetary interiors, and dwarf stars, depends strongly on microscopic physics modeling of warm dense matter and hot dense plasma. This complex state of matter consists of a transient mixture of degenerate and nearly free electrons, molecules, and ions. This regime challenges both experiment and analytical modeling, necessitating predictive ab initio atomistic computation, typically based on quantum mechanical Kohn-Sham density functional theory (KS-DFT). However, cubic computational scaling with temperature and system size prohibits the use of DFT through much of the warm dense matter regime. A recently developed stochastic approach to KS-DFT can be used at high temperatures, with the exact same accuracy as the deterministic approach, but the stochastic error can converge slowly and it remains expensive for intermediate temperatures (< 50 eV). Here we have developed a universal mixed stochastic-deterministic algorithm for DFT at any temperature. This approach leverages the physics of KS-DFT to seamlessly integrate the best aspects of these different approaches. We demonstrate that this method significantly accelerated self-consistent field calculations for temperatures from 3 to 50 eV, while producing stable molecular dynamics and accurate diffusion coefficients.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1975

Hot ion plasma production in HIP-1 using water-cooled hollow cathodes

A steady-state ExB plasma was formed by applying a strong radially inward dc electric field near the mirror throats. Most of the results were for hydrogen, but deuterium and helium plasmas were also studied. Three water-cooled hollow cathodes were operated in the hot-ion plasma mode with the following results: (1) thermally emitting cathodes were not required to achieve the hot-ion mode; (2) steady-state operation (several minutes) was attained; (3) input powers greater than 40 kW were achieved; (4) cathode outside diameters were increased from 1.2 cm (uncooled) to 4.4 cm (water-cooled); (5) steady-state hydrogen plasma with ion temperatures from 185 to 770 eV and electron temperatures from 5 to 21 eV were produced. Scaling relations were empirically obtained for discharge current, ion temperature, electron temperature, and relative ion density as a function of hydrogen gas feed rate, magnetic field, and cathode voltage. Neutrons were produced from deuterium plasma, but it was not established whether thay came from the plasma volume or from the electrode surfaces.

Reinmann, J. J.↗
NASA NTRS1981

The X-ray spectrum of a hot interstellar plasma

The soft X-ray spectrum of a hot, low density, optically thin plasma in collisional ionization equilibrium is calculated using current atomic data. Many Fe collision strengths differ from previous calculations. The spectra from individual elements are presented for use in abundance determinations from X-ray observations. Collision strengths and line energies, sorted both according to energy and according to ion, are tabulated.

Shull, J. M.↗
NASA NTRS1986

Magnetospheric energetic ions from the earth's ionosphere

In the decade and a half since the initial discovery that the earth's own ionosphere could at times contribute measurably to the hot plasma in the magnetosphere, significant progress has been made in both current knowledge and understanding of this connection. It is now known that ions of ionospheric origin are found in all major regions of the magnetosphere and at its boundaries. The source region in the ionosphere and the acceleration and transport processes involved in coupling the cold ionospheric plasma to the hot magnetospheric plasma are complex and variable. The large scale morphology of the ionospheric outflow and its distribution throughout the magnetosphere is now understood and progress is being made in the understanding of the fundamental physical processes involved. In this paper attention is given to the large scale morphology and current understanding of the sources for ionospheric ions found in various regions of the magnetosphere and their transport.

Shelley, E. G.↗