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At least 289 records · Page 16

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DOE OSTI2026

Assessing plasma face component thermal response to rotating 3D magnetic fields for SPARC tokamak

Thermal response simulations of plasma-facing components (PFCs) in the SPARC tokamak, performed with the HEAT code, show that three-dimensional (3D) heat loads resulting from stationary n=1 perturbations require highly radiative scenarios, with up to 95% of the power crossing the separatrix (P SOL ) being radiated, to maintain PFC temperatures within acceptable operational limits, whereas the application of slowly rotating 3D fields substantially reduces the thermal loads. The HEAT module, developed to predict heat loads from non-axisymmetric plasmas, is extended to model time-dependent heat flux patterns generated by rotating 3D fields, and a comprehensive thermal analysis is performed on PFCs subjected to both the maximum and minimum power loads, as well as to rotating heat flux distributions, to evaluate the temperature evolution for varying perturbation amplitudes and rotation frequencies. The extension of this analysis to 3D fields with toroidal mode number n=2 shows that this configuration leads to weaker localized heat flux peaks relative to the n=1 case, enabling safe operation with less than 80% of the power radiated when static 3D fields of low amplitude are applied, while using slowly rotating fields at higher amplitudes. These results indicate that n=2 perturbations are generally less detrimental to divertor power exhaust, emphasizing the strong dependence of divertor power exhaust on the characteristics of the applied 3D fields.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1986

Thermal equilibrium of a cryogenic magnetized pure electron plasma

The thermal equilibrium correlation properties of a magnetically confined pure electron plasma (McPEP) are related to those of a one-component plasma (OCP). The N-particle spatial distribution rho sub s and the Helmholtz free energy F are evaluated for the McPEP to O(lambda sub d-squared/a-squared), where lambda sub d is the thermal de Broglie wavelength and is an interparticle spacing. The electron gyromotion is allowed to be fully quantized while the guiding center motion is quasi-classical. The distribution rho sub s is shown to be identical to that of a classical OCP with a slightly modified potential. To O(lambda sub d-squared/a-squared) this modification does not affect that part of F that is caused by correlations, as long as certain requirements concerning the size of the plasma are met. This theory is motivated by a current series of experiments that involve the cooling of a magnetically confined pure electron plasma to the cryogenic temperature range.

Dubin, D. H. E.↗

DOE OSTI2025

SciDAC ISEP: Integrated Simulation of Energetic Particles in Burning Plasmas

The objective of the SciDAC Center for Integrated Simulation of Energetic Particles in Burning Plasmas (ISEP) is to improve physics understanding of energetic particle (EP) confinement and EP interactions with burning thermal plasmas through large-scale simulations. The ISEP center will develop a multiscale and multiphysics ISEP framework for a predictive capability of EP physics and deliver an EP module incorporating both first-principles simulations and high fidelity reduced transport models to the fusion whole device modeling (WDM) project. The ISEP framework will enable us to perform long time, global kinetic simulations of EP physics in burning plasmas, by utilizing the full power of the next generation supercomputers. Our research and development activities will build on fruitful collaborations with computer scientists and applied mathematicians to offer enabling technologies for performance scalability, portability, solvers, coupling for integration with the fusion WDM project, and long-term preservation of data.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS2010

Can the Plasmaspheric Plume Significantly Contribute to Magnetosheath Densities?

Intervals of strong magnetospheric convection electric fields can result in the removal of large portions of the outer plasmasphere and its transport to the vicinity of the magnetopause. Of growing interest is the disposition of that plasma and its possible influence on the processes operating in the regions contributed to by this dense thermal plasma of ionospheric origin. Plasmaspheric plasma may recirculate within the outer magnetosphere through the flanks to become part of the plasmasheet, be entrained on reconnected magnetic field lines drawn anti-sunward over the polar cap, or be lost into the magnetosheath flow and into the solar wind. Of interest here is whether it is reasonable to anticipate that the plume material is sufficient to contribute substantially to magnetosheath densities at the magnetopause where it could influence reconnection between the interplanetary and terrestrial magnetic fields. We present the results of model simulations of plasmaspheric plume and magnetosheath plasmas in the context of several storm-time event periods. Plume and magnetosheath densities are compared as a function of location and storm phase. The short answer is, "yes", but not always and not at all locations. The full answer will be presented.

Gallagher, Dennis↗

DOE OSTI2024

Ripple-induced neoclassical toroidal viscous torque in Augmented-First Plasma operation phase in ITER

Abstract A systematic calculation is performed on the ripple-induced neoclassical toroidal viscous (NTV) torque for new ITER scenarios designed for the Augmented-First Plasma (A-FP) operation phase with the full tungsten wall, where the plasma-wall gap is varied in view of mitigating the impact of tungsten wall-plasma interactions. The torque calculation includes drift kinetic response of the plasma thermal and energetic particles to the n = 18 ( n is the toroidal harmonic number) ripple field. For the plasma scenario with ~45 cm plasma-wall gap at the outboard mid-plane and considering the corrected ripple level of 0.17% by the ferritic steel inserts, the computed net NTV torque acting on the plasma column is in the sub-Nm level. However, with decreasing the plasma-wall gap, the computed net NTV torque can reach a level comparable to that produced by the neutral-beam momentum injection in ITER. Ripple correction by ferritic inserts reduces the net torque by a factor of 3.3 for all the three A-FP scenarios considered. The n ω d = l ω b (with ω d and ω b being the toroidal precession and bounce frequencies of trapped particles, respectively, and l an integer number) type of resonance-enhancement of the NTV torque, due to thermal particles, is found to be weak in ITER despite high- n of 18. The same also holds for the ITER 10 MA steady state scenario from the D-T operation phase, where the aforementioned resonance associated with fusion-born alphas is also included. The ripple-induced NTV torque is well below that produced by the resonant magnetic perturbation applied for controlling the type-I edge-localized mode in ITER.

ITER↗

NASA NTRS1986

Cosmic-ray shock acceleration in oblique MHD shocks

A one-dimensional, steady-state hydrodynamical model of cosmic-ray acceleration at oblique MHD shocks is presented. Upstream of the shock the incoming thermal plasma is subject to the adverse pressure gradient of the accelerated particles, the J x B force, as well as the thermal gas pressure gradient. The efficiency of the acceleration of cosmic-rays at the shock as a function of the upstream magnetic field obliquity and upstream plasma beta is investigated. Astrophysical applications of the results are briefly discussed.

Webb, G. M.↗

NASA NTRS1996

Plasma and energetic particle properties of dispersionless substorm injections at geosynchronous orbit

Using a year's worth of geosynchronous spacecraft data, the substorm associated behavior of the thermal plasma in the plasma sheet in relation to energetic particle injections is reviewed. Five classes of injection events were found: ion injections without accompanying electron injection at 21 local time (LT); ion injection followed a few minutes later by an electron injection at 22 LT; simultaneous ion and electron injection close to midnight; electron injections followed by an ion injection at 01 LT; and pure electron injections at 02 LT. The thermal electrons show a significant increase in temperature and pressure at substorm onset, while the density and thermal ion signatures are typically weak. Energetic ions are found to contribute to the total ion pressure and temperature. Preexisting perpendicular anisotropies in the thermal electrons and ions are reduced during the substorm growth phase, but are re-enhanced after onset.

Birn, J.↗

NASA NTRS1972

Heating of the solar flare plasma by high energy electrons.

Discussion of the heating of the ambient plasma by high-energy electrons in solar flares. It is shown that for large flares the heating is enough to produce a thermal plasma with a temperature up to 10 to the 7th K rapidly in the initial phase of the flares. Thus thermal bremsstrahlung in addition to nonthermal bremsstrahlung should be considered for the X-ray emission of solar flares in the initial phase.-

Cheng, C.-C.↗

NASA NTRS1981

Dissipation and turbulent heating of plasma in Jupiter's magnetosphere

Voyager 1 observations of plasma waves in the dayside Jovian magnetosphere which show a correlation with measurements of localized concentrations of cool thermal plasma are presented. This moderately intense broadband electrostatic noise is shown to be of sufficient intensity to accelerate superthermal ions to energies approximately 1 keV and higher. This process can account for the extensive heating of plasma in the magnetosphere and can energize a fraction of heavy ions to injection threshold for a high-energy second stage acceleration mechanism. A brief discussion of the relation of this noise to Jovian magnetospheric dynamics is included.

Barbosa, D. D.↗

NASA NTRS1992

Modeling of the near-electrode regions of arcjets. I - Coupling of the flowfield to the non-equilibrium boundary layers

A model for arc attachment at an anode in contact with a flowing thermal plasma is described. Current limitations are identified which arise when the convective transport of ions into the electrical, thermal and hydrodynamic boundary layers is incapable of supplying the loss of ions through three-body recombination in the volume, and catalytic recombination on the electrode surface. It is shown that the anode current where this condition is achieved can be exceeded provided there is a significant Joule heating in the boundary layer. The saturation current (current density above which the anode must emit ions) is found to substantially increase with increasing free stream velocity and anode temperature.

Cappelli, Mark A.↗

DOE OSTI2024

Cross-scale interaction between microturbulence and meso-scale reversed shear Alfvén eigenmodes in DIII-D plasmas

Abstract This paper reports global nonlinear gyrokinetic simulations that couple meso-scale reversed shear Alfvén eigenmodes (RSAEs) driven by energetic particles (EPs) and ion temperature gradient (ITG) microturbulence driven by thermal plasma, using equilibrium and profiles from DIII-D discharge #159243. In simulations focusing only on the ITG, electrostatic ITG drives a huge thermal ion heat transport, which is reduced by a factor of 10 to a level close to the experimental value in electromagnetic simulation due to finite β effect. In the simulations coupling the RSAE and ITG, ITG can scatter the resonant EP nonlinearly trapped by the RSAE and damp the zonal flows generated by the RSAE. The regulation of the RSAE by the ITG greatly reduces the initial saturation amplitude of the RSAE but increases the RSAE amplitude and associated EP transport to experimental levels in the quasi-steady state. The RSAE effects on the ITG, specifically the stronger zonal flows generated by the RSAE and the RSAE frequency modulation of the ITG-induced thermal ion heat transport, in turn, leads to a reduction of the thermal ion heat transport by more than a factor of 2 . For a stronger background ITG, the regulation of the RSAE by the ITG is stronger, while the RSAE effects on the ITG are weaker. This work highlights the importance of cross-scale coupling in the dynamics of the AE turbulence and EP transport.

Physics↗

NASA NTRS1970

Thermal relaxation in one- and two-dimensional plasma models

Thermal relaxation rate in one and two dimensional electron plasma models with positive background, using particle in cell simulation

Montgomery, D.↗

DOE OSTI2023

Understanding the cold plasma synthesis of ammonia with model metal catalysts through plasma diagnostics (Final Report)

The industrial synthesis of ammonia, which amounts to over 200 million tons annually, is the most energy-intensive chemical process. Therefore, there is a critical need and increased interest in exploring less energetic routes to produce ammonia. Not only does ammonia have a direct impact on the food market, but also it has the potential as a fuel and hydrogen carrier. Recently, plasma catalysis has emerged as a promising alternative for synthesizing ammonia at mild (pressure, temperature and power) conditions. The key to this catalytic process is the synergy between the plasma and the catalyst, where the non-equilibrium plasma allows the generation of excited species, which recombine at the catalyst surface to form ammonia. However, our current understanding of this process is in its infancy. In this respect, model metals are ideal candidates for gaining a basic understanding of this reaction. Moreover, a major roadblock to rationally designing novel effective catalysts for plasma-assisted ammonia production is the need for fundamental aspects of this process. Through a comprehensive plan that integrates model metals as catalysts and world-class diagnostics, the proposed work aims to provide fundamental knowledge about the nature of reactive processes occurring during plasma-assisted catalysis and to demonstrate the selective production of ammonia, catalyzed by employing selected metals under non-thermal plasma conditions. Toward this goal, the central thrust of this proposal was to demonstrate that the synergy between plasma and rationally selected model metals will boost ammonia yields during plasma-assisted ammonia synthesis by delaying hydrogen recombination. Specifically, we aimed to (1) understand the formation and role of gas-phase active species such as NH, N 2 , N 2 + and Ha during the plasma-enhanced synthesis of ammonia through OES and FTIRAS using different reaction configurations: a) only plasma (non-packed DBD reactor) and b) packed DBD reactor with metal nanoparticles. This proposal was awarded/recommended with a run time on the PCRF facility FY20.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2007

Inner Magnetospheric Electric Fields Derived from IMAGE EUV

The local and global patterns of plasmaspheric plasma transport reflect the influence of electric fields imposed by all sources in the inner magnetosphere. Image sequences of thermal plasma G:istribution obtained from the IMAGE Mission Extreme Ultraviolet Imager can be used to derive plasma motions and, using a magnetic field model, the corresponding electric fields. These motions and fields directly reflect the dynamic coupling of injected plasmasheet plasma and the ionosphere, in addition to solar wind and atmospheric drivers. What is being learned about the morphology of inner magnetospheric electric fields during storm and quite conditions from this new empirical tool will be presented and discussed.

Gallagher, D. L.↗

DOE OSTI2024

Europa modifies Jupiter’s 1 plasma sheet

Jupiter's plasma sheet has been understood to be primarily composed of Io-genic sulfur and oxygen, along with protons at lower mass density. These ions move radially away from Jupiter, filling its magnetosphere. The material in the plasma sheet interacts with Europa, which is also a source of magnetospheric pickup ions, primarily hydrogen and oxygen. Juno's thermal plasma instrument JADE, the Jovian Auroral Distributions Experiment, has provided comprehensive in situ observations of the composition of Jupiter's plasma sheet ions with its Time-of-Flight mass-spectrometry capabilities. Here, we present observations of the magnetospheric composition in the Europa-Ganymede region of Jupiter's magnetosphere. We find material from Europa is intermittently present at comparable densities to Io-genic plasma. The intermittency of Europa-genic signatures suggests Europa's neutral oxygen toroidal cloud is more localized to Europa's vicinity than its hydrogen cloud. These observations reveal a more complex and compositionally diverse magnetosphere than previously thought.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2024

Europa Modifies Jupiter's Plasma Sheet

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1987

Plasmasphere and magnetosphere structure from ISEE-1 and DE-1

The density structure of the plasmapause region was investigated using the two satellites, ISEE-1 and DE-1 to obtain complementary radial and latitudinal profiles. Data from the plasma wave receivers were to be used to obtain total electron density, and from the ion mass spectrometers to determine thermal plasma morphology.

Olsen, R. C.↗

NASA NTRS1984

A radio study of the flat spectrum component in CTB 80

Polarization data obtained from high resolution radio observations of the compact, flat spectrum core of CTB 80 allow the extraction of information on the magnetic field and thermal plasma. The magnetic field direction projected onto the plane of the sky that is derived from the average rotation measure reveals a component that runs tangentially along the southern and western periphery of the radio plateau. The thermal density suggested by the depolarization rate is sufficient, if the plasma has a temperature of several million deg, to account for the X-ray emission detected by the Einstein Observatory. Attention is given to the possible nature of a small scale feature near the edge of the radio plateau, which agrees in position with the brightest radio peak.

Strom, R. G.↗