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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Theory and observations of electrostatic ion waves in the cold Io torus

A study of the ELF plasma wave environment of the cold Io torus in Jupiter's magnetosphere is made. Voyager 1 data are presented which show three distinct types of electrostatic ion waves occurring there: the Buchsbaum ion-ion mode just below the proton cyclotron frequency f(cp), hydrogen Bernstein modes at (n + 1/2) f(cp), and lower hybrid waves near f(LHR). The presence of these waves at their characteristic frequencies is consistent with a predominantly heavy ion plasma composed of singly ionized sulfur and oxygen ions along with a small admixture of protons. The hydrogen Bernstein modes are tightly confined to the magnetic equator, occurring within + or - 4 deg of it, while the Buchsbaum mode is localized to the dense heavy ion plasma of the cold torus near the centrifugal equator. A general theory for excitation of the waves based on the ion pickup process is developed.

Barbosa, D. D.↗
NASA NTRS1990

The structure of the Birkeland current system in the post-midnight plasma sheet

Simultaneous magnetic field and particle measurements by AMPTE/CCE with magnetic field measurements by GOES 5 and GOES 6 clarify the structure of the field-aligned Birkeland current system in the post-midnight region of the near-earth magnetotail. The current system, consisting of current sheets flowing in opposite directions, exists near the boundary region of the plasma sheet; its magnetic effects are confined mainly to the current region because of its structure. During the expansion phase of substorms, a single-sheet current system is formed in the boundary region of the plasma sheet and net current is probably present in one meridian plane. This type of current system produces the substorm-related transient variations in the azimuthal (D) component normally observed at synchronous orbit.

Nagai, Tsugunobu↗
NASA NTRS1990

Electrostatic electron and ion cyclotron harmonic waves in Neptune's magnetosphere

Voyager 2 observations of electrostatic electron and ion cyclotron waves detected in Neptune's magnetosphere are presented. Both types of emission appear in a frequency band above the electron and ion (proton) cyclotron frequencies, respectively, and are tightly confined to the magnetic equator occurring within a few degrees of it. The electron cyclotron modes including an intense upper hybrid resonance emission excited by an unstable loss cone distribution of low-density superthermal electrons. The ion cyclotron waves are interpreted as hydrogen Bernstein modes including an intense lower hybrid resonance emission excited by an unstable ring distribution of low-density pickup N(+) ions deriving from the satellite Triton.

Barbosa, D. D.↗
NASA NTRS1993

Star and cluster formation in NGC 1275

Luminous, blue, and unresolved objects have been found by imaging the nuclear region of the central galaxy in the Perseus Cluster, NGC 1275. Stellar formation in a cooling flow in which gas clouds confined by weak magnetic fields are allowed to remain at low densities is favored. Cloud-cloud collisions and coagulation in the high cloud density environment at the center of the galaxy then causes some clouds to become gravitationally unstable and to form globular clusters.

Richer, Harvey B.↗
NASA NTRS1993

Self-consistent electrostatic potential due to trapped plasma in the magnetosphere

A steady state solution for the self-consistent electrostatic potential due to a plasma confined in a magnetic flux tube is considered. A steady state distribution function is constructed for the trapped particles from the constants of the motion, in the absence of waves and collisions. Using Liouville's theorem, the particle density along the geomagnetic field is determined and found to depend on the local magnetic field, self-consistent electric potential, and the equatorial plasma distribution function. A hot anisotropic magnetospheric plasma in steady state is modeled by a bi-Maxwellian at the equator. The self-consistent electric potential along the magnetic field is calculated assuming quasineutrality, and the potential drop is found to be approximately equal to the average kinetic energy of the equatorially trapped plasma. The potential is compared with that obtained by Alfven and Faelthammar (1963).

Miller, Ronald H.↗
NASA NTRS1995

Relativistic hadrons and the origin of relativistic outflows in active galactic nuclei

We examine the hydrodynamic origin of relativistic outflows in active galactic nuclei (AGN). Specifically, we propose that the presence of a population of relativistic hadrons in the AGN 'central engine' and the associated neutron production suffices to produce outflows which under rather general conditions could be relativistic. The main such condition is that the size of the neutron production region be larger than the neutron flight path tau(sub n) approximately 3 x 10(exp 13) cm. This condition guarantees that the mean energy per particle in the proton fluid, resulting from the decay of the neutrons outside their production region, be greater than the proton rest mass. The expansion of this fluid can then lead naturally to a relativistic outflow by conversion of its internal energy to directed motion. We follow the development of such flows by solving the mass, energy as well as the kinetic equation for the proton gas in steady state, taking into account the source terms due to compute accurately the adiabatic index of the expanding gas, and in conjunction with Bernoulli's equation the detailed evolution of the bulk Lorentz factor. We further examine the role of large-scale magnetic fields in confining these outflows to produce the jets observed at larger scales.

Contopoulos, John↗
NASA NTRS1996

Fusion Propulsion and Power for Future Flight

There are innovative magnetic and electric confinement fusion power and propulsion system designs with potential for: vacuum specific impulses of 1500-2000 seconds with rocket engine thrust/mass ratios of 5-10 g's; environmentally favorable exhaust emissions if aneutronic fusion propellants can be used; a 2 to 3-fold reduction in the mass of hypersonic airliners and SSTO aerospace planes; a 10 to 20 fold reduction in Mars expedition mass and cost (if propellant from planetary atmospheres is used); and feasibility or in-feasibility of these systems could be confirmed with a modest applied research and exploratory development cost.

Froning, H. D., Jr.↗
NASA NTRS2012

Future Gamma-Ray Imaging of Solar Eruptive Events

Solar eruptive events, the combination of large solar flares and coronal mass ejections (CMEs), accelerate ions to tens of Gev and electrons to hundreds of MeV. The energy in accelerated particles can be a significant fraction (up to tens of percent) of the released energy and is roughly equipartitioned between ions and electrons. Observations of the gamma-ray signatures produced by these particles interacting with the ambient solar atmosphere probes the distribution and composition of the accelerated population, as well as the atmospheric parameters and abundances of the atmosphere, ultimately revealing information about the underlying physics. Gamma-ray imaging provided by RHESSI showed that the interacting approx.20 MeV/nucleon ions are confined to flare magnetic loops rather than precipitating from a large CME-associated shock. Furthermore, RHESSI images show a surprising, significant spatial separation between the locations where accelerated ions and electrons are interacting, thus indicating a difference in acceleration or transport processes for the two types of particles. Future gamma-ray imaging observations, with higher sensitivity and greater angular resolution, can investigate more deeply the nature of ion acceleration. The technologies being proven on the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS), a NASA balloon instrument, are possible approaches for future instrumentation. We discuss the GRIPS instrument and the future of studying this aspect of solar eruptive events.

Shih, Albert↗
DOE OSTI2016

On the utility of non thermal plasmas

Nonthermal plasmas have properties which can differ substantially even from thermal plasmas of the same density and energy. In practical applications, many of these differences have utility that can be exploited, often with waves. The goal of this thesis is to explore three such applications of nonthermal plasma for the purposes of wave amplification and, ultimately, controlled nuclear fusion. First, we discuss the outstanding potential for a shaped plasma technology that relies on ionizing a beam of aerosol particles. This ionization results in a Coulomb explosion, yielding a highly nonthermal distribution for the plasma in the target volume. Homogeneous, high aspect ratio plasma couplers such as these could be used in a Raman amplification scheme to attain the next generation of laser intensities. Such a powerful laser could be used to study radiation reaction and vacuum pair production, among many other applications. We describe the conditions under which sufficiently dense aerosol beams can be prepared and provide some experimental validation of these claims. Second, we survey the prospects for controlled p-11B fusion in both magnetic and inertial confinement schemes. Whereas most studies have focused on mitigating the bremsstrahlung loss channel, we focus on nonthermal manipulations of the bulk plasma which could improve the reactivity. In particular, we present upper bounds on the p-11B reactivity using alpha channeling to efficiently heat the proton distribution in both schemes. Finally, we place a sharp limit on the energy that can be extracted from a non-thermal particle distribution using waves. In the quasilinear regime of wave-particle interaction, waves rearrange the densities of states in phase space in a diffusive fashion. A salient consequence is that only certain, generally nonthermal, plasma states can be reached. We characterize this restricted state space and thereby reduce the problem of maximizing energy extraction to linear programming. Varying the connectedness of the phase space so that e.g. particles may only be diffused to parts of phase space close in energy, we describe the implications for the state space and the solution of the optimization problem.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Supporting Fusion at the Idaho National Laboratory

The Fusion Safety Program at Idaho National Laboratory has supported efforts to develop magnetic and inertial confinement fusion energy devices for commercial energy power development since 1979. In addition to our DOE less than hazard category 3 tritium handling facility STAR, we also have unique capabilities such as an adaptation of the severe accident code MELCOR developed specifically for fusion, and integrated modeling capabilities using the MOOSE Finite Element Code. In this presentation, we cover our unique experimental capabilities for investigating tritium sorption, solubility and permeation including in molten salts. We also show the application of MELCOR-TMAP to predict thermal hydraulics and tritium migration in normal and accident conditions. Finally, we demonstrate high-fidelity modeling capabilities found within the open-source MOOSE finite element framework as well as fuel-cycle modeling using TMAP8.

70 - PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Progress in extending high poloidal beta scenarios on DIII-D towards a steady-state fusion reactor and impact of energetic particles

To prepare for steady-state operation of future fusion reactors (e.g. the International Thermonuclear Experimental Reactor and China Fusion Engineering Test Reactor (CFETR)), experiments on DIII-D have extended the high poloidal beta ( β P ) scenario to reactor-relevant edge safety factor q 95 ~ 6.0, while maintaining a large-radius internal transport barrier (ITB) using negative magnetic shear. Excellent energy confinement quality ( H 98y2 > 1.5) is sustained at high normalized beta ( β N ~ 3.5). This high-performance ITB state with Greenwald density fraction near 100% and q min ≥ 3 is achieved with toroidal plasma rotation V tor ~ 0 at ρ ≥ 0.6. This is a key result for reactors expected to have low V tor . At high β P (≥1.9), large Shafranov shift can stabilize turbulence leading to a high confinement state with a low pedestal and an ITB. At lower β P (<1.9), negative magnetic shear in the plasma core contributes to turbulence suppression and can compensate for reduced Shafranov shift to continue to access a large-radius ITB and excellent confinement with low V tor , consistent with the results of gyrofluid transport simulations. These high- β P cases are characterized by weak/no Alfvén eigenmodes (a.e.) and classical fast-ion transport. At high density, the fast-ion deceleration time decreases and Δ β fast is lower; these reduce a.e. drive. The reverse-shear Alfvén eigenmodes are weaker or stable because the negative magnetic shear region is located at higher radius, away from the peaked fast-ion profile. Resistive wall modes can be a limitation at simultaneous high β N , low internal inductance, and low rotation. Analysis suggests that additional off-axis external current drive could provide a more stable path at reduced q 95 . Based on a DIII-D high- β P plasma with large-radius ITB, two scenarios are proposed for CFETR Q = 5 steady-state operation with ~1 GW fusion power: a lower-$l_i$($l_i$ ~ 0.66) and a higher-$l_i$($l_i$ ~ 0.75) case. Using a Landau closure model, multiple energetic particle (EP) effects on the a.e. stability are analyzed modifying the growth rate of the a.e.s triggered by the neutral-beam-injection EPs and alpha particles, although the stabilizing/destabilizing effect is weak for the cases analyzed. The stabilizing effects of the combined EP species β , energy, and density profile in CFETR need further investigation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Magnetic structure and magnetodielectric behavior of the chiral magnet CoTeMoO 6

We investigate the magnetic structure and magnetodielectric behavior of the chiral magnet CoTeMoO 6 (CTMO) through neutron diffraction, magnetization, and magnetodielectric measurements, complemented by density functional theory (DFT) calculations. Our findings reveal a canted magnetic structure with moments confined to the ab plane, giving rise to weak ferromagnetism under an external magnetic field. Additionally, we observe magnetodielectric coupling that strongly correlates with the magnetic ordering temperature and magnetic structure. Furthermore, these results are discussed in the context of potential mechanisms involving spin-dependent p-d hybridization and spin-phonon coupling.

Canted magnetism↗
DOE OSTI2019

Field reconstruction from proton radiography of intense laser driven magnetic reconnection

Magnetic reconnection is a process that contributes significantly to plasma dynamics and energy transfer in a wide range of plasma and magnetic field regimes, including inertial confinement fusion experiments, stellar coronae and compact, highly magnetized objects like neutron stars. Laboratory experiments in different regimes can help refine, expand and test the applicability of theoretical models to describe reconnection. Laser-plasma experiments exploring magnetic reconnection at moderate intensities (I L ~ 10 14 Wcm -2 ) have been performed previously, where the Biermann battery effect self-generates magnetic fields and the field dynamics studied using proton radiog- raphy. At high laser intensities (I L λ$2\atop{L}$ > 10 18 Wcm -2 μm 2 ), relativistic surface currents and the time-varying electric sheath fields generate the azimuthal magnetic fields. Numerical modeling of these intensities has shown the conditions within the magnetic field region can reach the threshold where the magnetic energy can exceed the rest mass energy such that σ cold = B 2 /(μ 0 n e m e c 2 ) > 1 [A. E. Raymond, et al., Phys. Rev. E, 98, 043207 (2018)]. Presented here is the analysis of the proton radiography of a high-intensity (~ 10 18 Wcm -2 ) laser driven magnetic reconnection geometry. Lastly, the path integrated magnetic fields are recovered using a “field-reconstruction algorithm” to quantify the field strengths, geometry and evolution.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Ground state energy of an exciton in a spherical quantum dot in the presence of an external magnetic field

The problem of an exciton trapped in a three dimensional Gaussian quantum dot is studied in the presence of an external magnetic field. A variational method is employed to obtain the ground state energy of the exciton as a function of the quantum dot size, the confinement strength and the magnetic field. It is also shown that the variation of the size of the exciton with the radius of the quantum dot.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Neutronics of Advanced-Fuel Fusion Experiments with DT Triggering

Nuclear fusion studies are currently devoted to the Deuterium-Tritium (DT) fuel cycle, the easiest way to reach ignition. The recent stress on safety by the world community has stimulated the research on other fuel cycles, based on advanced reactions, such as Deuterium-Helium-3 (DHe). With DHe, it is not necessary to breed and fuel tritium. The DHe cycle has a very low presence of energetic fusion neutrons, due to DD and DT side reactions, and it has the possibility to obtain electrical power by direct energy conversion of the protons produced by the fusion reactions. DHe fusion has its own set of problems, such as the availability of {sup 3}He and the attainment of the higher plasma parameters. To explore the possibilities of DHe plasmas, a burning plasma experiment at high magnetic field and high plasma densities is particularly attractive. Ignitor is a proposed compact high-magnetic field tokamak, aimed at studying plasma-burning conditions in Deuterium-Tritium plasmas. The Ignitor experiment is designed to reach ignition under controlled DT burning conditions. The machine parameters have been established, on the basis of existing knowledge of the confinement properties of high density plasmas. The scientific goal of the Ignitor experiment is to approach, for the first time, the ignition conditions of a magnetically confined D-T plasma. However, the plasma density limit in Ignitor being well above the optimal density for DT ignition, is potentially suitable to the higher densities required for DHe burning. In fact, Ignitor has been designed also to explore conditions where 14.7-MeV protons and 3.6-MeV alpha particles produced by the DHe reactions can supply a significant amount of thermal energy to a well-confined plasma. In particular, Ignitor can sustain plasma currents exceeding those required to confine proton orbits at birth, and has more than sufficiently high densities so that the slowing-down time of both the protons and the DT alpha particles is shorter than the electron energy replacement time of the thermal plasma in which they are produced. Preliminary analyses show that a fusion power PF around 2 MW, may be reached. As a start, Ignitor can perform initial studies at the level of approximately 1 MW of power in charged particles from the DHe reaction in a mostly DT plasma. CANDOR, a design evolution of Ignitor in the direction of a reactor using a DHe fuel cycle, has been proposed; it is a feasibility study of a high-field DHe experiment of larger dimensions and higher fusion power than Ignitor, however still based on the core Ignitor technologies. The main characteristics of the CANDOR machine are the following: the major radius Ro is about double than Ignitor, plasma currents up to 25 MA with toroidal magnetic fields B{sub T} = 13 T can be produced. Unlike Ignitor, CANDOR would operate with higher values of poloidal beta around unity and the central part of the plasma column in the Second Stability region. The characteristic times over which the plasma discharge can be sustained are longer by more than a factor of 4 than those of Ignitor. To produce such a strong magnetic field in a larger machine, the toroidal field coils have been divided into two sets of coils and the central solenoid (air core transformer) is placed between them in the inboard part. In CANDOR, the DHe burning regime can be reached, by a combination of ICRF heating and alpha particle heating due to DT fusion reactions, which take the role of a sort of trigger. Thanks to this fact, and unlike other proposed DHe fusion experiments, CANDOR is capable of reaching DHe ignition using the existing technologies, and present knowledge of plasma confinement phenomena. With the initial use of DT, where tritium comprises some 50% of an initial lower density DT plasma, but is not added thereafter, the need for an intense auxiliary heating, which is one of the main technological drawbacks of DHe ignition, would be considerably alleviated, becoming feasible with the present technology. However, this method has the disadvantage of using tritium and of presenting a higher neutron flux (due to DT reactions) than 'pure' DHe plasmas, generating a neutron flux transient when passing from the initial DT trigger reaction to the final DHe burning plasma. However, for an experimental machine one-of-a-kind of relatively small dimensions, this is not an issue. (authors)

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

The energy confinement response of DIII-D plasmas to Resonant Magnetic Perturbations

Here, Resonant Magnetic Perturbations (RMPs) are a leading method for edge localized modes (ELMs) Control in fusion plasmas. However they can also cause a rapid degradation in energy confinement. In this paper we show that the energy confinement in low collisionality (v* e < 0.3) DIII-D ITER Similar Shape (ISS) plasmas often recovers after several energy confinement times for RMP amplitudes up to the threshold for ELM suppression. Immediately following the application of the RMP, the plasma stored energy decreases in proportion to the decrease in the line-averaged density during density "pump-out". Later in the discharge confinement recovery is observed in the thermal ion channel and is correlated with the increase in the ion temperature at the top of the H-mode pedestal. A correlation between the inverse scale length of the ion temperature (α/L Ti ) and the E x B shearing rate at the top of the pedestal is seen during the confinement recovery phase. Transport analysis reveals that the confinement improvement in the ion channel results from the self-similarity in the ion temperature profiles in the plasma core combined with the observed increase in α/L Ti in the plasma edge following density pump-out. In contrast the electron temperature scale length (α/L Ti ) remains essentially unchanged in response to the application of the RMP. At significantly higher RMP levels the edge EXB shearing rate and α/L Ti does not increase and the confinement does not recover following density pump-out.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Spinon Confinement and a Sharp Longitudinal Mode in Yb 2 Pt 2 Pb in Magnetic Field

Here, the fundamental excitations in an antiferromagnetic chain of spins-1/2 are spinons, de-confined fractional quasiparticles that when combined in pairs, form a triplet excitation continuum. In an Ising-like spin chain the continuum is gapped and the ground state is Neel ordered. Here, we report high resolution neutron scattering experiments, which reveal how a magnetic field closes this gap and drives the spin chains in Yb 2 Pt 2 Pb to a critical, disordered Luttinger-liquid state. In Yb 2 Pt 2 Pb the effective spins-1/2 describe the dynamics of large, Ising-like Yb magnetic moments, ensuring that the measured excitations are exclusively longitudinal, which we find to be well described by time-dependent density matrix renormalization group calculations. The inter-chain coupling leads to the confinement of spinons, a condensed matter analog of quark confinement in quantum chromodynamics. Insensitive to transverse fluctuations, our measurements show how a gapless, dispersive longitudinal mode arises from confinement and evolves with magnetic order.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗