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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Design of 30-T pulsed magnetic field generator for magnetized high-energy-density plasma experiments

We introduce the conceptual design of a high-voltage pulser intended to generate 30-T magnetic fields for magneto-inertial fusion experiments at the OMEGA facility. The pulser uses a custom capacitor bank and two externally triggered spark gaps to drive a multi-turn coil. This new high-voltage pulser is capable of storing 10 times more energy than the previous system, using a higher charge voltage (from 20 kV to 30 kV) and a larger capacitance (from 1 µF to 5 µF). Circuit simulations show that this pulser can deliver 100 kA into a 60-nH, 14-mΩ coil with a rise time of 1 μs. For a coil with 2 turns with an average coil diameter of 7.8 mm, this current translates into a 32-T peak magnetic field at coil center. This is an element of three increase in the peak magnetic field compared to the present generator magnetic field capabilities.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Numerical study of transition to supersonic flows in the edge plasma

The plasma scrape-off layer (SOL) in a tokamak is characterized by ion flow down a long narrow flux tube terminating on a solid surface. The ion flow velocity along a magnetic field line can be equal to or greater than sonic at the entrance of a Debye sheath or upstream in the presheath. This paper presents a numerical study of the transition between subsonic and supersonics flows. A quasineutral one-dimensional (1D) fluid code has been used for modeling of plasma transport in the SOL along magnetic field lines, both in steady state and under transient conditions. The model uses coupled equations for continuity, momentum, and energy balance with ionization, radiation, charge exchange, and recombination processes. The recycled neutrals are described in the diffusion approximation. Standard Bohm sheath criterion is used as boundary conditions at the material surface. Three conditions conducive for the generation of supersonic flows in SOL plasmas have been explored. It is found that in steady state high (attached) and low (detached) divertor temperatures cases, the role of particle, momentum, and energy loss is critical. For attached case, the appearance of shock waves in the divertor region if the incoming plasma flow is supersonic and its effect on impurity retention is presented. In the third case, plasma expansion along the magnetic field can yield time-dependent supersonic solutions in the quasineutral rarefaction wave. Such situations can arise in the parallel transport of intermittent structures such as blobs and edge localized mode filaments along field lines.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

Dynamic Formation of a Hot Field Reversed Configuration with Improved Confinement by Supersonic Merging of Two Colliding High-{beta} Compact Toroids

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-{beta} plasmoids preformed by the dynamic version of field-reversed {theta}-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{sub i}+T{sub e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Constraining preheat energy deposition in MagLIF experiments with multi-frame shadowgraphy

A multi-frame shadowgraphy diagnostic has been developed and applied to laser preheat experiments relevant to the Magnetized Liner Inertial Fusion (MagLIF) concept. The diagnostic views the plasma created by laser preheat in MagLIF-relevant gas cells immediately after the laser deposits energy as well as the resulting blast wave evolution later in time. The expansion of the blast wave is modeled with 1D radiation-hydrodynamic simulations that relate the boundary of the blast wave at a given time to the energy deposited into the fuel. This technique is applied to four different preheat protocols that have been used in integrated MagLIF experiments to infer the amount of energy deposited by the laser into the fuel. The results of the integrated MagLIF experiments are compared with those of two-dimensional LASNEX simulations. Here, the best performing shots returned neutron yields ~40–55% of the simulated predictions for three different preheat protocols

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Spatial measurements of electron energy distribution and plasma parameters in a weakly magnetized inductive discharge

Spatial characteristics of plasma parameters such as electron temperature, plasma density, plasma potential, and electron energy distribution (EED) were studied in inductively coupled plasma with an axial dc magnetic field. With dc magnetic field, the measured EEDs in the total electron energy scale are spatially coincided except cutting of the low electron energy part indicating the conserved non-local electron kinetics in an axial direction, even though the dc magnetic field is applied. Spatial distributions of the plasma densities at axial positions have almost same trends with various magnetic field strengths. We also discuss the reduction of the ambipolar potential along the axial direction as the applied magnetic field increased.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Design of the cryostat for High Field Vertical Magnet Testing Facility at Fermilab

High Field Vertical Magnet Test Facility (HFVMTF) is a joint project between the Office of High Energy Physics (HEP) and the Office of Fusion Energy Sciences (FES). Its construction is currently under way at Fermi National Accelerator Laboratory (Fermilab). As a part of the project a new double bath superfluid helium cryostat has been designed. The cryostat can accommodate magnets with up to 20 tonne weight and 1.3 m diameter. This paper discusses challenges and solutions for cryostat, lambda plate and heat exchanger design, and presents results of performance analysis.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Formation of buffer-gas-trap based positron beams

Presented here are experimental measurements, analytic expressions, and simulation results for pulsed, magnetically guided positron beams formed using a Penning-Malmberg style buffer gas trap. In the relevant limit, particle motion can be separated into motion along the magnetic field and gyro-motion in the plane perpendicular to the field. Analytic expressions are developed which describe the evolution of the beam energy distributions, both parallel and perpendicular to the magnetic field, as the beam propagates through regions of varying magnetic field. Simulations of the beam formation process are presented, with the parameters chosen to accurately replicate experimental conditions. The initial conditions and ejection parameters are varied systematically in both experiment and simulation, allowing the relevant processes involved in beam formation to be explored. These studies provide new insights into the underlying physics, including significant adiabatic cooling, due to the time-dependent beam-formation potential. Methods to improve the beam energy and temporal resolution are discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

SPECTRUM OF KINETIC-ALFVEN TURBULENCE

A numerical study of strong kinetic-Alfven turbulence at scales smaller than the ion gyroscale is presented, and a phenomenological model is proposed that argues that magnetic and density fluctuations are concentrated mostly in two-dimensional structures, which leads to their Fourier energy spectra E(k ){proportional_to}k {sup -8/3} , where k is the wavevector component normal to the strong background magnetic field. The results may provide an explanation for recent observations of magnetic and density fluctuations in the solar wind at sub-proton scales.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2002

Magnetized Target Fusion Driven by Plasma Liners

Magnetized target fusion is an emerging, relatively unexplored approach to fusion for electrical power and propulsion application. The physical principles of the concept are founded upon both inertial confinement fusion (ICF) and magnetic confinement fusion (MCF). It attempts to combine the favorable attributes of both these orthogonal approaches to fusion, but at the same time, avoiding the extreme technical challenges of both by exploiting a fusion regime intermediate between them. It uses a material liner to compress, heat and contain the fusion reacting plasma (the target plasma) mentally. By doing so, the fusion burn could be made to occur at plasma densities as high as six orders of magnitude higher than conventional MCF such as tokamak, thus leading to an approximately three orders of magnitude reduction in the plasma energy required for ignition. It also uses a transient magnetic field, compressed to extremely high intensity (100's T to 1000T) in the target plasma, to slow down the heat transport to the liner and to increase the energy deposition of charged-particle fusion products. This has several compounding beneficial effects. It leads to longer energy confinement time compared with conventional ICF without magnetized target, and thus permits the use of much lower plasma density to produce reasonable burn-up fraction. The compounding effects of lower plasma density and the magneto-insulation of the target lead to greatly reduced compressional heating power on the target. The increased energy deposition rate of charged-particle fusion products also helps to lower the energy threshold required for ignition and increasing the burn-up fraction. The reduction in ignition energy and the compressional power compound to lead to reduced system size, mass and R&D cost. It is a fusion approach that has an affordable R&D pathway, and appears attractive for propulsion application in the nearer term.

Thio, Y. C. Francis↗
DOE OSTI2012

Reconnection events in two-dimensional Hall magnetohydrodynamic turbulence

The statistical study of magnetic reconnection events in two-dimensional turbulence has been performed by comparing numerical simulations of magnetohydrodynamics (MHD) and Hall magnetohydrodynamics (HMHD). The analysis reveals that the Hall term plays an important role in turbulence, in which magnetic islands simultaneously reconnect in a complex way. In particular, an increase of the Hall parameter, the ratio of ion skin depth to system size, broadens the distribution of reconnection rates relative to the MHD case. Moreover, in HMHD the local geometry of the reconnection region changes, manifesting bifurcated current sheets and quadrupolar magnetic field structures in analogy to laminar studies, leading locally to faster reconnection processes in this case of reconnection embedded in turbulence. This study supports the idea that the global rate of energy dissipation is controlled by the large scale turbulence, but suggests that the distribution of the reconnection rates within the turbulent system is sensitive to the microphysics at the reconnection sites.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

The transfer between electron bulk kinetic energy and thermal energy in collisionless magnetic reconnection

By performing two-dimensional particle-in-cell simulations, we investigate the transfer between electron bulk kinetic and electron thermal energy in collisionless magnetic reconnection. In the vicinity of the X line, the electron bulk kinetic energy density is much larger than the electron thermal energy density. The evolution of the electron bulk kinetic energy is mainly determined by the work done by the electric field force and electron pressure gradient force. The work done by the electron gradient pressure force in the vicinity of the X line is changed to the electron enthalpy flux. In the magnetic island, the electron enthalpy flux is transferred to the electron thermal energy due to the compressibility of the plasma in the magnetic island. The compression of the plasma in the magnetic island is the consequence of the electromagnetic force acting on the plasma as the magnetic field lines release their tension after being reconnected. Therefore, we can observe that in the magnetic island the electron thermal energy density is much larger than the electron bulk kinetic energy density.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

PPPL Laboratory Directed Research and Development (Project Final Reports, FY2018 - FY2020)

The U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) is a collaborative national center for fusion energy science, basic sciences, and advanced technology. The Laboratory has three major missions: (1) to develop the scientific knowledge and advanced engineering to enable fusion to power the U.S. and the world; (2) to advance the science of nanoscale fabrication for technologies of tomorrow; and (3) to further the development of the scientific understanding of the plasma universe from laboratory to astrophysical scales. PPPL’s Laboratory Directed Research and Development (LDRD) program supports and encourages creativity and innovation and contributes to its long-term viability. New scientific and technical research areas emerge and are nurtured through the program. Furthermore, new capabilities are developed to enable the Laboratory to meet its and DOE’s missions. The program is used to systematically diversify the Laboratory’s programs and mission. In the last few years, the program has started projects in nanomaterial synthesis, microelectronics, advanced x-ray spectroscopy, high-energy-density physics, superconducting magnet technology, machine learning and artificial intelligence, 3D magnetic fields to optimize fusion plasmas, integration of permanent magnets with simple high-field magnets to reduce the cost of producing complex 3D magnetic fields, advanced computational methods for predictive understanding and control of fusion plasma, development of quantum computing algorithms for plasma physics, liquid metal plasma-facing components for fusion reactors, virtual engineering, and plasma-based space propulsion. The program is also the vehicle to recruit and train talented scientists and engineers with the new skills needed to perform the Laboratory’s mission. Many of the new hires through the program go on to become world-class scientists and engineers in their fields. This report provides descriptions and accomplishments of those LDRD projects that were completed during fiscal years 2018 through 2020.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Speculation on a Solar Chronometer for Climate

Solar activity has been correlated to climatic fluctuations and has been postulated as a major factor in quasi-periodic global climatic change. However, correlations are not explanations of physical mechanisms and do not couple cause with effect. A mechanism for a chronometer for solar output variability is proposed based on relations between properties of thermonuclear fusion, nuclear magnetic moment, and nuclear magnetic resonance. A fundamental oscillation of a nucleus with a net nuclear magnetic moment (NMM) is the precession of its axis of rotation when subjected to a magnetic field. Nuclear magnetic resonance (NMR) is the preferred frequency of precession for a nucleus of a particular isotope when placed in a magnetic field of specific intensity. The NMM for those isotopes involved in the proton-proton (p-p) chain pathway for solar fusion varies from strong positive to strong negative. Individual fusion events, for hydrogen and helium isotopes which release varying amounts of energy, may be controlled by NMR frequencies. The pulses of energy from fusion events occurring at NMR frequencies in the solar interior may be transformed into pressure or gravity waves that emerge as gravity or acoustic waves at the surface. Dictated by spherical harmonics, certain wavelengths may be reinforced and reenter the solar interior to modulate the fusion process. Qualitative analysis of solar and climatic data support the interaction of the three basic components of the chronometer, magnetic activity, oscillation frequency, and solar energy output.

Perry, Charles A.↗
DOE OSTI2011

Response to ''Comment on 'Heating of ions by low-frequency Alfven waves in partially ionized plasmas''' [Phys. Plasmas 18, 084703 (2011)]

The calculation of temperature in a plasma system that is not in thermal equilibrium remains a topic of debate. In our article [Dong and Paty, Phys. Plasmas 18, 030702 (2011)] we use the average kinetic energy to calculate the ''kinetic temperature'' in a non-equilibrium system to quantify the heating of ions by low-frequency Alfven waves in a partially ionized plasma (i.e., where collisions with neutrals can not be ignored). We implement a method previously used by Wang, Wu and Yoon [Wang, Wu and Yoon, Phys. Rev. Lett. 96, 125001 (2006)] and several others studying the effects of low frequency Alfven waves in collisionless plasmas. This method is appropriate for several reasons discussed in this response. Most notably, we implement it to investigate heating of the plasma population since the bulk velocity of the particle ensemble perpendicular to the ambient magnetic field remains zero during the numerical experiment.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Demonstration of reduced neoclassical energy transport in Wendelstein 7-X

Research on magnetic confinement of high-temperature plasmas has the ultimate goal of harnessing nuclear fusion for the production of electricity. Although the tokamak is the leading toroidal magnetic-confinement concept, it is not without shortcomings and the fusion community has therefore also pursued alternative concepts such as the stellarator. Unlike axisymmetric tokamaks, stellarators possess a three-dimensional (3D) magnetic field geometry. The availability of this additional dimension opens up an extensive configuration space for computational optimization of both the field geometry itself and the current-carrying coils that produce it. Such an optimization was undertaken in designing Wendelstein 7-X (W7-X), a large helical-axis advanced stellarator (HELIAS), which began operation in 2015 at Greifswald, Germany. A major drawback of 3D magnetic field geometry, however, is that it introduces a strong temperature dependence into the stellarator’s non-turbulent ‘neoclassical’ energy transport. Indeed, such energy losses will become prohibitive in high-temperature reactor plasmas unless a strong reduction of the geometrical factor associated with this transport can be achieved; such a reduction was therefore a principal goal of the design of W7-X. In spite of the modest heating power currently available, W7-X has already been able to achieve high-temperature plasma conditions during its 2017 and 2018 experimental campaigns, producing record values of the fusion triple product for such stellarator plasmas. The triple product of plasma density, ion temperature and energy confinement time is used in fusion research as a figure of merit, as it must attain a certain threshold value before net-energy-producing operation of a reactor becomes possible. Here we demonstrate that such record values provide evidence for reduced neoclassical energy transport in W7-X, as the plasma profiles that produced these results could not have been obtained in stellarators lacking a comparably high level of neoclassical optimization.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Partnership Center for High-fidelity Boundary Plasma Simulation

The University of Colorado Boulder contributed to the DOE Partnership Center for High‑fidelity Boundary Plasma Simulation (award DE‑SC0018271) by advancing gyrokinetic modeling of core–edge plasma interactions in tokamaks. Using the GEM and XGC codes, the project investigated turbulence spreading from the plasma edge to the core, finding that while edge‑driven trapped electron mode turbulence enhances core ion heat flux in DIII‑D L‑mode plasmas, it does not fully explain experimentally observed transport shortfalls, indicating a need for flux‑driven models. The team also demonstrated that edge micro‑instabilities are highly sensitive to small variations in magnetic equilibrium, particularly near the pedestal and edge, highlighting the importance of accurately characterizing equilibrium uncertainties. Significant progress was made in spatially coupling the core GEM and edge XGC simulations, with successful validation against standalone XGC results in realistic tokamak geometries, laying the groundwork for future extensions to kinetic electrons and electromagnetic effects.

42 ENGINEERING↗
DOE OSTI2014

Branches of electrostatic turbulence inside solitary plasma structures in the auroral ionosphere

The excitation of electrostatic turbulence inside space-observed solitary structures is a central topic of this exposition. Three representative solitary structures observed in the topside auroral ionosphere as large-amplitude nonlinear signatures in the electric field and magnetic-field-aligned current on the transverse scales of ∼10{sup 2}–10{sup 3} m are evaluated by the theories of electrostatic wave generation in inhomogeneous background configurations. A quantitative analysis shows that the structures are, in general, effective in destabilizing the inhomogeneous energy-density-driven (IEDD) waves, as well as of the ion acoustic waves modified by a shear in the parallel drift of ions. It is demonstrated that the dominating branch of the electrostatic turbulence is determined by the interplay of various driving sources inside a particular solitary structure. The sources do not generally act in unison, so that their common effect may be inhibiting for excitation of electrostatic waves of a certain type. In the presence of large magnetic-field-aligned current, which is not correlated to the inhomogeneous electric field inside the structure, the ion-acoustic branch becomes dominating. In other cases, the IEDD instability is more central.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Available energy from diffusive and reversible phase space rearrangements

Rearranging the six-dimensional phase space of particles in plasma can release energy. The rearrangement may happen through the application of electric and magnetic fields, subject to various constraints. The maximum energy that can be released through a rearrangement of a distribution of particles can be called its available or free energy. Rearrangement subject to phase space volume conservation leads to the classic Gardner free energy. Less free energy is available when constraints are applied, such as respecting conserved quantities. Furthermore, less energy is available if particles can only be diffused in phase-space from regions of high phase-space density to regions of lower phase-space density. The least amount of free energy is available if particles can only be diffused in phase space, while conserved quantities still need to be respected.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗