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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Enhanced plasma performance in C-2W advanced beam-driven field-reversed configuration experiments

TAE Technologies’ fifth-generation fusion device, C-2W (also called ‘Norman’), is the world’s largest compact-toroid device and has made significant progress in field-reversed configuration (FRC) plasma performance. C-2W produces record breaking, macroscopically stable, high-temperature advanced beam-driven FRC plasmas, dominated by injected fast particles and sustained in steady state, which is primarily limited by neutral-beam (NB) pulse duration. The NB power supply system has recently been upgraded to extend the pulse length from 30 ms to 40 ms, which allows for a longer plasma lifetime and thus better characterization and further enhancement of FRC performance. An active plasma control system is routinely used in C-2W to produce consistent FRC performance as well as for reliable machine operations using magnet coils, edge-biasing electrodes, gas injection and tunable-energy NBs. Google’s machine learning framework for experimental optimization has also been routinely used to enhance plasma performance. D

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1990

The beam-driven chromospheric evaporation model of solar flares - A model not supported by observations from nonimpulsive large flares

Most large solar flares exhibit hard X-ray emission which is usually impulsive, as well as thermal soft X-ray emission, which is gradual. The beam-driven chromospheric evaporation model of solar flares was proposed to explain the origin of the soft X-ray emitting flare plasma. A careful evaluation of the issue under discussion reveals contradictions between predictions from the theoretical chromospheric evaporation model and actual observations from a set of large X- and M-type flares. It is shown that although the soft X-ray and hard X-ray emissions are a result of the same flare, one is not a result of the other.

Feldman, U.↗
DOE OSTI2019

Modelling of beam-driven Alfvén modes in TJ-II plasmas

Here, the properties of hydrogen neutral beam injection driven Alfvén eigenmodes (AEs) in the TJ-II flexible heliac are investigated using a reduced magnetohydrodynamic (MHD) model coupled to a realistic MHD equilibrium. The simulation results of AE frequency and radial localization are found to be broadly consistent with experimental observations. The simulation results show that an AE with the same poloidal and toroidal harmonics persists under small variations in on-axis iota values, which is consistent with the experimental observations. The corresponding wave-particle resonance maps suggest, for low bounce harmonics, the possibility of describing nonlinear evolution of the AEs in TJ-II by a sum of two ion populations with different weighting factors, one of which is dominated by drag and the other by diffusion. As the bounce harmonic increases, the resonance region starts to expand and can cover a significant area of the particle phase space until this resonance region vanishes at high bounce harmonics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Machine Protection Studies of Fast Instability-Driven Beam Losses in the EIC Electron Storage Ring

Fast transverse beam instabilities represent one of the most challenging protection scenarios for the Electron-Ion Collider (EIC) electron storage ring (ESR). Coherent betatron oscillations driven by collective effects can grow rapidly and lead to substantial beam losses within only a few tens of turns, posing a threat to collimators, superconducting (SC) magnets, cryogenic systems, and detector components. A dedicated simulation framework based on distributed transverse excitations was developed to evaluate instability-driven beam losses in the ESR. A conservative instability rise time on the order of 10 turns was used to define a bounding protection scenario. Simulations show that the original two-collimator configuration is insufficient to localize losses under all operating conditions, whereas an optimized four-collimator configuration reduces loss leakage into protected regions by more than two orders of magnitude. Nevertheless, the most severe instability scenarios produce catastrophic beam impacts, with nearly half of the stored beam being intercepted by the collimators within a single turn, exceeding the preliminary estimated survivability limits of the baseline collimator design. The results demonstrate that collimation alone is insufficient to guarantee safe ESR operation and must be complemented by a fast machine-protection system. Dedicated turn-by-turn beam-position monitors and fast beam-loss monitors provide sufficient advance warning to detect instability growth and initiate a beam abort before equipment-damaging loss levels are reached. These findings establish quantitative requirements for the ESR machine-protection architecture and support the implementation of a multilayer protection strategy for both accelerator and detector systems.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Sunbeam: Near-sun statites as beam platforms for beam-driven rockets

Here, we outline a method of beamed power for propulsion that utilizes relativistic electron beams. The physics of charged particle beam propagation in the space plasma environment is discussed and the long-range (> 100 AU) advantage of relativistic electron beams is emphasized. A preliminary statite-based beam emitter for powering probes to 0.1c is proposed and the challenges in beamed-power uses are explored.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS1986

The effect of beam-driven return current instability on solar hard X-ray bursts

The problem of electrostatic wave generation by a return current driven by a small area electron beam during solar hard X-ray bursts is discussed. The marginal stability method is used to solve numerically the electron and ion heating equations for a prescribed beam current evolution. When ion-acoustic waves are considered, the method appears satisfactory and, following an initial phase of Coulomb resistivity in which T sub e/T sub i rise, predicts a rapid heating of substantial plasma volumes by anomalous ohmic dissipation. This hot plasma emits so much thermal bremsstrahlung that, contrary to previous expectations, the unstable beam-plasma system actually emits more hard X-rays than does the beam in the purely collisional thick target regime relevant to larger injection areas. Inclusion of ion-cyclotron waves results in ion-acoustic wave onset at lower T sub e/T sub i and a marginal stability treatment yields unphysical results.

Cromwell, D.↗
DOE OSTI2025

On the role of self-generated magnetic fields in focused ion beams driven by intense picosecond laser pulses

We investigate the physics of ion beam focusing in the interaction of intense picosecond laser pulses with concave foils, using two-dimensional particle-in-cell simulations. Curved targets have been observed to deliver brighter multi-MeV ion beams than flat targets, and they could be used to ignite pre-compressed ICF fusion capsules in a scheme called ion fast ignition. Focusing is achieved by shaping the target and relying on an ion acceleration mechanism in which the ions are accelerated normal to the target surface; subsequently, the plasma expansion grows magnetic fields that advect with the plasma and deflect ions away from the target symmetry axis, causing the focal spot to shift downstream from its geometric location. The drop in both electric and magnetic field strengths in the expanding plasma makes the ion beam envelope asymmetric with respect to the focusing plane.

Focused ion beam↗
NASA NTRS1984

Electrostatic hiss and the beam driven electron acoustic instability in the dayside polar cusp

In this study it is shown that the upward moving electron beams observed by DE-1 in the dayside polar cusp at 2 to 5 R sub E drive an electrostatic electron acoustic mode, rather than the whistler mode near resonance, as previously concluded. The characteristics of this instability are compared with the properties of hiss in the polar cusp observed by the Dynamics Explorer (DE-1) satellite. The hiss frequencies and funnel shaped frequency-time spectra are consistent with the electron acoustic mode. However, because the hiss often has a fluctuating magnetic field component near the axis of the funnel shape, the hiss is probably composed of both electron acoustic and whistler mode waves.

Tokar, R. L.↗
DOE OSTI2021

Signature of Collective Plasma Effects in Beam-Driven QED Cascades

QED cascades play an important role in extreme astrophysical environments like magnetars. Furthermore, they can also be produced by passing a relativistic electron beam through an intense laser field. Signatures of collective pair plasma effects in these QED cascades are shown to appear, in exquisite detail, through plasma-induced frequency upshifts in the laser spectrum. Remarkably, these signatures can be detected even in small plasma volumes moving at relativistic speeds. Strong-field quantum and collective pair plasma effects can thus be explored with existing technology, provided that ultradense electron beams are colocated with multipetawatt lasers.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Investigation of Proton Beam-Driven Fusion Reactions Generated by an Ultra-Short Petawatt-Scale Laser Pulse

We present results from a pitcher-catcher experiment utilizing a proton beam generated with nanostructured targets at a petawatt-class, short-pulse laser facility to induce proton-boron fusion reactions in a secondary target. A 45-fs laser pulse with either 400 nm wavelength and 7 J energy, or 800 nm and 14 J, and an intensity of up to 5 × 10 21 W/cm 2 was used to irradiate either thin foil targets or near-solid density, nanostructured targets made of boron nitride (BN) nanotubes. In particular, for 800 nm wavelength irradiation, a BN nanotube target created a proton beam with about five times higher maximum energy and about ten times more protons than a foil target. This proton beam was used to irradiate a thick plate made of boron nitride placed in close proximity to trigger 11 B (p, α) 2α fusion reactions. A suite of diagnostics consisting of Thomson parabola ion spectrometers, postshot nuclear activation measurements, neutron time-of-flight detectors, and differentially filtered solid-state nuclear track detectors were used to measure both the primary proton spectrum and the fusion products. From the primary proton spectrum, we calculated (p, n) and (α,n) reactions in the catcher and compare with our measurements. The nuclear activation results agree quantitatively and neutron signals agree qualitatively with the calculations, giving confidence that primary particle distributions can be obtained from such measurements. These results provide new insights for measuring the ion distributions inside of proton-boron fusion targets.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1992

Nonlocal analysis of finite-beam-driven instabilities

The fully kinetic integral eigenmode equation in wave-number space is used to describe the nonlocal behavior of electrostatic waves in an electron-beam plasma, which are studied in the low-temperature-beam regime and the warm-beam regime. The case of strongly magnetized electrons and unmagnetized ions, which corresponds to the waves in a frequency range from the lower-hybrid to the electron plasma frequency, is examined. Three wave modes are found. The first group consists of modes that have dispersive properties similar to the uniform, infinite beam-plasma system. Depending on the beam width, the growth rates are strongly reduced. The second group, surface modes, are localized at the periphery of the beam region and are less unstable than the unstable modes of the first group. The third group represents natural oscillations of the background plasma. These modes are virtually unaffected by the beam.

Serizawa, Y.↗
NASA NTRS1985

Beam-driven ion cyclotron harmonic resonances in the terrestrial foreshock

A terrestrial upstream wave event which demonstrates multiple, ion cyclotron harmonic resonances between the interplanetary wave population and an observed proton beam is analyzed. The techniques and parameters employed in the data analysis are discussed, including the use of differential and band-pass filters. An upstream wave event demonstrating multiple harmonic waves is examined, and the instability analysis relevant to the ion beam observations thought to be responsible for that event is discussed. It is shown that an observed bi-Maxwellian ion beam is capable of generating right and left-hand polarized waves through ion cyclotron harmonic resonance.

Smith, C. W.↗
DOE OSTI2019

Observation of a beam-driven low-frequency mode in Heliotron J

A low-frequency electromagnetic mode (LF-mode) has been observed in a stellarator/heliotron device, Heliotron J. The LF-mode is observed only in neutral beam heated plasmas with a co-current, which increases the rotational transform. The observed LF-mode peaks at rho = 0.86–0.91, where rho = r/a is the normalized minor radius. The LF-mode propagates in the ion diamagnetic drift direction, and the poloidal mode number is m ~ 6–8, determined with a combination of Mirnov coil arrays and 2D fast camera measurement. A high m number induces significant Doppler shift from the background ion flow. The frequency is corrected with both E × B rotation and the ion diamagnetic flow. The corrected frequency is almost consistent with the beta-induced Alfvén eigenmode gap evaluated with the STELLGAP code, although very close to the accumulation point. The mode could also be a global Alfvén eigenmode.

BAE↗
DOE OSTI2024

Fully Kinetic Simulations of Proton-beam-driven Instabilities from Parker Solar Probe Observations

The expanding solar wind plasma ubiquitously exhibits anisotropic nonthermal particle velocity distributions. Typically, proton velocity distribution functions (VDFs) show the presence of a core and a field-aligned beam. Novel observations made by the Parker Solar Probe (PSP) in the innermost heliosphere have revealed new complex features in the proton VDFs, namely anisotropic beams that sometimes experience perpendicular diffusion. In this study, we use a 2.5D fully kinetic simulation to investigate the stability of proton VDFs with anisotropic beams observed by PSP. Our setup consists of a core and an anisotropic beam population that drift with respect to each other. This configuration triggers a proton beam instability from which nearly parallel fast magnetosonic modes develop. Our results demonstrate that before this instability reaches saturation, the waves resonantly interact with the beam protons, causing perpendicular heating at the expense of the parallel temperature.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Beam-driven dynamics of aluminium dopants in graphene

Abstract Substituting heteroatoms into graphene can tune its properties for applications ranging from catalysis to spintronics. The further recent discovery that covalent impurities in graphene can be manipulated at atomic precision using a focused electron beam may open avenues towards sub-nanometer device architectures. However, the preparation of clean samples with a high density of dopants is still very challenging. Here, we report vacancy-mediated substitution of aluminium into laser-cleaned graphene, and without removal from our ultra-high vacuum apparatus, study their dynamics under 60 keV electron irradiation using aberration-corrected scanning transmission electron microscopy and spectroscopy. Three- and four-coordinated Al sites are identified, showing excellent agreement with ab initio predictions including binding energies and electron energy loss spectrum simulations. We show that the direct exchange of carbon and aluminium atoms predicted earlier occurs under electron irradiation, although unexpectedly it is less probable than the same process for silicon. We also observe a previously unknown nitrogen–aluminium exchange that occurs at Al–N double-dopant sites at graphene divacancies created by our plasma treatment.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Electron acceleration through two successive electron beam driven wakefield acceleration stages

Structure based wakefield acceleration may provide a viable approach for accelerating sufficiently large numbers of electrons and positrons at the high gradient needed to meet the luminosity, efficiency, and cost requirements of a future linear collider. An important step in proving its viability is the demonstration of acceleration in multiple stages. Here we show the results of the first experimental demonstration of staged two beam wakefield acceleration, conducted at the Argonne Wakefield Accelerator Facility (AWA), in which a 0.5 nC electron bunch gained equal amounts of energy in two stages (~2.4 MeV per stage, corresponding to an average acceleration gradient of ~70 MeV/m). Meanwhile 150MeV/m of acceleration in a single stage has been achieved. The demonstration experiment should be scalable to staged-acceleration at gradients of the order of 200 to 300 MeV/m. Furthermore, such a development would considerably reduce both the cost and footprint of both a future high-energy physics (HEP) collider, as well as future X-ray light sources.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Experimental Characterization of Electron-Beam-Driven Wakefield Modes in a Dielectric-Woodpile Cartesian Symmetric Structure

Photonic structures operating in the terahertz (THz) spectral region enable the essential characteristics of confinement, modal control, and electric field shielding for very high gradient accelerators based on wakefields in dielectrics. We report in this paper an experimental investigation of THz wakefield modes in a three-dimensional photonic woodpile structure. Selective control in exciting or suppressing of wakefield modes with a nonzero transverse wave vector is demonstrated by using drive beams of varying transverse ellipticity. Additionally, we show that the wakefield spectrum is insensitive to the offset position of strongly elliptical beams. Finally, these results are consistent with analytic theory and three-dimensional simulations and illustrate a key advantage of wakefield systems with Cartesian symmetry: the suppression of transverse wakes by elliptical beams.

43 PARTICLE ACCELERATORS↗