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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Experimental evaluation of two 36 inch by 47 inch graphite/epoxy sandwich shear webs

The design is described and test of two large (36 in. x 47 in.) graphite/epoxy sandwich shear webs. One sandwich web was designed to exhibit strength failure of the facings at a shear load of 7638 lbs/in., which is a characteristic loading for the space shuttle orbiter main engine thrust beam structure. The second sandwich web was designed to exhibit general instability failure at a shear load of 5000 lbs/in., to identify problem areas of stability critical sandwich webs and to assess the adequacy of contemporary analysis techniques.

Bush, H. G.↗
NASA NTRS1979

Fluctuations of inverted V electron fluxes

Fluctuations of low-energy electron fluxes during an inverted V event on Nov. 5, 1975 were detected by fixed-energy electrostatic analyzers used in the LEE (low-energy electron) experiment onboard the AE-D satellite. The flux fluctuations were observed at energies of 0.78, 1.38, and 2.62 keV, when these energies were below that of the monoenergetic beam. This suggests that the fluctuations might occur over a wide range of energies. The fluctuations were confined within a pitch angle of 15 degrees, the amplitude increasing with decreasing pitch angle. The oscillation frequencies centered around 1.75 Hz. Fluctuations at two energies were generally correlated. The heating of secondary electrons, deduced from an analysis of the distribution function, is attributed to anomalous heating by electron plasma wave turbulence, whose intensity was modulated by a low-frequency wave. The results are consistent with a model, according to which auroral precipitating electron beams enhance the anomalous resistivity at the topside ionosphere through parametric instabilities.

Lin, C. S.↗
NASA NTRS1979

Further laboratory measurements of the beam-plasma discharge

The paper presents laboratory measurements of the beam-plasma discharge (BPD) produced when an energetic electron beam traverses an initially neutral gas. The results show that the critical beam current is related to energy, magnetic field, and the system length by an empirical relationship at pressures below 2 times 10 to the -5th power torr. This relationship describes the accumulation of ambient plasma density collisionally produced by the beam to a critical value at which ignition occurs. Additional measurements of the narrow-band cyclotron-related waves observed at beam currents below BPD threshold do not clearly establish whether this instability is a precursor to the BPD.

Bernstein, W.↗
NASA NTRS1997

Nonlinear wave particle interaction in the Earth's foreshock

The possibility that ion beams could provide a free energy source for driving an ion/ion instability responsible for the ULF wave occurrence is investigated. For this, the wave dispersion relation with the observed parameters is solved. Secondly, it is shown that the ring-like distributions could then be produced by a coherent nonlinear wave-particle interaction. It tends to trap the ions into narrow cells in velocity space centered around a well-defined pitch-angle, directly related to the saturation wave amplitude in the analytical theory. The theoretical predictions with the observations are compared.

Mazelle, C.↗
DOE OSTI2025

RLGBS: Reinforcement Learning-Guided Beam Search for process optimization in a paper machine dryer section

Paper drying is responsible for over two-thirds of energy consumption in the U.S. pulp and paper industry, presenting significant potential for energy savings through optimization of process parameters. Current approaches often assume fixed operating conditions, neglecting dynamic ambient and process variations that limit achievable savings and real-world applicability. To this end, we develop a physics-based simulation environment for a paper machine dryer section and propose a reinforcement learning (RL) framework to minimize overall energy consumption by optimizing drying process parameters under diverse operating conditions. To mitigate overdrying and numerical instabilities caused by suboptimal local RL actions, we introduce Reinforcement Learning-Guided Beam Search (RLGBS), which explores multiple action sequences in parallel using beam search. Instead of making step-by-step decisions, RLGBS prioritizes solutions based on cumulative probability, reducing the impact of individual suboptimal actions. Experiments demonstrate that RLGBS achieves consistent energy savings under unseen operating conditions not encountered during training, outperforming conventional RL methods. While validated in drying optimization, this framework is broadly applicable to other RL-based industrial process control problems.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1990

Ion beam heating in the auroral zone

Recent satellite observations at high altitudes (above 5000 km) in the auroral zone have shown the existence of hybrid or bimodal ion beam distributions that are evidence of both parallel and perpendicular ion acceleration. To study the nonlinear effects of the ion-ion instability in terms of plasma heating, a numerical simulation parametric study has been performed. It was found that the parallel acceleration that forms the ion beams occurs on a time scale faster than ion-ion wave growth at low drifts; thus ion-ion wave growth is expected to occur primarily for higher drift speeds, which results in strong oblique heating of the ions (both hydrogen and oxygen) forming elevated ion conics.

Schriver, David↗
DOE OSTI2024

Ultrabroad-band x-ray source using a picosecond, laser-driven plasma accelerator

An ultrabroad-band x-ray source, with photon energies from 10 keV to >1 MeV, based on a picosecond laser-driven plasma accelerator, is characterized and used to radiograph high-energy-density-science relevant targets. The measured yield of 10 12 photons/shot is reaching the necessary photon yields to radiograph, in a single shot, high areal density objects and matter under extreme conditions. By focusing a short laser pulse (120 J, 1 ps) into a gas jet, a < 100 mrad electron beam with energies up to 350 MeV and up to 70 nC of charge was produced by a combination of laser self-modulation instability and direct laser acceleration. A foil placed at the exit of the gas jet is used to convert part of the electron beam energy into x rays through inverse bremsstrahlung and/or inverse Compton scattering, generating a bright, broad-band, high-photon-energy beam. This beam is used to radiograph a gold half hohlraum with a high-density sphere inside with relevant characteristics for high-energy-density science and inertial confinement fusion.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Search for Q ~0 Order near a Forbidden Bragg Position in Bi 2.1 Sr 1.9 CaCu 2 O 8+x with Resonant Soft X-ray Scattering

Identifying what broken symmetries are present in the cuprates has become a major area of research. Many authors have reported evidence for so-called “Q ~ 0” order that involves broken inversion, mirror, chiral, or time-reversal symmetry that is uniform in space. Not all these observations are well understood and new experimental probes are needed. Here we use resonant soft x-ray scattering (RSXS) to search for Q ~ 0 order in Bi 2.1 Sr 1.9 CaCu 2 O 8+x (Bi-2212) by measuring the region of a forbidden Bragg peak, (0,0,3), which is normally extinguished by symmetry but may become allowed on resonance if valence band order is present. Using circularly polarized light, we found that this reflection becomes allowed on the CuL 3 resonance for temperatures T c < T < T*, though remains absent in linear polarization and at other temperatures. This observation suggests the existence of spatially uniform valence band order near the pseudogap temperature. In addition, we observed periodic oscillations in the specular reflectivity from the sample surface that resemble thin film interference fringes, though no known film is present. These fringes are highly resonant, appear in all polarizations, and exhibit a period that depends on the location where the beam strikes the sample surface. We speculate that these fringes arise from interaction between some intrinsic valence band instability and extrinsic structural surface morphologies of the material. Our study supports the existence of some kind of Q ~ 0 broken symmetry state in Bi-2212 at intermediate temperatures. Further studies using a microfocused beam, which could disentangle microscopic effects from macroscopic heterogeneities, are needed to ascertain the universality of the effect.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Space charge fields in azimuthally symmetric beams: Integrated Green's function approach

Electromagnetic fields induced by the space charge in relativistic beams play an important role in Accelerator Physics. They lead to emittance growth, slice energy change, and the microbunching instability. Typically, these effects are modeled numerically since simple description exists only inthe limits of large- or small-scale current variations. In this paper we consider an axially symmetric charged beam inside a round pipe and find the solution of the space charge problem that is valid in the full range of current variations. We express the solution for the field components in terms of Green’s functions, which are fully determined by just a single function. We then find that this function is an on-axis potential from a charged disk in a round pipe, with transverse charge density ρ⊥(r), and it has a compact analythical expression. We finally provide an integrated Green’s function based approach for efficient numerical evaluation in the case when the transverse charge density stays the same along the beam

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Mitigation of space charge effects using electron column at IOTA ring

We investigate a novel method to mitigate space charge effects of high intensity proton beams propagating in circular accelerators by means of trapping and controlling electrons generated from beam-induced residual gas ionization. This compensation method uses Coulomb repulsion force between a proton beam and electrons to mitigate self-space charge effects of the beam if it passes through a plasma column. The transverse electron-proton (e-p) instability in the plasma column is well controlled by the longitudinal magnetic field of a solenoid magnet and the bias voltages on electrodes. In this report, we will show simulation results how to control distributions of electrons and ions as well as that of the proton beam inside the column.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Linear beam stability in periodic focusing systems: Krein signature and band structure

The general question of how a beam becomes unstable has been one of the fundamental research topics among beam and accelerator physicists for several decades. In this study, we revisited the general problem of linear beam stability in periodic focusing systems by applying the concepts of Krein signature and band structure. We numerically calculated the eigenvalues and other associated characteristics of one-period maps, and discussed the stability properties of single-particle motions with skew quadrupoles and envelope perturbations in high-intensity beams on an equal footing. In particular, an application of the Krein theory to envelope instability analysis was newly attempted in this study. Finally, the appearance of instabilities is interpreted as the result of the collision between eigenmodes of opposite Krein signatures and the formation of a band gap.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1973

Turbulent heating of colliding streams in the solar wind.

Turbulent heating of colliding plasma streams has previously been observed in the solar wind. The original data were interpreted in terms of a fluid model. It is contended that a plasma-kinetic description is the more appropriate theoretical approach and is necessary in order to better understand the microscopic physical phenomena that underlie all fluid models. Microscopic solar-wind parameters characteristic of conditions during the observations were used, together with the quasi-linear plasma-kinetic theory, to compute the expected magnetic field and temperature enhancements in the interaction region between two counterstreaming plasma beams. The physical mechanism of excitation is the electromagnetic two-stream instability in which Alfven waves are unstable. A total field in the interaction region of about 8 gamma and a change in temperature of about 100,000 K are obtained.

Goldstein, M. L.↗
NASA NTRS1986

Waves generated during electron beam emissions from the Space Shuttle

Observations from the SEPAC (Space Experiments with Particle Accelerators) experiment on Spacelab 1 Shuttle mission of waves generated during electron beam emissions are presented. The dependence of the wave intensity on the beam parameters and the Shuttle attitude is outlined, and the shape of the wave spectra are discussed. It is found that the noise in the 0.75- to 10 kHz band has a spectral shape that can be characterized by an f exp -n law, and that the VLF signal level depends on the beam angle to the magnetic field, the strongest emissions being observed for parallel beams. These features are found to be consistent with a drift wave instability.

Neubert, T.↗
NASA NTRS1987

Electromagnetic beam modes driven by anisotropic electron streams

A theory is presented which provides an explanation for recent laboratory observations of a 'new electromagnetic' mode in a non-Maxwellian high-beta plasma' and suggests a likely relevance of these modes to space plasmas. Unstable parallel-propagating waves, which can be beam modes or whistlers, depending mainly on the degree of velocity anisotropy in a weak electron beam, are found. In the beam-mode limit relevant to the experiment, this is a kinetic Weibel instability, enhanced by a parallel magnetic field. The frequency of the mode can be above or below the electron cyclotron frequency.

Goldman, Martin V.↗
NASA NTRS1995

Numerical Stability In Hyperbolic Boundary-Value Problems

Technical memorandum discusses stability of numerical solutions involving semidiscrete approximations to hyperbolic partial differential equations in initial-and-boundary-value problems. Topic of practical significance because hyperbolic partial differential equations arise in mathematical modeling of waves and blasts. Solutions often needed over restricted regions of unbounded spaces. Outer boundaries artificial, introduced only to limit domains of numerical solutions. Conditions at such artificial boundaries cause numerical instabilities that degrade computed solutions.

Warming, Robert F.↗
DOE OSTI2025

Isotopic mass effects of tritium-fueled high-performance TFTR supershots

An increase in total stored energy correlated with the addition of tritium fuel was observed in supershots during the TFTR DT campaign. This supershot regime had strikingly high, centrally peaked ion and electron temperatures, and the largest neutron emission rates observed in TFTR. This paper presents a study of the causes of this increase in stored energy in supershots. Twenty-six supershots have been recently reanalyzed with the TRANSP plasma analysis code. Early TRANSP simulations did not accurately match the measured magnitude and time evolutions of the neutron emission rates. This mismatch is attributed to neglecting apparent increases of trace amounts of heavy impurities during neutral beam injection. The new TRANSP runs were tuned to accommodate this and match the measured global neutron emission rates. These new runs also had improved fidelity in predicting the time histories and radial dependencies of measured DT neutron emission rates. That in turn adds confidence in the simulated thermal deuterium and tritium density profiles that are needed for calculating the average hydrogenic atomic mass profiles. Six subsets of these supershots had well matched toroidal field B tor , plasma current I p , flux geometry, and total injected neutral beam power. The mix of D and T beam ions was varied for different discharges. The magnitude of the increase of the thermal ion energy W i with added tritium was relatively small, and the total W tot increase is dominated by the increase in fast beam ions with T. Analyses at times before the occurrences of deleterious MHD instabilities yielded scaling of W tot with the volume-average isotopic mass consistent with previous publications. The relative fraction of fast energy ions is expected to be small in practical tokamak reactors. Thus the increase in stored energy W tot observed in TFTR supershots does not appear likely to be significantly helpful for producing useful fusion energy.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Laboratory tests of laser control of electron beams for future colliders

Laser-driven Compton backscattering (CBS) has been proposed as method for controlling the intensity of colliding bunches in the FCC-ee so as to avoid the flip-flop instability caused by intensity asymmetry in colliding bunches. Laser-based collimation has also been proposed as an indestructible collimator for high-intensity electron beams. We have initiated a laboratory-based test program of these concepts with the E344 experiment at FACET-II. In this paper, we describe simulations of laser–beam interactions at FACET-II and the relevant scaling for FCC-ee. We also describe the experimental setup and diagnostics that will be used to make the measurements at FACET-II.

accelerator physics↗
DOE OSTI2026

Laboratory Tests of Laser Control of Electron Beams for Future Colliders

Laser-driven Compton backscattering (CBS) has been proposed as method for controlling the intensity of colliding bunches in the FCC-ee so as to avoid the flip-flop instability caused by intensity asymmetry in colliding bunches. Laser-based collimation has also been proposed as an indestructible collimator for high-intensity electron beams. We have initiated a laboratory-based test program of these concepts with the E344 experiment at FACET-II. In this paper, we describe simulations of laser-beam interactions at FACET-II and the relevant scaling for FCC-ee. We also describe the experimental setup and diagnostics that will be used to make the measurements at FACET-II.

Accelerator Physics (physics.acc-ph)↗