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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 1,243 records · Page 69
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

The parallel diffusion of cosmic rays in a random magnetic field.

Within the quasi-linear approximation, the existence of the parallel diffusion coefficient for cosmic rays in a random magnetic field (homogeneous, isotropic), despite the slow decay of the interaction between particles and random field, is demonstrated. As an example, the results of a numerical calculation of the parallel diffusion coefficient for a Gaussian random-field correlation function are presented. The numerical results are corroborated by asymptotic analysis and are compared to those of other theories.

Klimas, A.↗
NASA NTRS1988

Multiple-encounter shock-drift acceleration in nearly perpendicular shocks

A model in which low-energy ions are accelerated by a nearly perpendicular MHD shock without upstream turbulence is presented. In the present scheme, vigorous particle cross-field scattering by downstream turbulence competes with the convection downstream, sending particles back to the shock front for acceleration. Some fraction of the low-energy ions are accelerated up to maximal energy prior to escaping upstream to possibly undergo diffusion shock acceleration. The model can explain particle injection of the diffusive shock acceleration along with ion acceleration during solar flares.

Chiueh, Tzihong↗
NASA NTRS2019

Electric Sail Propulsion for Deep Space Missions

Electrostatic Sail (E-sail) propulsion extracts momentum from the solar wind, which has minimal speeds of 400 km/sec, through electrostatic repulsion of the positively charged solar wind ions. This momentum exchange is accomplished by an array of multi-kilometer-length charged tethers biased to a high positive voltage, producing an electric field around the tethers that deflect the positively charged solar wind particles. This electric field grows in diameter as the spacecraft moves away from the sun, increasing the E-sail effective area. The growth of the E-sail effective area allows the created propulsive force to decrease at a rate closer to 1/r out to distances from the sun of up to 20 Astronomical Units (AU). This is unlike solar sail propulsion, where the thrust decreases at a rate of 1/r2 and is only effective out to distances of ~5 AU. The propulsive force is applied without expending any propellant. Although the thrust generated by an E-Sail is low, it can be applied continuously over a period of years (depending on the mission type), and can push a 500 kg spacecraft to tremendous velocities—as high as 12 AU per year—making the voyage to 600 AU in as few as 50 years after launch. The NASA Marshall Space Flight Center recently completed a NASA Innovative Advanced Concept (NIAC) study in which all of the major system- and subsystem-level aspects of an E-Sail-propelled vehicle were assessed and a maturation plan developed. If implemented, E-Sail propulsion could be realized and deployed as a viable option for space missions within a decade.

Interstellar Probe↗
DOE OSTI2021

Porous stabilized beds, methods of manufacture thereof and articles comprising the same

Disclosed herein is a method comprising disposing a first particle in a reactor; the first particle being a magnetic particle or a particle that can be influenced by a magnetic field, an electric field or a combination of an electrical field and a magnetic field; fluidizing the first particle in the reactor; applying a uniform magnetic field, a uniform electrical field or a combination of a uniform magnetic field and a uniform electrical field to the reactor; elevating the temperature of the reactor; and fusing the first particles to form a monolithic solid.

Klausner, James F.↗
DOE OSTI2023

Porous stabilized beds, methods of manufacture thereof and articles comprising the same

Disclosed herein is a method comprising disposing a first particle in a reactor; the first particle being a magnetic particle or a particle that can be influenced by a magnetic field, an electric field or a combination of an electrical field and a magnetic field; fluidizing the first particle in the reactor; applying a uniform magnetic field, a uniform electrical field or a combination of a uniform magnetic field and uniform electrical field to the reactor; elevating the temperature of the reactor; and fusing the first particles to form a monolithic solid.

Klausner, James F.↗
NASA NTRS1981

Effects of auroral-particle anisotropies and mirror forces on high-latitude electric fields

It is noted that, for most of the mechanisms for the strong electric fields that characterize the narrow regions in which there is acceleration and precipitation of ring current and/or plasma-sheet plasma, certain effects must be taken into account in simulations of auroral electric fields. The effects are those of auroral particle anisotropy, of mirror forces due to the inhomogeneous geomagnetic field, of auroral electron backscatter by the atmosphere, and of electron trapping by the combination of magnetic mirroring and electrostatic forces. What is more, the effects of the very strong perpendicular electric field must also be taken into account in a kinetic description of the Poisson equation in order to achieve a unified theory of the auroral electrostatic structure. Progress in these areas during the past few years is reviewed. It is shown that particle anisotropies and mirror forces can account for some basic electrostatic features of the quiet arc, while additional effects may be occurring in strong events in which the parallel potential drop is more than about 10 kV.

Chiu, Y. T.↗
NASA NTRS1977

Field ionization device used for measuring the pulse height defect of He/+/ in silicon

A neutral particle detector using field ionization and liquid-nitrogen-cooled solid state detectors has been developed to investigate the pulse height defect of low energy He(+) ions in silicon. The field ionization tip is fabricated from a short length of tungsten wire; a typical detector is of the surface-barrier Si type with a thin Au window and low capacitance (about 15 pF); the assembly is mounted in a cylindrical vacuum chamber which is pumped to about 10 to the -6th torr. As an example, pulse height distributions for He(+) and H(+) taken at tip bias of 25.7 kV are presented. The detected energy of the H and He ions are studied as a function of the actual energies of accelerated ions, for a detector having a gold front conducting surface layer of 32 micrograms/sq cm.

Curtis, C. C.↗
NASA NTRS1995

Global electric field determination in the Earth's outer magnetosphere using energetic charged particles

Although many properties of the Earth's magnetosphere have been measured and quantified in the past 30 years since it was discovered, one fundamental measurement (for zeroth order MHD equilibrium) has been made infrequently and with poor spatial coverage - the global electric field. This oversight is due in part to the neglect of theorists. However, there is renewed interest in the convection electric field because it is now realized to be central to many magnetospheric processes, including the global MHD equilibrium, reconnection rates, Region 2 Birkeland currents, magnetosphere ionosphere coupling, ring current and radiation belt transport, substorm injections, and several acceleration mechanisms. Unfortunately the standard experimental methods have not been able to synthesize a global field (excepting the pioneering work of McIlwain's geostationary models) and we are left with an overly simplistic theoretical field, the Volland-Stern electric field model. Single point measurements of the plasmapause were used to infer the appropriate amplitudes of this model, parameterized by K(sub p). Although this result was never intended to be the definitive electric field model, it has gone nearly unchanged for 20 years. The analysis of current data sets requires a great deal more accuracy than can be provided by the Volland-Stern model. The variability of electric field shielding has not been properly addressed although effects of penetrating magnetospheric electric fields has been seen in mid-and low-latitude ionospheric data sets. The growing interest in substorm dynamics also requires a much better assessment of the electric fields responsible for particle injections. Thus we proposed and developed algorithms for extracting electric fields from particle data taken in the Earth's magnetosphere. As a test of the effectiveness of these new techniques, we analyzed data taken by the AMPTE/CCE spacecraft in equatorial orbit from 1984 to 1989.

Eastman, Timothy E.↗
NASA NTRS1995

Low-energy ion acceleration at quasi-perpendicular shocks: Transverse diffusion

The problem of ion injection and acceleration at quasi perpendicular shocks has been the subject of some debate over the past two decades. It is widely known that these shocks efficiently accelerate particles that are well in the high-energy tail of the distribution. However, the issue of injection, or the acceleration of low-energy ions, has yet to reach a consensus. The fundamental issue is whether there is enough diffusion normal to the magnetic field for the particles to remain near the shock. Since transverse diffusion is a physical process that is not well understood in space plasmas, this is an important, and difficult issue to address. In this report, we will investigate the ion injection problem by performing test particle orbit integrations using synthesized turbulent fields. These fields are fully three-dimensional so that transverse diffusion is possible (cross-field diffusion is not possible in geometries where the electromagnetic fields are less than three dimensional). The synthesized fields are produced by superimposing a three-dimensional wave field on a background field. For completeness, we will compare the results from this model with the more well-established theories, such as the diffusive approximation and scatter-free shock drift acceleration. We will also compare these results with other numerical simulation techniques such as the well known hybrid simulation, and other test-particle calculations in which the shock fields are specified to have less than three dimensions. We will also discuss some recent relevant observations and how these compare with our results.

Giacalone, J.↗
DOE OSTI2023

Study on Electrostatic Separation of Quinoline Insolubles from Coal Tar Pitch

The feasibility of electrical separation in the removal of quinoline insoluble (QI) particles from coal tar pitch (CTP) was experimentally investigated. QI particle involvement prohibits the effective fabrication of high-quality value-added products, such as carbon fibers, from CTP. A substantial and sustainable CTP market exists around the world; therefore, a strong incentive exists to develop a viable technical approach to effectively and economically remove QI particles from CTP. The electrical separation method shows promise to achieve this technical goal (Cao et al., 2012). Even with the given setup (wire- cylinder adapted), critical issues remain to be addressed for this method to be applicable to the CTP: (1) identifying the wash oil used in the original QI separation, (2) understanding the mechanism of QI separation, (3) characterizing the deposit, and (4) identifying the QI. This study integrated a set of experimental and analysis techniques into the electrical separation tests to address the aforementioned issues. Key findings are as follows: 1. Electric current responses: • The electric current level of the CTP–wash oil solution reported by Cao et al. (2012) can be attained by using a mixture of 25% quinoline and 75% toluene for the CTPs examined in this study under the same electrical load condition. • The electric current tends to decrease during the test period because of the decreasing number of charged particles. • The reversed field corresponded to the configuration of electrostatic precipitation for positive corona discharge. The high electric field can result in dielectric breakdown and lead to an abrupt current surge. 2 Deposit response and solvent candidates: • Deposit of particles in CTP mixture can be effectively implemented in a wire-cylinder configuration as proposed and examined in this study. • Deposit depends on the solvents. Among the solvents tested, two- and three-part solvents that included quinoline and ethanol (i.e., 25% quinoline and 75% toluene; 50% quinoline and 50% toluene; and 33% wash oil, 33% BTX, and 34% ethanol) produced the highest deposit weight. • The deposit process examined in this study is derived from the charged particles. An appreciable relation exists between deposit weight and electric charge. 3. QI removal efficiency (RE): • The RE of the electrostatic separation can reach as high as 76.2% for Carbores, and 61.6% for Koppers. • The RE can be further enhanced if the field level increases from 0.16 kV/mm that was used in the current study to 0.23 kV/mm, according to the relation established between the RE and the electric field. 4. Testing of the modeling system: • The motion of particles is originally driven by the charge-based electric force in the cases tested. The solid particle separation mechanism is similar to that of QI deposition in CTP. • The mechanical movement of solid particles can be strongly affected by the gravitational and viscous forces in the electric field. 5. EDS analysis and chemical compositions: • The main chemical composition of deposit QI matches that of as-prepared CTP QI. The deposit QI is derived from the same group of the CTP QI. • In addition to carbon, the QI contains oxygen, sodium, aluminum, silicon, iron, and sulfur. The work for the near future is also discussed.

01 COAL, LIGNITE, AND PEAT↗
NASA NTRS1982

Data from ISEE-1 for the IMS period

It is pointed out that a great deal of data with potentially interesting collaborative applications has been obtained since the launch of ISEE-1 and ISEE-2 on October 22, 1977. ISEE-1 experiments are related to studies regarding electrons and protons, the plasma wave, the fast plasma, the plasma density, wave propagation, the E-field, cosmic rays and ions, energetic particles, the E-field, and ion composition. A diagram of the magnetosphere is presented, taking into account the approximate positions of the ISEE orbit at different times of the year. Procedures for obtaining data for collaborations are discussed. Early in the planning stage for the ISEE program it was suggested that collaborative experiments involving ISEE-1 and ISEE-3 on one side, and sounding rockets launched from the auroral zone on the other, might be a valuable approach for studying processes by which particles are precipitated into the auroral zone.

Ogilvie, K. W.↗
DOE OSTI2024

Effective field theory for dark matter absorption on single phonons

Single phonon excitations, with energies in the 1–100 meV range, are a powerful probe of light dark matter (DM). Utilizing effective field theory, we derive a framework to compute DM absorption rates into single phonons starting from general DM-electron, proton, and neutron interactions. We apply the framework to a variety of DM models: Yukawa coupled scalars, axionlike particles with derivative interactions, and vector DM coupling via gauge interactions or Standard Model electric and magnetic dipole moments. We find that GaAs or Al 2 O 3 targets can set powerful constraints on a U ( 1 ) B − L model, and targets with electronic spin ordering are similarly sensitive to DM coupling to the electron magnetic dipole moment. Lastly, we make the code, (an extension of the existing code which computes general DM–single phonon scattering rates), publicly available. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Search for new physics using effective field theory in 13 TeV pp collision events that contain a top quark pair and a boosted Z or Higgs boson

A data sample containing top quark pairs ($\mathrm{t\bar{t}}$) produced in association with a Lorentz-boosted Z or Higgs boson is used to search for signs of new physics using effective field theory. The data correspond to an integrated luminosity of 138 fb$^{-1}$ of proton-proton collisions produced at a center-of-mass energy of 13 TeV at the LHC and collected by the CMS experiment. Selected events contain a single lepton and hadronic jets, including two identified with the decay of bottom quarks, plus an additional large-radius jet with high transverse momentum identified as a Z or Higgs boson decaying to a bottom quark pair. Machine learning techniques are employed to discriminate between $\mathrm{t\bar{t}}$Z or $\mathrm{t\bar{t}}$H events and events from background processes, which are dominated by $\mathrm{t\bar{t}}$ + jets production. No indications of new physics are observed. The signal strengths of boosted $\mathrm{t\bar{t}}$Z and $\mathrm{t\bar{t}}$H production are measured, and upper limits are placed on the $\mathrm{t\bar{t}}$Z and $\mathrm{t\bar{t}}$H differential cross sections as functions of the Z or Higgs boson transverse momentum. The effects of new physics are probed using a framework in which the standard model is considered to be the low-energy effective field theory of a higher energy scale theory. Eight possible dimension-six operators are added to the standard model Lagrangian and their corresponding coefficients are constrained via fits to the data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1978

Adiabatic particle motion in a nearly drift-free magnetic field - Application to the geomagnetic tail

An investigation is made of the adiabatic particle motion occurring in an almost drift-free magnetic field. The dependence of the mean drift velocity on the equatorial pitch angle and the variation of the local drift velocity along the trajectories is studied. The fields considered are two-dimensional and resemble the geomagnetic tail. Derivations are presented for instantaneous and average drift velocities, bounce times, longitudinal invariants, and approximations to the adiabatic Hamiltonian. As expected, the mean drift velocity is significantly smaller than the instantaneous drift velocities found at typical points on the trajectory. The slow drift indicates that particles advance in the dawn-dusk direction rather slowly in the plasma sheet of the magnetospheric tail.

Stern, D. P.↗
DOE OSTI2021

Factorization at subleading power and endpoint divergences in h → γγ decay. Part II. Renormalization and scale evolution

Building on the recent derivation of a bare factorization theorem for the b-quark induced contribution to the h → γγ decay amplitude based on soft-collinear effective theory, we derive the first renormalized factorization theorem for a process described at subleading power in scale ratios, where λ = m b /M h « 1 in our case. We prove two refactorization conditions for a matching coefficient and an operator matrix element in the endpoint region, where they exhibit singularities giving rise to divergent convolution integrals. The refactorization conditions ensure that the dependence of the decay amplitude on the rapidity regulator, which regularizes the endpoint singularities, cancels out to all orders of perturbation theory. We establish the renormalized form of the factorization formula, proving that extra contributions arising from the fact that “endpoint regularization” does not commute with renormalization can be absorbed, to all orders, by a redefinition of one of the matching coefficients. We derive the renormalization-group evolution equation satisfied by all quantities in the factorization formula and use them to predict the large logarithms of order $αα^2_sL^k$ in the three-loop decay amplitude, where $L=ln(-M^2_h/m^2_b)$ and k = 6, 5, 4, 3. We find perfect agreement with existing numerical results for the amplitude and analytical results for the three-loop contributions involving a massless quark loop. On the other hand, we disagree with the results of previous attempts to predict the series of subleading logarithms $~αα^n_sL^{2n+1}$

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Freezing-in hadrophilic dark matter at low reheating temperatures

If the reheating temperature at the end of inflation is low, of order 10 MeV, then dark matter produced through ultraviolet freeze-in has a large direct detection cross section. We study such a scenario in which dark matter is hadrophilic. This leads to dark matter-nucleon scattering cross sections of interest for near-future experiments for dark matter masses in the range of 100 keV–100 MeV. We explore how these predictions vary if reheating is non-instantaneous.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗