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Time-dependent density-functional-theory calculations of the nonlocal electron stopping range for inertial confinement fusion applications

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Physical Review E 2023年第3期108卷 035206-035206页

作者： K. A. Nichols S. X. Hu A. J. White V. N. Goncharov D. I. Mihaylov L. A. Collins N. R. Shaffer V. V. Karasiev Laboratory for Laser Energetics University of Rochester Rochester New York 14623-1299 USA Department of Physics and Astronomy University of Rochester Rochester New York 14623-1299 USA Department of Mechanical Engineering University of Rochester Rochester New York 14623-1299 USA Los Alamos National Laboratory Los Alamos New Mexico 87545 USA

Nonlocal electron transport is important for understanding laser-target coupling for laser-direct-drive (LDD) inertial confinement fusion (ICF) simulations. Current models for the nonlocal electron mean free path in radiation-hydrodynamic codes are based on plasma-physics models developed decades ago; improvements are needed to accurately predict the electron conduction in LDD simulations of ICF target implosions. We utilized time-dependent density functional theory (TD-DFT) to calculate the electron stopping power (SP) in the so-called conduction-zone plasmas of polystyrene in a wide range of densities and temperatures relevant to LDD. Compared with the modified Lee-More model, the TD-DFT calculations indicated a lower SP and a higher stopping range for nonlocal electrons. We fit these electron SP calculations to obtain a global analytical model for the electron stopping range as a function of plasma conditions and the nonlocal electron kinetic energy. This model was implemented in the one-dimensional radiation-hydrodynamic code lilac to perform simulations of LDD ICF implosions, which are further compared with simulations by the standard modified Lee-More model. Results from these integrated simulations are discussed in terms of the implications of this TD-DFT-based mean-free-path model to ICF simulations.

关键词： Fast particle effects in plasmas Plasma transport Plasma-particle interactions Hot dense plasma Inertially confined plasmas Ab initio molecular dynamics First-principles calculations in plasma physics Hydrodynamics test-particle methods

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Nonresonant Scattering of Relativistic Electrons by Electromagnetic Ion Cyclotron Waves in Earth’s Radiation Belts

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Physical Review Letters 2022年第13期129卷 135101-135101页

作者： Xin An Anton Artemyev Vassilis Angelopoulos Xiaojia Zhang Didier Mourenas Jacob Bortnik Department of Earth Planetary and Space Sciences University of California Los Angeles California 90095 USA CEA DAM DIF Arpajon 91297 France Laboratoire Matière en Conditions Extrêmes Paris-Saclay University CEA Bruyères-le-Châtel 91190 France Department of Atmospheric and Oceanic Sciences University of California Los Angeles California 90095 USA

Electromagnetic ion cyclotron waves are expected to pitch-angle scatter and cause atmospheric precipitation of relativistic (>1 MeV) electrons under typical conditions in Earth’s radiation belts. However, it has been a long-standing mystery how relativistic electrons in the hundreds of keV range (but <1 MeV), which are not resonant with these waves, precipitate simultaneously with those >1 MeV. We demonstrate that, when the wave packets are short, nonresonant interactions enable such scattering of hundred-keV electrons by introducing a spread in wave number space. We generalize the quasilinear diffusion model to include nonresonant effects. The resultant model exhibits an exponential decay of the scattering rates extending below the minimum resonant energy depending on the shortness of the wave packets. This generalized model naturally explains observed nonresonant electron precipitation in the hundreds of keV concurrent with >1 MeV precipitation.

关键词： Space & astrophysical plasma Space science Space weather Earth's magnetosphere Magnetized plasma Perturbative methods Satellite data analysis test-particle methods

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Fractional Transport in Strongly Turbulent Plasmas

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Physical Review Letters 2017年第4期119卷 045101-045101页

作者： Heinz Isliker Loukas Vlahos Dana Constantinescu Department of Applied Mathematics University of Craiova RO-1100 Craiova Romania

We analyze statistically the energization of particles in a large scale environment of strong turbulence that is fragmented into a large number of distributed current filaments. The turbulent environment is generated through strongly perturbed, 3D, resistive magnetohydrodynamics simulations, and it emerges naturally from the nonlinear evolution, without a specific reconnection geometry being set up. Based on test-particle simulations, we estimate the transport coefficients in energy space for use in the classical Fokker-Planck (FP) equation, and we show that the latter fails to reproduce the simulation results. The reason is that transport in energy space is highly anomalous (strange), the particles perform Levy flights, and the energy distributions show extended power-law tails. Newly then, we motivate the use and derive the specific form of a fractional transport equation (FTE), we determine its parameters and the order of the fractional derivatives from the simulation data, and we show that the FTE is able to reproduce the high energy part of the simulation data very well. The procedure for determining the FTE parameters also makes clear that it is the analysis of the simulation data that allows us to make the decision whether a classical FP equation or a FTE is appropriate.

关键词： Nonlinear phenomena in plasmas particle acceleration in plasmas Plasma turbulence Solar corona Fokker–Planck equation Stochastic analysis test-particle methods

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Absorption and Transport Effects Induced in Plasmas by the Interaction of Electrons with Laser Speckles

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Physical Review Letters 2022年第21期129卷 215001-215001页

作者： M. Sherlock P. Michel Lawrence Livermore National Laboratory California 94551 United States

We show that the ponderomotive force associated with laser speckles can scatter electrons in a laser-produced plasma in a manner similar to Coulomb scattering. Analytic expressions for the effective collision rates are given. The electron-speckle collisions become important at high laser intensity or during filamentation, affecting both long- and short-pulse laser intensity regimes. As an example, we find that the effective collision rate in the laser-overlap region of hohlraums on the National Ignition Facility is expected to exceed the Coulomb collision rate by 1 order of magnitude, leading to a fundamental change to the electron transport properties. At the high intensities characteristic of short-pulse laser-plasma interactions (I≳1017 W cm−2), the scattering is strong enough to cause the direct absorption of laser energy, generating hot electrons with energy scaling as E≈1.44(I/1018 W cm−2)1/2 MeV, close to experimentally observed results.

关键词： High intensity laser-plasma interactions High-energy-density plasmas Laser-plasma interactions Plasma transport Inertially confined plasmas First-principles calculations in plasma physics Fokker-Planck & Vlasov model test-particle methods

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Thresholdless stochastic particle heating by a single wave

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Physical Review E 2023年第6期107卷 065201-065201页

作者： F. Sattin D. F. Escande Consorzio RFX (CNR ENEA INFN Università di Padova Acciaierie Venete SpA) Corso Stati Uniti 4 35127 Padova Italy Aix-Marseille Université CNRS PIIM UMR 7345 Marseille France

Stochastic heating is a well-known mechanism through which magnetized particles may be energized by low-frequency electromagnetic waves. In its simplest version, under spatially homogeneous conditions, it is known to be operative only above a threshold in the normalized wave amplitude, which may be a demanding requisite in actual scenarios, severely restricting its range of applicability. In this paper we show, by numerical simulations supported by inspection of the particle Hamiltonian, that allowing for even a very weak spatial inhomogeneity completely removes the threshold, trading the requirement upon the wave amplitude with a requisite upon the duration of the interaction between the wave and particle. The thresholdless chaotic mechanism considered here is likely to be applicable to other inhomogeneous systems.

关键词： Laboratory studies of space & astrophysical plasmas particle acceleration in plasmas Plasma waves Space & astrophysical plasma Space science Wave-wave, wave-particle interactions Magnetized plasma Phase space dynamics test-particle methods

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Marginally stable circular orbits in stationary axisymmetric spacetimes

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Physical Review D 2016年第2期94卷 024015-024015页

作者： Shabnam Beheshti Edgar Gasperín School of Mathematical Sciences Queen Mary University of London Mile End Road London E1 4NS United Kingdom

We derive necessary and sufficient conditions for the existence of marginally stable circular orbits (MSCOs) of test particles in a stationary axisymmetric (SAS) spacetime which possesses a reflection symmetry with respect to the equatorial plane; photon orbits and marginally bound orbits (MBOs) are also addressed. Energy and angular momentum are shown to decouple from metric quantities, rendering a purely geometric characterization of circular orbits for this general class of metrics. The subsequent system is analyzed using resultants, providing an algorithmic approach for finding MSCO conditions. MSCOs, photon orbits and MBOs are explicitly calculated for concrete examples of physical interest.

关键词： Astrophysical studies of gravity Classical black holes General relativity equations & solutions Accretion disk & black-hole plasma test-particle methods

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Simulating fusion reactions from Coulomb explosions within a transport approach

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Physical Review C 2022年第3期106卷 034604-034604页

作者： Zhe Zhu Jun Xu Guo-Qiang Zhang Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China University of Chinese Academy of Sciences Beijing 100049 China Shanghai Advanced Research Institute Chinese Academy of Sciences Shanghai 201210 China

We have studied nuclear fusion reactions from the Coulomb explosion of deuterium clusters induced by high-intensity laser beams within a transport approach. By incorporating the D+D →n+He3 channel, where D denotes deuterons, H2, as inelastic collisions based on the stochastic method, we have calibrated the neutron yield from the simulation in a box system with that from the reaction rate equation. After justifying the Coulomb explosion of a single cluster by comparing results with available theoretical limits, we then investigated the dynamics from Coulomb explosions of systems with different cluster numbers and different deuteron numbers in clusters. We find that the kinetic energy spectrum of deuterons at the final stage is different from that when neutrons are abundantly produced, corresponding to significantly different reaction rates. We also extrapolate the neutron yield result from small systems to large systems based on an intuitive parameterized form and compare with the available experimental result. The present framework can be extended by incorporating more channels, and useful for further studies of nuclear fusion reactions in plasma systems at higher energies reached in more recent experiments.

关键词： Nuclear fusion Plasma transport test-particle methods

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Accretion of a Vlasov gas onto a black hole from a sphere of finite radius and the role of angular momentum

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Physical Review D 2021年第8期104卷 083001-083001页

作者： Aldo Gamboa Carlos Gabarrete Paola Domínguez-Fernández Darío Núñez Olivier Sarbach Instituto de Ciencias Nucleares Universidad Nacional Autónoma de México Circuito Exterior C.U. A.P. 70-543 México D.F. 04510 México Instituto de Física y Matemáticas Universidad Michoacana de San Nicolás de Hidalgo Edificio C-3 Ciudad Universitaria 58040 Morelia Michoacán México Department of Physics School of Natural Sciences Ulsan National Institute of Science and Technology Ulsan 44919 Republic of Korea

The accretion of a spherically symmetric, collisionless kinetic gas cloud onto a Schwarzschild black hole is analyzed. Whereas previous studies have treated this problem by specifying boundary conditions at infinity, here the properties of the gas are given at a sphere of finite radius. The corresponding steady-state solutions are computed using four different models with an increasing level of sophistication, starting with the purely radial infall of Newtonian particles and culminating with a fully general relativistic calculation in which individual particles have angular momentum. The resulting mass accretion rates are analyzed and compared with previous models, including the standard Bondi model for a hydrodynamic flow. We apply our models to the supermassive black holes Sgr A* and M87*, and we discuss how their low luminosity could be partially explained by a kinetic description involving angular momentum. Furthermore, we get results consistent with previous model-dependent bounds for the accretion rate imposed by rotation measures of the polarized light coming from Sgr A* and with estimations of the accretion rate of M87* from the Event Horizon Telescope collaboration. Our methods and results could serve as a first approximation for more realistic black hole accretion models in various astrophysical scenarios in which the accreted material is expected to be nearly collisionless.

关键词： General relativity formalism Gravitation Relativistic kinetic theory Accretion disk & black-hole plasma Astronomical black holes Classical black holes Relativistic plasmas Fokker-Planck & Vlasov model Phase space dynamics test-particle methods

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Finite-length effects on cylindrical Langmuir probes

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Physical Review Research 2020年第2期2卷 023016-023016页

作者： Sigvald Marholm Richard Marchand Department of Physics University of Oslo P.O. Box 1048 Blindern N-0316 Oslo Norway Department of Physics University of Alberta Edmonton AB Canada T6G 2E1

Kinetic simulations are used to compute current characteristics of finite-length cylindrical probes, with particular attention to end effects. Currents collected per unit lengths, as a function of distance to the ends, are calculated and fitted to empirical analytic functions. These fits, in turn, can be interpolated and used to predict probe characteristics; that is, collected current as a function of applied voltage, for a broad range of physical parameters of relevance to laboratory and space plasma.

关键词： Laboratory studies of space & astrophysical plasmas Space & astrophysical plasma Space science Earth's ionosphere Electric & magnetic plasma measurements particle plasma measurements particle-in-cell methods Scaling methods test-particle methods

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Dissipative hydrodynamics of relativistic shock waves in a quark gluon plasma: Comparing and benchmarking alternate numerical methods

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Physical Review C 2020年第6期101卷 064904-064904页

作者： A. Gabbana S. Plumari G. Galesi V. Greco D. Simeoni S. Succi R. Tripiccione Università di Ferrara and INFN-Ferrara I-44122 Ferrara Italy Bergische Universität Wuppertal D-42119 Wuppertal Germany Department of Physics and Astronomy University of Catania 1-95125 Catania Italy Laboratori Nazionali del Sud INFN-LNS I-95123 Catania Italy University of Cyprus CY-1678 Nicosia Cyprus Center for Life Nano Science @ La Sapienza Italian Institute of Technology Viale Regina Elena 295 I-00161 Roma Italy Istituto Applicazioni del Calcolo National Research Council of Italy Via dei Taurini 19 I-00185 Roma Italy

This paper presents numerical cross comparisons and benchmark results for two different kinetic numerical methods, capable of describing relativistic dissipative fluid dynamics in a wide range of kinematic regimes, typical of relevant physics applications, such as transport phenomena in quark-gluon plasmas. We refer to relativistic lattice Boltzmann versus Monte Carlo test-particle methods. Lacking any realistic option for accurate validation vis-á-vis experimental data, we check the consistency of our results against established simulation packages available in the literature. We successfully compare the results of the two aforementioned numerical approaches for momentum integrated quantities like the hydrostatic and dynamical pressure profiles, the collective flow, and the heat flux. These results corroborate the confidence of the robustness and correctness of these computational methods and on the accurate calibration of their numerical parameters with respect to the physical transport coefficients. Our numerical results are made available as Supplemental Material, with the aim of establishing a reference benchmark for other numerical approaches.

关键词： Quark-gluon plasma Relativistic heavy-ion collisions Shock waves Lattice-Boltzmann methods Relativistic hydrodynamics test-particle methods

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