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Flexural Models for Vacuum-Packed particles as a Variable-Stiffness Mechanism in Smart Structures

Physical Review Applied 2022年第4期17卷 044018-044018页

作者： J. David Brigido Steve G. Burrow Benjamin K.S. Woods Piotr Bartkowski Robert Zalewski University of Bristol Queen’s Building—University Walk Bristol BS8 1TR United Kingdom Warsaw University of Technology Narbutta 84 Warsaw 02-524 Poland

Vacuum-packed particle (VPP) systems have been recently used in the development of smart structures due to their ability to actively change material stiffness through the mechanism of granular jamming. By altering the strength of the vacuum pressure applied to the particles, the material can be proportionally and reversibly transitioned from a liquidlike low-stiffness state to a stiff state. The ability to control material stiffness in this way opens up different possibilities for the design of morphing and smart structures by allowing them to soften during deformation to reduce actuation energy requirements and to then stiffen once the desired shape has been achieved to provide a zero-energy holding mechanism. The following research describes two useful models that predict the mechanical response of VPP beams under flexural loading. Firstly, four-point bending tests with digital image correlation strain mapping are performed in order to measure the axial and transverse strains in a bending beam made from vacuum-packed particles. The test results show a nonlinear mechanical response, including a change in beam thickness with deformation, that motivated an analytical model of the structure incorporating a nonlinear material stress model based on the Mohr-Coulomb failure envelope. In addition, finite-element simulations are implemented using a Johnson-Cook model extension to predict the response under loading of three-dimensional beam elements at different vacuum pressure levels. Lastly, the models are compared to the experimental results, indicating good agreement. Both methods are shown to be useful for predicting the variation of stiffness of vacuum-packed particle beams.

关键词： Bending Granular packing Mechanical deformation Plasticity Granular materials Smart materials Bend & torsion tests test-particle methods

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Kinetic analysis of the plasma sheath around an electron-emitting object with elliptic cross section

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Physical Review E 2021年第5期104卷 055204-055204页

作者： Luca Chiabó Sadaf Shahsavani Gonzalo Sánchez-Arriaga Bioengineering and Aerospace Engineering Department Universidad Carlos III de Madrid Leganés Madrid 28911 Spain

The structure of the sheath and the current exchange of two-dimensional electron-emitting objects with elliptic cross section immersed at rest in Maxwellian plasmas are investigated with an energy-conserving stationary Vlasov-Poisson solver free of statistical noise. The parameter domains for current collection within the orbital-motion-limited (OML) regime and current emission in space-charge-limited (SCL) conditions were studied by varying the characteristic dimension of the ellipse, its eccentricity, and the emission level. The analysis reveals the correlations between the onset of the non-OML and SCL regimes and the local curvature of the ellipse. As compared to nonemitting ellipses, electron emission broadens the parameter domain for OML current collection for ions and reduces considerably the current drop for non-OML conditions. Under identical plasma environments, elliptic bodies are more prone to operate under non-OML and SCL conditions than cylinders. Their emitted current in SCL conditions can be computed accurately from well-known results for cylinders if appropriate dimensionless variables and an equivalent radius are used. The role of the eccentricity, which acts as an integrability-breaking parameter, on the filamentation of the distribution function of the attracted species is studied.

关键词： Dusty or complex plasma Plasma sheaths & surfaces Phase space dynamics Plasma kinetic theory test-particle methods

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Transition to superdiffusive transport in turbulent plasmas

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Physical Review E 2024年第2期110卷 025204-025204页

作者： Matteo Stanzani Filippo Arlotti Guido Ciraolo Xavier Garbet Cristel Chandre CEA <a href="https://***/03hffat62">IRFM</a> F-13108 Saint-Paul-Lez-Durance France and <a href="https://***/01111rn36">University of Bologna</a> DIN 40136 Bologna Italy. CEA <a href="https://***/03hffat62">IRFM</a> F-13108 Saint-Paul-Lez-Durance France. CNRS <a href="https://***/035xkbk20">Aix Marseille Univ</a> <a href="https://***/042h2y225">I2M</a> 13009 Marseille France.

We investigate the motion of charged particles in a turbulent electrostatic potential using guiding-center theory. By increasing the Larmor radius, the dynamics exhibit close-to-ballistic transport properties. The transition from diffusive to ballistic transport is analyzed using nonlinear dynamics. It is found that twistless invariant tori in the guiding-center dynamics are responsible for this transition, drastically affecting transport properties of charged particles.

关键词： Chaos Nonlinear phenomena in plasmas Magnetically confined plasmas Phase space dynamics Phase space methods test-particle methods

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Analytical study of gyrophase, pitch angle, and normal speed of particles leaving an ideal magnetohydrodynamic discontinuity surface

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Physical Review E 2020年第2期102卷 023211-023211页

作者： William P. Wilkinson Division of Mathematical Sciences University of Brighton Lewes Road Brighton BN2 4GJ United Kingdom

particle populations that have velocity distributions with only a small spread of gyrophase angles are commonly observed in the vicinity of magnetohydrodynamic (MHD) discontinuity surfaces such as collisionless shocks. Previous theoretical particle trajectory studies have concentrated on ion behavior at an ideal planar Earth's bow shock and have either assumed that a gyrotropic incident initial velocity distribution is reflected at the surface or instead focused on unique fixed initial gyrophase and pitch angle values specified by the generation mechanism assumed for the particle. In this analytical study of trajectories of particles departing an ideal planar MHD surface we demonstrate that a particle's initial gyrophase and pitch angle determine completely whether it will escape the surface or return to it, regardless of its initial energy. We identify the region in initial gyrophase-pitch angle space which leads to trajectories that return to the surface of the discontinuity. The speed normal to the surface of a returning particle, which can affect its ability to traverse the discontinuity, is shown to increase or decrease compared to its initial value according only to the orientation of its guiding-center motion in the frame of reference in which the discontinuity is at rest and the incoming plasma flow is aligned with the constant magnetic field. The dependence of our results on the direction of the upstream magnetic field is illustrated. Our general analytical results are discussed in the context of observations at the Earth's bow shock.

关键词： Collisionless shock in plasma Shock waves & discontinuities in plasma Space & astrophysical plasma First-principles calculations in plasma physics test-particle methods

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Identification of Coupled Landau and Anomalous Resonances in Space Plasmas

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Physical Review Letters 2024年第3期133卷 035201-035201页

作者： Jing-Huan Li Xu-Zhi Zhou Zhi-Yang Liu Shan Wang Anton V. Artemyev Yoshiharu Omura Xiao-Jia Zhang Li Li Chao Yue Qiu-Gang Zong Craig Pollock Guan Le James L. Burch School of Earth and Space Sciences Institut de Recherche en Astrophysique et Planétologie CNES-CNRS Universite Toulouse III Paul Sabatier Toulouse 31028 France Institute of Geophysics and Planetary Physics Research Institute for Sustainable Humanosphere Department of Physics State Key Laboratory of Lunar and Planetary Sciences Macau University of Science and Technology Macau 999078 China Denali Scientific Fairbanks Alaska 99709 USA NASA San Antonio Texas 78238 USA

Wave-particle resonance, a ubiquitous process in the plasma universe, occurs when resonant particles observe a constant wave phase to enable sustained energy transfer. Here, we present spacecraft observations of simultaneous Landau and anomalous resonances between oblique whistler waves and the same group of protons, which are evidenced, respectively, by phase-space rings in parallel-velocity spectra and phase-bunched distributions in gyrophase spectra. Our results indicate the coupling between Landau and anomalous resonances via the overlapping of the resonance islands.

关键词： Space & astrophysical plasma Space science Wave-wave, wave-particle interactions Whistler plasma waves Interplanetary magnetic field Magnetized plasma Solar wind Electric & magnetic plasma measurements particle plasma measurements Satellite data analysis test-particle methods

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Relativistic slingshot: A source for single circularly polarized attosecond x-ray pulses

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Physical Review E 2020年第6期102卷 061201(R)-061201(R)页

作者： Jingwei Wang Sergei V. Bulanov Min Chen Bifeng Lei Yuxue Zhang Rishat Zagidullin Veronika Zorina Wei Yu Yuxin Leng Ruxin Li Matt Zepf Sergey G. Rykovanov State Key Laboratory of High Field Laser Physics CAS Center for Excellence in Ultra-intense Laser Science Shanghai Institute of Optics and Fine Mechanics (SIOM) Chinese Academy of Sciences (CAS) Shanghai 201800 China Collaborative Innovation Center of IFSA Shanghai Jiao Tong University Shanghai 200240 China Institute of Physics ASCR v.v.i. (FZU) ELI-Beamlines Project 182 21 Prague Czech Republic Key Laboratory for Laser Plasmas (MoE) School of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China Helmholtz Institute Jena Fröbelstieg 3 07743 Jena Germany Faculty of Physics and Astronomy Friedrich-Schiller-Universität Jena 07743 Jena Germany Center for Computational and Data-Intensive Science and Engineering Skolkovo Institute of Science and Technology Moscow 121205 Russia

We propose a mechanism to generate a single intense circularly polarized attosecond x-ray pulse from the interaction of a circularly polarized relativistic few-cycle laser pulse with an ultrathin foil at normal incidence. Analytical modeling and particle-in-cell simulation demonstrate that a huge charge-separation field can be produced when all the electrons are displaced from the target by the incident laser, resulting in a high-quality relativistic electron mirror that propagates against the tail of the laser pulse. The latter is efficiently reflected as well as compressed into an attosecond pulse that is also circularly polarized.

关键词： High intensity laser-plasma interactions X-ray generation in plasmas Relativistic plasmas particle-in-cell methods test-particle methods

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Semiclassical description of electron dynamics in extended systems under intense laser fields

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Physical Review B 2021年第7期104卷 075157-075157页

作者： Mizuki Tani Tomohito Otobe Yasushi Shinohara Kenichi L. Ishikawa Department of Nuclear Engineering and Management Graduate School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Kansai Photon Science Institute National Institutes for Quantum and Radiological Science and Technology (QST) Kyoto 619-0215 Japan Photon Science Center Graduate School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Research Institute for Photon Science and Laser Technology The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-0033 Japan

We propose a semiclassical approach based on the Vlasov equation to describe the time-dependent electronic dynamics in a bulk simple metal under an ultrashort intense laser pulse. We include in the effective potential not only the ionic Coulomb potential and mean-field electronic Coulomb potential from the one-body electron distribution but also the exchange-correlation potential within the local-density approximation (LDA). The initial ground state is obtained by the Thomas-Fermi model. To numerically solve the Vlasov equation, we extend the pseudoparticle method, previously used for nuclei and atomic clusters, to solids, taking the periodic boundary condition into account. We apply the present implementation to a bulk aluminum (fcc) conventional unit cell irradiated with a short laser pulse. The optical conductivity, refractive index, extinction coefficient, and reflectivity as well as energy absorption calculated with the Vlasov-LDA method are in excellent agreement with the results by the time-dependent density-functional theory and experimental references.

关键词： Laser-plasma interactions Plasma production & heating by laser beams, laser-foil, laser-cluster Elemental metals First-principles calculations in plasma physics Laser ablation test-particle methods Time-dependent DFT

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particle transport at arbitrary timescales with Poisson-distributed collisions

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Physical Review E 2019年第5期100卷 052134-052134页

作者： M. Baquero-Ruiz F. Manke I. Furno A. Fasoli P. Ricci École Polytechnique Fédérale de Lausanne (EPFL) Swiss Plasma Center (SPC) CH-1015 Lausanne Switzerland

We develop a model to investigate the time evolution of the mean location and variance of a random walker subject to Poisson-distributed collisions at constant rate. The collisions are instantaneous velocity changes where a new value of velocity is generated from a model probability function. The walker is persistent, which means that it moves at constant velocity between collisions. We study three different cases of velocity transition functions and compute the transport properties from the evolution of the variance. We observe that transport can change character over time and that early times show features that, in general, depend on the initial conditions of the walker.

关键词： Diffusion Plasma transport Random walks Transport phenomena Brownian dynamics Stochastic analysis Stochastic analysis methods Stochastic processes & statistics test-particle methods

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Interaction of Ultraintense Radially-Polarized Laser Pulses with Plasma Mirrors

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Physical Review X 2020年第4期10卷 041064-041064页

作者： N. Zaïm D. Guénot L. Chopineau A. Denoeud O. Lundh H. Vincenti F. Quéré J. Faure LOA CNRS École Polytechnique ENSTA Paris Institut Polytechnique de Paris 181 Chemin de la Hunière et des Joncherettes 91120 Palaiseau France Department of Physics Lund University SE-22100 Lund Sweden Lasers Interactions and Dynamics Laboratory (LIDyL) Commissariat à l’Énergie Atomique Université Paris-Saclay DSM/IRAMIS CEN Saclay 91191 Gif sur Yvette France

We present experimental results of vacuum laser acceleration (VLA) of electrons using radially polarized laser pulses interacting with a plasma mirror. Tightly focused, radially polarized laser pulses have been proposed for electron acceleration because of their strong longitudinal electric field, making them ideal for VLA. However, experimental results have been limited until now because injecting electrons into the laser field has remained a considerable challenge. Here, we demonstrate experimentally that using a plasma mirror as an injector solves this problem and permits us to inject electrons at the ideal phase of the laser, resulting in the acceleration of electrons along the laser propagation direction while reducing the electron beam divergence compared to the linear polarization case. We obtain electron bunches with few-MeV energies and a 200-pC charge, thus demonstrating, for the first time, electron acceleration to relativistic energies using a radially polarized laser. High-harmonic generation from the plasma surface is also measured, and it provides additional insight into the injection of electrons into the laser field upon its reflection on the plasma mirror. Detailed comparisons between experimental results and full 3D simulations unravel the complex physics of electron injection and acceleration in this new regime: We find that electrons are injected into the radially polarized pulse in the form of two spatially separated bunches emitted from the p-polarized regions of the focus. Finally, we leverage on the insight brought by this study to propose and validate a more optimal experimental configuration that can lead to extremely peaked electron angular distributions and higher energy beams.

关键词： High intensity laser-plasma interactions Laser-plasma interactions Laser driven electron acceleration Plasma acceleration & new acceleration techniques particle-in-cell methods test-particle methods

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Simulating pitch angle scattering using an explicitly solvable energy-conserving algorithm

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Physical Review E 2020年第3期102卷 033302-033302页

作者： Xin Zhang Yichen Fu Hong Qin Princeton Plasma Physics Laboratory and Department of Astrophysical Sciences Princeton University Princeton NJ 08540 USA

particle distribution functions evolving under the Lorentz operator can be simulated with the Langevin equation for pitch-angle scattering. This approach is frequently used in particle-based Monte-Carlo simulations of plasma collisions, among others. However, most numerical treatments do not guarantee energy conservation, which may lead to unphysical artifacts such as numerical heating and spectra distortions. We present a structure-preserving numerical algorithm for the Langevin equation for pitch-angle scattering. Similar to the well-known Boris algorithm, the proposed numerical scheme takes advantage of the structure-preserving properties of the Cayley transform when calculating the velocity-space rotations. The resulting algorithm is explicitly solvable, while preserving the norm of velocities down to machine precision. We demonstrate that the method has the same order of numerical convergence as the traditional stochastic Euler-Maruyama method. The numerical scheme is benchmarked by simulating the pitch-angle scattering of a particle beam and comparing with the analytical solution. Benchmark results show excellent agreement with theoretical predictions, showcasing the remarkable long-time accuracy of the proposed algorithm.

关键词： Plasma transport Plasma-particle interactions Brownian dynamics Fokker–Planck equation Langevin equation Monte Carlo methods Stochastic differential equations test-particle methods

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