Zeitschriftenartikel: „PIC numerical simulations“

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Liu, Jian, Zhi Yu und Hong Qin. „A Nonlinear PIC Algorithm for High Frequency Waves in Magnetized Plasmas Based on Gyrocenter Gauge Kinetic Theory“. Communications in Computational Physics 15, Nr. 4 (April 2014): 1167–83. http://dx.doi.org/10.4208/cicp.150313.051213s.

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AbstractNumerical methods based on gyrocenter gauge kinetic theory are suitable for first principle simulations of high frequency waves in magnetized plasmas. The δf gyrocenter gauge PIC simulation for linear rf wave has been previously realized. In this paper we further develop a full-f nonlinear PIC algorithm appropriate for the nonlinear physics of high frequency waves in magnetized plasmas. Numerical cases of linear rf waves are calculated as a benchmark for the nonlinear GyroGauge code, meanwhile nonlinear rf-wave phenomena are studied. The technique and advantage of the reduction of the numerical noise in this full-f gyrocenter gauge PIC algorithm are also discussed.

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Bacchini, Fabio. „RelSIM: A Relativistic Semi-implicit Method for Particle-in-cell Simulations“. Astrophysical Journal Supplement Series 268, Nr. 2 (01.10.2023): 60. http://dx.doi.org/10.3847/1538-4365/acefba.

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Abstract We present a novel Relativistic Semi-Implicit Method (RelSIM) for particle-in-cell (PIC) simulations of astrophysical plasmas, implemented in a code framework ready for production runs. While explicit PIC methods have gained widespread recognition in the astrophysical community as a reliable tool to simulate plasma phenomena, implicit methods have been seldom explored. This is partly due to the lack of a reliable relativistic implicit PIC formulation that is applicable to state-of-the-art simulations. We propose the RelSIM to fill this gap: our new method is relatively simple, being free of nonlinear iterations and only requiring a global linear solve of the field equations. With a set of one- and two-dimensional tests, we demonstrate that the RelSIM produces more accurate results with much smaller numerical errors in the total energy than standard explicit PIC, in particular when characteristic plasma scales (skin depth and plasma frequency) are heavily underresolved on the numerical grid. By construction, the RelSIM also performs much better than the relativistic implicit-moment method, originally proposed for semi-implicit PIC simulations in the relativistic regime. Our results are promising to conduct large-scale (in terms of duration and domain size) PIC simulations of astrophysical plasmas, potentially reaching physical regimes inaccessible by standard explicit PIC codes.

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Konior, Wojciech. „Particle-In-Cell Electrostatic Numerical Algorithm“. Transactions on Aerospace Research 2017, Nr. 3 (01.09.2017): 24–45. http://dx.doi.org/10.2478/tar-2017-0020.

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Abstract Existing global models of interaction between the solar wind (SW) and the local interstellar medium (LISM) describe the heliosphere that arises as a result of this interaction. There is a strong motivation to develop a kinetic model using the Particle-in-Cell (PIC) method to describe phenomena which appear in the heliosphere. This is however a long term scientific goal. This paper describes an electrostatic Particle-in-Cell numerical model developed in the Institute of Aviation in Warsaw, which includes mechanical and charge exchange collisions between particles in the probabilistic manner using Direct Simulation Monte Carlo method. This is the first step into developing simulations of the heliosphere incorporating kinetic effects in collisionless plasmas. In this paper we focus only on presenting the work, which have been done on the numerical PIC algorithm.

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Sary, G., und L. Gremillet. „Hybrid Zakharov-kinetic simulation of nonlinear stimulated Raman scattering“. Physics of Plasmas 29, Nr. 7 (Juli 2022): 072103. http://dx.doi.org/10.1063/5.0090211.

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We present a novel 2D reduced numerical model for stimulated Raman scattering (SRS) in laser fusion plasmas in which envelope equations for the electromagnetic fields are coupled to a hybrid description of the electron species. Specifically, the electron distribution is split between a bulk part described by a Zakharov-like linear model and a kinetic tail discretized using a particle-in-cell-like (PIC) scheme. By avoiding to sample the bulk-electron distribution, this approach greatly reduces the numerical cost of SRS simulations compared with PIC codes, while still being able to describe the nonlinear evolution of the electron tail and trapping-related kinetic phenomena. First, our model is shown to reproduce accurately the linear Landau damping of an infinitesimal electron plasma wave (EPW) whose phase velocity falls into the tail of the electron distribution. Then, applying it to the simulation of the trapped-particle modulational instability of a large-amplitude EPW, results comparable to those of previously published 2D Vlasov simulations are obtained. Finally, we simulate the excitation of kinetic backward SRS from a single strong laser speckle ([Formula: see text]) in an underdense ([Formula: see text]) plasma, which drives an EPW with wavenumber [Formula: see text]. The model predictions fairly agree with the results of a PIC simulation regarding the kinetic saturation mechanisms (i.e., trapped-particle instabilities), and with experimental data and Vlasov simulations related to the frequency shift of nonlinear EPWs. For this SRS simulation, we estimate that our hybrid model is over an order of magnitude less costly than an equivalent PIC simulation due to the lower particle count.

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Pinto, Martin Campos, Mathieu Lutz und Marie Mounier. „Electromagnetic PIC simulations with smooth particles: a numerical study“. ESAIM: Proceedings and Surveys 53 (März 2016): 133–48. http://dx.doi.org/10.1051/proc/201653009.

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Greenwood, Andrew D., Keith L. Cartwright, John W. Luginsland und Ernest A. Baca. „On the elimination of numerical Cerenkov radiation in PIC simulations“. Journal of Computational Physics 201, Nr. 2 (Dezember 2004): 665–84. http://dx.doi.org/10.1016/j.jcp.2004.06.021.

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Genco, Filippo, und Ahmed Hassanein. „Numerical simulations of laser ablated plumes using Particle-in-Cell (PIC) methods“. Laser and Particle Beams 32, Nr. 2 (28.03.2014): 305–10. http://dx.doi.org/10.1017/s0263034614000196.

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AbstractLaser ablation of graphite materials in the presence of an external magnetic field is studied with the use of the newly developed HEIGHTS-PIC particle-in-cell code and compared with both theoretical and experimental results. Carbon plumes behavior controlled by a strong magnetic field is of interest to evaluate the plume shielding effects to protect the original exposed target from further damage and erosion. Since intense power deposition on plasma facing components is expected during Tokamaks loss of plasma confinement events such as disruptions, vertical displacements event, runaway electrons, or during normal operating conditions such as edge-localized modes, it is critical to better understand the evolving target plasma behavior for more accurate prediction of the potential damage created by these high-energetic dumps which may not be easily mitigated without loss of structural and functional performance of the plasma facing components. Numerical experiments have been performed to provide benchmarking conditions for the HEIGHTS-PIC simulation package originally designed to evaluate the erosion of the Tokamak surfaces, splashing of the melted/ablated-vaporized material, and transport into the bulk plasma with consequent plasma contamination. Evolving target plasma temperature and density are calculated and compared with measured reported values available into literature for similar conditions and show good agreement with the HEIGHTS-PIC package predictions.

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Miloch, W. J. „Numerical simulations of dust charging and wakefield effects“. Journal of Plasma Physics 80, Nr. 6 (25.06.2014): 795–801. http://dx.doi.org/10.1017/s0022377814000300.

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Charging of dust grains and related phenomena are fundamental problems in the physics of complex plasmas. The relative motion of grains and plasma breaks the symmetry in dust charging and gives rise to the wake in plasma density and potential, which can significantly influence the dynamics of other grains. This paper gives an overview of dust charging in two- and multi-component plasma flows and related wake effects, and presents recent results from self-consistent particle-in-cell (PIC) simulations. The role of wakefields is considered in the context of charging of downstream grains.

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COULAUD, O., E. SONNENDRÜCKER, E. DILLON, P. BERTRAND und A. GHIZZO. „Parallelization of semi-Lagrangian Vlasov codes“. Journal of Plasma Physics 61, Nr. 3 (April 1999): 435–48. http://dx.doi.org/10.1017/s0022377899007527.

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We describe the parallel implementation of semi-Lagrangian Vlasov solvers, which are an alternative to particle-in-cell (PIC) simulations for the numerical investigation of the behaviour of charged particles in their self-consistent electromagnetic fields. The semi-Lagrangian method, which couples the Lagrangian and Eulerian points of view, is particularly interesting on parallel computers, since the solution is computed on grid points, the number of which remains constant in time on each processor, unlike the number of particles in PIC simulations, and thus greatly simplifies the parallelization process.

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Xu, Xinlu, Peicheng Yu, Samual F. Martins, Frank S. Tsung, Viktor K. Decyk, Jorge Vieira, Ricardo A. Fonseca, Wei Lu, Luis O. Silva und Warren B. Mori. „Numerical instability due to relativistic plasma drift in EM-PIC simulations“. Computer Physics Communications 184, Nr. 11 (November 2013): 2503–14. http://dx.doi.org/10.1016/j.cpc.2013.07.003.

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Lopez Ortega, Alejandro, und Ioannis G. Mikellides. „2D Fluid-PIC Simulations of Hall Thrusters with Self-Consistent Resolution of the Space-Charge Regions“. Plasma 6, Nr. 3 (11.09.2023): 550–62. http://dx.doi.org/10.3390/plasma6030038.

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Many hybrid simulations of Hall thrusters, where electrons and ions are solved using hydrodynamics and particle-in-cell methods, respectively, assume that the ionized gas is quasi-neutral everywhere in the computational domain and apply so-called thin-sheath approximations to account for space-charge effects near solid boundaries. These approximations do not hold along boundaries near the exit of the thruster or in the near plume regions, where the plasma conditions can lead to Debye lengths on the order of or higher than the local grid resolution. We present a numerical scheme that fully resolves the conditions of the ionized gas in space-charge regions of any thickness and that is coupled consistently to a global hybrid simulation of Hall thrusters. We verify the numerical results with the closed-form solution for a Langmuir sheath in a simplified one-dimensional example, and then again in simulations where the model is integrated in a 2D multifluid/PIC axial–radial code called Hall2De. The new capability to resolve numerically large sheaths around solid boundaries in Hall thrusters allows for significantly more accurate assessments of ion sputtering, thus improving thruster lifetime predictions.

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Domguia, Ulrich Simo, und Raoul Thepi Siewe. „Controlling Pulse-Like Self-Sustained Oscillators Using Analog Circuits and Microcontrollers“. International Journal of Robotics and Control Systems 2, Nr. 4 (12.02.2023): 107–19. http://dx.doi.org/10.31763/ijrcs.v3i1.802.

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Using simulation from analog electronic circuits and from a microcontroller, this paper considers the control or synchronization of pulse-like self-sustained oscillators described by the equations derived from the chemical system known as Brusselator. The attention is focused on the effect of proportional control when the Brusselator is subjected to disturbances such as pulse-like oscillations and square signals. The analog electronic circuits simulation is based on Multisim, while the microcontroller simulation uses mikroC software and PIC 18F4550. In order to determine the intervals for which the synchronization is effective, the equations of the Brusselator are solved numerically using the fourth-order Runge-Kutta method. As software used for conducting numerical simulations, FORTRAN 95 version PLATO is used for numerical simulation and MATLAB for plotting curves using the data generated from FORTRAN simulations. It has been shown that the control is effective for some values of the proportional control parameter. A good qualitative and quantitative agreement is found from the results of the numerical simulation and those obtained from the analog electronic circuits as well as those delivered by the microcontroller. Since the oscillations delivered by the heart are pulsed oscillations, this study gives an idea of how to control the heart frequency of an individual whose heart is subject to certain disturbances related to stress or illness, to name just a few examples.

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Yang, Fuxiang, Jie Li, Chuanfu Xu, Dali Li, Haozhong Qiu und Ao Xu. „MPI Parallelization of Numerical Simulations for Pulsed Vacuum Arc Plasma Plumes Based on a Hybrid DSMC/PIC Algorithm“. Aerospace 9, Nr. 10 (23.09.2022): 538. http://dx.doi.org/10.3390/aerospace9100538.

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The transport characteristics of the unsteady flow field in rarefied plasma plumes is crucial for a pulsed vacuum arc in which the particle distribution varies from 1016 to 1022 m−3. The direct simulation Monte Carlo (DSMC) method and particle-in-cell (PIC) method are generally combined to study this kind of flow field. The DSMC method simulates the motion of neutral particles, while the PIC method simulates the motion of charged ions. A hybrid DSMC/PIC algorithm is investigated here to determine the unsteady axisymmetric flow characteristics of vacuum arc plasma plume expansion. Numerical simulations are found to be consistent with the experiments performed in the plasma mass and energy analyzer (EQP). The electric field is solved by Poisson’s equation, which is usually computationally expensive. The compressed sparse row (CSR) format is used to store the huge diluted matrix and PETSc library to solve Poisson’s equation through parallel calculations. Double weight factors and two timesteps under two grid sets are investigated using the hybrid DSMC/PIC algorithm. The fine PIC grid is nested in the coarse DSMC grid. Therefore, METIS is used to divide the much smaller coarse DSMC grid when dynamic load imbalances arise. Two parameters are employed to evaluate and distribute the computational load of each process. Due to the self-adaption of the dynamic-load-balancing parameters, millions of grids and more than 150 million particles are employed to predict the transport characteristics of the rarefied plasma plume. Atomic Ti and Ti2+ are injected into the small cylinders. The comparative analysis shows that the diffusion rate of Ti2+ is faster than that of atomic Ti under the electric field, especially in the z-direction. The fully diffuse reflection wall model is adopted, showing that neutral particles accumulate on the wall, while charged ions do not—due to their self-consistent electric field. The maximum acceleration ratio is about 17.94.

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Godfrey, Brendan B., und Jean-Luc Vay. „Numerical stability of relativistic beam multidimensional PIC simulations employing the Esirkepov algorithm“. Journal of Computational Physics 248 (September 2013): 33–46. http://dx.doi.org/10.1016/j.jcp.2013.04.006.

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Wang, Yao-Ting, Jian Chen, He-Ping Li, Dong-Jun Jiang und Ming-Sheng Zhou. „Analysis and particle-in-cell simulation on the similarity relation during an ion extraction process“. Journal of Physics: Conference Series 2147, Nr. 1 (01.01.2022): 012013. http://dx.doi.org/10.1088/1742-6596/2147/1/012013.

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Abstract Ion extraction time is one of the key parameters for an ion extraction process. Particle-in-cell (PIC) simulation can provide a detailed description on the charged-particle behaviours during the ion extraction process in a decaying plasma. However, the PIC modelling is a very time-consuming task with very small space step (~ Debye length) and time step (~ inverse of plasma frequency), as well as a massive number of macro-particles, especially for the cases in multi-dimensions and large geometrical sizes. In this paper, based on the sheath expansion and ion-acoustic rarefaction wave propagation model, a similarity relation of ion extraction time with different geometrical sizes of the ion extraction regions is established. The theoretical analysis shows that, by changing the magnitude of the externally applied voltage to keep the ion extraction flux equal, the ion extraction time is proportional to the geometrical size ratio. Then, the PIC simulations on the ion extraction process are conducted, which show that there exists a good consistency with the theoretical analysis and previous experimental data. This research is helpful for promoting numerical simulations facing actual ion extraction processes with large geometrical sizes and provides theoretical guidance for improving the ion extraction efficiencies in applications.

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Gallo, Giuseppe, Adriano Isoldi, Dario Del Gatto, Raffaele Savino, Amedeo Capozzoli, Claudio Curcio und Angelo Liseno. „Numerical Aspects of Particle-in-Cell Simulations for Plasma-Motion Modeling of Electric Thrusters“. Aerospace 8, Nr. 5 (15.05.2021): 138. http://dx.doi.org/10.3390/aerospace8050138.

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The present work is focused on a detailed description of an in-house, particle-in-cell code developed by the authors, whose main aim is to perform highly accurate plasma simulations on an off-the-shelf computing platform in a relatively short computational time, despite the large number of macro-particles employed in the computation. A smart strategy to set up the code is proposed, and in particular, the parallel calculation in GPU is explored as a possible solution for the reduction in computing time. An application on a Hall-effect thruster is shown to validate the PIC numerical model and to highlight the strengths of introducing highly accurate schemes for the electric field interpolation and the macroparticle trajectory integration in the time. A further application on a helicon double-layer thruster is presented, in which the particle-in-cell (PIC) code is used as a fast tool to analyze the performance of these specific electric motors.

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Moskalev, Dmitrii, Andrei Kozlov, Uliana Salgaeva, Victor Krishtop und Anatolii Volyntsev. „Applicability of the Effective Index Method for the Simulation of X-Cut LiNbO3 Waveguides“. Applied Sciences 13, Nr. 11 (23.05.2023): 6374. http://dx.doi.org/10.3390/app13116374.

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Photonic integrated circuits (PIC) find applications in the fields of microwaves, telecoms and sensing. Generally, PICs are fabricated on a base of isotropic materials such as SOI, Si3N4, etc. However, for some applications, anisotropic substrates such as LiNbO3 are used. A thin film of LiNbO3 on an insulator (LNOI) is a promising material platform for complex high-speed PICs. The design and simulation of PICs on anisotropic materials should be performed using rigorous numerical methods based on Maxwell’s equations. These methods are characterized by long calculation times for one simulation iteration. Since a large number of simulation iterations are performed during the PIC design, simulation methods based on approximations should be used. The effective index method (EIM) is an approximation-based method and is widely applied for simulations of isotropic waveguides. In this study, the applicability of EIM for simulations of anisotropic waveguides is analyzed. The results obtained by EIM are compared with the calculation results of a rigorous finite-difference frequency-domain (FDFD) method for evaluation of the EIM’s applicability limits. In addition, radiation losses in waveguides with rough sidewalls are estimated using the Payne–Lacey model and EIM. The results demonstrate the applicability of EIM for the simulation of anisotropic LNOI-based waveguides with cross-section parameters specified in this paper.

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Bourgeois, Pierre-Louis, und Xavier Davoine. „New mitigation approach to numerical Cherenkov radiation in PIC simulations of wakefield accelerators“. Journal of Computational Physics 413 (Juli 2020): 109426. http://dx.doi.org/10.1016/j.jcp.2020.109426.

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Yuan, Tiannan, Junxue Ren, Jun Zhou, Zhe Zhang, Yibai Wang und Haibin Tang. „The effects of numerical acceleration techniques on PIC-MCC simulations of ion thrusters“. AIP Advances 10, Nr. 4 (01.04.2020): 045115. http://dx.doi.org/10.1063/1.5113561.

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Chen, Qiang. „Kinetic energy partitions in electron–ion PIC simulations of ABC fields“. Nukleonika 68, Nr. 1 (01.03.2023): 25–28. http://dx.doi.org/10.2478/nuka-2023-0004.

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Abstract We explore the kinetic energy partitions between electrons and ions in the 2-D magnetostatic equilibria called Arnold–Beltrami–Childress (ABC) fields, using particle-in-cell (PIC) numerical simulations. We cover a wider range of ion–electron temperature combinations and get different results compared to previous studies of the Harris-layer-type magnetic reconnection simulations. We find that the initial ion–electron enthalpy ratio is an important indicator. The particle species that dominates the total enthalpy will also dominate the kinetic energy gains and the momentum distribution peaks, but the other species have higher nonthermal energy fractions because both species show similar maximum energies.

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PUKHOV, A. „Three-dimensional electromagnetic relativistic particle-in-cell code VLPL (Virtual Laser Plasma Lab)“. Journal of Plasma Physics 61, Nr. 3 (April 1999): 425–33. http://dx.doi.org/10.1017/s0022377899007515.

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The three-dimensional particle-in-cell (PIC) code VLPL (Virtual Laser Plasma Lab) allows, for the first time, direct fully electromagnetic simulations of relativistic laser–plasma interactions. Physical results on relativistic self-focusing in under-dense plasma are presented. It is shown that background plasma electrons are accelerated to multi-MeV energies and 104 T magnetic fields are generated in the process of self-focusing at high laser intensities. This physics is crucial for the fast ignitor concept in inertial confinement fusion. Advances in the numerical PIC algorithm used in the code VLPL are reviewed here.

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Faraji, F., M. Reza und A. Knoll. „Enhancing one-dimensional particle-in-cell simulations to self-consistently resolve instability-induced electron transport in Hall thrusters“. Journal of Applied Physics 131, Nr. 19 (21.05.2022): 193302. http://dx.doi.org/10.1063/5.0090853.

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The advent of high-power Hall thrusters and the increasing interest toward their use as a primary propulsion system for various missions have given a new boost to the efforts aiming at self-consistent predictive modeling of this thruster technology. In this article, we present a novel approach, which allows enhancing the predictive capability of one-dimensional particle-in-cell (PIC) simulations to self-consistently capture the wave-induced electron transport due to the azimuthal instabilities in Hall thrusters. The so-called “pseudo-2D” PIC scheme resulting from this approach is extensively tested in several operating conditions. The results are compared against a well-established 2D3V axial–azimuthal reference case in terms of the axial profiles of the time-averaged plasma properties, the azimuthal electric field fluctuations and their dispersion features, and the contributions of the force terms in the electron azimuthal momentum equation to the cross-field mobility. We have demonstrated that the pseudo-2D PIC provides a prediction of the above aspects that compares very closely in almost all conditions with those from the full-2D simulation. In addition, the sensitivity of the pseudo-2D simulation results to the numerical parameters associated with our approach is assessed in detail. The outcomes of these analyses have casted light on the next steps to further improve the approach.

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Ghorbanalilu, Mohammad, und Elahe Abdollahazadeh. „Extension of temperature anisotropy Weibel instability to non-Maxwellian plasmas by 2D PIC simulation“. Laser and Particle Beams 36, Nr. 1 (29.12.2017): 1–7. http://dx.doi.org/10.1017/s0263034617000842.

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AbstractThe Weibel instability driven by temperature anisotropy is investigated in a two-dimensional (2D) particle-in-cell simulation in non-extensive statistics in the relativistic regime. In order to begin the simulation, we introduced a new 2D anisotropic distribution function in the context of non-extensive statistics. The heavy ions considered to be immobile and form the neutralizing background. The numerical results show that non-extensive parameterqplays an important role on the magnetic field saturation time, the time of reduction temperature anisotropy, evolution time to the quasi-stationary state, and the peak energy density of magnetic field. We observe that the instability saturation time increases by increasing the non-extensive parameterq. It is shown that structures with superthermal electrons (q< 1) could generate strong magnetic fields during plasma thermalization. The simulation results agree with the previous simulations for an anisotropic Maxwellian plasma (q= 1).

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PATIN, D., E. LEFEBVRE, A. BOURDIER und E. D'HUMIÈRES. „Stochastic heating in ultra high intensity laser-plasma interaction: Theory and PIC code simulations“. Laser and Particle Beams 24, Nr. 2 (Juni 2006): 223–30. http://dx.doi.org/10.1017/s0263034606060320.

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In the first part, the theoretical model of the stochastic heating effect is presented briefly. Then, a numerical resolution of the Hamilton equations highlights the threshold of the stochastic effect. Finally, Particle-In-Cell (PIC) code simulations results, for experimentally relevant parameters, are presented in order to confirm the acceleration mechanism predicted by the one-particle theoretical model. This paper gives the conditions on the different experimental parameters in order to have an optimization of the stochastic heating.

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Lehmann, Götz. „Efficient Semi-Lagrangian Vlasov-Maxwell Simulations of High Order Harmonic Generation from Relativistic Laser-Plasma Interactions“. Communications in Computational Physics 20, Nr. 3 (31.08.2016): 583–602. http://dx.doi.org/10.4208/cicp.oa-2015-0019.

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AbstractWe describe a relativistic semi-Lagrangian scheme for the numerical solution of the relativistic Vlasov-Maxwell system. The implementation strategy on a modern non-unified memory access (NUMA) architecture using the OpenMP framework is discussed. We demonstrated that close to perfect scaling can be obtained on modern many-core, multi-socket systems. Application of this code to the problem of relativistic generation of high-harmonic laser radiation is demonstrated. The results are compared to particle-in-cell (PIC) simulations, indicating in particular that for warm plasma the Vlasov simulation is superior. We discuss the impact of plasma temperature on the radiation spectrum and show that the efficiency of harmonic generation depends on the plasma temperature.

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Crouseilles, Nicolas, Guillaume Latu und Eric Sonnendrücker. „Hermite Spline Interpolation on Patches for Parallelly Solving the Vlasov-Poisson Equation“. International Journal of Applied Mathematics and Computer Science 17, Nr. 3 (01.10.2007): 335–49. http://dx.doi.org/10.2478/v10006-007-0028-x.

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Hermite Spline Interpolation on Patches for Parallelly Solving the Vlasov-Poisson EquationThis work is devoted to the numerical simulation of the Vlasov equation using a phase space grid. In contrast to Particle-In-Cell (PIC) methods, which are known to be noisy, we propose a semi-Lagrangian-type method to discretize the Vlasov equation in the two-dimensional phase space. As this kind of method requires a huge computational effort, one has to carry out the simulations on parallel machines. For this purpose, we present a method using patches decomposing the phase domain, each patch being devoted to a processor. Some Hermite boundary conditions allow for the reconstruction of a good approximation of the global solution. Several numerical results demonstrate the accuracy and the good scalability of the method with up to 64 processors. This work is a part of the CALVI project.

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Orozco, E. A., J. D. González, J. R. Beltrán und V. E. Vergara. „Simulation of bunched electron-beam acceleration by the cylindrical TE113 microwave field“. International Journal of Modern Physics A 34, Nr. 36 (30.12.2019): 1942030. http://dx.doi.org/10.1142/s0217751x19420302.

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We report a detailed simulation of a bunched electron-beam accelerated in a TE[Formula: see text] cylindrical cavity immersed in a static inhomogeneous magnetic field using a relativistic full electromagnetic particle-in-cell (PIC). This type of acceleration concept is known as Spatial AutoResonance Acceleration (SARA) in which the magnetic field profile is such that it keeps the electron-beam in the acceleration regime along their trajectories. In this work, the numerical experiments are carried out including a bunched electron-beam with the concentrations in the range [Formula: see text]–[Formula: see text][Formula: see text]cm[Formula: see text] in a TE[Formula: see text] cylindrical microwave field, at a frequency of 2.45 GHz and an amplitude of 15 kV/cm. The electron energy reaches values up to 250 keV without significant unfocusing effect that can be used as a basis to produce hard X-ray. Additionally, a comparison between the data obtained from the full electromagnetic PIC simulations and the results derived from the relativistic Newton–Lorentz equation in a single particle approximation is carried out.

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ARDA, İBRAHİM, und İSMAİL RAFATOV. „Development and benchmark of a 1d3v electrostatic PIC/MCC numerical code for gas discharge simulations“. Turkish Journal of Physics 47, Nr. 4 (25.08.2023): 198–213. http://dx.doi.org/10.55730/1300-0101.2746.

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LIMPOUCH, J., O. KLIMO, V. BÍNA und S. KAWATA. „Numerical studies on the ultrashort pulse K-α emission sources based on femtosecond laser–target interactions“. Laser and Particle Beams 22, Nr. 2 (Juni 2004): 147–56. http://dx.doi.org/10.1017/s0263034604222091.

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K-α emission is an intense short-pulse line source well suited for X-ray diagnostic techniques with subpicosecond and micrometer resolution. Numerical simulations are performed here in a search for laser–target interaction regimes where both high efficiency of laser energy transformation to X-ray emission and ultrashort X-ray pulses are achieved. We use the one-dimensional PIC code for the description of the laser interaction with the plasma layer at the target surface. Fast electron transport into the target is treated by our newly developed Monte Carlo code with temporal resolution that is described here in detail. Our simulations reveal extremely short ∼200 fs FWHM bright K-α X-ray pulses emitted from targets heated by 120-fs pulses of a table-top laser. Laser energy conversion efficiency to K-α line emission as high as 6 × 10−5 is noticed. Integration of the emitted energy over the focal spot is carried out to improve the simulation accord with published experimental data. Negligible impact of self-induced electric fields on K-α emission is found for conducting target materials at moderate laser intensities [lsim ]1017 W/cm2.

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Klion, Hannah, Revathi Jambunathan, Michael E. Rowan, Eloise Yang, Donald Willcox, Jean-Luc Vay, Remi Lehe, Andrew Myers, Axel Huebl und Weiqun Zhang. „Particle-in-cell Simulations of Relativistic Magnetic Reconnection with Advanced Maxwell Solver Algorithms“. Astrophysical Journal 952, Nr. 1 (01.07.2023): 8. http://dx.doi.org/10.3847/1538-4357/acd75b.

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Abstract Relativistic magnetic reconnection is a nonideal plasma process that is a source of nonthermal particle acceleration in many high-energy astrophysical systems. Particle-in-cell (PIC) methods are commonly used for simulating reconnection from first principles. While much progress has been made in understanding the physics of reconnection, especially in 2D, the adoption of advanced algorithms and numerical techniques for efficiently modeling such systems has been limited. With the GPU-accelerated PIC code WarpX, we explore the accuracy and potential performance benefits of two advanced Maxwell solver algorithms: a nonstandard finite-difference scheme (CKC) and an ultrahigh-order pseudo-spectral method (PSATD). We find that, for the relativistic reconnection problem, CKC and PSATD qualitatively and quantitatively match the standard Yee-grid finite-difference method. CKC and PSATD both admit a time step that is 40% longer than that of Yee, resulting in a ∼40% faster time to solution for CKC, but no performance benefit for PSATD when using a current deposition scheme that satisfies Gauss’s law. Relaxing this constraint maintains accuracy and yields a 30% speedup. Unlike Yee and CKC, PSATD is numerically stable at any time step, allowing for a larger time step than with the finite-difference methods. We found that increasing the time step 2.4–3 times over the standard Yee step still yields accurate results, but it only translates to modest performance improvements over CKC, due to the current deposition scheme used with PSATD. Further optimization of this scheme will likely improve the effective performance of PSATD.

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Korzhimanov, Artem V. „Model for Proton Acceleration in Strongly Self-Magnetized Sheath Produced by Ultra-High-Intensity Sub-Picosecond Laser Pulses“. Quantum Beam Science 9, Nr. 1 (20.01.2025): 4. https://doi.org/10.3390/qubs9010004.

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Recently, it has been experimentally shown that the sheath acceleration of protons from ultra-thin metal targets irradiated by sub-picosecond laser pulses of intensities above 1021 W/cm2 is suppressed compared to well-established models. This detrimental effect has been attributed to a self-generation of gigagauss-level quasi-static magnetic fields in expanded plasmas on the rear side of a target. Here we present a set of numerical simulations which support this statement. Based on 2D full-scale PIC simulations, it is shown that the scaling of a cutoff energy of the accelerated protons with intensity deviates from a well-established Mora model for laser pulses with a duration exceeding 500 fs. This deviation is showed to be connected to effective magnetization of the hottest electrons producing at the maximum of the laser pulse intensity. We propose a modification of the Mora model which incorporates the effect of the possible electron magnetization. Comparing it to the simulation results shows that by appropriately choosing a single fitting parameter, the model produces results that quantitatively coincide with simulations.

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Jipa, Florin, Laura Ionel und Marian Zamfirescu. „Advances in Design and Fabrication of Micro-Structured Solid Targets for High-Power Laser-Matter Interaction“. Photonics 11, Nr. 11 (25.10.2024): 1008. http://dx.doi.org/10.3390/photonics11111008.

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Accelerated particles have multiple applications in materials research, medicine, and the space industry. In contrast to classical particle accelerators, laser-driven acceleration at intensities greater than 1018 W/cm2, currently achieved at TW and PW laser facilities, allow for much larger electric field gradients at the laser focus point, several orders of magnitude higher than those found in conventional kilometer-sized accelerators. It has been demonstrated that target design becomes an important factor to consider in ultra-intense laser experiments. The energetic and spatial distribution of the accelerated particles strongly depends on the target configuration. Therefore, target engineering is one of the key approaches to optimizing energy transfer from the laser to the accelerated particles. This paper provides an overview of recent progress in 2D and 3D micro-structured solid targets, with an emphasis on fabrication procedures based on laser material processing. Recently, 3D laser lithography, which involves Two-Photon Absorption (TPA) effects in photopolymers, has been proposed as a technique for the high-resolution fabrication of 3D micro-structured targets. Additionally, laser surface nano-patterning followed by the replication of the patterns through molding, has been proposed and could become a cost-effective and reliable solution for intense laser experiments at high repetition rates. Recent works on numerical simulations have also been presented. Using particle-in-cell (PIC) simulation software, the importance of structured micro-target design in the energy absorption process of intense laser pulses—producing localized extreme temperatures and pressures—was demonstrated. Besides PIC simulations, the Finite-Difference Time-Domain (FDTD) numerical method offers the possibility to generate the specific data necessary for defining solid target material properties and designing their optical geometries with high accuracy. The prospects for the design and technological fabrication of 3D targets for ultra-intense laser facilities are also highlighted.

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Petrov, George M., und Jack Davis. „Parallelization of an Implicit Algorithm for Multi-Dimensional Particle-in-Cell Simulations“. Communications in Computational Physics 16, Nr. 3 (September 2014): 599–611. http://dx.doi.org/10.4208/cicp.070813.280214a.

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AbstractThe implicit 2D3V particle-in-cell (PIC) code developed to study the interaction of ultrashort pulse lasers with matter [G. M. Petrov and J. Davis, Computer Phys. Comm. 179, 868 (2008); Phys. Plasmas 18, 073102 (2011)] has been parallelized using MPI (Message Passing Interface). The parallelization strategy is optimized for a small number of computer cores, up to about 64. Details on the algorithm implementation are given with emphasis on code optimization by overlapping computations with communications. Performance evaluation for 1D domain decomposition has been made on a small Linux cluster with 64 computer cores for two typical regimes of PIC operation: “particle dominated”, for which the bulk of the computation time is spent on pushing particles, and “field dominated”, for which computing the fields is prevalent. For a small number of computer cores, less than 32, the MPI implementation offers a significant numerical speed-up. In the “particle dominated” regime it is close to the maximum theoretical one, while in the “field dominated” regime it is about 75-80 % of the maximum speed-up. For a number of cores exceeding 32, performance degradation takes place as a result of the adopted 1D domain decomposition. The code parallelization will allow future implementation of atomic physics and extension to three dimensions.

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Echeverría, Sebastián, Pablo S. Moya und Denisse Pastén. „On the multifractality of plasma turbulence in the solar wind“. Proceedings of the International Astronomical Union 15, S354 (Juni 2019): 371–74. http://dx.doi.org/10.1017/s1743921320000514.

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AbstractIn this work we have analyzed turbulent plasma in the kinetic scale by the characterization of magnetic fluctuations time series. Considering numerical Particle-In-Cell (PIC) simulations we apply a method known as MultiFractal Detrended Fluctuation Analysis (MFDFA) to study the fluctuations of solar-wind-like plasmas in thermodynamic equilibrium (represented by Maxwellian velocity distribution functions), and out of equilibrium plasma represented by Tsallis velocity distribution functions, characterized by the kappa (κ) parameter, to stablish relations between the fractality of magnetic fluctuation and the kappa parameter.

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Frazzitta, Andrea, Alberto Bacci, Arianna Carbone, Alessandro Cianchi, Alessandro Curcio, Illya Drebot, Massimo Ferrario et al. „First Simulations for the EuAPS Betatron Radiation Source: A Dedicated Radiation Calculation Code“. Instruments 7, Nr. 4 (08.12.2023): 52. http://dx.doi.org/10.3390/instruments7040052.

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X-ray production through betatron radiation emission from electron bunches is a valuable resource for several research fields. The EuAPS (EuPRAXIA Advanced Photon Sources) project, within the framework of EuPRAXIA, aims to provide 1–10 keV photons (X-rays), developing a compact plasma-based system designed to exploit self-injection processes that occur in the highly nonlinear laser-plasma interaction (LWFA) to drive electron betatron oscillations. Since the emitted radiation spectrum, intensity, angular divergence, and possible coherence strongly depend on the properties of the self-injected beam, accurate preliminary simulations of the process are necessary to evaluate the optimal diagnostic device specifications and to provide an initial estimate of the source’s performance. A dedicated tool for these tasks has been developed; electron trajectories from particle-in-cell (PIC) simulations are currently undergoing numerical analysis through the calculation of retarded fields and spectra for various plasma and laser parameter combinations. The implemented forward approach evaluation of the fields could allow for the integration of the presented scheme into already existing PIC codes. The spectrum calculation is thus performed in detector time, giving a linear complex exponential phase; this feature allows for a semi-analitical Fourier transform evaluation. The code structure and some trajectories analysis results are presented.

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BRET, ANTOINE, A. STOCKEM, F. FIUZA, C. RUYER, L. GREMILLET, R. NARAYAN und L. O. SILVA. „Relativistic collisionless shocks formation in pair plasmas“. Journal of Plasma Physics 79, Nr. 4 (03.04.2013): 367–70. http://dx.doi.org/10.1017/s0022377813000354.

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AbstractCollisionless shocks are ubiquitous in astrophysics and in the laboratory. Recent numerical simulations and experiments have shown how these can arise from the encounter of two collisionless plasma shells. When the shells interpenetrate, the overlapping region turns unstable, triggering the shock formation. As a first step toward a microscopic understanding of the process, we here analyze in detail the initial instability phase. On the one hand, 2D relativistic PIC simulations are performed where two unmagnetized, symmetric, and initially cold pair plasmas collide. On the other hand, the instabilities at work are analyzed, as well as the field at saturation and the seed field which gets amplified. For mildly relativistic motions and onward, Weibel modes with ω=0+iδ govern the linear phase. We derive an expression for the duration of the linear phase in reasonable agreement with the simulations.

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Garasev, Mikhail, und Evgeny Derishev. „Generation and decay of the magnetic field in collisionless shocks“. Proceedings of the International Astronomical Union 12, S324 (September 2016): 62–65. http://dx.doi.org/10.1017/s1743921317001156.

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AbstractWe present the results of numerical particle-in-cell (PIC) simulations of the magnetic field generation and decay in the upstream of collisionless shocks. We use the model, where the magnetic field in the incoming flow is generated by continuous injection of anisotropic electron-positron pairs. We found that the continuous injection of anisotropic plasma in the upstream of the shock-wave generates the large-scale, slowly decaying magnetic field that is later amplified during the passage of the shock front. In our simulations the magnetic field energy reached ~0.01 of the equipartition value, after that it slowly decays on the time scale proportional to the duration of the injection in the upstream. Thus, the magnetic field survives for a sufficiently long time, and supports efficient synchrotron radiation from relativistic shocks, e.g., in GRBs.

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Usui, H., H. Matsumoto und R. Gendrin. „Numerical simulations of a three-wave coupling occurring in the ionospheric plasma“. Nonlinear Processes in Geophysics 9, Nr. 1 (28.02.2002): 1–10. http://dx.doi.org/10.5194/npg-9-1-2002.

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Abstract. We studied a three-wave coupling process occurring in an active experiment of microwave power transmission (MPT) in the ionospheric plasma by performing one-dimensional electromagnetic PIC (Particle-In-Cell) simulations. In order to examine the spatial variation of the coupling process, we continuously emitted intense electromagnetic waves from an antenna located at a simulation boundary. In the three-wave coupling, a low-frequency electrostatic wave is excited as the result of a nonlinear interaction between the forward propagating pump wave and backscattered wave. In the simulations, low-frequency electrostatic bursts are discontinuously observed in space. The discontinuity of the electrostatic bursts is accounted for by the local electron heating due to the bursts and the associated modification of the wave dispersion relation. In a case where the pump wave propagates along the geomagnetic field Bext , several bursts of Langmuir waves are observed. Since the first burst consumes a part of the pump wave energy, the pump wave is weakened and cannot trigger the three-wave coupling beyond the region where the burst occurs. Since the dispersion relation of the Langmuir wave is variable, due to the local electron heating by the burst, the coupling condition eventually becomes unsatisfied and the first interaction becomes weak. Another burst of Langmuir waves is observed at a different region beyond the location of the first burst. In the case of perpendicular propagation, the upper hybrid wave, one of the mode branches of the electron cyclotron harmonic waves, is excited. Since the dispersion relation of the upper hybrid wave is less sensitive to the electron temperature, the coupling condition is not easily violated by the temperature increase. As a result, the three-wave coupling periodically takes place in time and eventually, the transmission ratio of the microwaves becomes approximately 20%, while almost no attenuation of the pump waves is observed after the first electrostatic burst in the parallel case. We also examined the dependency of the temporal growth rate for the electrostatic waves on the amplitude of the pump wave.

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Andreev, Andrey D. „Direct comparison of analytically derived “Fedosov” solution with experimental measurements and numerical simulations of relativistic thin annular electron beam generation and propagation in magnetically insulated coaxial diode of SINUS-6 high-current electron-beam accelerator“. Physics of Plasmas 29, Nr. 7 (Juli 2022): 073106. http://dx.doi.org/10.1063/5.0093039.

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The analytically derived solution for a thin annular electron-beam generation in a magnetically insulated coaxial diode (MICD), also known as “Fedosov solution,” is validated by direct experimental measurements of current–voltage (I–V) characteristics of MICD driven by the high-current electron-beam accelerator SINUS-6 and numerical particle-in-cell (PIC) simulations of a thin annular electron-beam generation and propagation in computer model of MICD of corresponding geometry and initial/boundary conditions. The experimental measurements of I–V characteristics of MICD are performed by monitoring and analyzing a voltage applied to MICD and an electron-beam current generated by an explosive-emission cathode of MICD. Numerical simulations of MICD operation are performed using ICEPIC code. The comparisons of analytically derived “Fedosov” solution with experimentally measured I–V characteristics of MICD as well as with results of ICEPIC simulations of a three-dimensional computer model of MICD operation are analyzed, and a conclusion is made that all three measures are pretty much consistent with each other. The appliance of the analysis is purposed now in using SINUS-6 accelerator for designing, prototyping, and studying different variants of O-type slow-wave high-power microwave/millimeter-wavelength vacuum electronic devices.

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Betz, Michael, Hermann Nirschl und Marco Gleiss. „Development of a New Solver to Model the Fish-Hook Effect in a Centrifugal Classifier“. Minerals 11, Nr. 7 (22.06.2021): 663. http://dx.doi.org/10.3390/min11070663.

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Centrifugal air classifiers are often used for classification of particle gas flows in the mineral industry and various other sectors. In this paper, a new solver based on the multiphase particle-in-cell (MP-PIC) method, which takes into account an interaction between particles, is presented. This makes it possible to investigate the flow process in the classifier in more detail, especially the influence of solid load on the flow profile and the fish-hook effect that sometimes occurs. Depending on the operating conditions, the fish-hook sometimes occurs in such apparatus and lead to a reduction in classification efficiency. Therefore, a better understanding and a representation of the fish-hook in numerical simulations is of great interest. The results of the simulation method are compared with results of previous simulation method, where particle–particle interactions are neglected. Moreover, a validation of the numerical simulations is carried out by comparing experimental data from a laboratory plant based on characteristic values such as pressure loss and classification efficiency. The comparison with experimental data shows that both methods provide similar good values for the classification efficiency d50; however, the fish-hook effect is only reproduced when particle-particle interaction is taken into account. The particle movement prove that the fish-hook effect is due to a strong concentration accumulation in the outer area of the classifier. These particle accumulations block the radial transport of fine particles into the classifier, which are then entrained by coarser particles into the coarse material.

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ESIRKEPOV, T., R. BINGHAM, S. BULANOV, T. HONDA, K. NISHIHARA und F. PEGORARO. „Coulomb explosion of a cluster irradiated by a high intensity laser pulse“. Laser and Particle Beams 18, Nr. 3 (Juli 2000): 503–6. http://dx.doi.org/10.1017/s0263034600183211.

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Clusters represent a new class of laser pulse targets which show both the properties of underdense and of overdense plasmas. We present analytical and numerical results (based on 2D- and 3D-PIC simulations) of the Coulomb explosion of the ion cloud that is formed when a cluster is irradiated by a high-intensity laser pulse. For laser pulse intensities in the range of 1021−1022 W/cm2, the laser light can rip electrons from atoms almost instantaneously and can create a cloud made of an electrically nonneutral plasma. Ions can then be accelerated up to high energy during the Coulomb explosion of the cloud.

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Cerutti, Benoît, Alexander A. Philippov und Guillaume Dubus. „Dissipation of the striped pulsar wind and non-thermal particle acceleration: 3D PIC simulations“. Astronomy & Astrophysics 642 (Oktober 2020): A204. http://dx.doi.org/10.1051/0004-6361/202038618.

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Context. The formation of a large-scale current sheet is a generic feature of pulsar magnetospheres. If the magnetic axis is misaligned with the star rotation axis, the current sheet is an oscillatory structure filling an equatorial wedge determined by the inclination angle, known as the striped wind. Relativistic reconnection could lead to significant dissipation of magnetic energy and particle acceleration, although the efficiency of this process is debated in this context. Aims. In this study, we aim at reconciling global models of pulsar wind dynamics and reconnection in the stripes within the same numerical framework in order to shed new light on dissipation and particle acceleration in pulsar winds. Methods. To this end, we perform large three-dimensional particle-in-cell simulations of a split-monopole magnetosphere, from the stellar surface up to 50 light-cylinder radii away from the pulsar. Results. Plasmoid-dominated reconnection efficiently fragments the current sheet into a dynamical network of interacting flux ropes separated by secondary current sheets that consume the field efficiently at all radii, even past the fast magnetosonic point. Our results suggest there is a universal dissipation radius solely determined by the reconnection rate in the sheet, lying well upstream from the termination shock radius in isolated pair-producing pulsars. The wind bulk Lorentz factor is much less relativistic than previously thought. In the co-moving frame, the wind is composed of hot pairs trapped within flux ropes with a hard broad power-law spectrum, whose maximum energy is limited by the magnetization of the wind at launch. Conclusions. We conclude that the striped wind is most likely fully dissipated when it enters the pulsar wind nebula. The predicted wind particle spectrum after dissipation is reminiscent of the Crab Nebula radio-emitting electrons.

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Mishra, Bharat. „Overview of Numerical Simulations for Calculating In-Plasma β-Decay Rates in the Framework of PANDORA Project“. EPJ Web of Conferences 275 (2023): 02001. http://dx.doi.org/10.1051/epjconf/202327502001.

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β-decay rates are essential inputs in stellar nucleosynthesis models to explain observed nuclear abundances. While current models continue to use terrestrial values, experiments in storage rings indicate strong divergence between decay rates of neutral and ionised atoms [1], necessitating renewed investigations into stellar decay rates. The PANDORA project aims at measuring lifetimes of specific radio-isotopes trapped in an ECR plasma (which mimics astrophysical environments to some extent) and compare them with theoretical predictions [2], consequently verifying the models and allowing decay rate estimation for any isotope in the stellar interior. We present here a simulation scheme to characterise the space-resolved charge state and level population distribution of buffer and radio-isotope ions in ECR ion sources in order to calculate in-plasma decay rates. The algorithm is based on a Particle-in-Cell Monte Carlo (PIC-MC) routine that simultaneously models charge transport with collision-radiative processes. Preliminary results from the simulation are also shown, along with important takeaways for code-optimisation.

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Yang, Chen, Haochuang Wu, Kangjie Deng, Hangxing He und Li Sun. „Study on Powder Coke Combustion and Pollution Emission Characteristics of Fluidized Bed Boilers“. Energies 12, Nr. 8 (13.04.2019): 1424. http://dx.doi.org/10.3390/en12081424.

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The fluidized reactor is widely used in a number of chemical processes due to its high gas-particle contacting efficiency and excellent performance on solid mixing. An improved numerical framework based on the multiphase particle-in-cell (MP-PIC) method has been developed to simulate the processes of gas–solid flow and chemical reactions in a fluidized bed. Experiments have been carried out with a 3-MW circulating fluidized bed with a height of 24.5 m and a cross section of 1 m2. In order to obtain the relationship between pollutant discharge and operating conditions and to better guide the operation of the power plant, a series of tests and simulations were carried out. The distributions of temperature and gas concentration along the furnace from simulations achieved good accuracy compared with experimental data, indicating that this numerical framework is suitable for solving complex gas–solid flow and reactions in fluidized bed reactors. Through a series of experiments, the factors affecting the concentration of NOx and SOx emissions during the steady-state combustion of the normal temperature of powder coke were obtained, which provided some future guidance for the operation of a power plant burning the same kind of fuel.

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Acosta, Belén, Denisse Pastén und Pablo S. Moya. „Reversibility of Turbulent and Non-Collisional Plasmas: Solar Wind“. Proceedings of the International Astronomical Union 15, S354 (Juni 2019): 363–66. http://dx.doi.org/10.1017/s1743921320000137.

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AbstractWe have studied turbulent plasma as a complex system applying the method known as Horizontal Visibility Graph (HVG) to obtain the Kullback-Leibler Divergence (KLD) as a first approach to characterize the reversibility of the time series of the magnetic fluctuations. For this, we have developed the method on Particle In Cell (PIC) simulations for a magnetized plasma and on solar wind magnetic time series, considering slow and fast wind. Our numerical results show that low irreversibility values are verified for magnetic field time series associated with Maxwellian distributions. In addition, considering the solar wind plasma, our preliminary results seem to indicate that greater irreversibility degrees are reached by the magnetic field associated with slow solar wind.

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Liu, Qi, Yong Li, Yanlin Hu und Wei Mao. „Effects of Magnetic Field Gradient on the Performance of a Magnetically Shielded Hall Thruster“. Aerospace 10, Nr. 11 (05.11.2023): 942. http://dx.doi.org/10.3390/aerospace10110942.

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The objective of this study is to investigate the effects of a magnetic field gradient on the performance of a magnetically shielded Hall thruster. The Particle-in-cell with Monte Carlo collision method (PIC-MCC) is used to simulate the discharge process of the thruster. The performance and plasma characteristics are obtained in conditions with different magnetic field gradients by numerical simulations. As the maximum of the gradient is increased from 1.2 to 3.33 T/m, the electron number density near the channel exit decreases, which leads to less ionization and a weaker radial electric field. As a result, the thrust and specific impulse are decreased, while the plume divergence angle is reduced.

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Formenti, A., M. Galbiati und M. Passoni. „Modeling and simulations of ultra-intense laser-driven bremsstrahlung with double-layer targets“. Plasma Physics and Controlled Fusion 64, Nr. 4 (28.02.2022): 044009. http://dx.doi.org/10.1088/1361-6587/ac4fce.

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Abstract High-energy bremsstrahlung emission can occur owing to electron scattering in the nuclei or ions Coulomb field following the relativistic-electron generation in high-intensity laser interaction with plasmas. Such emission of photons in the keV–MeV energy range is of interest to characterize the relativistic-electron populations and develop laser-based photons sources. Even if it is a well-established and widely studied emission process, its modeling in laser-plasma scenarios needs further investigation. Moreover, advanced near-critical double-layer targets (DLTs), consisting in a low-density foam deposited on a thin solid substrate, have never been explored extensively for bremsstrahlung photon emission. Therefore, in this paper, we show the rationale, advantages, limitations, application regime, and complementarity of different modeling approaches and apply them to the unconventional configuration based on DLTs. We use multi-dimensional particle-in-cell (PIC) simulations coupled with a Monte Carlo strategy to simulate bremsstrahlung in two ways: integrated into the PIC loop itself or after the simulation with two separate codes. We also use simplified semi-analytical relations to retrieve the photon properties starting only from information on the relativistic electrons. With these tools, we investigate bremsstrahlung emission when an ultra-intense laser (0.8 µm wavelength, 30 fs duration, a 0 = 20 and 3 µm waist) interacts with DLTs having different properties. Despite some limitations of the numerical tools, we find that all approaches significantly agree on the characteristics of ~1–100 MeV photon emission. This points to the possibility of adopting the different modeling approaches in a complementary way while at the same time identifying the best suited for a specific scenario. Regardless, DLTs appear to overall boost the high energy photon emission while at the same time enabling control of the emission itself.

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Böttcher, Markus, Matthew G. Baring, Edison P. Liang, Errol J. Summerlin, Wen Fu, Ian A. Smith und Parisa Roustazadeh. „Diagnosing particle acceleration in relativistic jets“. Proceedings of the International Astronomical Union 10, S313 (September 2014): 153–58. http://dx.doi.org/10.1017/s1743921315002100.

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AbstractThe high-energy emission from blazars and other relativistic jet sources indicates that electrons are accelerated to ultra-relativistic (GeV - TeV) energies in these systems. This paper summarizes recent results from numerical studies of two fundamentally different particle acceleration mechanisms potentially at work in relativistic jets: Magnetic-field generation and relativistic particle acceleration in relativistic shear layers, which are likely to be present in relativistic jets, is studied via Particle-in-Cell (PIC) simulations. Diffusive shock acceleration at relativistic shocks is investigated using Monte-Carlo simulations. The resulting magnetic-field configurations and thermal + non-thermal particle distributions are then used to predict multi-wavelength radiative (synchrotron + Compton) signatures of both acceleration scenarios. In particular, we address how anisotropic shear-layer acceleration may be able to circumvent the well-known Lorentz-factor crisis, and how the self-consistent evaluation of thermal + non-thermal particle populations in diffusive shock acceleration simulations provides tests of the bulk Comptonization model for the Big Blue Bump observed in the SEDs of several blazars.

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Sidorov, I. A., und A. B. Savel’ev. „Numerical 1D PIC-simulations of ion acceleration during laser-plasma interaction: Optimization of a two-component multilayered target structure“. Plasma Physics Reports 36, Nr. 13 (Dezember 2010): 1107–11. http://dx.doi.org/10.1134/s1063780x10130040.

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Pokhotelov, O. A., R. Z. Sagdeev, M. A. Balikhin, V. N. Fedun und G. I. Dudnikova. „Nonlinear Mirror and Weibel modes: peculiarities of quasi-linear dynamics“. Annales Geophysicae 28, Nr. 12 (01.12.2010): 2161–67. http://dx.doi.org/10.5194/angeo-28-2161-2010.

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Abstract. A theory for nonlinear evolution of the mirror modes near the instability threshold is developed. It is shown that during initial stage the major instability saturation is provided by the flattening of the velocity distribution function in the vicinity of small parallel ion velocities. The relaxation scenario in this case is accompanied by rapid attenuation of resonant particle interaction which is replaced by a weaker adiabatic interaction with mirror modes. The saturated plasma state can be considered as a magnetic counterpart to electrostatic BGK modes. After quasi-linear saturation a further nonlinear scenario is controlled by the mode coupling effects and nonlinear variation of the ion Larmor radius. Our analytical model is verified by relevant numerical simulations. Test particle and PIC simulations indeed show that it is a modification of distribution function at small parallel velocities that results in fading away of free energy driving the mirror mode. The similarity with resonant Weibel instability is discussed.

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