Download or read book Modeling Collisional Processes in Plasmas Using Discontinuous Numerical Methods written by Sean Miller and published by . This book was released on 2016 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid-based plasma models are typically applied to parameter regimes where a local thermal equilibrium is assumed. The applicability of this regime is valid for many plasmas, however, it is limited to plasma dynamics dominated by collisional effects. This study attempts to extend the validity of the collisional fluid regime using an anisotropic 13-moment fluid model derived from the Pearson type-IV probability distribution. The model explicitly evolves the heat flux hyperbolically alongside the density, momentum, and energy in order to capture dynamics usually restricted to costly kinetic models. Each particle species is modeled individually and collectively coupled through electromagnetic and collision operators. To remove electromagnetic divergence errors inherent to numerical representations of Maxwell’s equations, both hyperbolic and parabolic cleaning methods are presented. The plasma models are implemented using high-order finite volume and discontinuous Galerkin numerical methods designed for unstructured meshes. The unstructured code framework, numerical methods, and plasma models were developed in the University of Washington’s WARPXM code for use on heterogeneous accelerated clusters.
Download or read book Modern Methods in Collisional Radiative Modeling of Plasmas written by Yuri Ralchenko and published by Springer. This book was released on 2016-02-25 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a compact yet comprehensive overview of recent developments in collisional-radiative (CR) modeling of laboratory and astrophysical plasmas. It describes advances across the entire field, from basic considerations of model completeness to validation and verification of CR models to calculation of plasma kinetic characteristics and spectra in diverse plasmas. Various approaches to CR modeling are presented, together with numerous examples of applications. A number of important topics, such as atomic models for CR modeling, atomic data and its availability and quality, radiation transport, non-Maxwellian effects on plasma emission, ionization potential lowering, and verification and validation of CR models, are thoroughly addressed. Strong emphasis is placed on the most recent developments in the field, such as XFEL spectroscopy. Written by leading international research scientists from a number of key laboratories, the book offers a timely summary of the most recent progress in this area. It will be a useful and practical guide for students and experienced researchers working in plasma spectroscopy, spectra simulations, and related fields.
Download or read book Modeling Plasma Systems Using a Domain hybridized Physical Model written by Andrew Ho and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasma models have regions of validity that depend on local parameters.In some problems a computationally expensive, high-fidelity model is required in a small subset of the domain while lower-cost reduced models can adequately describe the plasma behavior everywhere else. The goal of this research is to investigate methods for spatially coupling the various plasma models such that the simplest plasma model that is locally valid can maintain global physical fidelity while improving computational efficiency. This research has two primary components. The first component is investigating numerical methods which can efficiently couple the various plasma models. Mixed implicit-explicit (ImEx) temporal solution schemes are investigated to produce schemes which are numerically stable when the time scales of interest span several orders of magnitude, and the physics of interest is dominated by long time scale physics. The spatial discretization method of choice is based on the discontinuous Galerkin (DG) method. Traditional DG methods are capable of producing numerical schemes with high spatial accuracy, but produce large and stiff implicit systems. To address this deficiency, the traditional DG scheme is augmented with a hybridized discontinuous Galerkin (HDG) scheme which is specifically designed to handle implicit temporal schemes. The second component of this research is investigating methods for making the plasma model dynamically (re-)decomposed based on local plasma conditions to produce an adaptive scheme. These metrics can be derived by examining the mathematical differences between the plasma models. This approach allows the determination of relative scale on which non-charge-neutral effects are significant, as well as which metrics are dependent on local gradients or purely on local conditions. Key metrics comparing the MHD and two-fluid models include examining charge neutrality, two-temperature effects, Hall effects, and finite-electron-mass effects.
Download or read book Numerical Simulation of Collisionless Kinetic Plasma Turbulence written by Daniel W. Crews and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hot plasma dissipates energy on scales comparable to the modes of collective oscillation through a turbulent cascade of the distribution function in its phase space. This phase space turbulence is responsible for augmenting fluid transport coefficients beyond predictions from collisional theories, a phenomenon termed anomalous transport. This work studies collisionless kinetic phase space turbulence using spectral and high-order discontinuous Galerkin numerical methods to produce highly resolved simulations of the kinetic equation. Based on these simulations intuition is built for the physics of anomalously enhanced transport, critical studies are performed on reduced models such as quasilinear theory, and mechanisms are identified by which macroscopic plasma properties are altered by microscopic turbulence. Novel results on discontinuous Galerkin method can be found within, such as a new way of thinking about the discrete differential operators of finite element methods as partial sums of orthogonal polynomial completeness theorems. Phase space eigenfunctions are studied in detail for both the electrostatic and electromagnetic pictures in the unmagnetized and strongly magnetized regimes, and utilized in a novel way to produce the initial conditions of continuum kinetic simulations. The nonlinear phase space structures of electron cyclotron instabilities are studied for loss-cone distributions. In addition, highly resolved simulations are presented for Langmuir and Weibel turbulence in two-dimensional configuration space.
Download or read book Computational Methods for Kinetic Models of Magnetically Confined Plasmas written by J. Killeen and published by Springer. This book was released on 1986-04 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Because magnetically confined plasmas are generally not found in a state of thermodynamic equilibrium, they have been studied extensively with methods of applied kinetic theory. In closed magnetic field line confinement devices such as the tokamak, non-Maxwellian distortions usually occur as a result of auxiliary heating and transport. In magnetic mirror configurations even the intended steady state plasma is far from local thermodynamic equilibrium because of losses along open magnetic field lines. In both of these major fusion devices, kinetic models based on the Boltzmann equation with Fokker-Planck collision terms have been successful in representing plasma behavior. The heating of plasmas by energetic neutral beams or microwaves, the production and thermalization of a-particles in thermonuclear reactor plasmas, the study of runaway electrons in tokamaks, and the performance of two-energy compo nent fusion reactors are some examples of processes in which the solution of kinetic equations is appropriate and, moreover, generally necessary for an understanding of the plasma dynamics. Ultimately, the problem is to solve a nonlinear partial differential equation for the distribution function of each charged plasma species in terms of six phase space variables and time. The dimensionality of the problem may be reduced through imposing certain symmetry conditions. For example, fewer spatial dimensions are needed if either the magnetic field is taken to be uniform or the magnetic field inhomogeneity enters principally through its variation along the direction of the field.
Download or read book A Kinetic Vlasov Model for Plasma Simulation Using Discontinuous Galerkin Method on Many core Architectures written by Noah Reddell and published by . This book was released on 2016 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances are reported in the three pillars of computational science achieving a new capability for understanding dynamic plasma phenomena outside of local thermodynamic equilibrium. A continuum kinetic model for plasma based on the Vlasov-Maxwell system for multiple particle species is developed. Consideration is added for boundary conditions in a truncated velocity domain and supporting wall interactions. A scheme to scale the velocity domain for multiple particle species with different temperatures and particle mass while sharing one computational mesh is described. A method for assessing the degree to which the kinetic solution differs from a Maxwell-Boltzmann distribution is introduced and tested on a thoroughly studied test case. The discontinuous Galerkin numerical method is extended for efficient solution of hyperbolic conservation laws in five or more particle phase-space dimensions using tensor-product hypercube elements with arbitrary polynomial order. A scheme for velocity moment integration is integrated as required for coupling between the plasma species and electromagnetic waves. A new high performance simulation code WARPM is developed to efficiently implement the model and numerical method on emerging many-core supercomputing architectures. WARPM uses the OpenCL programming model for computational kernels and task parallelism to overlap computation with communication. WARPM single-node performance and parallel scaling efficiency are analyzed with bottlenecks identified guiding future directions for the implementation. The plasma modeling capability is validated against physical problems with analytic solutions and well established benchmark problems.
Download or read book Discontinuous Galerkin Methods for Vlasov Models of Plasma written by and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Vlasov-Poisson equations describe the evolution of a collisionless plasma, represented through a probability density function (PDF) that self-interacts via an electrostatic force. One of the main difficulties in numerically solving this system is the severe time-step restriction that arises from parts of the PDF associated with moderate-to-large velocities. The dominant approach in the plasma physics community for removing these time-step restrictions is the so-called particle-in-cell (PIC) method, which discretizes the distribution function into a set of macro-particles, while the electric field is represented on a mesh. Several alternatives to this approach exist, including fully Lagrangian, fully Eulerian, and so-called semi-Lagrangian methods. The focus of this work is the semi-Lagrangian approach, which begins with a grid-based Eulerian representation of both the PDF and the electric field, then evolves the PDF via Lagrangian dynamics, and finally projects this evolved field back onto the original Eulerian mesh. We present a semi-Lagrangian and a hybrid semi-Lagrangian method for solving the Vlasov Poisson equations, based on high-order discontinuous Galerkin (DG) spatial representations of the solution. The Poisson equation is solved via a high-order local discontinuous Galerkin (LDG) scheme. The resulting methods are high-order accurate, which is demonstrably important for this problem in order to retain the rich phase-space structure of the solution; mass conservative; and provably positivity-preserving. We argue that our approach is a promising method that can produce very accurate results at relatively low computational expense. We demonstrate this through several examples for the (1+1)D case, using both the hybrid as well as the full semi-Lagrangian method. In particular, the methods are validated on several numerical test cases, including the two-stream instability problem, Landau damping, and the formation of a plasma sheath. In addition, we propose a (2+2)D method that promises to be a productive avenue of future research. The (2+2)D method incorporates local time-stepping methods on unstructured grids in physical space and semi-Lagrangian time stepping on Cartesian grids in velocity space. This method is again high-order, mass conservative, and provably positivity-preserving.
Download or read book Computational Methods for Collisional Plasma Physics written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Modeling the high density, high temperature plasmas produced by intense laser or particle beams requires accurate simulation of a large range of plasma collisionality. Current simulation algorithms accurately and efficiently model collisionless and collision-dominated plasmas. The important parameter regime between these extremes, semi-collisional plasmas, has been inadequately addressed to date. LLNL efforts to understand and harness high energy-density physics phenomena for stockpile stewardship require accurate simulation of such plasmas. We have made significant progress towards our goal: building a new modeling capability to accurately simulate the full range of collisional plasma physics phenomena. Our project has developed a computer model using a two-pronged approach that involves a new adaptive-resolution, ''smart'' particle-in-cell algorithm: complex particle kinetics (CPK); and developing a robust 3D massively parallel plasma production code Z3 with collisional extensions. Our new CPK algorithms expand the function of point particles in traditional plasma PIC models by including finite size and internal dynamics. This project has enhanced LLNL's competency in computational plasma physics and contributed to LLNL's expertise and forefront position in plasma modeling. The computational models developed will be applied to plasma problems of interest to LLNL's stockpile stewardship mission. Such problems include semi-collisional behavior in hohlraums, high-energy-density physics experiments, and the physics of high altitude nuclear explosions (HANE). Over the course of this LDRD project, the world's largest fully electromagnetic PIC calculation was run, enabled by the adaptation of Z3 to the Advanced Simulation and Computing (ASCI) White system. This milestone calculation simulated an entire laser illumination speckle, brought new realism to laser-plasma interaction simulations, and was directly applicable to laser target physics. For the first time, magnetic fields driven by Raman scatter have been observed. Also, Raman rescatter was observed in 2D. This code and its increased suite of dedicated diagnostics are now playing a key role in studies of short-pulse, high-intensity laser matter interactions. In addition, a momentum-conserving electron collision algorithm was incorporated into Z3. Finally, Z3's portability across diverse MPP platforms enabled it to serve the LLNL computing community as a tool for effectively utilizing new machines.
Download or read book Development of a Complexity Reduced Collisional Radiative Model for Multiphysics Plasma Simulations written by Richard Jun Espino Abrantes and published by . This book was released on 2018 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: The influence of plasma physics on modern technology spans many disciplines beyond the fields of physics and engineering. The fundamental operation of forthcoming plasma physics devices are becoming increasingly complex, producing transient plasma structures and instabilities that can affect any of these devices' nominal performance conditions. One set of underlying physical phenomenon that can impact the plasma evolution in these devices derives from the atomic kinetics. A fully-resolved numerical simulation of these plasma systems involves solving the time-dependent atomic kinetics using a collisional-radiative model. However, a plasma simulation that includes such an atomic model exacerbates the problem's dimensionality because of the resolution of the atomic structure and number of atomic levels that must be resolved. The goal of this dissertation is to develop and implement state-of-the-art complexity reduction techniques to accurately simulate the atomic kinetics in reasonable computational times, without restricting the model to any atomic species or any single application. This approach will enable researchers to assess and analyze complex features of new plasma devices and experiments impacted by atomic kinetics. The collisional-radiative model's rate equations were first extended to include energy equations to study laser-induced breakdown events. This study was used to verify processes affected by energy transfers due to the energy equations' coupling to the atomic state densities' rate equations. Here, multiphoton ionization and inverse Bremsstrahlung were used as the laser source terms to simulate laser-induced breakdown events similar to experimental conditions found in the literature. Once the simulations were deemed sufficient to capture the atomic kinetics observed in breakdown experiments, the entire kinetics model was used as the foundation to implement and investigate the effect of complexity-reduction algorithms. The techniques explored in this work included the quasi-steady-state (QSS) solution, uniform grouping, and Boltzmann grouping. These techniques were then tested against isothermal and Planckian irradiation test cases; amongst all of the reduction algorithms, the Boltzmann grouping technique was found to hold the most promise for its flexible representation of atomic state distributions across a wide range of plasma regimes. The collisional-radiative model's symbiotic connection with atomic codes additionally allows these models to become tools to be used for spectroscopic analysis. Spectral images of chlorine generated for the NLTE-10 workshop verified high-density, high-temperature spectral data obtained from a newly-constructed spectrometer called OHREX. Accurate comparisons were observed among the present findings, results from other collisional-radiative models in the scientific community, and the OHREX experimental data presented at the workshop. Additionally, spectral comparisons between the model and a low-density, low temperature inductively-coupled argon plasma at the Air Force Research Laboratory were attempted. It was found that spectral comparisons were poorly matched as a result of the preferential disposition of atomic codes for high-Z ions. Hence, additional analysis is needed to properly capture detailed atomic kinetics for low-Z applications.
Download or read book Fully Implicit Kinetic Modelling of Collisional Plasmas written by and published by . This book was released on 1996 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes a numerical technique, Matrix-Free Newton Krylov, for solving a simplified Vlasov-Fokker-Planck equation. This method is both deterministic and fully implicit, and may not have been a viable option before current developments in numerical methods. Results are presented that indicate the efficiency of the Matrix-Free Newton Krylov method for these fully-coupled, nonlinear integro-differential equations. The use and requirement for advanced differencing is also shown. To this end, implementations of Chang-Cooper differencing and flux limited Quadratic Upstream Interpolation for Convective Kinematics (QUICK) are presented. Results are given for a fully kinetic ion-electron problem with a self consistent electric field calculated from the ion and electron distribution functions. This numerical method, including advanced differencing, provides accurate solutions, which quickly converge on workstation class machines. It is demonstrated that efficient steady-state solutions can be achieved to the non-linear integro-differential equation, obtaining quadratic convergence, without incurring the large memory requirements of an integral operator. Model problems are presented which simulate plasma impinging on a plate with both high and low neutral particle recycling typical of a divertor in a Tokamak device. These model problems demonstrate the performance of the new solution method.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1989 with total page 988 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1984 with total page 1294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Introduction to Plasma Physics written by R.J Goldston and published by CRC Press. This book was released on 2020-07-14 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introduction to Plasma Physics is the standard text for an introductory lecture course on plasma physics. The text’s six sections lead readers systematically and comprehensively through the fundamentals of modern plasma physics. Sections on single-particle motion, plasmas as fluids, and collisional processes in plasmas lay the groundwork for a thorough understanding of the subject. The authors take care to place the material in its historical context for a rich understanding of the ideas presented. They also emphasize the importance of medical imaging in radiotherapy, providing a logical link to more advanced works in the area. The text includes problems, tables, and illustrations as well as a thorough index and a complete list of references.
Download or read book Turbulence in the Solar Wind written by Roberto Bruno and published by Springer. This book was released on 2016-10-07 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an overview of solar wind turbulence from both the theoretical and observational perspective. It argues that the interplanetary medium offers the best opportunity to directly study turbulent fluctuations in collisionless plasmas. In fact, during expansion, the solar wind evolves towards a state characterized by large-amplitude fluctuations in all observed parameters, which resembles, at least at large scales, the well-known hydrodynamic turbulence. This text starts with historical references to past observations and experiments on turbulent flows. It then introduces the Navier-Stokes equations for a magnetized plasma whose low-frequency turbulence evolution is described within the framework of the MHD approximation. It also considers the scaling of plasma and magnetic field fluctuations and the study of nonlinear energy cascades within the same framework. It reports observations of turbulence in the ecliptic and at high latitude, treating Alfvénic and compressive fluctuations separately in order to explain the transport of mass, momentum and energy during the expansion. Further, existing models are compared with direct observations in the heliosphere. The problem of self-similar and anomalous fluctuations in the solar wind is then addressed using tools provided by dynamical system theory and discussed on the basis of available models and observations. The book highlights observations of Yaglom’s law in solar wind turbulence, which is one of the most important findings in fully developed turbulence and directly related to the long-lasting and still unsolved problem of solar wind plasma heating. Lastly, it includes a short chapter dedicated to the kinetic range of fluctuations, which has recently been receiving more attention from the space plasma community, since this is inherently related to turbulent energy dissipation and consequent plasma heating. It particularly focuses on the nature and role of the fluctuations populating this frequency range, and discusses several model predictions and recent observational findings in this context.
Download or read book Fusion Energy Update written by and published by . This book was released on 1978 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Principles of Magnetohydrodynamics written by J. P. Goedbloed and published by Cambridge University Press. This book was released on 2004-08-05 with total page 644 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook provides a modern and accessible introduction to magnetohydrodynamics (MHD). It describes the two main applications of plasma physics, laboratory research on thermo-nuclear fusion energy and plasma astrophysics of the solar system, stars and accretion disks, from the single viewpoint of MHD. This approach provides effective methods and insights for the interpretation of plasma phenomena on virtually all scales, from the laboratory to the universe. It equips the reader with the necessary tools to understand the complexities of plasma dynamics in extended magnetic structures. The classical MHD model is developed in detail without omitting steps in the derivations and problems are included at the end of each chapter. This text is ideal for senior-level undergraduate and graduate courses in plasma physics and astrophysics.
Download or read book JJAP written by and published by . This book was released on 1993 with total page 756 pages. Available in PDF, EPUB and Kindle. Book excerpt:
