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Author: Nina Hanzlikova Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
During 20th century few branches of science have proved themselves to be more industrially applicable than Plasma science and processing. Across a vast range of discharge types and regimes, and through industries spanning semiconductor manufacture, surface sterilisation, food packaging and medicinal treatment, industry continues to find new usefulness in this physical phenomenon well into 21st century. To better cater to this diverse motley of industries there is a need for more detailed and accurate understanding of plasma chemistry and kinetics, which drive the plasma processes central to manufacturing. Extensive efforts have been made to characterise plasma discharges numerically and mathematically leading to the development a number of different approaches. In our work we concentrate on the Particle-In-Cell (PIC) - Monte Carlo Collision (MCC) approach to plasma modelling. This method has for a long time been considered computationally prohibitive by its long run times and high computational resource expense. However, with modern advances in computing, particularly in the form of relatively cheap accelerator devices such as GPUs and co-processors, we have developed a massively parallel simulation in 1 and 2 dimensions to take advantage of this large increase in computing power. Furthermore, we have implemented some changes to the traditional PIC-MCC implementation to provide a more generalised simulation, with greater scalability and smooth transition between low and high (atmospheric) pressure discharge regimes. We also present some preliminary physical and computational benchmarks for our PIC-MCC implementation providing a strong case for validation of our results.
Author: Nina Hanzlikova Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
During 20th century few branches of science have proved themselves to be more industrially applicable than Plasma science and processing. Across a vast range of discharge types and regimes, and through industries spanning semiconductor manufacture, surface sterilisation, food packaging and medicinal treatment, industry continues to find new usefulness in this physical phenomenon well into 21st century. To better cater to this diverse motley of industries there is a need for more detailed and accurate understanding of plasma chemistry and kinetics, which drive the plasma processes central to manufacturing. Extensive efforts have been made to characterise plasma discharges numerically and mathematically leading to the development a number of different approaches. In our work we concentrate on the Particle-In-Cell (PIC) - Monte Carlo Collision (MCC) approach to plasma modelling. This method has for a long time been considered computationally prohibitive by its long run times and high computational resource expense. However, with modern advances in computing, particularly in the form of relatively cheap accelerator devices such as GPUs and co-processors, we have developed a massively parallel simulation in 1 and 2 dimensions to take advantage of this large increase in computing power. Furthermore, we have implemented some changes to the traditional PIC-MCC implementation to provide a more generalised simulation, with greater scalability and smooth transition between low and high (atmospheric) pressure discharge regimes. We also present some preliminary physical and computational benchmarks for our PIC-MCC implementation providing a strong case for validation of our results.
Author: E. A. Orozco Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
A lot of plasma physics problems are not amenable to exact solutions due to many reasons. It is worth mentioning among them, for example, nonlinearity of the motion equations, variable coefficients or non lineal conditions on known or unknown borders. To solve these problems, different types of approximations which are combinations of analytical and numerical simulation methods are put into practice. The problem of plasma behavior in numerous varieties of a minimum-B magnetic trap where the plasma is heated under electron cyclotron resonance (ECR) conditions is the subject of numerical simulation studies. At present, the ECR minimum-B trap forms the principal part of the multi-charge ion sources.There are different numerical methods to model plasmas. Depending of both temperature and concentration, these can be classified in three main groups: fluid models, kinetic models and hybrid models. The fluid models are the most simple way to describe the plasma from macroscopic quantities, which are used for the study of highly collisional plasmas where the mean free path is much smaller than size of plasma (l_mfp “ L). The kinetic models are the most fundamental way to describe plasmas through the distribution function in phase-space for each particle specie; which are used for the study of weakly collisional (l_mfp ∼ L) or collision-less plasmas (l_mfp ” L) from the solution of the Boltzmann or Vlasov equation, respectively [2]. For kinetic simulations there are different method to solve the Boltzmann or Vlasov equation, being the Particle-In-Cell (PIC) codes one the most popular. The hybrid model combine both the fluid and kinetic models, treating some components of the system as a fluid, and others kinetically; which are used for the study of plasmas, may use the PIC method for the kinetic treatment of some species, while other species (that are Maxwellian) are simulated with a fluid model.In this work, a scheme of the relativistic Particle-in-Cell (PIC) code elaborated for an ECR plasma heating study in minimum-B traps is presented. For a PIC numerical simulation, the code is applied to an ECR plasma confined in a minimum-B trap formed by two current coils generating a mirror magnetic configuration and a hexapole permanent magnetic bars to suppress the MHD instabilities.The plasma is maintained in a cylindrical chamber excited at TE_111 mode by 2.45 GHz microwave power. In the obtained magnetostatic field, the ECR conditions are fulfilled on a closed surface of ellipsoidal type. Initially, a Maxwellian homogeneous plasma from ionic temperature of 2 eV being during 81.62 ns, that correspond to 200 cycles of microwaves with an amplitude in the electric field of 1 kV/cm is heated. The electron population can be divided conditionally into a cold group of energies smaller than 0.2 keV, a warm group whose energies are in a range of 3 - 10 keV and hot electrons whose energies are found higher than 10 keV.
Author: Publisher: ISBN: Category : Languages : en Pages : 4
Book Description
The modeling of collisions among particles in space plasma media poses a challenge for computer simulation. Traditional plasma methods are able to model well the extremes of highly collisional plasmas (MHD and Hall-MHD simulations) and collisionless plasmas (particle-in-cell simulations). However, neither is capable of trealing the intermediate, semi-collisional regime. The authors have invented a new approach to particle simulation called Quiet Monte Carlo Direct Simulation (QMCDS) that can, in principle, treat plasmas with arbitrary and arbitrarily varying collisionality. The QMCDS method will be described, and applications of the QMCDS method as 'proof of principle' to diffusion, hydrodynamics, and radiation transport will be presented. Of particular interest to the space plasma simulation community is the application of QMCDS to kinetic plasma modeling. A method for QMCDS simulation of kinetic plasmas will be outlined, and preliminary results of simulations in the limit of weak pitch-angle scattering will be presented.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
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.
Author: Publisher: ISBN: Category : Languages : en Pages : 4
Book Description
We propose a computational method to self-consistently model small angle collisional effects. This method may be added to standard Particle-In-Cell (PIC) plasma simulations to include collisions, or as an alternative to solving the Fokker-Planck (FP) equation using finite difference methods. The distribution function is represented by a large number of particles. The particle velocities change due to the drag force, and the diffusion in velocity is represented by a random process. This is similar to previous Monte-Carlo methods except we calculate the drag force and diffusion tensor self- consistently. The particles are weighted to a grid in velocity space and associated Poisson equations'' are solved for the Rosenbluth potentials. The motivation is to avoid the very time consuming method of Coulomb scattering pair by pair. First the approximation for small angle Coulomb collisions is discussed. Next, the FP-PIC collision method is outlined. Then we show a test of the particle advance modeling an electron beam scattering off a fixed ion background. 4 refs.
Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
We present 2-D simulations of both beam-driven and laser-driven plasma wakefield accelerators, using the object-oriented particle-in-cell code XOOPIC, which is time explicit, fully electromagnetic, and capable of running on massively parallel supercomputers. Simulations of laser-driven wakefields with low ((almost equal to)1016 W/cm2) and high ((almost equal to)1018 W/cm2) peak intensity laser pulses are conducted in slab geometry, showing agreement with theory and fluid simulations. Simulations of the E-157 beam wakefield experiment at the Stanford Linear Accelerator Center, in which a 30 GeV electron beam passes through 1 m of preionized lithium plasma, are conducted in cylindrical geometry, obtaining good agreement with previous work. We briefly describe some of the more significant modifications of XOOPIC required by this work, and summarize the issues relevant to modeling relativistic electron-neutral collisions in a particle-in-cell code.
Author: Jordan Paul DeHaven Publisher: ISBN: Category : Particles (Nuclear physics) Languages : en Pages : 24
Book Description
Collisions between particles in a hot plasma can be ignored in many high-temperature plasma simulations. However, at lower temperatures, collisional effects play a significant role in determining the plasma's overall behavior. While fluid modeling can accurately capture collisional effects (with some limitations), proper definition of boundary conditions for fluid modeling depend on accurate assumptions about the kinetic (real) behavior of plasma near material surfaces, where the plasma sheath dominates the plasma behavior. This thesis project is an attempt to develop a tool to elucidate sheath and presheath plasma behavior in the presence of strong collisional effects. Using the Particle In Cell (PIC) method, a Coulomb collisional model is implemented to study near-surface plasma behavior. The information gleaned from this project could provide important refinement of boundary conditions for fluid codes, and more generally, insights into kinetic behavior of the collisional plasma sheath.
Author: Nina Hanzlikova
Author: Nina Hanzlikova
Author: E. A. Orozco
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Author: Emi Kawamura
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Author: Reginald Francis Abdul
Author: Jordan Paul DeHaven
Author: Kumar Balasubramanian