Author: 吳昺璋Publisher:
ISBN:
Category :
Languages : en
Pages : 71
Book Description
Investigation of Coulomb Collisional Effects on Plasma Wave Echo by Using Particle-in-Cell Simulation
Author: 吳昺璋PIC Modeling of Coulomb Collisional Effects in a Wall-bounded Plasma
Author: Jordan Paul DeHavenPublisher:
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.
A Particle-in-cell Method for Modeling Small Angle Coulomb Collisions in Plasmas
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.
Particle-in-Cell Simulation of Capacitively Coupled Plasma in The Presence of Coulomb Collisions and Secondary Electron Emission
Author: Investigation of Particle-in-Cell Acceleration Techniques for Plasma Simulations
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 24
Book Description
COLISEUM is an application framework that integrates plasma propagation schemes and arbitrary 3D surface geometries. Using Particle-in-Cell (PIC) schemes to model the plasma propagation, high fidelity modeling of the plasma and its interaction with the surfaces is possible. In order to improve the computational performance of the Particle-in-Cell (PIC) scheme within COLISEUM (AQUILA), accelerate techniques have been developed that significantly decrease the amount of CPU time needed to obtain a steady-state solution. These schemes have been demonstrated to decrease the CPU time from 3 to 24 times with little appreciable differences in the global particle properties and number densities. This work investigates the differences in the local plasma properties that result from the application of the different acceleration techniques. In particular, the number densities and velocity distributions of the ions and neutrals demonstrate that the solution acceleration schemes produce very similar solutions outside the main path of the plasma source. Within the main path of the plasma source the local plasma properties show marked differences that might be associated with the time steps associated with these schemes and/or the collision modeling scheme within AQUILA.
Particle-in-cell Simulations of Bounded Plasma Discharges Applied to Low Pressure High Density Sources and Positive Columns
Author: Emi KawamuraEffect of Fokker-planck Collisions on Plasma Wave Echoes
Author: George L. JohnstonPublisher:
ISBN:
Category :
Languages : en
Pages : 16
Book Description
The effect on plasma wave echoes of Coulomb collisions described by a complete Fokker-Planck collision term is determined theoretically by application, in first and second orders, of the particular integral of a linearized kinetic equation which is capable of describing a Fokker-Planck collisional kinetic equation in the resonant region. (Author).
Efficient Modeling of Plasma Wake Field Acceleration Experiments Using Particle-in-cell Methods
Author: Weiming AnPublisher:
ISBN:
Category :
Languages : en
Pages : 159
Book Description
There is no clear path for building a particle accelerator at the energy frontier beyond the Large Hadron Collider (LHC). One option that is receiving attention is to use plasma wave wakefields driven by intense particle beams. Recent experiments conducted at the Stanford Linear Accelerator Center (SLAC) show that accelerating gradients in such wakefields in excess of 50 GeV/m can be sustained over meter scales. Based on this, a linear collider concept of staging one-meter long plasma cells together has been proposed. A facility at SLAC has been built to study the physics in one stage. In this dissertation we describe improvements and enhancements to a highly efficient simulation model for simulating current experiments at SLAC as well as parameters beyond the reach of current experiments. The model is the quasi-static particle-in-cell (PIC) code QuickPIC. A modified set of quasi-static field equations were developed, which reduced the number of predictor corrector iteration loops and an improved source deposit scheme was developed to reduce the parallel communication. These improvements led to a factor of 5 to 8 (depending on the simulation parameters) speedup compared with the previous set of field equations and deposition scheme. Several new modules were also added to QuickPIC, including the multiple field ionization and improved beam and plasma particle diagnostics. We also used QuickPIC to study the optimum plasma density for maximizing the acceleration field for fixed electron beam parameters. QuickPIC simulations were also used to study and design two-bunch PWFA experiments at SLAC including methods for mitigating the ionization-induced beam head erosion. The mitigation methods can enhance the energy gain in two-bunch PWFA experiments at SLAC by a factor of 10 for the same beam parameters. For beam parameters beyond SLAC but perhaps necessary for a future collider, QuickPIC was used to study how the ultra high electric fields of a tightly focused second electron bunch could lead to ion motion, which disrupts the focusing fields on the second bunch. The resulting nonlinearity in the transverse focusing force of the plasma wake will lead to emittance growth. We used QuickPIC to carry out the first fully self-consistent high resolution simulation on the effects of ion motion for PWFA linear collider problems. Preliminary results showed that the plasma-ion-motion-induced emittance growth was limited to less than a factor of 2. In addition to the electron beam driven PWFA, we also study how a short proton beam can excite a large plasma wake. Such short proton beams are currently not experimentally available. We therefore also study how long proton beams such as those at Fermi National Laboratory and CERN may drive a large plasma wake through a self-modulation instability. A linear theory for the self-modulation instability is presented under the wide beam limit. QuickPIC simulations show that the self-modulation of a long proton beam in a plasma may lead to the micro-bunching of the beam and excite a large plasma wake.
Particle-in-cell simulation of a cusp-confined plasma with Monte Carlo collisions
Author: Christian David Zuniga BarahonaPublisher:
ISBN:
Category :
Languages : en
Pages : 302
Book Description
Joint Experimental and Theoretical Investigations in Plasma Physics
Author: A. Y. WongPublisher:
ISBN:
Category :
Languages : en
Pages : 7
Book Description
The research involved studies with a Q-machine plasma. Specific topics of research are (1) collisional effects on electrostatic ion cyclotron waves and (2) cyclotron echo phenomena.