arXiv subjects

K. L. Cartwright

Publications and source records attributed to K. L. Cartwright.

3 recordsLinked to original sources

arXiv2012

An Arbitrary Curvilinear Coordinate Method for Particle-In-Cell Modeling

A new approach to the kinetic simulation of plasmas in complex geometries, based on the Particle-in- Cell (PIC) simulation method, is explored. In the two dimensional (2d) electrostatic version of our method, called the Arbitrary Curvilinear Coordinate PIC (ACC-PIC) method, all essential PIC operations are carried out in 2d on a uniform grid on the unit square logical domain, and mapped to a nonuniform boundary-fitted grid on the physical domain. As the resulting logical grid equations of motion are not separable, we have developed an extension of the semi-implicit Modified Leapfrog (ML) integration technique to preserve the symplectic nature of the logical grid particle mover. A generalized, curvilinear coordinate formulation of Poisson's equations to solve for the electrostatic fields on the uniform logical grid is also developed. By our formulation, we compute the plasma charge density on the logical grid based on the particles' positions on the logical domain. That is, the plasma particles are weighted to the uniform logical grid and the self-consistent mean electrostatic fields obtained from the solution of the logical grid Poisson equation are interpolated to the particle positions on the logical grid. This process eliminates the complexity associated with the weighting and interpolation processes on the nonuniform physical grid and allows us to run the PIC method on arbitrary boundary-fitted meshes.

physics.plasm-ph↗

arXiv2004

Priliminary Modeling of Air Breakdown with the ICEPIC code

Interest in air breakdown phenomena has recently been re-kindled with the advent of advanced virtual prototyping of radio frequency (RF) sources for use in high power microwave (HPM) weapons technology. Air breakdown phenomena are of interest because the formation of a plasma layer at the aperture of an RF source decreases the transmitted power to the target, and in some cases can cause significant reflection of RF radiation. Understanding the mechanisms behind the formation of such plasma layers will aid in the development of maximally effective sources. This paper begins with some of the basic theory behind air breakdown, and describes two independent approaches to modeling the formation of plasmas, the dielectric fluid model and the Particle in Cell (PIC) approach. Finally we present the results of preliminary studies in numerical modeling and simulation of breakdown.

physics.plasm-ph↗

arXiv2004

Hybrid Particle-Fluid Modeling of Plasmas

There are many interesting physical processes which involve the generation of high density plasmas in large volumes. However, when modeling these systems numerically, the large densities and volumes present a significant computational challenge. One technique for modeling plasma physics, the particle in cell (PIC) approach, is very accurate but requires increasing computation time and numerical resolution as the density of the plasma grows. In this paper we present a new technique for mitigating the extreme computational load as the plasma density grows by combining existing PIC methods with a dielectric fluid approach. By using both descriptions in a hybrid particle-fluid model, we now can probe the physics in large volume, high density regions. The hybrid method also provides a smooth transition as the plasma density increases and the ionization fraction grows to values that are well described by the fluid description alone. We present the hybrid technique and demonstrate the validity of the physical model by benchmarking against a simple example with an analytic solution.

physics.comp-ph↗