Particle-in-cell charged-particle simulations, plus Monte Carlo collisions with neutral atoms, PIC-MCC

Abstract

Many-particle (meaning 1OOO's) charged-particle plasma simulations using spatial meshes for the electromagnetic field solutions, particle-in-cell (PIC) merged with Monte Carlo collision (MCC) calculations, are coming into wide use for application to partially ionized gases. This paper emphasizes the development of PIC computer experiments since the 1950's starting with one-dimensional (1-D) chargedsheet models, the addition of the mesh, and fast direct Poisson equation solvers for 2-D and 3-D. The finite-size particle-in-mesh (finite AZ, At) theory of Langdon [51]-[53] is presented in part to display the effects of too small Ao/Ax, even for Maxwellian velocity distributions, as a caution, for example, when some ions are cooled to background gas temperatures by charge exchange. Early work on adding collisions to 1-D chargesheet models by Burger [28] and Shanny et aL[76] are presented, with many of the elements of current Monte Carlo codes. Bounded plasma modeling is presented with electrode charges and external R, L, C, and V(t), Z(t) sources now in use on fast desktop computers as real-time computer experiments, complementing analytic modeling and laboratory experiments. The addition of Monte Carlo collisions (usually done with irregular timesteps) to PIC (usually done with uniform At's) is displayedas a developing art, relying on experimental total cross sections and approximate analytical differential cross sections to produce changes in charged-particle speed and direction due to collisions with neutrals, so far including elastic, excitation, ionization, charge exchange, and attachment processes. r. INTRODUCTIONHE plasma medium, consisting of electrons, ions, neutral T atoms and molecules, and particles, is very complicated to understand. Theory and modeling provide guide-lines for design of devices; experiments provide a variety of measurements.Simulations provide insight, and numbers, computer experiments. Interactions among this trio have proven effective and efficient in advancing plasma science and engineering.This report leads the reader through the development over the past four decades of many-particle particle-in-cell (PIC) simulations and into including charged-particle collisions with neutral atoms using Monte Carlo methods. Some mention will be made of doing Coulomb collisions using PIC codes. We then provide some details of adding the collisions between the charged particles and neutral atoms. The result is many-particle simulations with many of the features met in low-temperature collisional plasmas; for example, with applications to plasmaassisted materials processing, but also related to warmer plasmas at the edges of magnetized fusion plasmas.Collisionless many-particle plasma simulation is rich in history and may rate as one of the success stories in physics and engineering using the modern digital computer, along with such advances as numerical wind tunnels and space craft control and communications-both complementing theory and experiment and, in some cases, being the main ingredient. This ...

Realistic modeling of ion cloud motion in a Fourier transform ion cyclotron resonance cell by use of a particle‐in‐cell approach

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