A monte-carlo code for computing transport coefficients in weakly ionized gas

Summary form only given. A Monte-Carlo code (MCSwarm) has been developed to compute transport coefficients in a weakly ionized gas. The MCSwarm code includes rotational and vibrational effects as well as excitation, ionization, and attachment reactions to determine the electron mobility, mean electron energy, and ionization and attachment rates. The MCSwarm code is time accurate and correctly handles both electric and magnetic fields with arbitrary orientation. A wide variety of common gases have been implemented including N₂, O₂ , Ar, Ne, SF₆, H₂, etc. The output of the MCSwarm code is a table of steady-state transport coefficients for a specified range of E/p and B/p values where E is the electric field, B is the magnetic field, and p is the gas pressure. When coupled with a particle-in-cell (PIC) code, this table of transport coefficients can be used to model time-dependent charge and current neutralization processes when an electron beam is injected into a gas. This is a reasonable approach provided the collisional mean-free path is small compared to any length scales of interest and the energy equilibration time is short compared to the time scales of interest. The PIC code Quicksilver (QS) has been modified to use the transport tables from the MCSwarm code. This newly modified QS is being used to simulate recent experiments at the Naval Research Laboratory where ~100 keV electrons with current densities between 10 A/cm² and 1 kA/cm² are injected into various pressures of either N₂ or dry air. Comparisons of code results with this data will be presented