Efficient numerical algorithm for multi-level ionization of high-atomic-number gases

Abstract

An efficient numerical algorithm for the laser driven multi-level ionization of high-atomic-number gases is proposed and implemented in an electromagnetic particle-in-cell code SPACE. The algorithm is based on analytical solutions to the system of differential equations describing ionization evolution. Using analytical solutions resolves the multiscale issue of ionization due to different characteristic time scales of ionization processes and the main code time step. Algorithm efficiency is improved by using a locally-reduced system of differential equations. The effects of the orbital quantum numbers and their projections have been examined. The algorithm is applied to the study of ionization injection of electrons into laser-driven plasma wakefields.