Time-dependent collisional-radiative model for quantitative study of nonequilibrium plasma

In this paper fully time-dependent collisional-radiative (CR) calculations are used to study the highly dynamic nonequilibrium anode plasma in a magnetically insulated-diode experiment. The CR model for the C i-C iv atomic system is described in detail, including the radiative and collisional rates and the level structure of the system. The electron temperature is determined by comparing time-dependent line intensities for C ii and C iii ions to calculations of level-population ratios in which continuous particle injection from the anode surface into the plasma is taken into account. The electron temperature is approximately 7 eV. The time-dependent injected fluxes and the fluxes accelerated away from the plasma for C i, C ii, and C iii are determined by inverting the coupled CR rate equations. The calculated extracted flux near the end of the pulse is consistent with the measured carbon-ion current drawn from the plasma. Injection of excited particles is also investigated and is found to be important during the rise of the current pulse (≤50 ns). The importance of including multiple branching for ionization into excited final states is also shown. The time-dependent cooling rate due to inelastic electron-ion collisions and radiative processes is derived for general level-population distributions and is used to investigate the anode plasma. This work should also be relevant in the study of other pulsed-power nonequilibrium plasmas, such as recombining plasmas that have applications for UV and x-ray lasers.