Implicit coupling of ionisation dynamics and electron energy balance in laser target simulations

The authors describe a new algorithm for the calculation of ionisation and recombination in rapidly changing plasmas. It solves the coupled equations governing the plasma ionic composition and the electron energy balance. It has been designed to run with a large time-step and yet be free of energy coupling instabilities. It has been incorporated in a standard one-dimensional Lagrangian code to model the plasma evolution in a laser-irradiated target and has been compared to existing steady-state and time-dependent ionisation models. The improvement in accuracy of hydrogen-like and helium-like population calculations is investigated and attention is drawn to the localisation of X-ray emissions of each charge state.