Non-stationary plasma ionisation kinetics in ECR ion sources

Several techniques for feeding metals into an ECR ion source that are intrinsically pulsed (laser ablation, MEVVA injection) may prove advantageous, but they require studies of the ionisation time and of the extracted current stability. Notwithstanding that an arbitrary number of plasma elements is allowed, the nonlinear kinetic equation for ion concentrations in a 0-dimensional plasma model can be written in a compact matrix form, which possesses band properties. Efficient and stable computer codes are thus possible. Numerical simulations of the ion charge state distribution are presented, showing that repetition rate of metal feeding must be moderately high (larger than 20 Hz) for good ECR performance and confirming the estimate from analytical solution of linearized models; charge exchange effect is now included in this estimate. (orig.)