Ion temperature effects on ion charge-state distributions of an electron cyclotron resonant ion source

A method is described for determining ion cyclotron resonance (ICR) heating effects on multiply charged-ion energy distributions using a Monte Carlo fit to experimental time-of-flight spectrometer data. The method is general but is used here specifically to separate the effects of plasma ambipolar potential spread and ion temperature in an electron cyclotron resonance (ECR) heated magnetic mirror ion source (MIMI) [Phys. Fluids 28, 3116 (1985)]. A steady-state equilibrium model is also developed that models the relevant atomic processes occurring in MIMI plasmas. This model and the Monte Carlo analysis are used to relate the effect of midplane ICR heating on end loss ion charge state distributions to its effect on the confined ion distributions. The model allows for collisional, moderately collisional, and collisionless confinement, specific to each charge state in the distribution. Both experiment and modeling show that increased ion temperature causes a shift to lower-Z ion populations in both the confined and end loss charge-state distributions