Monte Carlo model of charge-state distributions for electron cyclotron resonance ion source plasmas

Abstract

A computer model for an Electron Cyclotron Resonance Ion Source (ECRIS) plasma is under development that currently incorporates non-Maxwellian distribution functions, multiple atomic species, and ion confinement due to the ambipolar potential that arises from fast electrons. Atomic processes incorporated into the model include multiple ionization and multiple charge-exchange with rate coefficients calculated for non-Maxwellian distributions. The electron distribution function is calculated using a Fokker-Planck code with an ECR heating term. The Monte Carlo method is used to calculate the charge-state distribution (CSD) of the ions. The Monte Carlo ion tracking is verified by CSD comparison with a conventional 0-D fluid model, similar to Shirkov's (1992). The Monte Carlo method is chosen for future extension to a 1-D axial model. Axial variations in the plasma parameters could affect confinement, CSD and extraction. The electron Fokker-Planck code is to be extended to 1-D axial by bounce-averaging.