Numerical Simulations of Processes in Electron Cyclotron Resonance Ion Sources

Abstract:  Electron Cyclotron Resonance Ion Sources (ECRIS) produce intense and stable DC beams of highly charged ions for injection into accelerators, for studies in atomic physics, and other applications. The sources are the open minimum-B magnetic traps that confine a plasma heated by absorption of microwaves at the ECR surface. Confinement times of charged particles in a stable ECRIS plasma are large, which allows producing highly charged ions in a step-by-step ionization chain by bombardment with energetic plasma electrons. Analysis of complicated processes that influence the source dynamics is essential for finding ways for ECRIS improvement. We develop a Particle-in-Cell Monte-Carlo Collisions code for numerical modeling of plasmas in Electron Cyclotron Resonance Ion Sources. Ions in ECRIS plasmas are supposed to be confined by a small dip in the globally positive plasma potential. Various processes are taken into account when calculating the ion movement in the plasma including ionization of particles in electron-ion collisions, charge-exchange collisions with neutral atoms, ion neutralization in collisions with the source walls, etc. Parameters of the electron plasma component are calculated by assuming stochastic heating of electrons at ECR surface. The main parameters of the ECRIS are obtained such as charge-state-distributions of extracted ion beams and spatial distributions of fluxes inside the source. Explanations for some effects in the sources are given. Using the simulated source parameters, the shape of the plasma emissive surface can be calculated, which allows the detailed ion extraction simulations.