Spatial distributions of plasma potential and density in electron cyclotron resonance ion source

TL;DR

This study uses the NAM-ECRIS model to analyze the spatial distributions of plasma potential and density in an electron cyclotron resonance ion source, revealing complex profiles and the effects of biased electrodes on ion extraction.

Contribution

It introduces a detailed iterative modeling approach to map plasma profiles and explains the influence of electron trapping and biased electrodes on ion distribution.

Findings

Plasma density peaks near the ECR surface and source axis.

Ion-trapping potential dips are around 0.01-0.05 V at density maxima.

Biased electrodes create electron strings that enhance ion extraction.

Abstract

The Numerical Advanced Model of Electron Cyclotron Resonance Ion Source (NAM-ECRIS) is applied for studies of the physical processes in the source. Solutions of separately operating electron and ion modules of NAM-ECRIS are matched in iterative way such as to obtain the spatial distributions of the plasma density and of the plasma potential. Results reveal the complicated profiles with the maximized plasma density close to the ECR surface and on the source axis. The ion-trapping potential dips are calculated to be on the level of ~(0.01-0.05) V being located at the plasma density maxima. The highly charged ions are also localized close to the ECR surface. The biased electrode effect is due to an electron string along the source axis formed by reflection of electrons from the biased electrode and the extraction aperture. The string makes profiles of the highly charged ions more peaked on the source axis, thus increasing the extracted ion currents.