Numerical investigations of the minimum-B effect in Electron Cyclotron Resonance Ion Source

TL;DR

This study uses a 3D particle-in-cell model to analyze how the magnetic field configuration affects the performance of an Electron Cyclotron Resonance Ion Source, revealing an optimal minimum-B value for electron confinement.

Contribution

It provides the first detailed numerical investigation of the minimum-B effect in an ECR ion source using the NAM-ECRIS model, identifying the optimal magnetic field configuration.

Findings

Optimal normalized minimum-B value is ~0.8, matching experimental data.

Electron energies increase with higher minimum-B due to better confinement.

Energy spectra show nonadiabatic electron losses causing spectral bumps.

Abstract

The three-dimensional particle-in-cell model NAM-ECRIS is used for investigation of how the DECRIS-PM Electron Cyclotron Resonance Ion Source is reacting to changes in the source magnetic configuration. The accent is made on changes in the magnetic field at the magnetic trap center, the minimum-B value. It is calculated that the optimal normalized value of the field is ~0.8, close to the experimental observations. The reasons for existence of the optimum are discussed. It is observed that the electron energies are increasing with the increased minimum-B values due to enhanced confinement of the energetic electrons in the plasma. Bumps in energy spectra of the radially lost electrons are observed and explained to be due to nonadiabatic losses of electrons.