Modelling RF-plasma interaction in ECR ion sources

D Mascali ,Lorenzo Lega,M Mazzaglia ,G Castro ,L Neri ,L Celona ,G Torrisi ,O Leonardi ,A Galatà ,E Naselli ,G Sorbello ,S Gammino

doi:10.1051/epjconf/201715703054

Abstract

This paper describes three-dimensional self-consistent numerical simulations of wave propagation in magnetoplasmas of Electron cyclotron resonance ion sources (ECRIS). Numerical results can give useful information on the distribution of the absorbed RF power and/or efficiency of RF heating, especially in the case of alternative schemes such as mode-conversion based heating scenarios. Ray-tracing approximation is allowed only for small wavelength compared to the system scale lengths: as a consequence, full-wave solutions of Maxwell-Vlasov equation must be taken into account in compact and strongly inhomogeneous ECRIS plasmas. This contribution presents a multi-scale temporal domains approach for simultaneously including RF dynamics and plasma kinetics in a “cold-plasma”, and some perspectives for “hot-plasma” implementation. The presented results rely with the attempt to establish a modal-conversion scenario of OXB-type in double frequency heating inside an ECRIS testbench.

Highlights

Three-dimensional self-consistent numerical simulation of full-wave RF fields in inhomogeneous non-uniformly magnetized Electron cyclotron resonance ion sources (ECRIS) plasma is a big challenge
This paper describes three-dimensional self-consistent numerical simulations of wave propagation in magnetoplasmas of Electron cyclotron resonance ion sources (ECRIS)
Ray-tracing approximation is allowed only for small wavelength compared to the system scale lengths: as a consequence, full-wave solutions of Maxwell-Vlasov equation must be taken into account in compact and strongly inhomogeneous ECRIS plasmas

Summary

Introduction

Three-dimensional self-consistent numerical simulation of full-wave RF fields in inhomogeneous non-uniformly magnetized ECRIS plasma is a big challenge. A criticality in microwave-heated magnetoplasmas occurs near the resonance regions, where the plasma becomes a spatial dispersive medium, and the hot magnetized plasmas response has to be considered In this case, the dielectric tensor depends on the wave vector and the wave solution needs to be calculated by means of iterations. The kinetic code solves equation (2) for each simulated particle applying the relativistic Boris scheme [10, 14]: the calculation stops as soon as all the particles hit the chamber walls, while at each time step particles positions are stored in a matrix forming a 3D density map This map is the output of the kinetic code, and, once rescaled to real values, is used as local electron density ne(x,y,z) to compute again the electromagnetic field {E(r), H(r)}. Hereby we show results up to step 1, i.e. after the evaluation of the magnetized plasma action on RF and viceversa

Full-Wave simulation strategy

Numerical Results and Discussion

Electromagnetic field applied to the particles

Conclusions