Anisotropic Electron Heating in an Electron Cyclotron Resonance Thruster with Magnetic Nozzle

TL;DR

This study uses advanced simulations to analyze how electromagnetic waves heat electrons anisotropically in an ECR thruster with a magnetic nozzle, revealing localized heating effects and trapped electron populations.

Contribution

It introduces a PIC simulation approach with a semi-Lagrangian Maxwell solver to investigate electron heating mechanisms in an ECR thruster with magnetic confinement.

Findings

Anisotropic electron heating occurs only inside the coaxial chamber.

A trapped electron population with higher perpendicular energy exists in the plume.

Heating is localized along a Doppler-broadened zone.

Abstract

In a grid-less Electron Cyclotron Resonance (ECR) plasma thruster with a diverging magnetic nozzle, the magnitude of the ambipolar field accelerating the positive ions depends of the perpendicular energy gained by the electrons. This work investigates the heating of the electrons by electromagnetic waves, taking their bouncing motion into account in a confining well formed by the magnetic mirror force and the electrostatic potential of the thruster. An electromagnetic Particle-In-Cell (PIC) code is used to simulate the plasma in a magnetic field tube. The code's Maxwell solver is based on a semi-Lagrangian scheme known as the Constrained Interpolation Profile (CIP) which enables larger time steps. The results show that anisotropic plasma heating takes place exclusively inside the coaxial chamber, along a Doppler-broadened zone. It is also shown that a trapped population of electrons with a larger perpendicular energy exists in the plume.