Anisotropic electron heating in an electron cyclotron resonance thruster with magnetic nozzle

Abstract

In a grid-less electron cyclotron resonance plasma thruster with a diverging magnetic nozzle, the magnitude of the ambipolar field accelerating the positive ions depends on 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 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 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.

ECRA thruster advances: 30W and 200W prototypes latest performances

“…Wachs et al [26] demonstrated that this effect is due to inelastic electron-neutral collisions in the thruster plume, which consume a significant part of the jet power and ultimately decrease the ion energy. Even though the mean free path of an electron is large compared to the size of the plume for pressure levels presented here (from 33 km at 1.2 × 10-7 mbar to 202 m at 2.0 × 10-5 mbar), the pendular motion of a part of the electron population trapped in the plume [34] and the large size of the acceleration region in the plume explain this result [26].…”

“…The H2020 MINOTOR project aims at increasing the Technology Readiness Level (TRL) of the ONERA thruster prototype. All the different aspects of the thruster development were tackled: prototype optimization and testing, numerical simulation tools development [32][33][34], Power Processing Unit (PPU) development, system impact assessment and scaling up with the development of a 200 W thruster. The present paper recounts part of the results obtained during the prototype optimizations and testing studies.…”