Plasma detachment mechanisms in a magnetic nozzle

Abstract

An axisymmetric model of the supersonic expansion of a collisionless, totally ionized plasma in a divergent magnetic nozzle and the DIMAGNO simulation code are being used to study the plasma detachment from the guiding magnetic field, taking into account the effects of the induced magnetic field generated by the plasma electric currents. The azimuthal electric currents carried by the plasma from the discharge chamber or created within the nozzle are the central feature for both thrust generation and plasma detachment. These currents are mainly electronic and have a globally diamagnetic character, as their induced field lowers the total field around the axis and increases nozzle divergence rate. This paper focuses on the role of the plasma-generated magnetic field and the detachment issue, particularized for the case of a helicon thruster (although conclusions extracted herein might be easily generalizable to other thruster types). A viable alternative detachment mechanism based on plasma self-demagnetization is investigated. * Student, AIAA Student Member (mario.merino@upm.es) † Professor, AIAA Member

Two-Fluid and PIC-Fluid Code Comparison of the Plasma Plume in a Magnetic Nozzle

“…For instance, the plasma-induced magnetic field, which can play an important role in detachment, can be taken into account with a simple iteration procedure. 15 The influence of collisions was recently studied with a perturbation analysis. 9,16 The dominant electron inertia effects (finite Larmor radius effects) can be easily incorporated into the model.…”

Influence of Electron and Ion Thermodynamics on the Magnetic Nozzle Plasma Expansion

“…In the following, the induced magnetic field that the plasma generates is neglected, assuming a low-plasma β (although it can be easily included with an iterative approach [40]), keeping only the applied magnetic field, which satisfies r B = ∇ψ × 1 θ , with ψ the magnetic streamfunction.…”

Two-dimensional plasma expansion in a magnetic nozzle: Separation due to electron inertia

“…For the simulations presented here, we will consider the applied magnetic field generated by a solenoid of radius R S ¼ 3:5R and extending from z ¼ À2.5 R to z ¼ 2.5 R, Fig. 1(a), and we will restrict the analysis to a low-density plasma so that the induced magnetic field is negligible (its inclusion can be carried out iteratively 16 ). Thus, the throat is located at z ¼ 0 and að0; rÞ ¼ 0.…”