Two dimensional particle-in-cell simulation model for Hall type thrusters

Abstract

In this master's thesis, a two-dimensional model of a Hall type thruster, was developed, to include secondary electron emission at the wall, ion recombination at the wall, diffuse reflection for neutrals bouncing off of the wall, wall potential calculation based on the collected wall charge and a steady state non-uniform magnetic field found in Hall thruster configurations. The model used a non-collisional, two dimensional in regular space and three dimensional in phase space, particle-in-cell (PIC) formulation for simulation of the plasma, while a separate model accounted for particle collisions, using Argon-electron elastic, excitation and ionization cross-sections. The collision model used an electron-neutral collision frequency on the same order as the electron plasma frequency, which made the neutral density to be on the order of 1025m- 3 Such a large neutral density implied that ion-neutral interactions, typically neglected in Hall thrusters, must also be taken into account. However, in this simulation they were neglected. Proceeding forward, the simulation size was 50x20 Debye lengths. Cell size was half of the plasma Debye length, in both dimensions. Time step was based on the condition that the electron gyroradius be ten times the Debye length, for a given electron temperature of 10 eV and maximum magnetic field of 0.8 Tesla, which made the electron density to be on the order of 10-2 0m - 3 . Neutral particle injection rate assumed a particle temperature of 1000K. Electron injection rate from the cathode equaled the electron collection rate at the anode. Ion and neutral mass were set to 1000 times that of the electron mass, in an attempt to accelerate plasma phenomena. Simulation of the model proceeded for 50000 iterations or 7.11 x 10- 9 seconds, which was equivalent to three ion passes through the simulation. Results analysis consisted of studying simulation output at different points in time. It was concluded that the simulation here does not simulate an actual Hall thruster, but introduces some computer models for it.