A Fully Kinetic Self-Similar Particle Simulation of Ion Thruster Discharge Chamber

Abstract

A 2D fully kinetic particle-in-cell plus Monte Carlo collision (PIC/MCC) model was developed to study the physical characteristics of the ion thruster discharge chamber <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> . The PIC method is used to track the four major particles in the discharge chamber, including primary electrons, secondary electrons, ions and neutral atoms. The MCC method is used to describe the collisions between particles, the elastic, excitation and ionization collisions for electrons, and the elastic and charge exchange collisions for ions are considered. The motion of charged particles is affected by dynamic electric field and external magnetic field, in which the electric field is obtained by solving Poisson equation with DADI (Dynamic Alternating Direction Implicit Iteration) method <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Such a full kinetic model is challenging because it requires a huge number of grids and computation time. Therefore, a self-similar scaling scheme proposed by Taccogna is used to simplify the discharge chamber model <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . This scaling scheme reduces the size of discharge chamber while keeping the main physical parameters (Knudsen number, specific impulse, and electron magnetization process) unchanged. It shortens the computation time and is helpful for analyzing the actual physical characteristics of the discharge chamber. In this work, a 20-cm diameter axisymmetric cylindrical model with three rings of magnets is established to test the discharge chamber. The steady-state results such as the electric potential distributions and particle number density distributions are obtained, and the neutral atom density variation and its effects on plasma distribution are discussed.