Simulations of plasma sheaths using continuum kinetic models

摘要

Summary form only given. When plasma interacts with a surface, a plasma sheath forms at the interface, which is typically a region of net positive space charge. Ions, accelerated by the electric field in the sheath region, and hot electrons are known to cause emission from the surface. This can have consequences for devices such as Hall thrusters as electron emissions can increase the rate of erosion of the electrodes affecting performance and longevity of the thrusters - an important concern for space-bound missions. The length-scale of sheaths is small in comparison to the undisturbed plasma (on order of the Debye length, λD) yet the sheath has a global effect on plasma and needs to be included self-consistently in computer simulations. This usually means resolving the Debye length and the plasma oscillation frequency, which makes global and complex simulations extremely demanding in terms of the computational cost.We will present simulations of classical sheaths using a continuum kinetic model where we directly solve the Boltzmann equation for each of the ion and electron species using the discontinuous Galerkin method. Furthermore, we will present results of sheaths in the presence of magnetic fields. We will build on the work of Loizu et al. on the magnetic presheath in the cold ion limit, which uses relatively small magnetic field incident angles due to its application to tokamaks. In our work we plan to focus on Hall thruster relevant geometries with magnetic field perpendicular to the surface. We will also extend previous studies of magnetized sheaths and presheaths with warm ions.