Modeling Electron Impact Ionization

Electron impact ionization is the mainstay for plasma-based flow control actuators because it actuates in less than microseconds and the electrode configuration can be made nonintrusive to oncoming stream. In addition, when the actuator is not needed, unlike most mechanical flow control devices, it will not be parasitic and degrade performance of aerospace vehicles. The space charges induce an additional electric field potential that makes it different from the corona discharge. This chapter presents the best physics-based, multifluid model for the electron impact ionization. The physics for electron impact ionization is well known through the luminary contributions by Townsend, the ionization is evolving from the electrons collision, secondary emission, and avalanche. The secondary emission from cathode arises as controlling mechanism for all electron impact ionization. A high concentration of positive charges over an electrode creates an extremely high electrical field potential, which is comparable to the magnitude in a nuclei.