The Plasma Sheath as a Nonlinear Element

Abd Elfattah Elgendy, Ralf Peter Brinkmann

DPG Früh­jahrs­ta­gung, Han­no­ver, Ger­ma­ny 08-12 März


P 17.5 The formation of a non-neutral, electron depleted boundary sheath in front of material surfaces is a universal plasma phenomenon; it is due to the facts that i) the electrons in a plasma are much more mobile than the ions, and that ii) the plasma is much larger than its own Debye lenght . The boundary sheath scales with and comprises therefore only a small fraction of the plasma. Yet, it is responsible for many aspects of its macroscopic behavior. A thorough understanding of its properties is therefore of paramount theoretical as well as practical importance. The multitude of scientific research devoted to the sheath bears witness to this statement. This work will focus on the global behavior of the sheath, i.e., the relation between the electrical current through the sheath and the overall voltage drop across it. Effective "lumped element" models will be studied which allow to describe the sheath dynamics in simple, though nonlinear engineering terms like resistance, capacitance, and inductance. It will be investigated how such models can be derived from a more detaild represantation of the sheath physics, and how their properties depend on the parameters of the discharge as a whole. The accuracy of the models will be critically assessed by comparison with more elaborate simulations and also experiments.

Tags: DPG Frühjahrstagung, Hannover, Lumped Circuit Element, Sheath Theory