Propagation of ion-acoustic wave in the presheath region of a plasma sheath system

Abstract

In a bounded plasma system, the plasma reorganizes itself to attain an equilibrium state through ambipolar flows. Conventional understanding of the collisional presheath is that it is the result of ambipolar processes, which establish a time-independent plasma sheath potential profile. The associated steady-state electric field accelerates the ions to the ion-acoustic speed at the main Debye sheath entrance. The inadequacy in this mechanism is that it fails to explain the observation of the excess energy transmission factors for electrons and ions. Another more likely mechanism which can be invoked is that both collisional and collisionless presheaths are sustained partially by the collective process of ion-acoustic waves (IAWs). It is possible that the turbulent development of an IAW will yield not only particle fluxes of the right value, but also energy fluxes of the observed anomalous value. The first step in proceeding with this idea is to investigate the linear response of IAWs in a generalized collisional, source-driven, plasma presheath. Matrix formulation under eigenvalue treatment has been used for linear eigenmode characterization of the acoustic-wave propagation in the presheath region.