This proposal is a renewal of NSF grant ECS-8314488 on a Study of Nonlinear Wave Plasma Interaction. The experiments will concentrate on laboratory studies of two dimensional and time dependent plasma sheaths in DC and RF plasmas. Specific attention will be paid to the understanding of sheaths associated with Plasma Source Ion Implantation (PSII), a technique the PI's have recently begun to develop. Experiments will take advantage of previous emissive probe diagnostic development which allow plasma potential measurements with good spatial and temporal resolution. Studies of the spatial and temporal characteristics of DC, pulsed and sinusoidal sheaths will be conducted. Experiments will build on recent results which indicate that one-dimensional descriptions of sheaths cannot explain the self-consistent plasma potential far from electrodes or plasma potential dips near positive electrodes in filament produced plasmas. Continued development of PSII, which implants ions by applying large negative pulses to materials immersed in plasmas, requires an understanding of both two dimensional and pulsed sheath effects. Laboratory experiments will be combined with small scale efforts on computer modeling of experimental results. This renewal proposal will concentrate on laboratory studies oftwo dimensional plasma sheaths - one example of nonlinear plasma structures. Sheaths are non-neutral plasma regions that are almost always present at plasma boundaries and are sometimes found disconnected from boundaries, i.e. double layers. They are among the oldest known phenomena in plasmas yet many important aspects of them are poorly understood. They play an important role in many commercial devices and applications, and hence investigations of sheath phenomena can have considerable economic impact.
