Understanding microwave surface-wave sustained plasmas at intermediate pressure by 2D modeling and experiments

An Ar plasma sustained by a surfaguide wave launcher is investigated at intermediate pressure (200-2667Pa). Two 2D self-consistent models (quasi-neutral and plasma bulk-sheath) are developed and benchmarked. The complete set of electromagnetic and fluid equations and the boundary conditions are presented. The transformation of fluid equations from a local reference frame, that is, moving with plasma or when the gas flow is zero, to a laboratory reference frame, that is, accounting for the gas flow, is discussed. The pressure range is extended down to 80Pa by experimental measurements. The electron temperature decreases with pressure. The electron density depends linearly on power, and changes its behavior with pressure depending on the product of pressure and radial plasma size.