Grant: Discovery Grants Program - Individual

Plasmas are (weakly) ionised gases consisting of positive ions and free electrons. They can be found everywhere from astrophysical environment (stars, interstellar medium) to energy production and industrial applications (ion implantation, plasma etching, production of nanoparticles, Hall-effect thrusters, fusion devices, etc). In devices used for laboratory experiments or industrial applications, plasmas are confined and bound by the walls of the vessel. The plasma-wall interface (referred to as the plasma sheath) is a narrow region in which the quasi-neutrality condition applicable to bulk plasmas does not hold. The sheath plays a major role in determining the plasma discharge parameters and affects the flows of particles and the heat to the surface. Plasma-surface (or plasma-wall) interactions are thus common to all laboratory plasma systems. Plasmas containing large solid particles (dusts) are called dusty plasmas. Due to interactions with the plasma electrons and ions, dusts acquire net electric charges. In laboratory low-temperature plasmas, dusts are usually charged negatively due to high electron mobility. Sheaths form in the vicinity of dusts affecting plasma species fluxes on dust surfaces and dust transport. Understanding dust interactions with the surrounding plasma requires a good comprehension of sheath formation around small floating solid grains and an accurate knowledge of local plasma parameters (electric fields, ion velocity distribution function). Hence, the problem can be widened to a more general study of plasma-surface interactions (PSI), plasma-dust interactions being only one aspect of it. While sheath formation in front of conducting surface in non-magnetised collision-less low-temperature plasma is known, sheath formation in front of surfaces emitting particles or in magnetised plasma is still poorly understood. The long term objectives of the proposed research are to gain deep understanding on sheath formation and on the transport and dynamics of dust particles in plasmas. They can be formulated under two major themes: (i) Electric fields and Ion velocity distribution function in the sheath, (ii) Dynamics of dust particles in plasmas. Short term objectives include: (1) Studies of sheaths parameters in front of different surfaces using state-of-the-art laser based diagnostics; (2) Dynamics and transport of dusts in conventional gas discharges; (3) Dynamics, transport and lifetime of dust particles in tokamaks; (4) Theoretical and numerical studies on sheath formation in front of emissive surfaces in plasmas. HQPs will be involved in all steps of this research program which focus on a highly applicable area of plasma physics and technology.