Session WF1: Perspective in Current Trends and Future of Plasma Science I

Live

Low-temperature plasmas have always been driven by industry, from lighting and gas lasers to materials processing for microelectronics, or by potential new applications like cancer treatment or agriculture. In all of the above, plasma science has been highly interdisciplinary and plasma physics was only a (small) part of the all picture. Atomic and molecular physics, spectroscopy and lasers, plasma chemistry, surface science, and even biology were at least as important as basic plasma physics. Plasma thrusters have recently become the main (and soon the only?) engines of newly launched satellites. Even if the market is much smaller than microelectronics, there is a considerable industrial interest in plasma science to improve the thruster performances. Historically, plasma physics has been the most important aspect of the research, and some of the plasma physicists interested in this topic had background in fusion or space plasmas, where instabilities and anomalous or turbulent transport is crucial. In this talk, it will be shown that other areas of plasma science have become extremely important in the field of plasma thrusters. New designs and new propellant based on molecular gases are considered or used and consequently many topics like plasma-surface interactions, plasma chemistry, negative ions, are now being investigated. Plasma thrusters are therefore a fascinating playground for low-temperature plasma scientists.   

Live

Plasma technology utilizing high-frequency sources has tremendous effects on society via assisting the development of modern electronic circuits, photovoltaic devices, medical implants and techniques, etc. The talk will address the question “how deeply do we really understand the physics of these plasma sources?” It will be shown that, in contrast to common belief, a variety of fundamental aspects is not well understood. As new experimental, theoretical and simulation approaches result in significantly deeper insights, aiding both the advance of physics and the optimization of the manifold applications, some misconceptions and new fundamental research questions could be revealed recently. Examples related to electron power absorption, charged particle dynamics, and the formation of particle distribution functions will be discussed. Efficient, knowledge-based control of these characteristics, e.g., by using hybrid plasma sources and/or voltage waveform tailoring has been shown to be possible, and represents an emerging research field in plasma technology. A synergistic combination of state of the art experimental techniques and high-performance computations (based on validated models and verified codes) can lead to another level of understanding of these plasma sources. Experimental approaches provide now access to time resolution well within the radiofrequency excitation periods. Numerical modeling extended to 2D or 3D allows a description of practical plasma sources in the important operation regime where kinetic effects prevail. Modeling relies, however, on elementary data on gas-phase and surface coefficients of which the knowledge is of key importance for obtaining accurate results, particularly in complex and application relevant gas mixtures.   

Live

The translational nature of research in low temperature plasmas places high emphasis on the relationship between fundamental plasma transport properties and the intended application. This is nowhere more true than for plasma-materials interactions. These interactions take many forms, from production of secondary electrons through ion or photon bombardment which then affects the fluxes of those ions and photons; to synergistic self-organization of plasmas that may result from multi-phase interactions or the topography of the surface. The manner of coupling between the surface and the plasma is to some degree a function of the mean-free-path (mfp) for electron and ions, and the surface structures producing the feedback. Plasma-surface interactions in lower pressure plasmas with longer mfp's certainly affect the properties of the plasma, but distributed over a larger volume with weaker feedback. Higher pressure plasmas with smaller mfp's can localize that feedback, leading to greater synergies. Using results from computational modeling, the synergies of interactions of atmospheric pressure plasmas with complex surfaces will be discussed, and contrasted with those occurring at low pressure. The conditions leading to self-organization and pattern-dependent plasma transport will be discussed.