Doctoral defence in Physics - Andrea Proto
Ph.D. student: Andrea Proto
Dissertation title: Electron power absorption in electronegative capacitively coupled discharges
Dr. Aranka Derzsi, Senior Research Fellow, Institute for Solid State Physics and Optics, Complex Fluids Department, Wigner Research Centre for Physics, Budapest, Hungary
Dr. Pascal Chabert, Professor, Laboratoire de Physique des Plasmas Ecole Polytechnique, Palaiseau, France
Advisor: Dr. Jón Tómas Guðmundsson, Professor at the Faculty of Physical Science, University of Iceland
Dr. Viðar Guðmundsson, Professor at the Faculty of Physical Science, University of Iceland
Dr. Ágúst Valfells, Professor and Department Chair at the Department of Engineering, Reykjavík University
Chair of Ceremony: Dr. Einar Örn Sveinbjörnsson, Professor and the Head of the Faculty of Physical Sciences, University of Iceland
The aim of this work is to explore the role of electronegativity and the electron power absorption mechanism in electronegative capacitively coupled oxygen and chlorine discharges. The fundamental mechanisms underlying the electron heating and the electron power absorption have been widely studied and discussed over the past decades. However, a fully consistent and general mathematical-physical explanation of the several physical mechanisms involved in the electron power transfer mechanism are still lacking. This is in particular true for the electronegative capacitively coupled discharges. These difficulties are related to the overall complexity of these systems and to the behavior of the plasma within the sheath region. In the first part the quenching probability of the single metastable molecule O2 (a1 ∆g ) on the electrodes is varied, along with the secondary emission yield for ion impact and electron reflection for a capacitively coupled oxygen discharge, in order to explore their influence on the electronegativity and the electron power absorption. In the second part, we explored the behavior of both the electric field and the electron power absorption in a capacitively coupled oxygen discharge within the pressure range 1.3 – 13 Pa and in a capacitively coupled chlorine discharge within the pressure range 1 – 50 Pa, by comparing the physical quantities coming from the simulations to Boltzmann term analysis applied to the simulation
outputs. This allows us to determine the processes that contribute to electron power absorption. In oxygen discharge the electron power absorption mechanism depends on the discharge pressure. The electron power absorption is due to pressure heating and Ohmic heating. At low pressure (1.3 Pa) the electron temperature gradient term contributes to electron heating and the ambipolar term to electron cooling while the opposite is true at 13 Pa. The chlorine discharge is highly electronegative and at pressures > 10 Pa the Ohmic heating contribution to electron heating dominates. At lower pressure there is also a contribution from the electron temperature gradient.
About the doctoral candidate:
Andrea Proto completed a master degree in Ttheoretical Physics from the University of Pisa in 2017 a bachelor degree in Physics from the University of Pisa in 2012. He started his doctoral studies at the University of Iceland in 2018.
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