Ion source terms effect on collisional plasma sheath characteristics with non-extensively distributed electrons
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Ion source terms effect on collisional plasma sheath characteristics with non-extensively distributed electrons Mohamed El Bojaddaini1,a
, Hassan Chatei2
1 Physics Department, Faculty of Science and Techniques, Abdelmalek Essaadi University, Al-Hoceima,
Morocco
2 Laboratory of Physics of Matter and Radiations, Physics Department, Faculty of Science,
University Mohammed I, Oujda, Morocco Received: 25 December 2019 / Accepted: 17 August 2020 © Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A one-dimensional fluid model of an unmagnetized collisional plasma sheath consisting of q-non-extensive electrons and singly charged positive ions with finite temperature is developed and presented. The ions are described by the fluid model, which is based on the continuity and momentum equations of ions, while the electrons are considered obeying non-extensive distribution according to the Tsallis statistics. In this work, different ion source terms are used in order to compare their contribution. The modified Bohm sheath criterion is determined for different source terms to specify the ion velocity at sheath entrance. The model equations are solved numerically in the plasma-wall transition region. The effect of ion source terms on the collisional electropositive plasma sheath characteristics such as ion and electron density, electric potential, ion velocity, sheath width and space charge is investigated. The influence of the ionization frequency parameter on the sheath behavior has also been studied. The results obtained show a strong impact of ion source terms on the plasma sheath structure. It is also shown that the ion source terms effect increases significantly when the ionization frequency parameter increases.
1 Introduction It is well known that when a plasma is in contact with a material wall, which is the case of laboratory plasmas used for all practical applications, the wall is bombarded by electrons and is negatively charged with respect to the bulk of the plasma due to high mobility of electrons compared with that of ions. Therefore, an electric field emerges between the wall and the plasma, which results in an acceleration of the ions toward the wall and forces the electrons toward the plasma. Consequently, a thin layer characterized by the excess of positive space charge is created in front of the wall to balance the flow of the ions and electrons into the wall. This non-neutral layer is called plasma sheath and has a few Debye lengths width [1]. Plasma sheath is one of the most complex issues in plasma physics. It is enriched with a variety of physical and chemical phenomena, the understanding of which is a major stake for the control of industrial processes using the plasma–surface interaction. Hence, the study of plasma sheath layer characteristics is crucial because of the tremendous importance of this
a e-mail: [email protected] (corresponding author)
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Eur. Phys. J. Plus
(2020) 135:680
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