A computationally assisted spectroscopic technique to measure secondary electron emission coefficients in radio frequency plasmas
| Autor: | Mark Koepke, Zoltan Donko, Aranka Derzsi, Manaswi Daksha, Julian Schulze, Edmund Schuengel, Birk Berger, Ihor Korolov |
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| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
010302 applied physics
Argon Materials science Acoustics and Ultrasonics chemistry.chemical_element FOS: Physical sciences Electron Plasma Condensed Matter Physics 01 natural sciences Secondary electrons Physics - Plasma Physics 010305 fluids & plasmas Surfaces Coatings and Films Electronic Optical and Magnetic Materials Plasma Physics (physics.plasm-ph) chemistry Physics::Plasma Physics Ionization Secondary emission 0103 physical sciences Plasma diagnostics Atomic physics Excitation |
| Popis: | A Computationally Assisted Spectroscopic Technique to measure secondary electron emission coefficients ($\gamma$-CAST) in capacitively-coupled radio-frequency plasmas is proposed. This non-intrusive, sensitive diagnostic is based on a combination of Phase Resolved Optical Emission Spectroscopy and particle-based kinetic simulations. In such plasmas (under most conditions in electropositive gases) the spatio-temporally resolved electron-impact excitation/ionization rate features two distinct maxima adjacent to each electrode at different times within each RF period. While one maximum is the consequence of the energy gain of electrons due to sheath expansion, the second maximum is produced by secondary electrons accelerated towards the plasma bulk by the sheath electric field at the time of maximum voltage drop across the adjacent sheath. Due to these different excitation/ionization mechanisms, the ratio of the intensities of these maxima is very sensitive to the secondary electron emission coefficient $\gamma$. This sensitvity, in turn, allows $\gamma$ to be determined by comparing experimental excitation profiles and simulation data obtained with various $\gamma$-coefficients. The diagnostic, tested here in a geometrically symmetric argon discharge, yields an effective secondary electron emission coefficient of $\gamma = 0.066 \pm 0.01$ for stainless steel electrodes. |
| Databáze: | OpenAIRE |
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