Veröffentlichungen und Präsentationen

Microwave plasma sources with a resonant cavity have been widely used in microwave electrothermal thrusters as an electric propulsion device, in which free-floating plasma is ignited and sustained in a propellant gas. The resonant cavity microwave plasma has become increasingly attractive for material processing under medium to atmospheric pressures requiring a high growth rate due to its prominent advantages such as easy electrical breakdown and no electrodes, i.e., no contamination, etc.

In this work, a simulation study of microwave plasma sources with a resonant cavity is performed using COMSOL Multiphysics^® simulation software. 2.45 GHz microwave-excited plasmas are generated by a power of 100 W in pure argon and Ar/O₂ mixtures. TM₀₁₁ is applied for the resonant cavity, which causes that the electric field has the highest intensity on the axis at the two ends of the cavity. The gas pressure is 40 Torr and the gas temperature is assumed to be 300 K. 14 kinds of species involving dimer species of argon and 34 kinds of chemical reactions are considered.

The present work reveals the variation of electric field induced by the electromagnetic wave during the discharge. The effect of the small amount of oxygen in Ar/O₂ on the discharge is examined. The skin depth layer near the plasma surface, in which power is transferred from the electromagnetic field to the plasma electrons, is presented and the collisional skin depth is estimated.

Keywords: Microwave plasma, Resonant cavity, Collisional skin depth, COMSOL Multiphysics® simulation software

References

[1] M. M. Micci, S. G. Bilén, and D. E. Clemens, History and Current Status of the Microwave Electro- thermal Thruster, in Progress in Propulsion Physics, EUCASS Proceedings Series 1, 2009: 425-438.

[2] H. Tahara, K. Minami, T. Yasui, K. Onoe, Y. Tsubakishita and T. Yoshikawa, Jpn. J. Appl. Phys. 32, 1993: 1822-1828.

[3] M. S. Yildiz and M. Celik, AIP Advances 7, 2017: 045021.

[4] N. Balcon, G. J. M. Hagelaar, and J. P. Boeuf, IEEE Trans. Plasma Sci. 36 (5), 2008: 2782-2787.

[5] A. Meiners, Development, characterization and applications of non-thermal air plasma jets, Dissertation, Georg-August-Universität Göttingen, 2011.