Plasma and Fusion Research

Volume 15, 2405032 (2020)

Regular Articles

Atomic and Molecular Processes in Plasma Decomposition Method of Hydrocarbon Gas
Makoto OYA, Ryosuke IKEDA1) and Kazunari KATAYAMA
Faculty of Engineering Science, Kyushu University, Fukuoka 816-8580, Japan
1)
Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Fukuoka 816-8580, Japan
(Received 28 November 2019 / Accepted 19 March 2020 / Published 11 May 2020)

Abstract

In order to understand the decomposition process of hydrocarbons in a hydrogen (H) plasma, a Monte Carlo simulation of collisional transport of a methane (CH4) molecule was developed. The model simulates collision reactions with plasma ions and electrons (including dissociation, excitation, ionization, and charge exchange) and elastic collisions with residual H2 gas. The interaction with a surrounding wall was also considered (reflection from the wall, deposition on the wall, and reemission of carbon (C) and hydrocarbons (CHx) by physical and chemical sputtering). In a low-temperature plasma, because the decomposition process was mainly dominated by charge exchange with plasma ions followed by dissociative recombination with electrons, many neutral C and CHx species were obtained. At high temperature, the ionized Cy+ and CHx+ species were the dominant ones because of the dissociative ionization and excitation by electrons. Comparable to our previous experiment, the calculated decomposition rate of CH4 into neutral and ionized C atoms was ∼50% for a temperature of 15 eV and a density of 3.5 × 1017 m−3. Nevertheless, the calculated distribution of C and CHx deposits on the vessel wall were localized in the upstream of the plasma, which was different from the experimental setup.

Keywords

fusion reactor, hydrogen isotope recovery, hydrocarbon, plasma decomposition method, Monte Carlo simulation, ionization, dissociation, elastic collision, reflection, sputtering

DOI: 10.1585/pfr.15.2405032

Full Text

PDF format (1.8Mbytes) PDF Download

References

  • [1] Z. Wang et al., Rev. Sci. Instrum. 88, 093501 (2017).
  • [2] K. Katayama et al., Fusion Eng. Des. 82, 1381 (2010).
  • [3] S. Kasahara, Fusion Sci. Technol. 60, 1487 (2011).
  • [4] S. Kasahara, Master thesis, Kyushu University, 2011, unpublished.
  • [5] R.K. Janev and D. Reiter, Rep. Forshungszentrum Julich, Jul-3966 (2002).
  • [6] T. Motohiro and Y. Taga, Thin Solid Films 112, 161 (1984).
  • [7] K. Shiraishi and S. Takamura, J. Nucl. Mater. 176&177, 251 (1990).
  • [8] K. Ohya, AIP Conf. Proc. 1237, 47 (2010).
  • [9] J. Roth, J. Nucl. Mater. 266-269, 51 (1999).
  • [10] K. Ohya et al., 2010 Fusion Energy Conference, IAEA, THD/P3-04.
  • [11] W. Eckstein et al., Rep. Max-Planck-Institut für Plasmaphysik, IPP 9/82, 1993.