Plasma and Fusion Research

Volume 17, 2402027 (2022)

Regular Articles

Isotope Effect for Plasma Detachment in Helium and Hydrogen/Deuterium Mixture Plasmas
Xinyue GUO, Hirohiko TANAKA, Shin KAJITA1), Noriyasu OHNO, Shogo HATTORI and Keiji SAWADA2)
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
1)
Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8603, Japan
2)
Graduate School of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
(Received 6 January 2022 / Accepted 24 February 2022 / Published 13 May 2022)

Abstract

To investigate the isotope effect on the plasma detachment in helium (He) and hydrogen (H)/deuterium (D) mixture plasmas, we performed H2, D2 or He gas puffing into He plasma in the linear plasma device NAGDIS-II. Axial distributions of electron density (ne) and electron temperature (Te) were obtained using a movable Langmuir probe. Additionally, optical emission spectroscopy (OES) was applied to measure axial distributions of Balmer lines and He I lines. When the neutral gas pressure was high (ΔPn = 7∼10 mTorr), ne distribution in He-D2 mixture plasma was similar to that in pure He plasma, showing a sharp decrease at the downstream region where Te < 1 eV. In contrast, in He-H2 mixture plasma, a decrease in ne was confirmed from upstream region where Te > 1 eV. The upstream Hα/Hγ in He-H2 plasma was significantly larger than the Dα/Dγ in He-D2 plasma at the same Te. This result indicated that molecular activated recombination (MAR) processes significantly occurred in He-H2 plasma, while electron-ion recombination (EIR) processes were dominant in He-D2 and pure He plasmas.

Keywords

detached helium plasma, hydrogen/deuterium puffing, isotope effect, molecular activated recombination, electron-ion recombination

DOI: 10.1585/pfr.17.2402027

Full Text

PDF format ([an error occurred while processing this directive]bytes) PDF Download

References

  • [1] M. Bessenrodt-Weberpals et al., Nucl. Fusion 33, 1205 (1993).
  • [2] C.F.Maggi et al., Plasma Phys. Control. Fusion 60, 014045 (2018).
  • [3] H. Takahashi et al., Nucl. Fusion 58, 106028 (2018).
  • [4] B. Sieglin et al., Plasma Phys. Control. Fusion 58, 055015 (2016).
  • [5] H. Tanaka et al., Nucl. Mater. Energy 19, 378 (2019).
  • [6] M. Osakabe et al., Nucl. Fusion 62, 042019 (2022).
  • [7] M. Kobayashi et al., Nucl. Fusion 62, 056006 (2022).
  • [8] A.S. Kukushkin et al., Nucl. Mater. Energy 12, 984 (2017).
  • [9] N. Ohno et al., Phys. Rev. Lett. 81, 818 (1998).
  • [10] N. Ohno et al., Nucl. Mater. Energy 19, 458 (2019).
  • [11] Y. Hayashi et al., Contrib. Plasma Phys. 59, e201800088 (2019).
  • [12] D. Nishijima et al., Plasma Phys. Control. Fusion 44, 597 (2002).
  • [13] R.K. Janev, Atomic and Molecular Processes in Fusion Edge Plasmas (Plenum Press ⋅ New York and London 13350).