Plasma and Fusion Research

Volume 18, 2402043 (2023)

Regular Articles

Visible-Light Imaging of the Super-Alfvénic/Sonic Collisional Merging Process of Field-Reversed Configurations with a Contrast Medium-Mixed Plasmoid
Daichi KOBAYASHI, Taichi SEKI, Tomohiko ASAI, Keisuke HIRAMA, Reiji HAYATA, Kota ARAOKA, Tsutomu TAKAHASHI and Jordan MORELLI1)
College of Science and Technology, Nihon University, Tokyo 101-8308, Japan
1)
Department of Physics, Engineering Physics & Astronomy, Queen's University, Kingston, Ontario K7L 3N6, Canada
(Received 9 January 2023 / Accepted 4 April 2023 / Published 5 June 2023)

Abstract

The collisional merging formation process of field-reversed configurations (FRCs) was observed by using a recently developed spectroscopy system. The shape and boundary of the two plasmoids during the merging process were visualized by the “contrast medium” mixing. One of the two initial plasmoids captured a small amount of contrast medium (e.g., helium) diffused in a part of the vacuum vessel during the translation process. The contrast medium-mixed plasmoid merged with the other plasmoid which is without a contrast medium. The contrast-enhanced shape and internal structure of two plasmoids were observed using the spectroscopic systems with the line spectrum of the contrast medium ion. The emission distribution of the contrast medium ions inside the plasmoid was verified by visible-light computed tomography, which revealed that the contrast medium ions were captured only inside one plasmoid. In addition, the emission distribution resembled the density profile in the rigid rotor model, which is a pressure equilibrium model of FRCs. After the collision, the contrast medium ions diffused into the other side. This suggests the beginning of the merging with the plasmoid on the other side. The optically evaluated timescale of the merging was comparable with that observed by the internal magnetic measurements.

Keywords

field-reversed configuration, high beta plasma, FRC merging, spectroscopic imaging, magnetic reconnection

DOI: 10.1585/pfr.18.2402043

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References

  • [1] M. Tuszewski, Nucl. Fusion 28, 2033 (1988).
  • [2] L.C. Steinhauer, Phys. Plasmas 18, 070501 (2011).
  • [3] T. Asai, D. Kobayashi, T. Seki, Y. Tamura, T. Watanabe et al., Nucl. Fusion 61, 096032 (2021).
  • [4] M.W. Binderbauer, H.Y. Guo, M. Tuszewski, S. Putvinski, L. Sevier et al., Phys. Rev. Lett. 105, 045003 (2010).
  • [5] H. Gota, M.W. Binderbauer, T. Tajima, A. Smirnov, S. Putvinski et al., Nucl. Fusion 61, 106039 (2021).
  • [6] D. Kobayashi and T. Asai, Phys. Plasmas 28, 022101 (2021).
  • [7] T. Asai, T. Takahashi, J. Sekiguchi, D. Kobayashi, S. Okada et al., Nucl. Fusion 59, 056024 (2019).
  • [8] H. Tomuro, T. Asai, K. Iguchi, T. Takahashi and Y. Hirano, Rev. Sci. Instrum. 81, 10E525 (2010).
  • [9] T. Seki, T. Yamanaka, T. Asai, D. Kobayashi, T. Takahashi et al., Rev. Sci. Instrum. 93, 103520 (2022).
  • [10] D. Kobayashi, T. Seki, T. Asai, T. Takahashi J. Morelli et al., Rev. Sci. Instrum. 93, 103526 (2022).
  • [11] W. Lochte-Holtgreven Plasma Diagnostics (AIP press, New York, 1995) p. 184.
  • [12] T. Takahashi, H. Gota, T. Fujino, M. Okada, T. Asai et al., Rev. Sci. Instrum. 75, 5205 (2004).
  • [13] W.T. Armstrong, R.K. Linford, J. Lipson, D.A. Platts and E.G. Sherwood, Phys. Fluids 24, 2068 (1981).