Plasma and Fusion Research

Volume 18, 2401054 (2023)

Regular Articles

Initial Properties of Steady State RF Plasma Source by Two Turn Flat Loop Antenna for DEMO Relevant Divertor Simulation Experiment
Takumi SETO, Naomichi EZUMI, Reina MIYAUCHI, Naoki SHIGEMATSU, Takuma OKAMOTO, Satoshi TAKAHASHI, Kosuke TAKANASHI, Mafumi HIRATA, Satoshi TOGO, Mizuki SAKAMOTO, Takeru FURUKAWA1) and Shunjiro SHINOHARA2)
Plasma Research Center, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan
Kobe University, Kobe, Hyogo 657-8501, Japan
Tokyo University of Agriculture and Technology, koganei, Tokyo 184-8588, Japan
(Received 9 January 2023 / Accepted 15 March 2023 / Published 22 June 2023)


To study DEMO divertors, some linear devices have attempted to create DEMO-grade high-density steady-state divertor simulation plasma in a stronger magnetic field. Helicon plasma sources using a flat-type antenna, which are one of the methods of radio frequency (RF) plasma generation in magnetic field, are expected to achieve this. In this study, we developed a new RF plasma source with a two-turn flat-loop antenna with RF sources having a maximum output power of 30 kW in continuous waves. A two-turn flat-loop antenna is expected to have a large-diameter discharge, and its radial density profile can be controlled. In addition, a water-cooled, double-disc quartz window unit was installed for a high-density, high-power discharge. In the initial experiment, argon and hydrogen plasmas were generated, and the integrity of the new device up to 5 kW, was confirmed in a discharge experiment. The magnetic field conditions were changed in this experiment, and a mode change from capacitively coupled plasma (CCP) to inductively coupled plasma (ICP) during argon discharge was observed. Under the experimental conditions of this study, neither argon nor hydrogen produced helicon plasma. This study hereby, discusses the plasma characteristics and provides guidelines for future development.


divertor, linear device, plasma source, RF plasma, helicon plasma, argon, hydrogen

DOI: 10.1585/pfr.18.2401054


  • [1] N. Ohno, Plasma Phys. Control. Fusion 59, 034007 (2017).
  • [2] M. Sakamoto et al., Nucl. Mat. Energy 12, 1004 (2017).
  • [3] N. Ezumi et al., Nucl. Fusion 59, 066030 (2019).
  • [4] E.M. Hollmann, A. Yu. Pigarov and Z. Yan, J. Nucl. Mater 363-365, 359 (2007).
  • [5] R. Perillo et al., Phys. Plasmas 26, 102502 (2019).
  • [6] N. Asakura et al., Nucl. Fusion 61, 126057 (2021).
  • [7] K. Okano et al., Fusion Eng. Des. 136, 183 (2018).
  • [8] S. Shinohara, Adv. Phys. 3, 1420424 (2018).
  • [9] S. Shinohara and T. Tanikawa, Rev. Sci. Instrum. 75, 1941 (2004).
  • [10] S.C. Thakur et al., Plasma Sources Sci. Technol. 30, 055014 (2021).
  • [11] N. Ezumi, Contrib. Plasma Phys. 48, 5 (2008).
  • [12] S.C. Thakur et al., IEEE Trans. Plasma Sci. 43, 2754 (2015).
  • [13] S. Waseda et al., Plasma Fusion Res. 9, 3406125 (2013).
  • [14] K. Kondo et al., J. Appl. Phys. 27, 1560 (1988).
  • [15] B.P. Lavrov and A.V. Pipa, Opt. Specrosc. 92, 655 (2002).