Plasma and Fusion Research

Volume 13, 3402031 (2018)

Regular Articles

Response of Plasmas to Tungsten Pellet Injection in Neutral Beam Heated Discharges in Large Helical Device
Tetsutarou OISHI1,2), Shigeru MORITA1,2), Xianli HUANG1), Yang LIU2), Motoshi GOTO1,2) and the LHD Experiment Group1)
1)
National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho, Toki 509-5292, Japan
2)
Department of Fusion Science, SOKENDAI (Graduate University for Advanced Studies), 322-6 Oroshi-cho, Toki 509-5292, Japan
(Received 28 December 2017 / Accepted 19 March 2018 / Published 24 April 2018)

Abstract

Response of plasmas in Large Helical Device (LHD) to the tungsten pellet injection depends on both the total port-through power of the neutral beam injection (NBI) for heating, PNBI, and the line-averaged electron density, ne. The plasma can be sustained in the range of high PNBI and low ne while it collapses in the range of low PNBI and high ne. When the number of tungsten atoms enclosed in a pellet, NW, is small, plasma can survive in low PNBI and high ne range. Parameter space for plasma sustainment after the pellet injection is limited to lower ne range in more outward-shifted magnetic configuration. ne < 4.0 × 1013 cm−3 and NW < 1.2 × 1018 for Rax = 3.60 m, ne < 3.0 × 1013 cm−3 and NW < 8.7 × 1016 for Rax = 3.75 m, and ne < 2.0 × 1013 cm−3 and NW < 3.1 × 1016 for Rax = 3.90 m are appropriate parameter ranges for the plasma sustainment. This suggests that robustness against tungsten injection depends on the magnetic configurations.

Keywords

impurity pellet, plasma spectroscopy, magnetically confined fusion, impurity transport, tungsten

DOI: 10.1585/pfr.13.3402031

Full Text

PDF format (1.7Mbytes) PDF Download

References

  • [1] D.W. Ignat et al., Nucl. Fusion 39, 2137 (1999).
  • [2] R. Neu et al., Nucl. Fusion 45, 209 (2005).
  • [3] J. Roth et al., Plasma Phys. Control. Fusion 50, 103001 (2008).
  • [4] T. Oishi et al., Appl. Opt. 53, 6900 (2014).
  • [5] M.B. Chowdhuri et al., Rev. Sci. Instrum. 78, 023501 (2007).
  • [6] M.B. Chowdhuri, S. Morita and M. Goto, Appl. Opt. 47, 135 (2008).
  • [7] X.L. Huang et al., Rev. Sci. Instrum. 85, 11E818 (2014).
  • [8] H. Nozato et al., Rev. Sci. Instrum. 74, 2032 (2003).
  • [9] T. Oishi et al., Phys. Scr. 91, 025602 (2016).
  • [10] T. Oishi et al., Plasma Fusion. Res. 10, 3402031 (2015).
  • [11] S. Morita et al., AIP Conference Proceedings 1545, 143 (2013), Proceedings of ICAMDATA-2012, Gaithersburg, 30 Sept. - 4 Oct. 2012.
  • [12] Y. Liu et al., J. Appl. Phys. 122, 233301 (2017).
  • [13] S. Morita et al., Plasma Sci. Technol. 13, 290 (2011).