Plasma and Fusion Research

Volume 3, 049 (2008)

Rapid Communications

Plasma Current Sustainment by RF Power in ECH Start-up Plasma in the TST-2 Spherical Tokamak
Osamu WATANABE, Akira EJIRI, Takashi YAMAGUCHI, Junichi SUGIYAMA, Takuya OOSAKO, Yuuki ADACHI, Kotaro YAMADA, Hiroshi TOJO, Soichiro KAINAGA1), Yuichi TAKASE, Yoshihiko NAGASHIMA, Makoto SASAKI1) and Tetsuya MASUDA
Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8561, Japan
1)
Graduate School of Sciences, The University of Tokyo, Bunkyo 113-0033, Japan
(Received 21 May 2008 / Accepted 19 July 2008 / Published 20 August 2008)

Abstract

In the TST-2 spherical tokamak, a non-inductive start-up plasma produced by electron cyclotron heating (ECH) at 2.45 GHz (3-5 kW) is sustained by RF wave heating at 21 MHz (10-24 kW). A current jump, which occurs at a certain time when only ECH is used, can be induced earlier by the RF heating, and a constant plasma current is sustained even after the ECH power is turned off. The plasma current is sustained in both hydrogen and deuterium plasmas, as long as the RF power exceeds a threshold level, which is lower for deuterium plasma. The maximum sustainment time by the the RF power alone was 40 ms, limited by the RF pulse length. According to CCD camera images of the total plasma light, the major radii are almost the same, but the RF-sustained plasma has a more peaked profile, compared with the distribution of an ECH-sustained plasma.

Keywords

non-inductive current drive, RF heating, spherical tokamak

DOI: 10.1585/pfr.3.049

Full Text

PDF format (763Kbytes) PDF Download

References

  • [1] C.B. Forest et al., Phys. Rev. Lett. 68, 3559 (1992).
  • [2] T. Maekawa et al., Nucl. Fusion 45, 1439 (2005).
  • [3] J. Sugiyama et al., Plasma Fusion Res. 3, 026 (2008).
  • [4] T. Yoshinaga et al., Phys. Rev. Lett. 96, 125005 (2006).

This paper may be cited as follows:

Osamu WATANABE, Akira EJIRI, Takashi YAMAGUCHI, Junichi SUGIYAMA, Takuya OOSAKO, Yuuki ADACHI, Kotaro YAMADA, Hiroshi TOJO, Soichiro KAINAGA, Yuichi TAKASE, Yoshihiko NAGASHIMA, Makoto SASAKI and Tetsuya MASUDA, Plasma Fusion Res. 3, 049 (2008).