 |
 |
 |
A. Fujisawa, H. Iguchi, S. Lee, K. Tanaka,
T. Minami, Y. Yoshimura, M. Osakabe, K. Matsuoka,
S. Okamura, H. Idei, S. Kubo, S. Ohdachi,
S. Morita, R. Akiyama, K. Toi, H. Sanuki,
K. Itoh, K. Ida, A. Shimizu, S. Takagi,
C. Takahashi, M. Kojima, S. Hidekuma, S. Nishimura,
M. Isobe, A. Ejiri, N. Inoue, R. Sakamoto,
Y. Hamada, M. Fujiwara
National Institute for Fusion Science, Oroshi-cho, Toki, Japan 509-5292
Abstract. A new kind of oscillatory steady state is discovered in observation
of potential with a heavy ion beam probe in Compact Helical System
Heliotron/Torsatron. Bulk plasma parameters, such as electron temperature
and density profile, change being synchronized with the pulsation of
potential. The phenomenon can be regarded as successive transitions between
two bifurcative states of the plasma. The pulsation can be self-sustained
and create a dynamic steady state in low density plasma with electron
cyclotron heating. The cause of phenomenon is associated with the
bifurcation nature of radial electric field, that is inherent with toroidal
helical plasmas. This paper presents two examples of the phenomenon in
different density regimes. Dependence of pulsation characteristics on
several parameters is described. The bifurcation property predicted by a
neoclassical theory is presented for comparison with the experimental
observations.
IAEA 2001
