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M. Nagata, M. Haruoka, S. Kano, N. Yuasa,
N. Fukumoto, T. Uyama
Faculty of Engineering, Himeji Institute of Technology, Shosha, Himeji, Hyogo, Japan
Abstract. In the Helicity Injected Spherical Torus (HIST) device, spherical
torus (ST) plasmas with 100 kA toroidal currents have been successfully
sustained by coaxial helicity injection. Internal magnetic configurations with
the closed poloidal flux of helicity-driven ST plasmas have been revealed by
intensive internal magnetic measurements. As the configuration approaches a
tokamak from a spheromak, the n = 1 mode being essential for current drive
becomes less effective, resulting in the flux amplification level being
decreased although the total toroidal current has increased. The transition
from a hollow current profile to a peaked one in the tokamak operation has
been observed for the first time during the helicity injection process. This
may be explained by an Ohmic induction effect using the open flux column.
IAEA 2001
