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K. Hayase, Y. Sato, S. Kiyama,
M. Watanabe*, K. Sugisaki
Electrotechnical Laboratory, Tsukuba, Ibaraki, 305-8568 Japan
* Permanent Address: Faculty of Engineering, Iwate University, Morioka,
Iwate, Japan
Abstract. The divertor discharge of reversed field pinch (RFP) is being
studied in TPE-2M. To understand the recycling process and the
characteristic divertor plasma behaviors, the device was reconstructed so as
to have an enough divertor space. In the new device the shell is installed
in the vacuum vessel. The major and minor radii of the shell are 0.87 and
0.28 m respectively. Visible spectroscopic observation showed that both
light and heavy impurity lines decreased, while
D
from the
diverter plate region increased. This indicates that the divertor acts
effectively in the new structural configuration. The newly found phenomenon
in this vacuum vessel - shell structure is a large-amplitude axis
oscillation of plasma column along with the divertor point direction, that
is, the shell cut direction. It seems to be induced by the large shell cut
angle or its structural form. This sort of large amplitude oscillation may
enhance the flux loss in RFP. In the improved shell structure, in which the
open angle of shell cut was reduced to a half (15 degrees) and the shape of
shell inner surface was made quasi-circular, that oscillation is effectively
suppressed. The loop voltage is relatively high in both cases, which seems
due to the large - angle shell cut.
IAEA 2001
