Initial Results from the Tokapole-II Poloidal Divertor Device
A. P. Biddle, R. N. Dexter, R. J. Groebner, D. J. Holly, B.
Lipschultz,
M. W. Phillips, S. C. Prager, J. C. Sprott
University of Wisconsin, Madison,
Wisconsin, United States of America
(Manuscript received 30 March 1979; Final version received 7 July 1979)
ABSTRACT
The latest in a series of internal-ring devices, called Tokapole II,
has
recently begun operation at the University of Wisconsin. Its purpose is
to permit the study of the production and confinement of hot, dense
plasmas
in either a toroidal octupole (with or without toroidal field) or a
tokamak
with a four-node poloidal divertor. The characteristics of the device
and
the results of its initial operation are described here. Quantitative
measurements
of impurity concentration and radiated power have been made. Poloidal
divertor
equilibia of square and dee shapes have been produced, and an
axisymmetric
instability has been observed with the inverse dee. Electron cyclotron
resonance heating is used to initiate the breakdown near the axis and
to
control the initial influx of impurities. A 2-MW RF source at the
second
harmonic of the ion cyclotron frequency is available and has been used
to double the ion temperature when operated at low power with an
unoptimized
antenna. Initial results of operation as a pure octupole with poloidal
Ohmic heating suggest a tokamak-like scaling of density (n ~ Bp) and
confinement
time (tau ~ n).
Ref: A. P. Biddle, R. N. Dexter, R. J. Groebner, D. J. Holly, B.
Lipschultz,
M. W. Phillips, S. C. Prager, and J. C. Sprott,
Nuclear
Fusion 9, 1509-1518 (1979)
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