Transport Reduction by Current Profile Control in the Reversed-field Pinch
J. S. Sarff, A. F. Almagri, M. Cekic, C. -S. Chaing, D. Craig,
D. J. Den Hartog, G. Fiksel, S. A. Hokin, R. W. Harvey, H. Ji, C. Litwin,
S.c. Prager, D. Sinitsyn, C. R. Sovinec, J. C. Sprott,
and E. Uchimoto
Department of Physics, University
of Wisconsin, Madison, Wisconsin 53706
(Received 21 November 1994; accepted 28 February 1995)
ABSTRACT
An auxiliary poloidal inductive electric field applied to a reversed-field
pinch (RFP) plasma reduces the current density gradient, slows the growth
of m=1 tearing fluctuations, suppresses their associated sawteeth,
and doubles the energy confinement time. This experiment attacks
the dominant RFP plasma loss mechanism of parallel streaming in a stochastic
magnetic field. The auxiliary electric field flattens the current
profile and reduces the magnetic fluctuation level. Since a toroidal
flux change linking the plasma is required to generate the inductive poloidal
electric field, the current drive is transient to avoid excessive perturbation
of the equilibrium. To sustain and enhance the improved state, noninductive
current drivers are being developed. A novel electrostatic current
drive scheme uses a plasma source for electron injection, and the lower-hybrid
wave is a good candidate for radio-frequency current drive.
Ref: J. S. Sarff, A. F. Almagri, M. Cekic, C. -S. Chaing, D. Craig,
D. J. Den Hartog, G. Fiksel, S. A. Hokin, R. W. Harvey, H. Ji, C. Litwin,
S.c. Prager, D. Sinitsyn, C. R. Sovinec, J. C. Sprott,
and E. Uchimoto, Phys. Plasmas 2, 2440-2446 (1995)
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