Fluctuation and transport reduction by current profile control in MST

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:178188

Sarff, J; Almagri, A; Cekic, M ^[1]

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1. Univ. of Wisconsin, Madison, WI (United States). Dept. of Physics; and others

The dominant energy loss mechanism in the reversed field pinch (RFP) results from parallel streaming in a stochastic magnetic field. This stochasticity results from magnetic fluctuations which accompany m = 1, n {approximately}2R/a tearing (or resistive kink) instabilities in the plasma core. Inductive, electrostatic, and rf current drive are being explored as techniques to reduce the tearing fluctuation and the associated energy loss. For example, by applying an auxiliary poloidal inductive electric field to the MST RFP plasma, the current density gradient is reduced, the growth of the m = 1 tearing fluctuations slows, and the energy confinement time doubles. Sawteeth associated with the m = 1 instabilities are also suppressed. Since a toroidal flux change linking the plasma is required, inductive current drive must be transient to avoid excessive perturbation of the equilibrium. To sustain and enhance the improved plasma, electrostatic and rf current drivers are being developed. The novel electrostatic current drive scheme utilizes a plasma source for electron injection. This compact source features high current density with good directional control while maintaining low impurity injection. An individual source generates 1 kA of current, so {approximately}30 sources will be placed in the edge of the plasma to achieve the MHD predicted current drive required for tearing stabilization. A theoretical and computational analysis of lower-hybrid (slow) wave current drive indicates good feasibility.

• OSTI ID: 178188
• Report Number(s): CONF-950612--; ISBN 0-7803-2669-5
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ELECTRIC CURRENTS
ENERGY LOSSES
FEASIBILITY STUDIES
INSTABILITY GROWTH RATES
LOWER HYBRID CURRENT DRIVE
MST DEVICE
SAWTOOTH OSCILLATIONS
STABILIZATION
TEARING INSTABILITY