PPPL-3158 Preprint: January 1996 UC-420
SPREADING OF WAVE-DRIVEN CURRENTS
IN A TOKAMAK
D. W. Ignat, R. Kaita, S. C. Jardin, and M. Okabayashi
Plasma Physics Laboratory
Princeton University
P. O. Box 451
Princeton, New Jersey
USA 08543
ABSTRACT. Lower hybrid current drive (LHCD) in the tokamak Princeton Beta Experiment-Modification
(PBX-M) is computed with a dynamic model in order to understand an actual discharge aimed at raising the
central q above unity. Such configurations offer advantages for steady-state operation and plasma stability. For
the particular parameters of this PBX-M experiment, the calculation found singular profiles of plasma current
density J and safety factor q developing soon after LHCD begins. Smoothing the lower hybrid-driven current
and power using a diffusion-like equation and a velocity-independent diffusivity for fast-electron current brought
the model into reasonable agreement with the measurements if Dfat : 1.0 m2/s. Such a value for Dfast is in the
range suggested by other work.
PACS: 52.35.Fp 52.35.Hr 52.40.Db 52.50.Gj
January 4, 1996
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MASTER
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