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Externally-driven H-mode studies in CCT

1996; IOP Publishing; Volume: 38; Issue: 8 Linguagem: Inglês

10.1088/0741-3335/38/8/026

1361-6587

George Tynan, J.R. Liberati, Patrick Pribyl, Robert J. Taylor, B. Wells,

Fusion materials and technologies

Test particle radial flux surface excursions are reduced during the H-mode. Particle transport is reduced by a factor of 10 in the H-mode, but energy confinement increases are small. In the H-mode the evolution of poloidally resolved turbulent statistics are not explained by published theory. Turbulent momentum transport leads to a concentration of poloidal momentum within the transport barrier, and compressibility leads to poloidal shock-like phenomena. The electron distribution functions may be modified by this shock, leading to kinetic instabilities. A physics-based understanding of the H-mode must therefore include toroidal effects combined with an adequate treatment of particle orbits, plasma compressibility and associated kinetic effects, and at least a two-species model of turbulent transport. The results suggest that rapid poloidal core-plasma rotation could form core transport barriers without reliance on fluid shear or reversed magnetic shear effects.