Peaked density profile circular limiter H-modes on TFTR

Circular limiter H-modes are obtained on TFTR during high power neutral beam heating. The transition is usually from the supershot to the H-mode rather than the usual L- to H- transition, and thus is obtained in a low recycling environment with core fueling mainly from the heating beams. As a result, the density and pressure profiles are highly peaked at the center. Global confinement time, {tau}{sub E}, is enhanced over L-mode scaling by up to {approx} 2.5 times. The onset of ELMs shortly after the H-mode transition appears to limit {tau}{sub E}. Limiter H-modes of up to 1.5 sec duration have been realized. 18 refs., 4 figs.