THE H-REGIME OF ASDEX
The H-mode is a confinement regime of neutral injection heated plasmas where the usual degradation of confinement properties is avoided. In some cases even the Ohmic confinement is exceeded: In quiescent H-phases, a global energy confinement time of 120 ms has been achieved. This improvement is caused by a reduction of the electron thermal diffusivity. At the H-transition a transport barrier develops at the plasma edge which gives rise to steep edge gradients, a low power outflow and finally causes edge localized modes. The barrier seems to develop at high edge electron and ion temperatures. Therefore, the H-mode has only been observed in divertor discharges with low impurity radiation and recycling cooling. Hence the edge ion temperature is determined by neoclassical ion transport which also seems to affect the H-transition which is found to depend on the ion grad-B drift direction. The location of the edge barrier indicates a crucial role of the separatrix and suggests that the H-mode is not accessible in non-diverted configurations.
Bibliographic Reference: COURSE AND WORKSHOP ON BASIC PHYSICAL PROCESSES OF TOROIDAL FUSION PLASMAS, VARENNA (ITALY), AUG. 26-SEPT. 3, 1985 VOL. I, PP. 65-85 EUR 10418 EN (1986) FS, VOL. I AND VOL. II, 733 P., BFR 3600 FOR BOTH VOLUMES, EUROFFICE, LUXEMBOURG, POB 1003
Record Number: 1989125079600 / Last updated on: 1987-12-01
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