Disappearance of giant ELMs and appearance of minute grassy ELMs in JT-60U high-triangularity discharges
- 1 May 2000
- journal article
- Published by IOP Publishing in Plasma Physics and Controlled Fusion
- Vol. 42 (5A) , A247-A253
- https://doi.org/10.1088/0741-3335/42/5a/329
Abstract
In JT-60U H-mode plasmas, giant (type I) ELMs disappear and minute grassy ELMs appear when triangularity δ, edge safety factor q95 and βp are high enough. Complete suppression of giant ELMs was observed at δ0.45, q956 and βp1.6. At higher δ (0.54), giant ELMs can disappear at a lower q95 (~4.0). In the grassy ELMy H-mode, edge temperature and pressure can be higher than those in giant ELMy H-mode and a favourable confinement can be sustained without an increase of the impurity concentration. An edge stability analysis suggests that the edge plasma is accessing the second stability regime of the high n ballooning mode in the grassy ELMy discharges.Keywords
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