Characteristics of Type I and Type III ELM Precursors in ASDEX Upgrade
The temporal evolution of the edge electron pressure gradient during the development of a type I edge localized mode (ELM) shows that proximity of the edge pressure gradient to the ideal ballooning limit is not sufficient to trigger a type I ELM. Thus, the magnetohydrodynamic (MHD) structure of ELMs is investigated further. The present discussion focuses on the phenomenology of type I and type III ELM precursors. The ELM precursor types are well distinguished by their frequency behaviour and mode structure. The type I ELM precursor oscillation originates from a thin layer close to the plasma edge. For type III ELMs, on the contrary, the edge pressure gradient has a much stronger influence as indicated by their occurrence during L mode.
Bibliographic Reference: Article: Nuclear Fusion, Vol. 38 (1998) No.1, pp. 111-116
Record Number: 199810523 / Last updated on: 1998-05-05
Original language: en
Available languages: en