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Abstract

At present, the striations observed on the H(alpha) or H(beta) emission signal of ablated pellets are not well understood. An attractive explanation of these striations would be a limitation of the ablation process due to the smaller amount of energy available on resonant magnetic surfaces. To evaluate the ability of the latter to produce the observed features, a model has been developed which takes into account the Maxwellian distribution of electrons, the proportion of trapped particles, the geometric effects linked with the shear and the finite lifetime of the filaments. In tokamaks, it is found that this model is unable to reproduce the observed striations for smooth q-profiles but that the general shape of the H(alpha) or H(beta) signal can be fitted by introducing local flattenings (e.g. small magnetic islands) around resonant surfaces. In low shear stellarators, striations (rather shallow) due to rational q-values can exist in the absence of magnetic islands, but only if a suprathermal electron tail is present.

Additional information

Authors: PEGOURIE B, Département de Recherches sur la Fusion Contrôlée, CEN-Cadarache, 13108 Saint-Paul-lez-Durance (FR);DUBOIS M A, Département de Recherches sur la Fusion Contrôlée, CEN-Cadarache, 13108 Saint-Paul-lez-Durance (FR)
Bibliographic Reference: Article: Nuclear Fusion, Vol. 29 (1989), No. 5, pp. 745-751
Record Number: 198911050 / Last updated on: 1994-12-01
Category: PUBLICATION
Original language: en
Available languages: en