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'Snakes' are observed in Tore Supra after injection of high velocity solid hydrogen or deuterium pellets ablated inside the q = 1 surface. They are detected, immediately after the ablation, as oscillations in the line integrated densities of the central interferometer channels. The corresponding oscillations in the soft X ray signals detach from the noise about 70 ms later. Snakes survive sawtooth crashes, but are nevertheless affected by them. Variations, during the about 500 ms long lifetime of the snake radius, of the rotation frequency and of the rotation direction are discussed, stressing the effects of the sawtooth crashes. Combined simulations have indicated that the impurity density inside the snake is much larger than that outside it. Since a change of regime seems to appear about 80 ms after the snake formation on the soft X ray, it seem plausible that impurity accumulation takes place at this time. A stability criterion taking into account both impurity and bootstrap effects is presented; the result agrees with the model proposed by Wesson.

Additional information

Authors: PECQUET A L ET AL, CEA, CEN Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: Article: Nuclear Fission, Vol. 37 (1997) No. 4, pp. 451-465
Record Number: 199710800 / Last updated on: 1997-07-02
Original language: en
Available languages: en