Session GP1 - Poster Session IV.
POSTER session, Tuesday afternoon, October 30
Exhibit Hall B,
Stable equilibria with a large, saturated m=1 island are observed on FTU after pellet injection. The island lifetime may exceed the resistive diffusion time The mode structure can be analysed in detail when a bright X-ray emission spot forms at the island o-point. When the island width is within 20% of the q=1 radius, its contours closely resemble the linear eigenfunction of the m=1 mode (although the amplitude is well within the non-linear range), i.e. the o-point is displaced towards the plasma center and is surrounded by nested crescents, with the tips of the outer crescent connected by a long ribbon. Larger islands have a smaller poloidal extent and nearly circular contours. The island survives sawtooth crashes, and its evolution during the sawtooth cycle will be used to analyse the trigger mechanism. Island rotation is very slow just after pellet injection, and then it increases along with the electron diamagnetic velocity. Island braking is observed when coupling with higher m modes occurs. These results will be used to discuss the role of diamagnetic stabilisation in the island saturation amplitude.