Current profile optimisation during RF-assisted current ramp-up in Tore Supra
Xavier L Litaudon, E. Joffrin, T. Aniel, Vladimir A. Basiuk, A. Bécoulet, M Erba, F. Imbeaux, Didier Moreau, Yves Peysson, I. Voitsekhovitch · AIP conference proceedings · 1997
Non-inductive current ramp-up experiments have been performed on Tore Supra to enhance the core confinement by creating a central weak magnetic shear region with the safety factor above one. Just after the Lower Hybrid assisted current ramp-up phase, electron temperature transitions have been obtained for the first time at low edge safety factor (qa≈3.5, Ip≈1.6 MA) with 3.5MW of additional power. The improved confinement region concerns the central part of the discharge (r/a⩽0.3) where the q-profile is flat or marginally reversed. In fully driven 0.8 MA discharges preceded by a fast current ramp-up phase, regular central electron temperature relaxations between a high and a low confinement state are sometimes observed and are analysed.