Session GP1 - Poster Session IV.
POSTER session, Tuesday afternoon, October 30
Exhibit Hall B,
ELMy H-mode discharges are characterised by a decrease of confinement and fuelling efficiency when applying heavy gas puff to increase the density. Nevertheless quasi-stationary (up to 12 energy confinement times) discharges could be achieved with averaged values of n/n_GW\geq0.85, H98(y,2)\simeq1 and \beta_n\simeq1.8 in the phase following the D puff ("afterpuff" regime). The heavy D puff degrades the confinement but brings the density near n_GW thanks to the Ar seeding which counteracts the decrease of fuelling efficiency. After the switch-off of the strong D puff H-mode confinement quality is recovered whereas the density can be maintained by a careful refuelling in D and Ar. This regime shows peaked density profiles and moderate Z_eff (\simeq2). Best results were obtained with the X-point lying on the septum of the divertor. Effects of X-point position and plasma configuration changes as well as ELM behaviour will be discussed.