Advances In Multi-Megawatt, Long Pulse Operation In Tore Supra

The lower hybrid current drive (LHCD) system of Tore Supra has been upgraded for long pulse operation at higher power (7-8MW). The two launchers have coupled on plasma 3.8MW and 2.7MW separately. This new power capability allows extending the operational domain of Tore Supra for long pulses at higher current and density. 38 long (20s-155s) discharges with very low loop voltage (V-L=30-60mV) were performed with combined LHCD (5-5.7MW) and ICRH (1-3MW) powers, with up to 1GJ of injected energy. Higher LHCD efficiency, with respect to the previous long discharges, is reported. MED stability of these discharges is very sensitive to the LHCD power and parallel wave index, in particular in the preforming phase. The ICRH power also has a beneficial effect on the MED stability.