IMPROVED CONFINEMENT IN HIGH L(I) LOWER-HYBRID DRIVEN STEADY-STATE PLASMAS IN TORE-SUPRA

The global energy confinement of combined ohmic and lower hybrid drive n TORE SUPRA plasmas has been analysed at various densities. In contra diction to the L mode ITER scaling law, this analysis indicates that t he global energy confinement time depends strongly on the plasma densi ty. Furthermore, the thermal electron energy content of steady state d ischarges is found to be in good agreement with the global Rebut-Lalli a-Watkins (RLW) scaling law. Current ramp experiments show an enhancem ent of the global energy confinement with the internal inductance, l(i ). These results have been extended to steady state regimes with lower hybrid current drive. Improved confinement has been obtained in a hig h l(i) steady state plasma (l(i) = 1.7), where the modification of the current profile by lower hybrid waves leads to an increase in the cen tral value of the safety factor (qpsi(0) almost-equal-to 2). In this c ase, the global confinement time is shown to exceed the value predicte d by the RLW scaling law by 40%.