Improved confinement in high li lower hybrid driven steady state plasmas in TORE SUPRA

The global energy confinement of combined ohmic and lower hybrid driven TORE SUPRA plasmas has been analysed at various densities. In contradiction to the L mode ITER scaling law, this analysis indicates that the global energy confinement time depends strongly on the plasma density. Furthermore, the thermal electron energy content of steady state discharges is found to be in good agreement with the global Rebut-Lallia-Watkins (RLW) scaling law. Current ramp experiments show an enhancement of the global energy confinement with the internal inductance, li. These results have been extended to steady state regimes with lower hybrid current drive. Improved confinement has been obtained in a high li steady state plasma (li=1.7), where the modification of the current profile by lower hybrid waves leads to an increase in the central value of the safety factor (qψ(0) ≈ 2). In this case, the global confinement time is shown to exceed the value predicted by the RLW scaling law by 40%