Profile Control in JET with Off-axis Lower Hybrid Current Drive

摘要

1. Full LH current drive up to 3MA has been obtained in X-point plasmas with n_e <2.0×10~(19)m~(-3). The current drive efficiency, η_(CD), reached 0.25-0.30×10~(20)m~(-2)A/W, which is in accordance with the requirements for advanced tokamak scenarios in ITER.rn2. For I_P>2MA the LH driven current profile is broader than the ohmic profile. The peak in the current profile is located at approximately mid radius, as is suitable for profile control applications, including shear optimised scenarios.rn3. Analysis of loop voltage profiles indicate that overdriving of the plasma current is taking place in low density discharges (n_e <1.1×10~(19)m~(-3)) with high LH power, but a quantitative analysis is difficult in these conditions and there are still discrepancies between measured and calculated efficiency in some discharges.rn4. Full suppression of sawteeth has been achieved with LHCD and T_(e0)>8keV has been obtained in low density discharges.rn5. Promising results with LHCD profile control before hot ion H-modes have been obtained.rn6. LHCD experiments in the forthcoming campaign at JET will aim at improving MHD stability and confinement of hot-ion H-modes and at studying shear optimised scenarios.