High Confinement Hybrid Scenario in JET and its Significance for ITER
In the last campaigns, JET has extended the hybrid scenario with q profile close to unity in the plasma core to higher confinement (H98y2 up to 1.4-1.5) for both high and low triangularity. This has been achieved by creating a large region of weak magnetic in the plasma core. With these performances, 50% of the total current is generated non-inductively would produce in ITER a discharge of 1000s duration. The effect of this broad q profiles shape could reduce transport in the core in particular in the low shape scenario which also has the strongest rotation gradients. With broad q profile neoclassical tearing mode stability is shown to be improved. The pedestal does not seem to depend crucially on the modification of the magnetic shear, but shows a constant improvement with power and b. This improvement is more pronounced at low shape than low shape. High shapes can also be affected by high recycling flux that can impact on the pedestal confinement. Given the inapplicability of existing confinement scaling law at bN higher than 2, the extrapolation of these scenarios to ITER is using instead a dimensionless approach. There is good prospect to produce in ITER long pulse operation with Q approaching 10 but there are large uncertainties in particular with respect to the role of rotation on transport.