Scenario Development at JET with the New ITER-like Wall

In the recent JET experimental campaigns with the new ITER-like Wall (JET-ILW), major progress has been achieved in the characterisation and operation of the H-mode regime in metallic environment: i) plasma breakdown has been achieved at the first attempt and X-point L-mode operation recovered in a few days of operation, ii) stationary and stable type I ELMy Hmodes with bN~1.4 have been achieved in low and high triangularity ITER­like shape plasmas and are showing that their operational domain at H = 1 is significantly reduced with the JET-ILW mainly because of the need to inject large amount of gas (above 1022D/s) to control core radiation. iii) in contrast the hybrid H-mode scenario has reached H factor of 1.2 to 1.3 at bN of 3 for 2 to 3s. iv) in comparison to carbon equivalent discharges, total radiation is similar but the edge radiation is lower and Zeff of the order of 1.3-1.4. At low gas fuelling rate (below 0.5 1022D/s) and low ELM frequency (typically less than 10Hz), strong core radiation peaking is observed in H-mode discharges even when tungsten influx from the divertor is constant. High Z impurity transport from the plasma edge to the core appears to be the dominant factor to explain is paper reviews the major physics and operational achievements and challenges that an ITERlike wall configuration has to face to produce stable plasma scenarios with maximised performance.
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