Recent Results from the Lower Hybrid Current Drive Experiment on JET

The JET Lower Hybrid Current Drive (LHCD) prototype system has been in operation in the early part of the 1991 experimental campaign with generated power up to 2.7 MW at 3.7 GHz and coupled power to the plasma up to 2.4 MW. Experiments have focused so far on the determination of the performance limits of the system, both in terms of long pulse operation and of replacement of the ohmically driven plasma current. Further experiments have also been carried out to confirm early findings of central electron heating induced by LH when applied in combination with Ion Cyclotron Resonance Heating (ICRH). Long pulse operation has been obtained on JET with 2 MA, 1.9 T limiter plasmas with 1 minute current flat top where 40% of the required flux is provided by the combined application of the LH and ICRF systems. Full replacement of the inductive current has been observed in 1 MA, 3.4 T ohmic plasmas with 1.9 MW of LH power, with current drive efficiencies up to 〈ne〉 Icd/Plh∼0.35 1020 m −2 A/W with volume averaged ele...