JET-P(91)44

ICRF Heating and Synergistic LH and Fast-Wave Current Drive in JET

Ion cyclotron resonance heating (ICRH) experiments in JET have been carried out in a variety of scenarios using advanced antennas, phasing and matching techniques leading to improved plasma performances. A record ICRH power of 22MW has been coupled to the plasma in L-mode with tE @ l.3tG where tG refers to the Goldston Lmode prediction for the energy confiment time. Also, 3MW has been coupled for as long as l minute with little change in Zeff. ICRH produced H-modes have tE @ 2.8tG with a duration of 2.8s at power levels of <12MW. Pellet produced peaked-density profile reheated with ICRH have been combined with H-modes to produce Tio Teo and highest thermonuclear yield where the thermal triple fusion product nD(0) . tG . Tio (0) @ 7.8 . 1020 m­3 skeV has been achieved. Good confinement and ion heating (Tio Teo) have been demonstrated both in the two-minority scheme as well as in the high-minority heating scenario (H-minority in He3-plasmas) where nH/ne < 0.4 was reached. Unidirectional supcrthermal electrons (100-200keV) produced by lower-hybrid current drive (LHCD) system have been synergistically accelerated by transit-time magnetic pumping (TTMP) of fast-waves coupled by ICRH in the (0,0)-phasing of the antenna. This produces TTMP current drive even without phasing the ICRH antennas. Finally, in the minority current-drive scenario which is predicted to control the shear (dq/dr), marked differences in the sawteeth behaviour have been observed in experiments when the phase of the antennas was reversed while depositing power near the q = 1 surface.
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JETP91044 1.08 Mb