High power ion cyclotron resonance heating in JET

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Abstract
Ion Cyclotron Resonance Heating (ICRH) powers of up to 17 MW have been coupled to JET limiter plasmas. The plasma stored energy has reached 7 MJ with 13 MW of RF in 5 MA discharges with Zeff approximately=2. When Ip/Bphi approximately=1 MA/T the stored energy can be 50 % greater than the Goldston L mode scaling. This is due to transient stabilisation of sawteeth (up to 3 s) and to a significant energy content in the minority particles accelerated by RF (up to 30 % of the total stored energy). Central temperatures of Te approximately 11 keV and Ti approximately=8 keV have been reached with RF alone. (He3)D fusion experiments have given a 60 kW fusion yield (fusion rate of 2*1016 s-1 in the form of energetic fast particles (14.7 MeV(H), 3.6 MeV(He4)) in agreement with modelling. When transposing the same calculation to a (D)T scenario, Q is predicted to be between 0.2 and 0.8 using plasma parameters already achieved. For the first time, a peaked density profile generated by pellet injection could be reheated and sustained by ICRF for 1.2 s. Electron heat transport in the central region is reduced by a factor 2 to 3. The fusion product nio tau ETio reaches 2.2*1020 m-3.s.kev in 3 MA discharges which is a factor of 2.3 times larger than with the normal density profile.

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