<RESEARCH REPORT>POWER ABSORPTION AND CONFINEMENT STUDIES OF ICRF-HEATED PLASMA IN JIPP T-IIU TOKAMAK

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The energy confinement characteristics of ICRF-heated tokamak plasmas are studied at high input power density∿2MWm^<-3> volume averaged, on the JIPP T-IIU device (R=0.91m/a=0.23m). High electron and ion temperatures (T_e∿2.5keV, T_i∿2.0keV, at each maximum) have been achieved by the operation at a plasma current I_p of 280kA, plasma line-averaged electron density n^^-_e of 7×10^<13>cm^<-3> and input power of 2MW, with a suppression of total radiation loss (30 to 40% of the total input power) by a carbon coating on the vacuum vessel. The fraction of ICRF power absorbed by the plasma, α, is determined experimentally from the decay of the stored plasma energy just after the ICRF pulse is terminated. The value of α increases slightly with increasing electron density and decreases from 90 to 70% as the ICRF power is increased from 1MWm^<-3> to 2MWm^<-3> volume averaged. The global energy confinement time τ_E, defined by W_p/(P_<OH>+αP_<rf>), decreases by a factor of 2∿3 from that in ohmic plasmas as the heating power increases up to 2MW. It is found that the energy confinement time has a strong line-averaged electron density dependence as τ_E∝n^^-_e^<0.6>, which is obtained by the use of the measured absorbed power, while the Kaye-Goldston scaling predicts τ_E∝n^^-_e^<0.26>.
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