Structural Formation and Stability of High Heat Flux Plasma in Dynamic Gas Target Divertor

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Construction of High Heat Flux Plasma Device NAGDIS-IIHigh heat flux helium plasmas with the electron density of more than 10^<19>m^<-3> have been generated under the condition of gas pressure of around 1mTorr with the B field of 0.25 T.The hydrogen plasma has also been successfully generated to reach the density of 3*10^<18>m^<-3> by auxiliary heating of LaB_6 cathode. High frequency power up to 40KW with 0.2s pulse width has been injected into the phased array antenna although the power coupled to the plasma is only 10% of injected power.Finding of Density Threshold for Plasma DetachmentExperimental and analytical finding of density threshold to obtain adetached plasma. The reason comes from the electron energy loss channel through the e-i energy exchange.Clear Observation of Recombination Process in Detached PlasmasVisible continuum as well as a series of He Balmer spectral lines show consistently a partial local thermodynamic equilibrium with the plasma temperature of 0.1-0.3eV for detached recombining plasmas.Demonstration of Recombination-dependent Particle Flux to the TargetTemporal change in electron temperature (Te) has been obtained by modulating the discharge current. The particle flux to the target was found to be very sensitively dependent of Te, or the recombinations rate proportional to n_e・T^<-9/2>_.Generation of Heat Pulse with 50ms by Ion Cyclotron Resonance HeatingRF power of 4KW in net has been injected into the plasms, increasing the electron temperature. Plasma detachment was found to be modified dramatically. Research base on heat pulse like ELM effects on detached plasma was established.