15th Plasma Surface Interactions

Radiation enhancement and impurity behavior in JT-60U reversed shear discharges

H. Kubo^a,*, S. Sakurai^a, S. Higashijima^a, H. Takenaga^a, K. Itami^a, S. Konoshima^a, T. Nakano^a, Y. Koide^a, N. Asakura^a, K. Shimizu^a, T. Fujita^a, K. W. Hill^b
a Japan Atomic Energy Research Institute, Naka-machi, Naka-gun, Ibaraki-ken, 311-0193, Japan
^b Princeton Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543, USA

Abstract.
In order to extend the high-confinement reversed shear regime with an internal transport barrier (ITB) toward high radiation loss power, Ne and Ar injection have been investigated in JT-60U. With Ne injection, high confinement (H_89PL > 2.4, HH_98(y,2) > 1.6) and high radiation-loss-power fraction ( > 80%) were simultaneously obtained at high density ( > 0.7 n_GW). The radiation loss power was enhanced both in the main plasma and in the divertor plasma. With divertor plasma detachment and an X-point MARFE, the ITB was pronounced and the H_89PL factor reached 1.8. However, Ar injection resulted in excessive radiation loss enhancement inside the ITB. The Ne and the C density profile were similar to the electron density profile, and their accumulation was not significant. On the other hand, Ar showed accumulation inside the ITB.