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(EX/P2-03) Study of Integrated High-Performance Regimes with Impurity Injection in JT-60U Discharges

K.W. Hill¹⁾, W. Dorland²⁾, D.R. Ernst³⁾, D. Mikkelsen¹⁾, G. Rewoldt¹⁾, S. Higashijima⁴⁾, N. Asakura⁴⁾, H. Shirai⁴⁾, T. Takizuka⁴⁾, S. Konoshima⁴⁾, Y. Kamada⁴⁾, H. Kubo⁴⁾, Y. Miura^4)
 
1) Princeton University, PO Box 451, Princeton, NJ, USA
²⁾ Institute for Plasma Research, University of Maryland, College Park, MD, USA
³⁾ Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA, USA
⁴⁾ Japan Atomic Energy Research Institute, Naka-machi, Naka-gun, Ibaraki-ken, Japan

Abstract.  Argon seeding of ELMy H-mode with the outer strike point on the divertor dome has enabled extension to parameters approaching ITER requirements ( HH_{98(y, 2)} $\sim$ 1; n_e $\sim$ 0.8n_GW, the Greenwald density limit; and P_rad/P_heat $\sim$ 0.8).The maximum divertor heat flux due to ELMs decreased by a factor of $\sim$10 in plasmas with high triangularity (delta=0.5) and medium-delta (0.36),dome-top configurations. A possible reason for the change in ELM behavior in high-delta discharges without Ar might be access to second stability for ideal ballooning modes. Improved core tau at high n_e with Ar has been attributed to an increase in pedestal T_i and profile stiffness inside the pedestal. To understand the improved $\tau$ with Ar, GS2-code linear microinstability analyses have been done. For the dome-top case the maximum growth rate, gam(max), for the ITG/CTEM vanishes at r/a $\sim$ 0.63, and the T_i gradient increases inside this point. The ITG reappears when the Ar is reduced. Further GS2 calculations will study the sensitivity of gam(max) to impurity mass, n(I), dilution, T_i/T_e, etc. FULL-code calculations, including rotation, will further elucidate the reduced transport.

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