Return To: Session OV1 - Overviews 1 (Monday, 19 October)
Prev Page: Session OV1 - Overviews 1 (Monday, 19 October)
Next Page: (OV1/2) Physics of High Performance JET Plasmas in

(OV1/1) JT-60U High Performance Regimes

   
S. Ishida  and the JT-60 Team  (see Appendix of the paper)
 
Japan Atomic Energy Research Institute, Naka Fusion Research Establishment, Naka-machi, Naka-gun, Ibaraki-ken, Japan

Abstract
High performance regimes of JT-60U  plasmas are presented with an emphasis upon the results from the use of a semi-closed pumped divertor with W-shaped geometry. Plasma performance in transient and quasi steady states has been significantly improved in reversed shear  and high- $\rm\beta p$ regimes. The reversed shear regime elevated an equivalent $\rm Q_{DT}^{eq}$ transiently up to $\rm 1.25 (n_D(0)\tau_E T_i(0) = 8.6\times 10^{20} m^{-3}\cdot s \cdot keV)$ in a reactor-relevant thermonuclear dominant regime. Long sustainment of enhanced confinement with internal transport barriers  (ITBs) with a fully non-inductive current drive  in a reversed shear discharge was successfully demonstrated with LH wave injection. Performance sustainment has been extended in the high- $\rm\beta p$ regime with a high triangularity achieving a long sustainment of plasma conditions equivalent to $\rm Q_{DT}^{eq} \sim 0.16 (n_D(0)\tau_E T_i(0) \sim 1.4\times 10^{20} m^{-3}\cdot s \cdot keV)$ for $\sim$ 4.5 s with a large non-inductive current drive fraction of 60-70% of the plasma current. Thermal and particle transport  analyses show significant reduction of thermal and particle diffusivities around ITB resulting in a strong Er shear in the ITB region. The W-shaped divertor is effective for He ash exhaust demonstrating steady exhaust capability of $\rm\tau_{He^*}/\tau_E \sim 3-10$ in support of ITER . Suppression of neutral back flow and chemical sputtering effect have been observed while MARFE onset density is rather decreased. Negative-ion based neutral beam injection (N-NBI) experiments have created a clear H-mode  transition. Enhanced ionization cross-section due to multi-step ionization processes was confirmed as theoretically predicted. A current density profile  driven by N-NBI is measured in a good agreement with theoretical prediction. N-NBI induced TAE modes characterized as persistent and bursting oscillations have been observed from a low hot beta of $\rm < \beta_h > \sim 0.1-0.2\%$ without a significant loss of fast ions.

               

Read the full paper in PDF format.