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(CD1/1) Heating and Non-inductive Current Drive by Negative-ion based NBI in JT-60U

   
T. Oikawa , K. Ushigusa , C. B. Forest ¹, M. Nemoto , O. Naito , Y. Kusama , Y. Kamada , K. Tobita , S. Suzuki , T. Fujita , H. Shirai , T. Fukuda , M. Kuriyama , T. Itoh , Y. Okumura , K. Watanabe , L. Grisham ² and the JT-60 Team 
 
Japan Atomic Energy Research Institute, Naka Fusion Research Establishment, Naka-machi, Naka-gun, Ibaraki-ken, Japan
¹ University of Wisconsin-Madison
² Princeton Plasma Physics Laboratory

Abstract
Current drive and heating properties of negative-ion-based NBI  (N-NBI) have been studied comprehensively in JT-60U. It was confirmed from the shinethrough measurements of the injected beam(350keV) that multi-step ionization processes are essential in the ionization processes of high energy particles. A current density profile driven by N-NB was determined experimentally. That is in a good agreement with theoretical prediction, and N-NB driven current reached 0.6MA with $\rm E_B =$ 360keV and $\rm P_{\mbox{INJ}} =$ 3.7MW. Current drive efficiency $\rm\eta_{\mbox{CD}}$ is increased with the electron temperature and improved with beam energy. Injected fast ions are well confined in the enhanced confinement core with weak poloidal magnetic field of the reversed shear plasmas. Clear H-mode transition  was obtained with N-NB dominant heating, where the net absorbed power required for H-mode transition seemed similar to the previous result obtained in JT-60U  using positive-ion-based NBI  (P-NBI) heating. With the strong electron heating by N-NB (80% absorbed by the electron), H factor $\rm (=\tau_E/\tau_E^{\mbox{ITER89PL}})$ of 1.64 with $\rm T_e(0)=1.4T_i(0)$ was obtained in the steady-state ELMy phase.

   

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