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(EXP1/17) Particle Confinement and Transport in JT-60U

   
H. Takenaga , K. Nagashima , A. Sakasai , N. Asakura , K. Shimizu , H. Kubo , S. Higashijima , T. Oikawa , T. Fujita , Y. Kamada , N. Hosogane , M. Shimada  and the JT-60 Team 
 
Japan Atomic Energy Research Institute, Naka Fusion Research Establishment Naka-machi, Naka-gun, Ibaraki-ken, 311-0193, Japan

Abstract
Particle confinement and transport have been systematically analyzed for the improved confinement  modes in JT-60U . A scaling law for the total number of ions in the main plasma of ELMy H-mode  plasmas was proposed for the first time with confinement times of the particles supplied by NBI (center fuelling) and by recycling and gas-puffing  (edge fuelling) separately defined. The confinement time increases and decreases with density for center and edge fuelling, respectively. The comparison between the experimental data and the scaling was made for the high bp ELMy H-mode and reversed shear plasmas. The particle confinement was enhanced over the scaling by a factor of about 2 in the reversed shear  plasma. The particle diffusivity and convection velocity were also evaluated based on the perturbation technique using modulated helium gas-puffing in ELMy H-mode and reversed shear plasmas. The particle diffusivity and convection velocity were estimated to be $\rm0.4-2
m^2/s$ and -5.5 (inward) $\sim +2.5$ (outward) m/s for the ELMy H-mode plasma and to be $\rm0.2-2 m^2/s$ and -4 (inward) $\sim$ 0 m/s for the reversed shear plasma, respectively. The particle diffusivity was reduced by a factor of 5-6 around the internal transport barrier compared with that in the outside and inside regions in the reversed shear plasma.

  

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IAEA 1999