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(EX3/4) Study of Closed Divertor with Strong Gas-Puffing on the JFT-2M

H. Kawashima, S. Sengoku, T. Ogawa, H. Ogawa, K. Uehara, Y. Miura, H. Kimura and the JFT-2M Team

Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Tokai Annex, 2-4 Tokai-mura, Naka-gun, Ibaraki-ken, 319-1195 Japan

Abstract.  In order to improve the particle control capability of the divertor and to demonstrate the possibility of a dense and cold divertor with high confinement plasmas, a closed divertor study has been carried out on the JFT-2M tokamak. When a strong gas-puff is applied into the divertor chamber, a baffling effect is exhibited by enhanced radiation localization and high neutral pressure in the divertor chamber, low core fueling and sustainment of core confinement quality. The baffling effect is further enhanced with ExB flow and/or current in the scrape off layer induced by divertor biasing. A dense and cold divertor state ( n_e^div $\propto$ 4×10¹⁹m^{- 3} and T_e^div $\propto$ 4eV) by strong gas-puffing can be obtained together with the improved confinement modes. Furthermore, the improved core confinement is not affected significantly in the high density region ( $\overline{\mathrm{n_e}}$/n_e^G < 0.7). The UEDA-code simulation reproduces the baffling effect and a dense and cold divertor plasma with a closed divertor structure.

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