Heating and non-inductive current drive by negative ion based NBI in JT-60U

T. Oikawa, K. Ushigusa, C. B. Forest, 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

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The current drive and heating properties of negative ion based NBI have been studied comprehensively in JT-60U. It has been confirmed from shine-through measurements of the injected beam (350 keV) that multistep ionization processes are essential in the ionization processes of high energy particles. The profile of the current density driven by a negative ion based NB (N-NB) has been determined experimentally. This is in good agreement with the theoretical prediction, and N-NB driven current reached 0.6 MA with EB = 360 keV and PINJ = 3.7 MW. The current drive efficiency ηCD is increased by increasing electron temperature and improved by increasing beam energy. The fast ions from N-NBs are well confined in the enhanced confinement core by the weak poloidal magnetic field of reversed shear plasmas. A clear H mode transition was obtained with N-NB dominant heating, where the net absorbed power required for an H mode transition seemed similar to the previous result obtained in JT-60U using a low energy beam (90 keV). With the strong electron heating by N-NBI (80% absorbed by electrons), an H factor (= τEEITER-89PL) of 1.64 with Te(0) = 1.4Ti(0) was obtained in the steady state ELMy phase.

Original languageEnglish
Pages (from-to)435-443
Number of pages9
JournalNuclear Fusion
Issue numberSPEC. ISS. 3
Publication statusPublished - 2000


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