%AKamada, Yutaka
%ASato, Masayasu
%AKikuchi, Mitsuru
%AMori, Masahiro [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment]
%D1994
%I; Japan Atomic Energy Research Inst., Tokyo (Japan)
%J
%K70 PLASMA PHYSICS AND FUSION TECHNOLOGY, JT-60U TOKAMAK, EDGE LOCALIZED MODES, H-MODE PLASMA CONFINEMENT, BALLOONING INSTABILITY, BOOTSTRAP CURRENT, PLASMA RADIAL PROFILES, BETA RATIO, 700340, PLASMA WAVES, OSCILLATIONS, AND INSTABILITIES
%PMedium: X; Size: 22 p.
%TOnset of ELMs in JT-60U
%XThe ELMs limiting the energy confinement in JT-60U appear when the heating power is high enough compared to the threshold power for the L-H transition. The ELM-free phase is observed when n-bar{sub e} is lower than the threshold density n-bar{sub e}{sup th}. The threshold density n-bar{sub e}{sup th} increases with (B{sub t}{sup 2}/(Rq{sub eff}{sup 2}))l{sub i} which is a measure parameter for the ballooning stability, where q{sub eff} is the effective safety factor at the edge. The edge pressure gradient estimated by n-bar{sub e}{sup th} T{sub i} (95%)/(T{sub i} (95%){sup 0.5}/B{sub p} (a)) is proportional to (B{sub t}{sup 2}/(Rq{sub eff}{sup 2}))l{sub i} which allows us to understand that the ELMs are related to the ballooning instability. A time dependent analysis of the evolution of pressure and current profiles including the boot-strap current shows that the steep edge pressure gradient is close to the marginal value for the high-n ideal ballooning instability at the onset of ELMs. (author).
%0Technical Report
Japan Other: ON: DE95737209; TRN: JP9412117 JPN English