High performance and current drive experiments in the JAERI Tokamak-60 Upgrade*

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Abstract
Recent high‐fusion‐triple‐product and current drive experiments in the JAERI Tokamak‐60 Upgrade (JT‐60U) [Plasma Devices Oper. 1, 43 (1990)] are reported. The fusion triple product of 1.1×1021 m−3 s keV has been achieved in a more improved confinement mode (high‐βp H‐mode) in which the confinement is improved in the edge region as well as the core region. The most remarkable feature in the improved confinement mode is the multistage formation of transport barriers. The transport barrier was formed in the plasma interior first. After that, the transport barrier was formed in the edge region. For steady‐state operation and current profile control, lower hybrid current drive (LHCD) and neutral beam current drive (NBCD) experiments with bootstrap current contribution are also in progress. Full current drive of 3.6 MA has been achieved at a density of 1.1×1019 m−3 with a current drive efficiency of ne⋅Rp⋅ICD/PLH=2.5×1019 m−2 A W−1 with a 5.7 MW LH wave injection. Current profile control with various LH wave spectra and with NBCD were also demonstrated.