Confinement and divertor studies in Japan Tokamak JT-60U*

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Abstract
This paper presents confinement characteristics of H mode and high βP mode in Japan Tokamak JT‐60U [Plasma Devices Operat. 1, 43 (1990)], effects of current profiles, pressure profiles and sawtooth oscillations on the operational limits and energy confinement, and divertor characteristics. The operational regime required for core plasma performance and divertor conditions is discussed on the basis of the experimental results. The main parameters achieved in confinement studies are Ti(0)=38 keV, nd(0)Ti(0)τglobalE ∼ 4.4×1020 m−3 sec keV, H factor {defined by τE/τITER89P L modeE [Nucl. Fusion 30, 1999 (1990)]}∼3 at εβP∼0.5 in high βP mode and nd(0)Ti(0)τglobalE ∼ 2.5 × 2020 m−3 sec keV in H‐mode discharges with BT=4.2 T. Advantages of high q operation are suggested from studies on operational regime and confinement. The divertor study shows that a parameter ne qeff (qeff: effective safety factor) plays a role in characterizing divertor actions such as relaxing of heat flux profiles, radiation loss and deuterium recycling. High ne qeff operation is shown to be essential for the alleviation of heat load on the divertor.