Real-time measurement and feedback control of ion temperature profile and toroidal rotation using fast CXRS system in JT-60U

A fast charge exchange recombination spectroscopy (CXRS) system has been developed for the real-time measurement and feedback control of ion temperature (Ti) profile and toroidal rotation velocity (Vt) in JT-60U. In order to control Ti and Vt in real-time, the charge exchange recombination spectroscopy with high time resolution, the real-time processor system, and the real-time control system have been developed. Utilizing this system, real-time control of the Ti gradient between r/a ∼ 0.25–0.5 has been demonstrated with neutral beams at high beta plasmas (normalized beta βN ∼ 1.6–2.8). The strength of the internal transport barrier is controlled. Moreover, the real-time control of Vt has been demonstrated from counter (anti-parallel to the plasma current, Ip) to co (parallel to the Ip) direction. Then the behavior of edge localized mode (ELM) is changed by controlling the Vt.