Integration of high power, long pulse operation in Tore Supra in preparation for ITER

Abstract

Tore Supra routinely addresses the physics and technology of very long-duration plasma discharges, thus bringing key information on critical issues of long pulse/steady-state operation of ITER. During the last two years, its scientific programme has entered a new phase towards higher power long pulse. Considerable progress has been accomplished towards reliable and safe operation at multi-MW power level in an actively cooled plasma facing components (PFCs) environment. Discharges lasting several resistive times, with combined lower hybrid current drive and ion cyclotron resonant heating at high power level, in plasmas close to the Greenwald limit and Ti close to Te have been obtained. Improved confinement has been maintained together with q(0) ∼ 1.5 for durations up to 20 s. An advanced scheme for the physics and operational integration of plasma scenarios has been developed, and discharges at 7 MW total injected power level have been controlled in an MHD stable region for 60 s. The unique capability of the reflectometry system of Tore Supra has allowed detailed studies of particle/energy transport, and a weak dependence of confinement with β is corroborated by fluctuation measurements. A new mechanism is proposed to explain the D retention observed in long pulses. Analysis of large parallel flows in the scrape off layer (SOL) lends credence to the hypothesis that the SOL is fed by long range transport events that are created near the outboard midplane. Finally, new technological developments for in situ follow-up of PFCs ageing are reported.