DEVELOPMENT OF A COMPACT W-SHAPED PUMPED DIVERTOR IN JT-60U

In JT-60U, the modification to a W-shaped pumped divertor will be comp leted in May 1997, aiming to realize sufficient reduction in heat flux to the targets and good H-mode: confinement simultaneously. W-shaped geometry is optimized not only for forming radiative divertor plasmas and reducing the back flow of neutral particles but also for allowing various experimental configurations. Toroidally and poloidally segment ed divertor plates, dome and baffles are arranged in a W-shaped poloid al configuration. The pumping speed can be changed during a shot by va riable shutter valves in the three pumping ports under the outer baffl e. The net throughput is enough for particle control in the steady rad iative operations with high power NBI heating. Carbon fiber composite (CFC) tiles are used for the divertor targets and the divertor throat where large heal flux is expected. Gaps between two adjacent segments are carefully sealed to suppress the leak of neutral gas from the exha ust duct below the divertor and baffles. The strength of the whole str ucture is confirmed by an electromagnetic force analysis and structura l analysis carried out for disruptions of 3 MA discharges with a halo current. (C) 1998 Elsevier Science S.A. All rights reserved.