Role of divertor geometry on detachment and core plasma performance in JT60U

Experimental results related to the divertor geometry such as divertor plas ma detachment, neutral transport and plasma energy confinement, were compar ed in the open and W-shaped divertors. The ion flux near the outer strike p oint was larger than in the open divertor, and the electron temperature at the target, T-c(div), was reduced. Divertor detachment and x-point MARFEs o ccurred at (n) over bar(e) 10-20% lower than that for the open divertor. Al though the leakage of neutrals from the divertor to the main chamber decrea sed, a neutral source in the main chamber due to an interaction of the oute r scrape-off layer (SOL) plasma to the baffle plates became dominant above the baffle. Degradation in the enhancement factor of the energy confinement was observed similarly in the open and W-shaped diverters. The neutral den sity inside the separatrix was estimated to be a factor of 2-3 smaller, whi ch did not affect the energy confinement. (C) 1999 Elsevier Science B.V. Al l rights reserved.