Impurity behavior in high performance radiative discharges of JT-60U

Transport coefficients of impurities in reversed shear plasmas are evaluate d and compared with those in ELMy H-mode plasmas, The diffusivity is signif icantly reduced (similar to1/10) at the internal transport barrier, An inwa rd pinch velocity of -3 m/s is also observed at the ITB, The inward pinch v elocity increases as charge number of impurity increases. Effects of Ar see ding to the main plasma are investigated in ELMy H-mode, Argon seeding main tain improved confinement H-ITER89 = 1.4, the clear edge pedestal. the radi ation fraction of similar to 80% and the divertor detachment up to 70% of G reenwald limit. Moreover, argon seeding reduces type I ELM frequency less t han half, but the heat load of each ELM on the outer target plate does not change. Therefore, the reduction of energy losses due to ELMs probably caus es the improvement of edge confinement in Ar seeded cases, though the radia ted power inside the separatrix increases. (C) 2001 Published by Elsevier S cience B.V.