LIGHTLY-SEEDED OR NON-SEEDED, PARTIALLY DETACHED ITER DIVERTOR OPERATION

The ITER divertor scenario calls for the reduction of direct target lo ading to < 50 MW by the use of edge/divertor radiation, enhanced by a seeded recycling impurity, to 'detach' the divertor plasma from the ta rget plates. At this radiated power fraction core plasma confinement q uality is degraded, the radiation comes mainly from the X-point region and impurity control becomes difficult. In this paper we examine the possibility of using either no impurity seeding, or very light impurit y seeding, in an attached mode of operation to alleviate these problem s. It is concluded that such scenarios should be possible if an edge s eparatrix density of 5 X 10(19) m(-3), which corresponds approximately to the ITER design value, can he achieved.