Lightly- or non-seeded, partially detached ITER divertor operation

Abstract

The ITER divertor scenario calls for the reduction of direct target loading to < 50 MW by the use of edge/divertor radiation, enhanced by a seeded recycling impurity, to ‘detach’ the divertor plasma from the target plates. At this radiated power fraction core plasma confinement quality 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 impurity seeding, in an attached mode of operation to alleviate these problems. It is concluded that such scenarios should be possible if an edge separatrix density of 5 × 10 19 m −3, which corresponds approximately to the ITER design value, can be achieved.