It is envisaged that exhaust control in tokamak fusion reactors, e.g. NET, ITER and DEMO, will be achieved using poloidal divertors. The targets for these divertors, which will receive substantial quantities of heat from, and may be eroded by, the exhausted particles, present a significant engineering challenge. Here a systematic approach has been derived to identify viable design options given the limits imposed by the practicalities of cooling and structural integrity. As an example target designs for DEMO-DN (a DEMO version of NET-DN) are presented which are capable of handling a peak heat flux of 13 MW/m 2.
The exhaust particles and heat arrive at the target along the field lines which intersect it at a shallow angle of attack (--1ยฐ). Hence small perturbations in target or field geometry can lead to large changes in local heat flux, producing hot spots. Perturbations due to field ripple, thermal distortion, target manufacturing errors and discontinuities at junctions in the target assembly have been quantified. For the DEMO-DN example these perturbations produce significant, but seemingly manageable, hot spots.