Exploration of DTT conventional and advanced divertor configurations by means of edge simulation codes

The development of a reliable solution for the power and particle exhaust in a reactor, in order to ensure acceptable conditions at the walls while maintaining sufficient core performance, is recognised as one of the major research challenges towards the realisation of a fusion power plant [1]. In order to mitigate the risk that the conventional divertor solution that will be tested in ITER may not extrapolate to DEMO, alternatives must be developed. The role of the DTT facility is to bridge the gap between today's proof-of-principle experiments and DEMO [2]. DTT has been designed to study a large suite of alternative magnetic configurations, including flux flaring towards the target (X divertor), increasing the outer target radius (Super-X) and movement of a secondary x-point inside the vessel (X-point target) as well as the entire range of Snowflake (SF) configurations [3]. Here, first comparative edge studies of conventional Single Null (SN) and alternative configurations by using EDGE2D-EIRENE [4], TECXY [5] and SOLEDGE2D-EIRENE [6] codes will be presented. A closed divertor, with a full W wall, no impurity seeding and a high level of power crossing the separatrix PSOL?40MW, have been considered in the simulations. In addition, the transport coefficient has been set up constant and an outer midplane decay length of 3 mm has been assumed. A density scan for both the conventional and advanced configuration has been performed in order to investigate the behaviour of the different magnetic divertor solutions. In the conventional scenario high power loads are foreseen by the code independently from the density, with a peak values higher than 20 MW/m2. A similar behaviour is also observed in the case of partially detached conditions where the strike point electron temperature falls below 5 eV leading to a clear indication of the roll-over of the density and of the saturation current. However, this condition is reached for upstream density higher than the one foreseen even in the high density scenario. On the contrary, in case of a SF like configurations, manageable values of the power load are obtained also for the medium density scenario. Furthermore, the codes predict detachment conditions for lower value of the upstream density. This behaviour is probably related to the benefit deriving from the geometrical feature of the SF like configurations in terms of increase in the flux expansion and connection length.