Modeling of power exhaust in DEMO alternative divertor configurations with SOLEDGE2D-EIRENE

Modelling of power exhaust of the DEMO device is one of the activities required to evaluate the possibility to build a reliable fusion reactor. Indeed recognizing the difficulty of the standard Single Null (SN) divertor configuration to provide a solution compatible with present and foreseen solid divertor target technological solutions, many alternative divertor magnetic configurations have been proposed for DEMO. The aim of any alternative magnetic configurations is the reduction of the heat load on the divertor targets lowering the detachment thresholds and increasing the radiation power in the SOL. Among all proposed alternative magnetic configurations in this study the following ones have been compared to the SND: the flux flaring towards the target of a X divertor (XD), the increasing of the outer target radius of a Super-X divertor (SXD), the connection length increasing and strike points doubling of a Snowflake divertor in plus and minus variants (SFD-plus, SFD-minus) and finally the strike points doubling of the double-null divertor (DND). By using the 2D SOLEDGE2D-EIRENE [1] code here we present the first comparative study of these configurations performed with a fluid plasma code coupled to a neutral kinetic code. All configurations with nearly equal global parameters (major radius, plasma section and plasma current) have been modeled with a full W wall with unitary recycling, reasonable pumps, no impurity seeding and no drifts in two conditions: at various density but at the level of power crossing the separatrix PSOL=150MW, required in DEMO to operate in H-mode, at a fixed middle density nsep=2.5?1019 m-3 but different PSOL=50÷150 MW to simulate the effect of impurities. As transport parameters the couple ?? = 0.18 and D? = 0.42 m2/s which provides an upstream e-folding decay length of the power flowing channel on the outboard equator of ?q,u?3 mm for the SND in attached condition. Given the uncertainties in the transport parameters knowledge and on some physical phenomena the aim of the modeling was not to provide the "exact" evaluations of main exhaust parameters but to provide the best comparison between various configurations with a "state of the art" edge code. In these contest the simulations have shown different advantages of each alternative configuration against the others in terms of power load on targets and volume losses but in general alternative configurations performs equal or better than the SND one.