Development of DTT single null divertor scenario

Plasma exhaust to the divertor region is recognized by the EUROfusion roadmap [1] as one of the most critical issues to be solved towards the Demonstrative Fusion Power Plant (DEMO). The current technological limits for tungsten as plasma-facing components requires high radiated power fraction by impurities that may affect core performances. With current technological limits, the required radiative fraction in DEMO is about 90%. Current experiments cannot operate with plasma parameters relevant to DEMO divertor designing such as PTot/R and SOL neutral opacity. In order to bridge this gap, the Divertor Tokamak Test facility (DTT) is under construction in Italy. The main goal of DTT is to test highly radiating alternative divertor solutions, such as Advanced Divertor Configurations (ADC) and liquid metal divertor, in DEMO relevant regimes [2]. This work describes the contribution to divertor plasma modeling and development of the conventional Single Null scenario in DTT. The modeling is performed with two different edge numerical codes: SOLEDGE2D-EIRENE and SOLPS-ITER. The chosen scenario has 45 MW of input power, (the maximum prospected for the machine) medium density (ne,sep=5.0x1019m-3, ne/nG ? 0.5) and is the most challenging scenario in terms of power handling. With only Deuterium, the maximum input energy that allows partial detachment in this scenario is about 9 MW, so nitrogen, neon and argon cooling performances are tested. A scan on impurity seeding flux was performed for each impurity keeping the separatrix density constant. For each seeded element, the minimum level of impurity to obtain partial and deep detachment was calculated. Plasma detachment was demonstrated to be mandatory to keep power flux to the divertor below the maximum predicted for safe continuous operations. It was found that the minimum required Zeff increases with the increasing of the Z of the seeded element, but also that the highest radiative fractions (up to 90%) could not be obtained with lighter impurities; this behavior is related to the cooling rate trend of the seeded impurities. Finally, an investigation on the influence of impurity puffing position on the minimum Zeff required to obtain detachment was performed as well.