Highly radiating plasmas in negative triangularity with reactor-relevant seeding gases

The advantages of reactor-relevant, heavier noble gas seeding gases like Kr, Ar, and Ne are shown for negative triangularity (NT) plasmas at DIII-D. In this study, we combine the negative NT ELM free, high-performance scenario with a highly radiating mantle that was obtained with reactor-relevant seeding gases. We find that Kr and Ar seeding is advantageous in terms of the gas particles needed for effective divertor target heat flux mitigation, which also implies lower effects on fuel dilution and impurity accumulation. Seeding with Kr, Ar leads to a reduction of the parallel heat flux at the divertor entrance compared to N and Ne effectively reducing P_SOL the power that needs to be dissipated in the divertor. The possibility to radiate upstream to reduce P_SOL is one of the main advantages of NT. Impurity enrichment calculations demonstrate that Ar and Kr are retained more efficiently in the divertor. Thus, the use of high-Z impurities yields similar divertor conditions such as T_e and heat fluxes than low-Z gases with a reduced impurity concentration at the separatrix up to ~90% which is crucial for core-edge integration. We also show that cross-field drifts change the particle and impurity distribution. SOLPS-ITER simulations provide comprehensive insight into divertor and plasma boundary transport mechanisms and support the interpretations of the experimental results.