Simulation of Radiative Divertor Plasmas by Ar Seeding with the Full W-Wall in JT-60SA

Radiative divertor plasmas for JT-60SA with a full tungsten (W) wall, which is one of options in future, have been simulated with a SOL/divertor integrated code, SONIC. A conventional modified-coronal radiation (MCR) model with a finite confinement time is used for both Ar and W for the purpose of wide-range parameter surveys for the divertor plasma to obtain the required conditions (qt ≤ 10 MW/m2, nSepe−mid = 3∼8×1019 m−3, Prad < ∼30 MW), saving the calculation time. At low W density ratio (nW/ni = 1×10−5), due to low radiative power from W ions, Ar density ratio (nAr/ni ≥ 1.0×10−3) and a strong gas puff (Γp ≥ 3.0×1022s−1) are inevitable to suppress the divertor heat flux down to 10 MW/m2. Increasing nW/ni to 1×10−3 in the divertor region, the divertor heat load becomes low and the operative regions are expanded. While, the W production shall be suppressed since the W radiation is increased with replacement of Ar radiation and the particle recycling decreased. A Monte-Carlo module (IMPMC) implemented in SONIC for Ar seeding reveals that the spatial distribution of Ar ions is predominantly determined by shell structures of the Ar ions. The consistency between IMPMC and MCR calculations is demonstrated for the averaged nAr/ni ratio, the electron density and temperature profiles on the divertor target and typical parameter such as the divertor heat load. It shows that the detailed analysis with IMPMC model can be speedily obtained, using a steady state solution obtained by MCR model as an initial state