Simulation study of the impurity radiation in the quasi-snowflake divertor with Ar seeding for CFETR

Abstract

The snowflake divertor is considered as a possible candidate to exhaust the huge amount of power from core plasma for future fusion reactors. In this work, the radiative quasi-snowflake (QSF) divertor with argon seeding was studied by SOLPS5.0 simulation for the China Fusion Engineering Test Reactor. The relation between radiation power, P rad , electron density, n e, and effective ion charge, Z eff, was established based on the density and radiation fraction scan for both QSF and the ITER-like divertor (ILD). The comparison of radiative efficiency shows that QSF divertor is able to radiate more power with much lower impurity concentration than the ILD, when upstream density is relatively high. Further analyses are performed for the low ( n e,sep ~ 2.3 × 10 19 m −3 ) and high density cases ( n e,sep ~ 4.5 × 10 19 m −3 ). For low density cases, outer divertor plasma of QSF is firstly detached due to a much pronounced increase of outer divertor flux expansion, while the inner divertor detaches at first for the ILD configuration. Furthermore, the degree of detachment is much higher for the outer divertor in the QSF configuration under similar P rad , which can be beneficial for impurity screening in the outer divertor. For high density cases, both divertor targets of QSF are detached with relatively lower radiated power while the outer target of ILD is still attached. Z eff at outer mid-plane for QSF is obviously lower than that for ILD with similar P rad , which means better impurity screening in QSF.