SOLPS-ITER simulations of large power handling in the divertor for CFETR with full drifts

One of the major challenges for the 1GW class fusion reactor Chinese Fusion Engineering Testing Reactor (CFETR) is to handle huge power exhaust (200MW) efficiently. In the present work, the effects of seeding radiation impurities, such as argon (Ar) and neon (Ne) and increasing divertor leg length in CFETR are systemically investigated to evaluate the efficient reduction of the maximum steady-state power load at the divertor target to an engineering design level (less than 10 MWm^-2) by the SOLPS-ITER code package with full drifts. The modeling results show clearly that increasing radiation impurities Ar and Ne seeding rate with the fixed D₂ fueling gas injection rate can significantly reduce the target electron temperature and heat flux density for the reference divertor geometry, which can be both reduced further with higher D₂ injection rate. Moreover, the radiation efficiency for Ar is better than that for Ne. However, higher impurity seeding rate will cause higher impurity concentration in the core region, which can be controlled well by selecting the proper D₂ fueling gas injection rate and impurity seeding rate. Based on the reference geometry in CFETR, increasing the divertor leg length from 1.7m at present to 2.4m can also benefit reducing electron temperature and heat load at the target further. These results show that the divertor design with a longer leg and higher Z seeding such as Ar is appropriate to obtain the divertor scenario for CFETR divertor design.