Simulation studies of divertor power exhaust with neon seeding for CFETR with GW-level fusion power

A conventional single null divertor geometry has been proposed for Chinese fusion engineering testing reactor (CFETR) with fusion power up to gigawatt level. Modeling using the SOLPS5.0 code package shows promising results for divertor power exhaust by seeding with neon (Ne) and deuterium (D2). Partial detachment for both inner and outer divertor targets can be achieved with a peak heat load lower than 3 MW/m2. The effective ion charge number, Zeff, at the core boundary is below three, which can be further reduced by increasing the upstream D2 puffing rate. A higher D2 puffing rate helps to increase electron density (ne) in scrape-off layer (SOL) and the impurity screening ability. Based on the SOLPS modeling results, the lifetime of tungsten (W) divertor targets has been estimated by using the DIVIMP code, which indicates that W sputtering is mainly contributed by Ne ions at a far SOL region due to high electron and ion temperature (Te and Ti) there. Upstream D2 puffing can reduce the W erosion rate and W impurity concentration inside the separatrix due to decreasing Te and Ti at the far SOL region. The modeling results show a viable operation regime for the CFETR divertor.