Speaker
Description
Nitrogen with the high chemical activity can generate the complex chemical compounds with other elements (i.e. hydrogen, deuterium) in the plasma volume or in the divertor target material. These chemical processes of nitrogen impurity cannot be simulated in the modelling, which is attributed to the limited version of the current EMC3-EIRENE code. Nevertheless, these chemical effects can be summarized and modelled in an effective impurity recycling coefficient of the EMC3-EIRENE code. Accordingly, influence of nitrogen recycling on toroidally asymmetric heat load distribution with nitrogen seeding on the Chinese Fusion Engineering Testing Reactor (CFETR) X-divertor configuration has been performed by the three-dimensional (3D) edge fluid transport code package EMC3-EIRENE. The sensitivity studies of the recycling coefficient of nitrogen ions scanned from 0% to 100% show that the larger recycling coefficients of nitrogen ions lead to a significant increment of nitrogen particle content with different charge-states in the simulation volume. The increased contributions to total power loss induced by nitrogen impurities are found both for the in- and out-board seeding positions. While the peak values of electron temperature and heat load rapidly decrease with the larger recycling coefficients of nitrogen ions, especially for the high recycling coefficient cases. A more obvious toroidal asymmetry of heat load distribution is gained for the high nitrogen recycling coefficient compared to the low recycling coefficient scenarios. This is attributed to the toroidally enlarged deposition area of nitrogen ions on divertor targets and the higher power loss by nitrogen impurities as the recycling coefficient of nitrogen ions increases.