Increased radiation due to non-coronal effects on DIII-D and MAST-U with varying input power

Through SOLPS-ITER simulations of DIII-D and MAST-U, an X-divertor (XD) on DIII-D and a super X-divertor (SXD) on MAST-U were shown to have increased carbon emissivity (P (Rad)/n (e) n (I)) over corresponding standard divertors (SD) at similar degrees of partial detachment. The reasons behind the increased emissivity in the DIII-D XD and SXD are analyzed using a simple 0D transport model. From the transport model, it is seen that a major cause of the increased emissivity in the XD and SXD over the SDs is a shorter impurity confinement time. An additional cause (for the SXD) is an increase in the ratio of neutral hydrogen to electron density. The input power (P (in)) was varied and the XD had a higher emissivity at the higher P (in), unlike the SDs which had the emissivity decrease with increasing P (in). A basic geometrical reason is given to explain both the benefits of the XD over the SD as well as the increase in the XD's emissivity with P (in).

Automated summary

Through SOLPS-ITER simulations, it was found that the X-divertor (XD) on DIII-D and the super X-divertor (SXD) on MAST-U had higher carbon emissivity compared to the corresponding standard divertors (SD) at similar levels of partial detachment. A simple 0D transport model was used to analyze the reasons behind the increased emissivity in the XD and SXD. The results showed that the shorter impurity confinement time and the increase in the ratio of neutral hydrogen to electron density were the major causes for the increased emissivity.