SOLPS-ITER modeling of boosted carbon radiation through non-coronal effects in an X-divertor facilitating detachment in DIII-D

Through SOLPS-ITER simulations on DIII-D, we have demonstrated X-divertor (XD)'s abilities to boost carbon line radiation and hence to achieve similar detached conditions with just half the upstream density of the standard divertor (SD). Simulations suggest that the XD geometry vastly expands the carbon radiation volume near the target through the non-coronal effects that increase the carbon emissivity by an order of magnitude within range. The underlying mechanisms include the parallel and perpendicular transport of carbon impurities and the charge exchange with deuterium neutrals. Simplified physics models supported by simulation data indicate that the ultra shallow field angle in the XD plays a critical role in these mechanisms. (paper)