GITR Monte Carlo Predictive Simulations of the DIII-D SAS Divertor*

The Global Impurity Transport Code (GITR) is a 3D fully gyrokinetic Monte Carlo transport code that can track impurity particle motion in great detail, capturing full 3D gyro-orbits, prompt re-deposition, and long-range migration distributions.

One goal of the Small Angle Slot (SAS) divertor in the DIII-D tokamak is to reduce net erosion. GITR will be used to provide a high physics fidelity model for tracking gross erosion and re-deposition, and correspondingly, to determine the net erosion of W impurities along the SAS surface. GITR will also be used to simulate W migration along the SOL and deposition along the wall. A synthetic diagnostic in GITR will be used to predict leakage from the scrape-off layer into the core. 

Although GITR has been validated in a linear device, it has not yet been validated in a tokamak environment. Initial GITR simulations of W transport in the SAS divertor, in combination with experimental analyses, provide a validation opportunity for GITR predictions in a tokamak. This validation would allow GITR to be used to inform future designs of a SAS divertor geometry to further minimize net erosion and the leakage of W impurities into the core.