Modeling blob and hole-like impurity transport in the scrape-off layer of DIII-D*

A novel blob and hole-like impurity transport model has been implemented within the Monte Carlo SOL impurity transport code DIVIMP and subsequently benchmarked on DIII-D. Simulation results obtain simultaneous quantitative agreement with estimates of tungsten density at multiple locations. The model uses blob measurements from a reciprocating Langmuir probe as input. The blob/hole-like transport model hypothesizes that impurities encountering blobs/holes experience the same E_pol x B_T drift as the blobs/holes. Blobs carry impurities away from the core and holes transport impurities into the core. Simulations using blob/hole-like impurity transport are successfully performed on two DIII-D L-mode discharges with the outer strike point on W tiles: one in an open divertor configuration, and another in a slot-like closed divertor configuration. TGYRO simulations using soft X-ray data of W concentration predict core profiles of W density up to the ~separatrix (n_W~10¹⁵ m^-3). 3DLIM simulations constrained by W surface deposition patterns on far-SOL collector probes estimate the W density within the far-SOL (n_W~10¹² m^-3). DIVIMP with blob/hole-like transport matches the W density within 25% for both TGYRO and 3DLIM estimates by assuming impurities travel with blobs/holes for 10 us at a time.