Impact of Divertor Neutral Sourcing on Pedestal Performance in MAST-U

We present experimental observations of the effect of neutral sourcing on the edge pedestal of MAST-U, with interpretive modeling though a novel coupling between EPED and SOLPS. A series of experiments at MAST-U were performed to study the impact of neutral puffing at different levels of divertor closure on pedestal conditions. The temperature pedestal was observed to degrade when the divertor was opened and when neutrals were puffed from the divertor in both closed and open configurations, agreeing with findings on other machines. A higher performance density pedestal was observed in the open divertor configuration as expected, but the neutral puffing was insufficient to change the pedestal density in the closed divertor. Moreover, outer midplane passive D-α profiles were found to be correlated but not proportional to pedestal changes. Interpretive modeling of the experiment is shown with a first-of-its-kind, two-way coupling between EPED-SOLPS in the IPS framework. A recently improved neutral penetration model [1] with optimized transport coefficients fitted to MAST-U data is implemented to self-consistently predict the pedestal density a priori as an EPED input from a converged SOLPS solution. The pedestal conditions are then iterated towards a new SOLPS solution using a cross-field transport automated fitting technique to iterate a new SOLPS solution. The modular approach of the coupling scheme enables further refinement with physics-based models of pedestal heat and particle transport.