Automated UEDGE Modeling of the C-Mod Heat Flux Width Database

The Alcator C-Mod heat flux width database suggests a strong correlation of λ_q at the outer divertor target with the inverse square root of the volume-averaged plasma pressure [1], implying that a high-performance core will lead to challenging target heat fluxes. The C-Mod database was augmented with plasma midplane profiles, finding a correlation between λ_q and the edge plasma pressure but failing to observe a clear Spitzer-Härm scaling of λ_q = 2/7 λ_Te [2]. This work evaluates whether the edge plasma fluid model of the UEDGE code can explain the variation of λ_q in the database. 75 discharges from the database are modeled using an automated process that tunes transport coefficients to match experimental midplane profiles of n_e and T_e. The UEDGE and experimental values of λ_q measured in the divertor are found to be correlated, but UEDGE overestimates the heat flux width by an average factor of 1.8. The survey is repeated with UEDGE models of increased and reduced complexity. This UEDGE framework is successful in modeling a wide range of plasma conditions in C-Mod and could be extended to other devices.

[1] D. Brunner et al., Nuclear Fusion 58, (2018).

[2] S. Ballinger et al., Nuclear Fusion 62, (2022).