Experimental Inference and Modeling of Particle Transport in Alcator C-Mod and DIII-D Regimes without ELMs*

We present inferences of radial profiles of experimental impurity transport coefficients following laser blow-off (LBO) injections on both DIII-D and Alcator C-Mod. In most cases, we find agreement in diffusion profiles to within a factor of 2 with respect to NEO, TGLF and nonlinear CGYRO predictions, but significant discrepancies when hollow impurity profiles are experimentally observed. This suggests that turbulent transport models may be missing critical physics. We make use of an advanced Bayesian framework, leveraging a range of spectroscopic diagnostics and recent development of the Aurora package. Our investigation spans regimes without ELMs on both devices. On C-Mod, a novel forward model for the entire K-alpha spectrum of calcium has been combined with VUV spectroscopy. On DIII-D, analogous VUV measurements complement local CER density estimates for both intrinsic C and LBO-injected impurities. In all cases, the effect of charge exchange between background neutrals and impurities is extremely important for charge state balance in the pedestal, as indicated by C-Mod experimental D Lyman-alpha midplane measurements and SOLPS-ITER modeling.