Journal
NUCLEAR FUSION
Volume 61, Issue 12, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/1741-4326/ac32f2
Keywords
turbulence; particle transport; spectroscopy; Bayesian inference; impurities; neutrals; tokamaks
Categories
Funding
- DoE Award [DE-FG02-91-ER54109]
- National Energy Research Scientific Computing Center (NERSC)-a US DoE Office of Science User Facility [DE-AC02-05CH11231]
- Department of Energy [DE-SC0014264, DE-FC02-04ER54698, DE-SC0007880]
- U.S. Department of Energy (DOE) [DE-SC0007880] Funding Source: U.S. Department of Energy (DOE)
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Experimental inferences of cross-field impurity transport coefficients for AlcatorC-Mod plasmas show the impact of edge-localized modes on the results; consideration of line ratios across different spectral ranges improves accuracy of inferred coefficients; significant discrepancies in convection suggest difficulties in predicting flat or hollow impurity profiles.
We present experimental inferences of cross-field impurity transport coefficients for AlcatorC-Mod plasmas without edge-localized modes, leveraging a novel forward model for the entire Ca K- alpha spectrum, including satellite lines within the spectral range, to compare to high-resolution x-ray imaging crystal spectroscopy (XICS). These measurements are complemented by extreme ultra-violet (EUV) spectroscopy that constrains transport closer to the edge. Using new atomic data sets for both XICS and EUV analysis has enabled consideration of line ratios across both spectral ranges and has increased the accuracy of inferred transport coefficients. Inclusion of charge exchange between edge thermal neutrals and impurities is shown to be extremely important in C-Mod pedestals. Atomic D neutral densities from experimental D Ly( alpha ) measurements at the midplane are compared to SOLPS-ITER simulations, finding good agreement. Bayesian inferences of impurity transport coefficients are presented for L-, EDA H-, and I-mode discharges, making use of the Aurora package for forward modeling and combining our spectroscopic constraints. Experimentally inferred diffusion profiles are found to match turbulent transport models at midradius within uncertainties, using both quasilinear gyro-fluid TGLF SAT-1 and nonlinear ion-scale gyrokinetic CGYRO simulations. Significant discrepancies in convection are observed in some cases, suggesting difficulties in predictions of flat or hollow impurity profiles.
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