Speaker
Description
An empirical method for inferring MHD-induced anomalous fast ion transport from normalized Electron Cyclotron Emission (ECE) temperature fluctuation measurements is reported. The model developed infers a time-dependent, spatially varying anomalous fast ion diffusion profile directly from normalized temperature fluctuations such that $D_{fast} \propto dT/T$. The model is coupled to the Monte Carlo fast ion code NUBEAM within the plasma transport code TRANSP to simulate DIII-D plasmas, and found to reproduce experimental measurements from five different fast ion related diagnostics under strong Alfvén Eigenmode activity conditions: the volumetric neutron rate, the plasma stored energy, spatially resolved Main Ion and Fast Ion D-𝛼 spectra, and phase space resolved Imaging Neutral Particle Analyzer (INPA) measurements. The application of this method to a database of more than 40 DIII-D discharges, spanning a large fraction of the available DIII-D parameter space, finds the predicted neutron rates and stored energies agree with experiment with an average accuracy of 15% or better. Detailed analysis of select simulations using the D(ECE) fast ion transport model indicate critical-gradient-like behavior, with direct comparisons of D(ECE) predictions to the reduced critical gradient model TGLF-EP+Alpha finding strong agreement. Cross-comparison of empirical transport predictions against a suite of reduced fast ion transport modeling results from the codes KICK, RBQ, and TGLF-EP+Alpha finds the strongest agreement with TGLF-EP modeling, highlighting the efficacy of a local critical gradient fast ion transport modeling framework. This empirical modelling work demonstrates the efficacy and methodology behind a new standard tool for routine analysis of EP experiments which is accessible to non-experts, contains no “tuned” free parameters, and has trivial computational cost.