Gyrokinetic simulations compared with magnetic fluctuations diagnosed with a Faraday-effect radial interferometer-polarimeter in the DIII-D pedestal

Abstract Experimental data on electromagnetic fluctuations in DIII-D, made available by the Faraday-effect radial interferometer-polarimeter (RIP) diagnostic Chen (2016 Rev. Sci. Instrum. 87 11E108), is examined comparison with detailed gyrokinetic simulations using numerical experiment (GENE). The has unique capability of making internal measurements fluctuating magnetic fields ∫ n e δ B mathvariant="normal">r mathvariant="normal">d R . Local linear identify microtearing modes (MTMs) over a substantial range toroidal mode numbers (peaking at n = 15) frequencies good agreement experimental data. nonlinear reinforce this result producing frequency spectrum that diagnosed RIP. Simulated heat fluxes are expectations. However, fluctuation amplitudes substantially lower than Possible sources discrepancy discussed, notably fact diagnostics localized mid-plane—the poloidal location where predict to be smallest. Despite some discrepancies, several connections between and experiments, combined general criteria discriminating potential pedestal instabilities, strongly point MTMs as source observed fluctuations.