Implementation and application of two synthetic diagnostics for validatingsimulations of core tokamak turbulence

摘要

The deployment of multiple high-resolution, spatially localized fluctuation diagnostics on theDIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] opens the door to a new level of coreturbulence model validation. Toward this end, the implementation of synthetic diagnostics thatmodel physical beam emission spectroscopy and correlation electron cyclotron emission diagnosticsis presented. Initial results from their applications to local gyrokinetic simulations of two locationsin a DIII-D L-mode discharge performed with the GYRO code [J. Candy and R. E. Waltz, J. Comput.Phys. 186, 545 (2003)] are also discussed. At normalized toroidal flux p=0.5, we find very goodagreement between experiment and simulation in both the energy flows and fluctuation levelsmeasured by both diagnostics. However, at p=0.75, GYRO underpredicts the observed energy flowsby roughly a factor of 7, with rms fluctuation levels underpredicted by a factor of 3. Interestingly,at both locations we find good agreement in the shapes of the radial and vertical density correlationfunctions and in the shapes of the frequency power spectra. At both locations, the attenuation of theGYRO-predicted fluctuations due to the spatial averaging imposed by the diagnostics' spot sizes issignificant, and its incorporation via the use of synthetic diagnostics is shown to be essential forquantitative comparisons such as these.