Wavenumber-resolved turbulence investigations in the ASDEX upgrade tokamak and comparison to numerical simulations

A new Doppler reflectometer has been installed in W-band (75 - 105 GHz) on ASDEX Upgrade which is now working reliably. Owing to its steerable ellipsoidal mirror, the system allows for the measurement of the density turbulence level at different structure scales k = 5 - 25 cm^-1 in a large radial region reaching into the bulk plasma (depending on plasma parameters). In parallel, non-linear GENE simulations have been conducted in order to compare observed heat fluxes and turbulence levels with predictions from gyrokinetic simulation. In general, reasonable agreement is obtained between heat fluxes by varying the input gradients R/L_Ti only slightly (up to 20%). The radial turbulence level profile shows agreement in its general trend - An increase from plasma core towards the edge - but a discrepancy is found in the plasma response to additional ECRH heating: while the Doppler reflectometry turbulence level increases, the one from GENE decreases. Both scans in R/L_Te and the E ×B-shear are ongoing work in order to clarify these points.