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The first experimental campaigns of Wendelstein 7-X (W7-X) have shown thatturbulence plays a decisive role in the performance of neoclassically optimizedstellarators. This stresses the importance of understanding microturbulencefrom the theoretical and experimental points of view. To this end, this paperaddresses a comprehensive characterization of the turbulent fluctuations bymeans of nonlinear gyrokinetic simulations performed with the code stella intwo W7-X scenarios. In the first part of the paper, the amplitude of thedensity fluctuations is calculated and compared with measurements obtained byDoppler reflectometry (DR) in the OP1 experimental campaigns. It is found thatthe trend of the fluctuations along the radius is explained by the access ofthe DR system to different regions of the turbulence wavenumber spectrum. Inthe second part of the article, frequency spectra of the density fluctuationsand the zonal component of the turbulent flow are numerically characterized forcomparisons against future experimental analyses. Both quantities feature broadfrequency spectra with dominant frequencies of O(1)-O(10) kHz.

Electrostatic microturbulence in W7-X: comparison of local gyrokinetic simulations with Doppler reflectometry measurements