Scale resolved multi-field gyrokinetic code validation*

Achieving high values of density, ion temperature, and energy confinement times is crucial for future fusion reactors. These cannot be reached in today’s magnetic fusion devices. The values are limited, besides the geometry, mainly by turbulent transport. To design turbulence optimized devices, simulation codes need to be validated by experiments.

Validation work has already been done for a single or a small number of turbulence observables, where individual observables were reproduced by the simulation codes within the error bars of the measured quantities. A comprehensive validation should involve as many observables as possible at the same time - a challenging goal for both experiment and theory, which is tackled in this contribution.

We present a study, where a large set of experimental turbulence data is collected at ASDEX Upgrade in two plasma scenarios with varying electron temperature gradient lengths through ECRH. It includes wavenumber spectra, density and temperature fluctuation amplitudes, radial correlation lengths, and the cross-phase between density and temperature fluctuations. These quantities are measured using Doppler reflectometers and an electron cyclotron emission radiometer. They are compared to gyrokinetic turbulence simulations from the GENE code. To account for diagnostic effects in the measurement, sophisticated synthetic diagnostic modeling is applied.

The work shows the encouraging example of code validation, where a remarkable number of measured physics quantities are successfully reproduced by the code. We emphasize the simultaneous agreement between all experimental measurements and simulated turbulence quantities.

These findings provide a sound scientific justification for using codes such as GENE in the design of future fusion reactors.