Towards quantitative turbulence predictions with gyrokinetics

On the way to a better understanding and prediction of plasma turbulence, gyrokinetics is nowadays considered the best compromise between realism and efficiency in plasma theory. Although highly optimized for magnetically confined plasmas, corresponding applications still require massively parallelized codes which are able to exploit present-day supercomputers. The remarkable evolution of such tools from rather qualitative to more and more quantitatively reliable predictions over the last decade is exemplified with the gyrokinetic code GENE (genecode.org) -- an IPP born software package. Particular focus will be placed on the multi-scale nature of plasma turbulence -- both in its relation to macroscopic (machine-size) scales as well as its characteristic manifestations on ion- and electron-gyroradius scales. Verification studies as well as state-of-the-art comparisons with fluctuation measurements involving so-called synthetic diagnostics will be highlighted. Finally, an outlook is given on how these tools are actually integrated in reactor design and where future efforts need to be focused.