Fullwave Doppler reflectometry simulations for density turbulence spectra in ASDEX Upgrade using GENE and IPF-FD3D

Doppler reflectometry is an important microwave diagnostic for turbulent fusion plasmas. A microwave beam is scattered off density fluctuations, with wavenumbers according to incident frequency and relative direction. This way, a density fluctuation spectrum is measured. However, the correspondence between fluctuation power and scattered microwave power is strongly nonlinear. Studying these processes numerically therefore requires fullwave simulations (IPF-FD3D), with density fluctuations supplied by a separate plasma turbulence code (GENE). Earlier such attempts suffered from the low number of data points in the ‘interesting’ part of the spectrum, where a power law had to be fitted to 4 or 5 points. This has been overcome with recent simulations, which now show a much better agreement with experimental data.