Investigation of the Scattering Efficiency in Doppler Reflectometry by Two-Dimensional Full-Wave Simulations

Two-dimensional full-wave simulations of Doppler reflectometry in slab and curved geometries have been carried out with the finite-difference time-domain code IPF-FD3D. The goal is to find the instrument response function of the reflectometer that allows the recovery of the poloidal plasma-density-fluctuation-wavenumber spectrum by Doppler reflectometry at different angles of incidence. Apart from nonlinearities caused by high fluctuation levels, the scattering process is found to be strongly dependent on the angle of incidence on the cutoff layer, the beam parameters, and the plasma-density gradient length. In addition, the code was applied to the actual geometry of an ASDEX-Upgrade plasma.