Turbulence and beam size effects on reflectometry measurements

A two-dimensional code based on the WKB (Wenzel-Kramers-Brillouin) approxim ation is used to simulate reflectometry measurements in plasmas with turbul ence. In this work we aim to understand, first the role of turbulence in th e determination of density profiles with reflectometry and, second, the abi lity of reflectometry techniques to give reliable information on the charac teristics of the turbulence itself. The effects on the profile determinatio n of a rotating turbulence structure with nonperpendicular reflection are a nalyzed. The influence of the turbulence level, fluctuation wavelengths and antenna beam size on the density profile determination has been studied in static plasma with perpendicular launching. The code has been used to simu late correlation measurements. The results show the correlation of the refl ectometry signals for different turbulence parameters. Errors in the correl ation length increase when two-dimensional effects become important, though the homodyne signal works better than the phase. The correlation simulatio ns also show the way for new methods to determine the group delay and there fore the density profile. (C) 2001 American Institute of Physics.