2D MODELING OF RADIAL CORRELATION REFLECTOMETRY

The response of a radial correlation reflectometer to turbulent plasma fluctuations in a tokamak/stellarator is studied using a two-dimensio nal (2D) physical optics/distorted surface model. Reflectometer phase and power time signals are generated numerically using the Helmholtz e quation and simulated reflection layers. The layers are linked by a ra dial (wavenumber) k-spectrum with a common poloidal/transverse k-spect rum and a linear dispersion relation. The radial correlation lengths c omputed from phase fluctuations (L(r(phi))) and from power fluctuation s (L(r(P))) show variations with the poloidal k-spectral width, the su rface fluctuation amplitudes (weak and strong turbulence) and the micr owave beam width. L(r(P)) is always smaller than the true correlation length L(r(true)) (computed from the layer fluctuations) by a factor o f root 2 to 2 depending only on the fluctuation amplitude. L(r(phi)), however, is much larger than L(r(true)) for weak fluctuations and drop s with increasing fluctuation amplitude to less than L(r(true)). L(r(p hi)) also varies with the beam width and poloidal k-spectra, while L(r (P)) does not. A relationship, involving the rms phase fluctuation lev el, is found between L(r(phi)) and the true correlation length.