Microwave Imaging Reflectometry for the Measurement of Turbulent Fluctuations in Tokamaks
Author: E. Mazzucato
Date of PPPL Report: February 2004
Date of Revised PPPL Report: April 2004
Published in: Plasma Physics and Controlled Fusion 46 (2004) 1271-1282
This article describes a numerical study of microwave reflectometry for the measurement of turbulent fluctuations in tokamak-like plasmas with a cylindrical geometry. Similarly to what was found previously in plane-stratified plasmas, the results indicate that the characteristics of density fluctuations cannot be uniquely determined from the reflected waves if the latter are allowed to propagate freely to the point of detection, as in standard reflectometry. Again, we find that if the amplitude of fluctuations is below a threshold that is set by the spectrum of poloidal wave numbers, the local characteristics of density fluctuations can be obtained from the phase of reflected waves when these are collected with a wide aperture antenna, and an image of the cutoff is formed onto an array of phase-sensitive detectors.