Effect of Finite Density Fluctuations and of the Upper Hybrid Resonance on O-X Correlation Reflectometry
Authors: G.J. Kramer, R. Nazikian, and E. Valeo
Date of PPPL Report: February 2001
Submitted to: Plasma Physics and Controlled Fusion
The correlation between O-mode and X-mode reflectometer signals is studied with a 1-D reflectometer model taking into account the influence of finite density fluctuation levels and the upper hybrid resonance. It is found that a high level of O-X correlation can only be achieved for sufficiently small density fluctuation levels (typically much less than 1%) or very low magnetic field strengths. The influence of the upper hybrid resonance on the O-X correlation was found to also degrade the correlation between the O and X mode signals for very low magnetic field strengths or for very short density scale lengths. The extrapolation of these results to reactor-scale parameters indicates that the magnetic field strength can reliably be measured in the core plasma provided the density fluctuation level is typically much less than 1%.