Numerical modelling of tokamak plasma micro turbulence wave number spectrum reconstruction using radial correlation reflectometry data

Abstract

Radial correlation reflectometry (RCR) is used technique providing information on the tokamak plasma micro turbulence. The data interpretation in this technique using for probing simultaneously different frequencies is based on the hypothesis of high measurements localization. In essence, it is similar to that used in probe correlation method where the signal cross-correlation function (CCF) is identified with the turbulence CCF. Unfortunately according to a strict theoretical analysis, both numerical and analytical, this assumption is incorrect; nevertheless the analytical theory proposed here shows that it is possible to reconstruct the turbulence radial wave number spectra using the RCR experimental data. It is also demonstrated that the turbulence CCF is reconstructed more precisely than spectra. It is illustrated by numerical computations for FT-2 (Russian Federation) and Tore Supra (France) tokamaks. Capabilities of spatial inhomogeneous micro turbulence spectra reconstruction is investigated as the transport barrier characterization for example. Information is also reported on the limitations of this method.