Numerical modeling of micro turbulence wave number spectra reconstruction using radial correlation reflectometry: I. O-mode reflectometry at the linear plasma density profile

Abstract

Based on the one-dimensional analytical theory of radial correlation reflectometry (RCR), numerical models of RCR experiments have been built. Computations are carried out for O-mode at a simple linear plasma density profile under conditions relevant to experiments. The turbulence spectrum and cross correlation function reconstruction procedure is applied and its feasibility is demonstrated while the assumptions of the model are fulfilled. The limitations of the method are discussed. The numerical models of the RCR experiments, targeted at the reconstruction of the turbulence spectrum in tokamaks where the plasma density profile can be approximated by a linear density profile, are performed and show in most of the cases that the wave number spectra can be extracted. The RCR capabilities and dependences on the main experimental parameters are also studied.

Radial correlation reflectometry at oblique probing wave incidence (linear scattering theory predictions)

“…(See figure 1(a) where the probing and scattering wave trajectories and FS regions are shown for both cases.) According to (15), the FS is provided by fluctuations possessing radial wave number much smaller than poloidal one and thus appears to be non-local. In the case of a finite antenna beam width this condition is broadened, as prescribed by (14).…”

“…The first one [10,15,16] is based on the mathematical procedure of the turbulence spectrum reconstruction from the RCR data developed in the 1D theoretical model [10]. It uses the explicit expressions for the small-angle-scattering efficiency dependence on the fluctuation radial wavenumber [10].…”

Turbulence radial correlation length measurements using Doppler reflectometry in TJ-II

“…Based on this simple representation, a method to reconstruct the turbulence radial wavenumber spectrum and therefore the radial correlation length from reflectometry signals has been proposed. The demonstration of the method feasibility was shown in [14] within a one-dimensional numerical modelling for O-mode reflectometry. This method has been applied to estimate turbulence characteristics from experimental data obtained in the Tore Supra and FT-2 tokamaks [15,16].…”

Turbulence correlation properties measured with ultrafast sweeping reflectometry on Tore Supra

“…Reflectometry has long been used to measure turbulence fluctuations and correlation lengths mostly using fixed frequency systems. The conventional method of two-frequency reflectometry (radial correlation reflectometry) uses two separate microwave systems with different frequencies [1][2][3][4][5][6][7][8].…”