A theoretical investigation of the turbulent structures tilting measurements with radial correlation Doppler reflectometry

Abstract

A new technique for measuring the tilting of the turbulent structures is studied analytically within the framework of Born approximation. Probing with O-mode, linear density profile and slab geometry are considered. Analytical expressions are derived for scattering signal and crosscorrelation function of scattering signals valid for different probing frequencies. Comparison with previously used "intuitive model" is made, discrepancies pointed out and a more general expression for narrow probing beam is derived. General conclusions about the technique are made and a possible alternative is suggested. Analytical results are validated with linear numerical simulations employing reciprocity theorem, importance of poorly localized smallangle scattering is confirmed.

Impact of the turbulence wavenumber spectrum and probing beam geometry on Doppler reflectometry perpendicular velocity measurements

“…, where |h(k ⊥ )| is the underlying normalized perpendicular wavenumber spectrum of the density turbulence [9,23,24]. This linear approach is typically only valid in the plasma core.…”

“…Accordingly, DR probes several wavenumbers in a range of k ⊥,p ± ∆k ⊥ , where k ⊥,p is the central probed wavenumber. In the linear scattering theory, the back-scattered wave electric field E b (k ⊥ ) can be found applying the reciprocity theorem [23,24] or the physical optics model [26], such that in the k-space…”