Recovery of the characteristics of plasma turbulence from the radial correlation backscattering diagnostics

Abstract

Signals of the backscattering radial correlation Doppler diagnostics of plasma density fluctuations in the presence of the cutoff of the probing wave are analyzed theoretically with allowance for the curvature of magnetic surfaces. The scattering of the probing electromagnetic wave is considered in the linear (Born) approximation with respect to the amplitude of fluctuations. Using the Wentzel−Kramers−Brillouin approach, analytical expressions for the scattered signal and the correlation function of two scattered signals corresponding to oblique probing at different frequencies are derived. A criterion is obtained for the tilt angle of the antenna pattern at which the two-point turbulence correlation function can be measured directly. A method is proposed to recover the spectrum of plasma density fluctuations from the data on the radial wavenumbers even if this criterion is violated.