Thomson Scattering of Essentially Non-Gaussian Microwave Beams in Inhomogeneous Magnetized Plasma

Electrodynamic reciprocity theorem is used for developing a quantitative theory of scattering of finite-aperture non-Gaussian microwave beams on density fluctuations in a spatially inhomogeneous gyrotropic media. The principal result of this study consists in representation of spectral power density of scattered radiation detected by receiving antenna in the form of convolution of Wigner functions (characterizing arbitrary spatially inhomogeneous distributions of the probe field and the field of the receiving antenna) with the spectrum of the autocorrelation function of fluctuations of the dielectric response. As a non-trivial example of application of the developed theory to an actual problem, we discuss a non-standard scheme of Collective Thomson scattering (CTS) of high-power millimeter-wave radiation on plasma density fluctuations for diagnosing the velocity distribution function of energetic ions in fusion plasma. The scheme exploits a strong refraction of probing and scattered microwave beams reflecting from the cut-off layer in dense plasma and may be realized with the existing CTS diagnostic system at the GDT facility (Budker Institute, Novosibirsk, Russia), a one of the world-largest open magnetic traps operating for fusion research.