Microwave heating of a high-temperature plasma confined in a large-scale open magnetic trap, including all important wave effects like diffraction, absorption, dispersion and wave beam aberrations, is described for the first time within the first-principle technique based on consistent Maxwell's equations. With this purpose, the quasi-optical approach is generalized over weakly inhomogeneous gyrotrotropic media with resonant absorption and spatial dispersion, and a new form of the integral quasi-optical equation is proposed. An effective numerical technique for this equation's solution is developed and realized in a new code QOOT, which is verified with the simulations of realistic electron cyclotron heating scenarios at the Gas Dynamic Trap at the Budker Institute of Nuclear Physics (Novosibirsk, Russia).

A theory of ordinary and extraordinary wave coupling in the electron cyclotron frequency range in inhomogeneous magnetized plasmas of a toroidal magnetic trap is reconsidered. Reduced wave equations are studied taking into account the poloidal curvature of the magnetic flux surfaces in a tokamak geometry. Based on these equations, the wave field distributions in the vicinity of the coupling region are found in a semi-analytical form. Non-one-dimensional effects of the flux surface curvature on the mode-conversion efficiency in tokamak plasmas are identified and analyzed.

In this paper, we propose a collective Thomson scattering diagnostic for fast ion measurements for the gas-dynamic trap (GDT) facility at the Budker Institute. The diagnostic utilizes 54.5 GHz gyrotron usually used for electron cyclotron resonance heating as a source of probe radiation and is aimed at reconstruction of distributions over transverse and longitudinal velocities of NBIdriven ions in the plasma core. Here we present a feasibility study of this concept showing a possibility to receive a strong CTS signal of hundreds eVs for a wide range of GDT parameters. The main limitations come from the refraction of the probe and scattered radiation propagating in inhomogeneous plasma: to provide well-resolved CTS conditions the on-axis plasma density should be kept less than 1.5 · 10 13 cm −3 while usual GDT discharges correspond to the density of (0.9 − 1.3) · 10 13 cm −3 .

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