Plasma Diagnostics Using Collective Thomson Scattering of Microwave Radiation for the TRT Project

The capabilities of the ion velocity distribution function diagnostics based on recording collective Thomson scattering (CTS) spectra of microwave radiation are analyzed for the TRT (Tokamak with Reactor Technologies) project. This diagnostics can be used to study thermal ions, including determining the ion temperature, isotope composition, and effective charge of the plasma, and fast ions arising from plasma heating by neutral beams or fusion reactions. Possible scattering scenarios for a wide range of probing radiation frequencies from 70 to 400 GHz are considered. CTS scattering spectra are calculated for model parameters of the background plasma and fast ion distributions, the resolution and sensitivity of the CTS diagnostics are estimated, and requirements for the probing radiation source and receiving equipment are determined. Probing at a frequency of 82.6 GHz, corresponding to the lower boundary of the transparency window for the extraordinary wave of magnetized plasma, is optimal according to the analysis results. In this case, scattering is recorded at an angle close to a direct angle relative to the direction of propagation of the probing microwave beam. In this geometry, the analysis bandwidth of the scattered signal at the intermediate frequency is 0.1‒0.6 GHz for thermal ions and 0.8–3 GHz for fast ions. The possibility of using radiation at the frequency of electron cyclotron plasma heating is additionally considered. It is shown that plasma probing with the ordinary wave at a frequency of 230 GHz is possible; however, the sensitivity of this scheme drops by two orders of magnitude compared to the main one.