Ray-tracing analysis of Doppler backscattering diagnostic for tokamak with reactor technologies

This study discusses the scope of application of the Doppler backscattering (DBS) diagnostic for the tokamak with reactor technologies (TRT) project. This involved numerical modeling of the three-dimensional (3D) beam trajectories. Calculations were performed to investigate the propagation of microwaves in the V (40–75 GHz) and W (75–110 GHz) frequency ranges with O-mode polarization for the density profile of the base TRT scenario. Our analysis showed that the DBS system antenna on the TRT would need to be tilted in both the poloidal and toroidal directions in order to meet the condition \dfrack_\mathrmp\mathrma\mathrmrk_\mathrmp\mathrme\mathrmr\mathrmp < 10\mathrm\% . For the DBS system located in the equatorial plane it was shown that a wide range of poloidal and toroidal angles is available for the successful implementation of the diagnostic to study the core, pedestal and scrape-off layer (SOL) regions. The DBS system located at 35 cm above the equatorial plane would be more limited in measurements only covering the SOL and pedestal regions. A shift of the cut-offs in the toroidal direction highlighted the need for 3D analysis of the DBS data.