Preliminary assessment of ex-vessel waveguides for the ITER Plasma Position Reflectometer

tThis work describes the preliminary assessment of the different waveguide technologies for the ex-vessel transmission lines of the Plasma Position Reflectometer (PPR) in ITER. Using the available layoutinformation at the initial stage of the PPR design, several waveguide dimensions of both rectangularwaveguide and circular corrugated waveguides were evaluated; namely WR137, WR187, WR284, WR340and WR430 in case of rectangular waveguides and 31.75 mm, 63.5 mm, 76.2 mm and 88.9 mm diametersfor circular corrugated waveguides. In order to narrow the selection, an initial study was performed usingavailable results from literature to obtain ohmic losses and mode conversion in mitre bends. Once thepossibilities were trimmed, a final estimation was made using rigorous codes for the ohmic and mitrebend losses, also adding losses in waveguide gaps, on the selected candidates. This process led to thefinal estimation of performance for the preliminary routing of the PPR ex-vessel transmission lines. Thechosen solution was 88.9 mm internal diameter circular corrugated waveguide, as the best compromisebetween in-band performance and space constraints.