Benchmarking of the EM modelling of the ITER plasma position reflectometry in-vessel antennas with a metallic target using prototype tests

Studies have shown the importance of modelling the main surfaces of the narrow openings between blanket modules (BMs) through which the antennas of the ITER Plasma Position Reflectometry (PPR) systems located inside the vacuum vessel probe the plasma. This is especially important for the system located in the high-field side (gap 6), where the cut-outs in the surfaces of BMs strongly shape the antenna's radiation pattern, notably at lower frequencies. In addition, the (slanted) geometry of the first-wall (FW) panels may hinder the performance of the system by focusing the multiple reflections between the plasma and the FW back to the antenna. For the system located in the low-field side (gap 4), the opening between the BMs decreases towards the plasma, which together with the step in the top BM behind the antennas and the slanted arrangement of the FW panels also imposes challenges to the performance of the system. Comparisons of 3D electromagnetic (EM) simulations to laboratory tests of the antenna prototype, including mock-ups of the BMs aswell as a metallic target, aiming to benchmark the simulations, reveal good agreement.