Performance assessment of the new plasma position reflectometer antennas for the RFX-mod2 device

My thesis activity was dedicated to the characterization of the performances of the new antennas to be installed on the RFX-mod2 plasma position reflectometer (PPR). RFX-mod2 is the upgraded version of the RFX-mod device, in operation at Consorzio RFX(Padua) and dedicated to the study of magnetically confined plasmas. One of the new RFX-mod2 diagnostics will be a PPR system for real time control of plasma position within the vacuum chamber. The main goal of my thesis was, thus, to study performance, i.e. the radiation pattern, of the antennas which will be mounted on the PPR. In particular, according to the different assembly constraints, these antennas feature two different geometries: a pyramidal horn shape and a hoghorn shape. The important feature of these antennas is that they were built through additive manufacturing technique. Since such kind of antennas have never been used in any fusion machine, their characterization assumes a certain relevance. The experimental radiation patterns of the antennas were then compared with both the theoretical model and the numerically simulated patterns through the COMSOL Multiphysics software. As additional analysis, the experimental layout on RFX-mod2 was reproduced in laboratory using a metallic mirror with the goal of mimicking the performance on the plasma. This last step was important in order to have a first preliminary test on the functioning of the reflectometric system. Overall, the results indicate that both antennas have a good agreement, at least in the angular distribution of the emitted radiation, with respect to the simulated models. The hoghorn antenna, as expected, turns out to be more critical with a lower directivity and higher deviation from the simulated model, despite the angular distribution agrees with the simulated one.