Improvement of SPIDER diagnostic systems

Each ITER Neutral Beam Injector (NBI) will provide 16.5 MW hydrogen/deuterium particles, electrostatically accelerating negative ions to 1 MeV. The challenging ITER NBI requirements have never been simultaneously attained and are expected to be demonstrated at the ITER Neutral Beam Test Facility (NBTF), at Consorzio RFX (Italy). NBTF includes the MITICA experiment, full-scale NBI prototype with 1 MeV particle energy, and SPIDER, with 100 keV particle energy, devoted to test and optimise the full-scale ion source. The four years of SPIDER operation demonstrated beam acceleration with high current density, but also highlighted that the non-uniformity and divergence of the beam are too large to comply with the ITER requirements, and that the current density is still lower; moreover, these findings can be traced back to non-homogeneity of the source plasma, where negative ions are produced. SPIDER then entered a shutdown dedicated to the improvement of the various plants and of the diagnostic system. The proposed additional diagnostic systems are integrated with the existing ones and mainly aim at increasing the spatial resolution of the plasma measurements, at investigating profiles in other directions and at measuring other parameters. In parallel, most of the already existing diagnostics will be refurbished or improved.