Study of an alternative extraction electrode for particle accelerator of NIO1 experiment

The NIO1 experiment is a compact and modular negative ion source built at Consorzio RFX, Padua, with the aim to investigate the optimal configuration for a negative ion source of the type needed for the nuclear fusion experiment ITER. Negative ions, produced in a cold plasma, are extracted from it by an intense electric field, generated by applying a potential of some kilovolts to an electrode called "extraction grid" (EG). This electrode has permanent magnets in it, needed to deflect the electrons that are unavoidably extracted from the source. A new EG, completely redesigned with respect to the original one has been recently installed on NIO1. The aim of this thesis consists in following the installation of such electrode, contributing to the preliminary measurements of the embedded magnets. To evaluate the impact of the new electrode on the optics of the negative ion beam a set of numerical simulations were carried out. The calculations were performed using a numerical model developed ad hoc during the thesis. The model is based on the IBSimu environment, a tool commonly used to model accelerators in high energy physics. As part of my work I adapted IBSimu to describe for the first time an accelerator used in nuclear fusion field. The model was validated against similar codes, and finally used to interpret the experimental measurements performed in the NIO1 accelerator.