Caratterizzazione spaziale delle proprietà di plasma in una sorgente di ioni RF ad alta potenza e bassa pressione con un sistema di sonda Langmuir mobile

Neutral Beam Injection (NBI) is one of the most exploited additional heating techniques for fusion plasmas. In the ITER case, the NBI is required to provide a neutral beam with up to 1 MeV energy: this can only be obtained by neutralizing a precursor negative ion beam, given the higher neutralization efficiency of the latter compared to positive ion beams for high energies. The ITER NBI negative ion source is based on an Inductively Coupled Plasma (ICP) discharge, obtained by coupling Radio-Frequency (RF) antennas at a driving frequency of 1 MHz to the source plasma itself. To optimise the performances of such sources, the MINION experiment is in operation at Consorzio RFX since 2023. MINION shares the design of the ITER NBI source RF driver, which is the region where the inductive coupling takes place, and offers enhanced flexibility and diagnostic capability with respect to the ITER source 1:1 prototype. For these reasons, in 2025 MINION will be operated to test new RF power supplies as well as testing new solutions for the RF driver design. The main diagnostic systems to measure the plasma features in MINION are source emission spectroscopy (OES), visible cameras and a movable Langmuir probe. The aim of this thesis work is the spatial characterization of the plasma properties with the Langmuir probe. To this purpose, the following activities are carried out: 1) Commissioning of the movable Langmuir probe system, including simulations of the conditioning electronics for the Langmuir probe signal; 2) Preliminary deployment and test of the diagnostic systems in MINION plasma; 3) Characterization of the plasma properties in different operating conditions, including the preparation of a fit algorithm for inferring plasma density, potential and electron temperature from the Langmuir probe data.