Characterization of the RF plasma in negative ion source NIO1

The NIO1 experiment is a negative ion source built at Consorzio RFX, Padua, with the aim to investigate and optimize the negative ion production. With this purpose, a diagnostic of the plasma in the NIO1 source is essential. The study presented here was made with experimental and numerical approaches. The measurements on the plasma were made by using an electrostatic probe. The conditions of the magnetic field, pressure and RF power coupling inside the source were changed during the campaign of measurements, so it was possible to study the plasma parameters for each different conditions. Analysis of the measured data allowed to verify some important aspects on the plasma inside the NIO1 chamber. The numerical simulations are based on the adaption of an existing code to reproduce the conditions of the NIO1 source. The choices made to adapt it and to reproduce in the code some of the conditions created during the measurement campaign in NIO1 are described. The main aspects issued from the comparisons of simulation with experimental results are then shown.