Vialetto, Luca (2015) Data analysis of an optical emission spectroscopy diagnostic in NIO1 experiment. [Laurea triennale]
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Neutral Beam Injectors (NBI’s) will play a key role in future fusion reactors, but many open issues are still to be solved. Consorzio RFX in Padova will host the test bed for ITER NBI’s, with the aim of demonstrating the reliability of the present NBI design and of optimizing the performances. For this reason, another more flexible experiment has started named NIO1 (Negative Ion Optimization phase 1). In the process to study these new concepts and solutions, the measurements of the plasma parameters and of the extracted beam are of fundamental importance. A key diagnostic is the Optical Emission Spectroscopy (OES): its exploitation on NIO1 is the subject of this thesis. An overview of OES measurements and the methods adopted to analyze them will be given in the following chapters. Some of the plasma parameters could be deduced from OES only by comparison with the predictions of radiative models. The collisional radiative model that has been applied in this thesis is called YACORA and has been developed by IPP Garching. Here is an outline of the thesis: Chapter 1: Introduction to the physics of controlled thermonuclear fusion and the structure of neutral beam injectors. Chapter 2: A general overview of NIO1 experiment, diagnostic methods, in particular the Optical Emission Spectroscopy. Also the CR model is presented. Chapter 3: Analysis of measurements in air as a working gas. Both high and low resolution spectrometers are utilized. The main results are presented, such as electron temperature (Te), vibrational temperature (Tv) and rotational temperature (Tr). Chapter 4: The analysis of measurements with hydrogen as a working gas is presented. The main quantities obtained with measurements of low resolution spectrometer are: electron density (ne) and electron temperature (Te) along the LOS (line of sight) and Dissociation degree (nH=nH2 ). These are obtained by the method of line ratio and with the use of the CR model. The results and the errors of these estimates are presented and discussed.
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