Simulación de plasmas de dispositivos de fusión por confinamiento magnético tipo tokamak y stellarator. Validación experimental y aplicación al estudio del Heliac Flexible TJ-II

Abstract

In the study of the fusion by magnetic confinement it is crucial to know the physical behaviour of the confined plasma with detail. In this sense the simulation codes are a very useful tool to analyse the properties of the plasma. Throughout this thesis the properties of the plasma of tokamaks and stellarators has been studied and the transport code PRETOR, created in the JET, has been developed. These studies have been developed within the existing collaboration between the DFEN in the UPC and the Laboratorio Nacional de Fusión of the CIEMAT. The PRETOR code allows the simulation of the radial variation and the temporal evolution of the main physical magnitudes of a fusion plasma. The results of the simulation of the most important magnitudes of diverse shots are compared with the experimental data in order to evaluate the goodness of the models implemented in the code and to determine the correction of their results. From this comparison it's deduced that the simulated magnitudes present a good agreement with the experimental data although it must be stand out that the experimental errors are quite large and they not always are available. In the development of this thesis the code PRETOR has also been applied to the study of the shutdown emergency of ITER-DDR, with 1500 MW of fusion power operating in an ignition stationary state. The evolution of the plasma has studied with detail during the shutdown implemented by means of the interruption of the fuel injection. This method is effective to reduce the fusion power in tens of seconds avoiding a plasma disrupción in all the scenarios. Several modifications have been made in the code in order to make it more versatile and to adapt it to the specific arisen necessities. The most outstanding modification is the incorporation to PRETOR of more complex routine than that initially implemented in the code for the calculation of the additional power deposition by neutral beam injection. In the last years the investigation of stellarators has acquired an increasing importance due to the advantages that this type of devices presents. Besides it is necessary to emphasise that the Spanish program of fusion by magnetic confinement is focused in Flexible Heliac TJ-II in the asociación EURATOM-CIEMAT. For these reasons and in order to have a code able to simulate stellarators shots, PRETOR has been modified of substantial form to create the PRETOR-Stellarator version. This modification of the code presents an new aspect of the thesis in the international scope. The modules that have been adapted affect to the magnetic configuration, the transport of energy and particles and to the plasma geometry. Once the code has been modified, it has been applied to the analysis of TJ-II Flexible Heliac plasmas. The objective of this study is to verify that the modifications introduced in PRETOR allow to simulate correctly stellarators discharges. The results obtained with PRETOR are compared with that ones obtained with PROCTR code, a code used in the CIEMAT for the study of the TJ-II and others stellarators. The results demonstrate that the temperature profiles are reproduced correctly, these results are similar to the obtained ones with PROCTR. The experimental values of the radiated power and the stored energy in the plasma have been predicted satisfactorily by means of the simulation with PRETOR-Stellarator. The way open by this thesis will allow studying in depth the plasma of TJ-II flexible heliac, the code is available to be used in this device and to incorporate new modifications to adapt it to the necessities that will appear.