Bonjour,
Nous vous prions de bien vouloir trouver ci-dessous l’annonce de la prochaine soutenance de these de Yaakoub Boumendjel :
Avis de Soutenance
Monsieur Yaakoub Boumendjel
Soutiendra publiquement ses travaux de thèse intitulés
Titre:
Investigation of tungsten emission and its density determination in magnetically confined plasmas
Soutenance prévue le mardi 12 décembre 2023 à 10h00
Lieu : CEA – IRFM, salle René-Gravier, Bat 506
Et par Skype
Composition du jury:
Dr Lorella Carraro Rapporteure
Consorzio RFX, Italy
Pr Frank Rosmej Rapporteur
Sorbonne université
Dr Birger Buttenschoen Examinateur
IPP Greifswald, Germany
Pr Djamel Benredjem Examinateur
University Paris-Saclay
Dr Nicolas Lemoine Examinateur
IJL, University of Lorraine
Pr Alexandre Escarguel Examinateur
Aix-Marseille University
Pr Olivier Peyrusse Directeur de thèse
Aix-Marseille University
Pr Rémy Guirlet Co-Directeur de thèse
CEA-IRFM
Dr Corinne Desgranges Invitée
CEA-IRFM
Résumé:
Tungsten (W) is used as material for the inner walls of many tokamaks (AUG, WEST, ITER). In many devices with W wall components, plasma scenarios have been developed
aimed at minimizing W erosion from the plasma facing components and reducing W contamination of the confined plasma. A crucial criterion for the success of those scenarios is the core W density. For this reason, it is important to monitor carefully tungsten in these devices. The aim of this work is to improve our understanding of the complex tungsten spectral emission and provide a method to quantify the tungsten density at the plasma core from the measured spectra. The spectra measured in the EUV domain are very complex when tungsten penetrates to the plasma. One of the goals in this work is to ascertain the physics basis for the spectrum background that may affect the impurity density determination. The analysis of the experimental spectra measured in the 100-300 A reveals that the continuum emission is negligible with respect to the line emission, and the observed isolated lines are on the top of spectral features (quasi-continuum) that are emitted over this entire wavelength domain. We also provide a method to determine the temporal evolution of the tungsten density at the plasma core during the whole discharge from the measured spectral lines. However, random errors of less 20% in determining the impurity density cannot be avoided by this method due to the spectra background nature.
The other part of this work concerns the tungsten emission modelling in tokamak plasma conditions. The results of theoretical models of ionized populations (collisional-radiative models) are inconsistent with the experimental ones. To address this problem, a specific promotional strategy is used to provide a list of configurations we consider most relevant in these conditions, autoionizing states in particular. This choice of configurations, along with the standard methods for evaluating the configuration average collisional and radiative rates, are used in the calculations. The obtained results (.i.e average ionization) for tungsten are close to the experimental observations. This approach also allowed to capture the large complexity of highly ionized tungsten spectra.
Keywords: Tokamak, EUV spectroscopy, tungsten, colisionnal-radiative modelling
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