Monsieur Kirill AFONIN soutiendra publiquement ses travaux de thèse intitulés :

« Study of the transport of the boron powder
injected in the WEST tokamak plasma and its effect on the discharge performance »
dirigés par Dr. Alberto Gallo  

Composition du jury proposé :

Dr. Karl KRIEGER	MPG/IPP Garching	Rapporteur
Dr. Tom WAUTERS	ITER organization	Rapporteur
Dr. Davide CURRELI	University of Illinois	Examinateur
Dr. Cécile ARNAS	PIIM, CNRS/AMU	Examinatrice
Dr. Frédéric BROCHARD	Institut Jean Lamour	Président du jury
Dr. Yannick MARANDET	PIIM, CNRS/AMU	Directeur de thèse
Dr. Alberto GALLO	CEA Cadarache	Co-encadrant
Dr. Philippe MOREAU	CEA Cadarache	Membre invité

Keywords :

Fusion plasma, tokamak,WEST, wall conditioning, boron, IPD.

Abstract :

With ITER transitioning to tungsten (W) plasma-facing components (PFCs), study of wall conditioning techniques becomes an important subject for achieving high-yield fusion plasmas. Wall conditioning in tokamaks is necessary to remove unwanted impurities from the vessel, which otherwise would lead to increased radiative losses and fuel dilution, lowering the fusion energy yield. A novel conditioning technique that is currently being studied is boronization via boron (B) powder injection with an Impurity Powder Dropper (IPD). Boronization with an IPD device is performed by dropping B powder during a plasma pulse, where B powder is evaporated, B atoms are ionized and subsequently deposited on the PFCs. This method acts as an alternative to an established conditioning technique called Glow Discharge Boronization (GDB), where B is injected in form of diborane gas (B2D6) into a glow discharge between positively-charged electrodes and negatively-charged tokamak walls. B from B2D6 is ionized and deposited onto the walls, where it traps the light impurities, e.g. oxygen (O) which is introduced into the vessel during the vent of the machine or through unavoidable micro-leaks. Benefits of GDB are well-known, and boronization via IPD injections is being studied as an alternative with a similar effect but with a number of upsides: the injection can be performed on-demand without interrupting tokamak operation and does not require the usage of toxic and corrosive B2D6. This thesis attempts to extend the existing research of B study in pulses with IPD injections in two directions: the experimental part, where experiments with an IPD device installed on W Environment Steady-State Tokamak (WEST) are performed in an attempt to maximize the amount of B injected and the effects during and after the injections are studied, and the computational part, where WEST pulses with IPD are simulated using computational models to interpret the experimental results and gain insight into the injected B transport.

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