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Theses

Impurity transport in plasma fusion and its impact over the global confinement

Abstract : The energy of stars and the Sun in particular comes from nuclear fusion. At the center of the Sun, the temperature reached is 15 million degrees. With such a temperature, electrons are released from the nuclei, generating a plasma. The behavior of plasma is particularly complex since each particle is influenced by long-range interactions with all other particles. Plasma physics seeks to describe the evolution and behavior of such systems. In nuclear fusion, the inevitable presence of impurities is closely related to the fusion itself, to the presence of walls. A thorough understanding of the transport of impurities is crucial for the realization of the ITER project. During a plasma discharge, various impurities may be present simultaneously, for example, helium (He) as a reactant in the Deuterium (D)-Tritium (T) fusion reactions, argon (Ar) or nitrogen (Ni) which may be injected voluntarily to reduce the heat flux on the divertor, and heavy impurities - carbon (C) and tungsten (W) - from plasma-wall interactions. It is now well known that the accumulation of heavy impurities in the plasma core can cause a drop in reactor performance by diluting the main DT fuel and radiating energy. There are three different mechanisms by which impurity transport is generated: (i) turbulence, (ii) collisional effects (neoclassical transport), and (iii) MHD instabilities. During this thesis, we have limited ourselves to the electrostatic case, thus only the first two mechanisms have been studied numerically and therapeutically.In this manuscript, we have studied the turbulent and neoclassical transport of impurities in different configurations. The overall results obtained throughout this manuscript imply that heavy impurities tend to accumulate in the central region and are very sensitive to external conditions. Fortunately, it appears that appropriate use of an ion cyclotron resonance heating (ICRH) system can mitigate tungsten accumulation in the core by reducing poloidal asymmetry and increasing turbulent outward flow. The application of the ICRH heating system in GYSELA remains a future work.
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Submitted on : Wednesday, April 6, 2022 - 3:35:47 PM
Last modification on : Thursday, April 7, 2022 - 3:34:50 AM

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  • HAL Id : tel-03632878, version 1

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Kyungtak Lim. Impurity transport in plasma fusion and its impact over the global confinement. Plasma Physics [physics.plasm-ph]. Université de Lorraine, 2021. English. ⟨NNT : 2021LORR0186⟩. ⟨tel-03632878⟩

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