Samuele Mazzi’s thesis defence

Jury composition:

1. Pascale Hennequin, Ecole Polytechnique (CNRS), France — Commitee president
   Paola Mantica, National Research Council, Italy — Reviewer
   Olivier Sauter, Swiss Plasma Center (EPFL), Switzerland — Reviewer
   Alberto Loarte, ITER Organization — Examiner
   Carlos Hidalgo, CIEMAT, Spain — Examiner
   Gerardo Giruzzi, CEA Cadarache, France — Invited
   Jeronimo Garcia, CEA Cadarache, France — Thesis supervisor
   David Zarzoso, AMU (CNRS), France — Thesis supervisor
   Sadruddin Benkadda, AMU (CNRS), France — Thesis Director

Keywords: Fast Ions, Microturbulence, Tokamak

Abstract:
The exploitation of magnetically confined fusion plasmas as a sustainable and clean energy source is limited by the radially outward turbulent transport. Such transport is mainly induced by microinstabilities. Next-generation fusion devices will be mainly heated by the alpha particles born from the nuclear fusion reactions. Alpha particles must be well confined in order to transfer their energy to the bulk ions. However, very little knowledge is available regarding the interaction between alpha particles and microturbulence. Thus, unexpected turbulence and transport regimes may lead to further detrimental effects on the performance of future alpha-heated devices. The study of a tokamak scenario which can mimic the experimental conditions expected in future devices is hence crucial. Numerical investigations on the impact of fast ions on the turbulent transport driven by Ion Temperature Gradient and Trapped Electron Mode instabilities in real experiments have been carried out. It is shown that a suppression of the ion-scale turbulent transport may be achieved. Alfvén Eigenmodes (AEs) destabilized by the highly energetic ions through a wave-particle interaction play an essential role in the multi-scale mechanism leading to the turbulence suppression. Deep analyses further highlight the possibility to recognize hallmarks of the ion-scale transport reduction, regardless the dominant turbulent regime.