Fast ion simulations in toroidally asymmetric tokamaks - Model validation with fast ion probes at ASDEX Upgrade and predictive modelling of ITER

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

The world electricity demand is increasing due to the growing global population striving for an ever-improving standard of living. Fusion energy research has the goal of bringing the energy source of the stars to Earth. The leading scheme is to magnetically confine a very hot plasma within a tokamak reactor. This thesis studies the energetic particles produced by the external heating of the plasma and by the fusion reactions themselves. The energetic particles carry a risk of damaging the reactor walls, if they are allowed to escape the plasma. This may occur if the carefully tuned magnetic field is perturbed by, e.g., introducing components made out of ferromagnetic materials to the tokamak. A quantitative study of the confinement of the fast, energetic particles requires careful calculation of the perturbation, followed by detailed simulations of fast ion behaviour with validated tools. In this work, the perturbative effect of the European test blanket modules (TBMs) of ITER were analysed. The TBMs, containing ferromagnetic steel, are needed for testing the technology for breeding tritium fuel from lithium. The magnetisation of the TBMs was computed with the finite element method using a geometry of unprecedented detail. Subsequently, the ASCOT code was used to assess the confinement of neutral beam injected (NBI) deuterons and fusion alpha particles. As the main result, the TBMs were found to be compatible with fast ion confinement requirements, at least in the 15MA Q=10 inductive scenario, the baseline ITER plasma. The fast ion modelling tools were validated with measurements at the ASDEX Upgrade tokamak: the flux of NBI ions was measured with the fast ion loss diagnostics (FILD) and the flux of fusion protons with the activation probe. The ASCOT simulations are in qualitative agreement with FILD measurements. The activation probe facilitated quantitative analysis. This required the development of an adjoint Monte Carlo method for calculating charged particle fluxes to the wall. The new method was used in the fusion proton modelling, the results of which agree quite well with measurements even quantitatively. The work presented here affirms the viability of the TBM design. It also validates and expands the fast ion behaviour and diagnostics modelling toolbox.
Translated title of the contributionEnergeettisten ionien mallinnusta toroidaalisesti epäsymmetrisissä tokamakeissa
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Groth, Mathias, Supervisor
  • Kurki-Suonio, Taina, Advisor
Publisher
Print ISBNs978-952-60-6675-2
Electronic ISBNs978-952-60-6676-9
Publication statusPublished - 2016
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • nuclear fusion
  • plasma
  • tokamak
  • ITER
  • test blanket module
  • magnetisation
  • fast ion
  • activation probe
  • FILD

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