• Turbulence simulations

    Not only do collisions and the inhomogeneity of the magnetic field produce transport, but also turbulent fluctuations in the plasma do. The density and temperature gradients constitute free energy sources for the development of the so-called drift-wave turbulence [Horton-99], that can manifest due to the excitation of different types of instabilities: Ion temperature gradient (ITG) …

  • Impurity transport

    Click on the figure to see the temporal evolution. In magnetic confinement fusion, atomic species other than the fusion reactants (e.g. Deuterium and Tritium for the fuel mix envisaged for the first demonstration reactors) are termed “impurities”. The presence of even small concentration of impurities (especially high- Z ones) in the confinement volume has deleterious …

  • Neoclassical transport and density control

    Neoclassical transport is a fundamental aspect of stellarator plasma scenario development. As we have discussed, advanced stellarators are designed in order to minimize neoclassical radial transport. On the other hand, once designed, predictive 1D transport simulations based on neoclassical transport theory at the core, complemented with simple models for turbulent transport at the edge, allow …

  • Transport in optimized stellarators

    The three-dimensional geometry of the stellarator magnetic configuration (and therefore its increased number of degrees of freedom with respect to the axisymmetric configuration of the tokamak) can be used to generate the equilibrium magnetic field by means of external coils, instead of requiring a large plasma current to generate part of it, as in the …