Tungsten transport in tokamaks: towards real-time kinetic-theory-based plasma performance optimisation

P. Manas (1, 2) , C. Angioni (3) , E. Fable (3) , C. Stephens (3) , J.-F. Artaud (1, 2) , C. Bourdelle (1, 2) , P. Maget (1, 2) , J. Citrin (4) , K. van de Plassche (4) , F. Felici (5) , X. Yang (6)

1 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
2 IRFM - Institut de Recherche sur la Fusion par confinement Magnétique
3 Max Planck Institute for Physics
4 DIFFER - Dutch Institute for Fundamental Energy Research [Eindhoven]
5 EPFL - Ecole Polytechnique Fédérale de Lausanne
6 ASIPP - Institute of Plasma Physics, Chinese Academy of Sciences

Mechanisms by which tungsten dynamically accumulates in the core of tokamaks are identified in integrated modelling of an ASDEX-Upgrade discharge. Then the same modelling tools are applied to a WEST long pulse L-mode plasma. This modelling work on two disctinct tokamaks also stresses the validaty domain of reduced transport models, in this case QuaLiKiz. At AUG, a ramp-down of the Electron Cyclotron Resonance heating is analysed with a constant background Neutral Beam Injection heating until W accumulation is observed. It is found that the central ratio of the electron to the ion temperature, together with the central source of particles deposited by the beams play a key role. Indeed, while the central particle source yields more centrally peaked density profiles, leading to inward neoclassical convection of tungsten, large Te/Ti can compensate this unfavorable scenario by increasing turbulent particle diffusion. Such competition between Te/Ti and the central particle source is also investigated with fast transport models, in particular within the integrated modelling framework RAPTOR where the turbulent transport is computed from QuaLiKiz 10D neural network. This paves the way towards real-time-kinetic-theory-based plasma performance optimisation. Finally, modelled WEST plasmas with dominant electron heating showed the limits of the implemented collision operator in QuaLiKiz yielding an overstabilisation of Trapped Electron Mode, resulting in mispredictions of the kinetic profiles (electron density and temperature).

Domains: Physics [physics]

P. Manas, C. Angioni, E. Fable, C. Stephens, J.-F. Artaud, et al.. Tungsten transport in tokamaks: towards real-time kinetic-theory-based plasma performance optimisation. FEC 2020 - IAEA Fusion Energy Conference, May 2021, E-Conference, France. ⟨cea-03286833⟩