Collisionality driven turbulent particle transport changes in DIII-D H-mode plasmas

S. Mordijck (Corresponding Author), T. L. Rhodes, L. Zeng, A. Salmi, T. Tala, C. C. Petty, G. R. McKee, R. Reksoatmodjo, F. Eriksson, E. Fransson, H. Nordman

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Abstract

The results of the experimental dimensionless scan in this paper confirm that there is an increase in density peaking towards lower collisionality and that this can be partly linked to a shift in the turbulence regime from ITG towards TEM. However at the lowest collisionality, the changes in turbulence and transport are much more pronounced than expected from direct collisionality effect on the turbulence. In this paper, the collisionality, ν is varied by a factor 5, while keeping ρ , q, β, M, fixed. Additionally, a 3 Hz gas puff modulation is applied to modulate the electron density profile and extract the perturbed transport coefficients using two diagnostics. The transport analysis shows that the increase in density peaking at low ν is linked to an increase in the inward particle pinch and not an increase in core fueling. These observations are not only in agreement with prior modeling scans of how turbulence changes as a function of collisionality and its impact upon the particle fluxes, but also with the multi-machine database (Fable E. et al 2010 Plasma Phys. Control. Fusion 52 015007) (Angioni C. et al 2003 Phys. Rev. Lett. 90 205003). The changes in turbulence across the collisionality scan were captured at large scale by the BES and at smaller scale by the DBS. A comparison with gradient-driven GENE simulations showed similar trends at both scales. Moreover, the changes observed in overall transport are in agreement with gradient-driven TGLF particle flux simulations. This indicates that TGLF/GENE when given the gradients as input, are able to reproduce the experimentally observed turbulence changes.

Original languageEnglish
Article number066019
JournalNuclear Fusion
Volume60
Issue number6
DOIs
Publication statusPublished - Jun 2020
MoE publication typeA1 Journal article-refereed

Keywords

  • collisionality
  • tokamak
  • transport
  • turbulence

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    Mordijck, S., Rhodes, T. L., Zeng, L., Salmi, A., Tala, T., Petty, C. C., McKee, G. R., Reksoatmodjo, R., Eriksson, F., Fransson, E., & Nordman, H. (2020). Collisionality driven turbulent particle transport changes in DIII-D H-mode plasmas. Nuclear Fusion, 60(6), [066019]. https://doi.org/10.1088/1741-4326/ab81aa