Global gyrokinetic simulations of ITG turbulence in the magnetic configuration space of the Wendelstein 7-X stellarator

Abstract

We study the effect of turbulent transport in different magnetic configurations of the Weldenstein 7-X stellarator. In particular, we performed direct numerical simulations with the global gyrokinetic code GENE-3D, modeling the behavior of Ion Temperature Gradient turbulence in the Standard, High-Mirror and Low-Mirror configurations of W7-X. We found that the Low-Mirror configuration produces more transport than both the High-Mirror and the Standard configurations. By comparison with radially local simulations, we have demonstrated the importance of performing global non-linear simulations to predict the turbulent fluxes quantitatively.

Phase contrast imaging measurements and numerical simulations of turbulent density fluctuations in gas-fuelled ECRH discharges in Wendelstein 7-X

“…2014; Bañón Navarro et al. 2020). The PCI measurements, although toroidally and poloidally localised and line-integrated, are a good representation of fluctuations in W7-X.…”

“…A more detailed or even quantitative comparison of experimental and simulated spectra is not reasonable, since the simulation in (Bañón Navarro et al. 2020) does not closely match the experimental situation of the reference discharge. Nonlinear global simulations with GENE-3D including the background radial electric field are planned, which can then be directly compared with measurement data via the synthetic diagnostic.…”

“…A model density fluctuation background, which is derived from a simulation for W7-X with GENE-3D (Bañón Navarro et al. 2020), is rotated along the poloidal angle according to a predefined rotation velocity. The model is described in more detail in Appendix B.…”

“…Finally, for a direct comparison with the experimental wavenumber–frequency spectrum, the simulated neoclassical -profile, taken from figure 5, and a simulated fluctuation amplitude profile, taken from Bañón Navarro et al. (2020), are used as input for the model. Figure 9 shows the resulting wavenumber–frequency spectrum, which has very similar features as the experimental spectrum (figure 4).…”

“…Density fluctuations from global gyrokinetic simulation (Bañón Navarro et al. 2020) are rotated according to the simulated neoclassical -profile in figure 5.…”