Nonlinear ITG simulations in W7X

First nonlinear global ITG simulations carried out with EUTERPE in W7-X using experimental profiles were reported in [Sánchez er al. JPP 2020].

These simulations were carried out with adiabatic electrons and using density and temperature profiles from the experimental program 20181016_37. The simulation domain is radially restricted to r/a<0.5 for reducing the computational resources required.

The figures show the time evolution of the potential in one of these simulations in W7-X.

Figure 1. Electrostatic potential in one period of W7-X standard configuration (EIM_Ref_170) in a nonlinear simulation of ITGs for the program 20181016_37 carried out with EUTERPE.
Figure 2. Electrostatic potential at sector AEA21

Figure 1 shows the potential in a period of the device for r/a<0.45. The instability starts growing in the outer region of the computational domain and the turbulence extends toward the center as the unstable mode saturate.

Figures 2 and 3 show the potential at the planes of measurement of the Doppler reflectometry system, AEA21 and AEK51, in a nonlinear simulation in the configuration Ref_170_EIM of W7-X. In these plots, the zonal component of the potential is suppressed.

The simulation takes into account collisions, and uses experimental density and temperature profiles. The long-wavelength background electric field is not included in the simulation. Tools for the control of numerical noise and stabilization as described in [Sánchez er al. JPP 2020] are used.

Figure 3. Electrostatic potential at the sector AEK51.

Sánchez et al. Nonlinear gyrokinetic PIC simulations in stellarators with the code EUTERPE. Journal of Plasma Physics, 86 (5) 2020.