Simulations of drift resistive ballooning L-mode turbulence in the edge plasma of the DIII-D tokamak

Abstract

Results from simulations of electromagnetic drift-resistive ballooning turbulence for tokamak edge turbulence in realistic single-null geometry are reported. The calculations are undertaken with the BOUT three-dimensional fluid code that solves Braginskii-based fluid equations [X. Q. Xu and R. H. Cohen, Contrib. Plasma Phys. 36, 158 (1998)]. The simulation setup models L-mode edge plasma parameters in the actual magnetic geometry of the DIII-D tokamak [J. L. Luxon et al., Fusion Sci. Technol. 48, 807 (2002)]. The computations track the development of drift-resistive ballooning turbulence in the edge region to saturation. Fluctuation amplitudes, fluctuation spectra, and particle and thermal fluxes are compared to experimental data near the outer midplane from Langmuir probe and beam-emission-spectroscopy for a few well-characterized L-mode discharges in DIII-D. The simulations are comprised of a suite of runs in which the physics model is varied to include more fluid fields and physics terms. The simulations yield results for fluctuation amplitudes, correlation lengths, particle and energy fluxes, and diffusivities that agree with measurements within an order of magnitude and within factors of 2 or better for some of the data. The agreement of the simulations with the experimental measurements varies with respect to including more physics in the model equations within the suite of models investigated. The simulations show stabilizing effects of sheared E Â B poloidal rotation (imposed zonal flow) and of lower edge electron temperature and density. V C 2013 AIP Publishing LLC. [http://dx.

Comparison of edge turbulence imaging at two different poloidal locations in the scrape-off layer of Alcator C-Mod

“…3. The size scale (k pol L n~1 and k pol ρ s ~ 10 -2 ) and frequency range of this turbulence is at least qualitatively similar to that seen in previous SOL turbulence simulations [32][33][34][35]. The SOL in these plasmas is highly collisional (ν e * = L II /λ e ~100) and the beta is very low (~3x10 -5 ), so the turbulence is most likely dominated by resistive electrostatic instabilities.…”

“…SOL turbulence was modeled with the GBS code in a simplified toroidal geometry, and initial comparisons were made with TORPEX measurements [34]. Recently the BOUT code was used to calculate the edge and SOL turbulence in DIII-D, and the results appeared to agree well with midplane probe and BES measurements of turbulence [35].…”

“…Gyrofluid SOL simulations for C-Mod were compared with the outer midplane SOL turbulence, but only for a circular limited C-Mod plasma [33], and 2-D SOLT simulations were compared with EDA H-mode plasmas in C-Mod [27,59]. On other devices, 3-D turbulence simulations have been compared with experiments on TORPEX [34] and DIII-D [35], but it is not clear whether those results apply to the SOL conditions in C-Mod.…”

Turbulent transport regimes and the scrape-off layer heat flux width

“…27-37, and references therein. Of particular note in the context of boundary turbulence in divertor geometry are simulations using BOUT, [27][28][29][30] an electromagnetic three dimensional fluid turbulence code, which encompasses both the confined edge plasma and the SOL. The studies mentioned in this paragraph were not focused specifically on the SOL width, but they have shed valuable insight on the nature of edge and SOL turbulence, the characterization of transport fluxes, nonlinear saturation mechanisms, etc., which are important background to the material which follows in this paper.…”

Interchange Turbulence Model for the Edge Plasma in SOLEDGE2D‐EIRENE

“…The design of ITER plasma facing component relies strongly on transport codes predictions [1][2][3] in term of heat deposition. These transport codes use simplified models to describe the turbulent transport, a first principle direct numerical simulation of turbulent structures [4,5] being prohibitive in term of computational time. In transport codes, the turbulent cross-field transport is taken into account by diffusive terms, the turbulent diffusivity taking value from empirical estimation of plasma density and heat decay length in the scrape-off layer.…”