Abstract
Quantitative validation studies of flux-tube gyrokinetic Vlasov simulations on ion and electron heat transport are carried out for the JT-60U tokamak experiment. The ion temperature gradient (ITG) and/or trapped electron modes (TEM) driven turbulent transport and zonal flow generations are investigated for an L-mode plasma in the local turbulence limit with a sufficiently small normalized ion thermal gyroradius and weak mean radial electric fields. Nonlinear turbulence simulations by the GKV code successfully reproduce radial profiles of the ion and electron energy fluxes in the core region. The numerical results show that the TEM-driven zonal flow generation in the outer region is more significant than that in the core region with ITG- and ITG–TEM-dominated turbulence, leading to moderate transport shortfall of the ion energy flux. Error levels in the prediction of the ion and electron temperature gradient profiles in the core region are estimated as less than , based on a multiple flux matching technique, where the simulated ion and electron energy fluxes are simultaneously matched to the experimental values.
Highlights
Performance of particle and energy confinement in magnetic fusion plasmas is mainly influenced by turbulent transport driven by electrostatic and electromagnetic microinstabilities
The five-dimensional nonlinear turbulence simulation based on the gyrokinetic theory [see e.g., Refs. [1, 2] and references therein] is widely recognized as a promising way to address the turbulent transport issues, and one can find comprehensive reviews on the gyrokinetic simulations in Refs. [3, 4]
Systematic cross-code benchmark tests have confirmed that the ITG driven turbulent heat transport level in the global simulation well converges to the local flux-tube one in a limit of sufficiently small ion thermal gyroradius compared to the plasma size (a) and/or the characteristic profile width of the logarithmic ion temperature gradient (∆∇ ln Ti ), i.e., ρ∗ = ρti /a < 1/300 or ρ∗eff = ρti /∆∇ ln Ti < 1/300 [7, 8]
Summary
Performance of particle and energy confinement in magnetic fusion plasmas is mainly influenced by turbulent transport driven by electrostatic and electromagnetic microinstabilities. Great efforts have been devoted so far to development of the radially local simulation approaches and its extensions to global model, and the ion temperature gradient (ITG) and the trapped electron mode (TEM) driven turbulent transport has been extensively investigated. Characteristics of the ITG and/or TEM driven zonal flows, which depend on the radial position in the L-mode plasma, and the relation with the transport shortfall have not been investigated in earlier works. The first quantitative validation study on the ion and electron heat transport including the zonal flow analysis for a JT-60U tokamak plasma is presented.
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