Gyrokinetic simulations for turbulent transport of multi-ion-species plasmas in helical systems

M Nunami,M Nakata,S Toda,H Sugama

doi:10.1063/1.5142405

Abstract

The turbulent transport of magnetic confinement plasmas including multi-ion-particle-species in helical systems such as the Large Helical Device (LHD) [Takeiri et al., Nucl. Fusion 57, 102023 (2017)] and their plasma profile sensitivities are investigated by local flux-tube gyrokinetic simulations. In the multi-ion-species plasmas, while the heat transport of each particle species has slightly different sensitivity towards the plasma temperature gradients and the density gradients, there exist quite different dependencies in the particle transport on the radial gradient profiles of the plasma temperatures and densities between each particle species. Furthermore, in the LHD plasma with the carbon impurity hole structure [Ida et al., Plasma Phys. 16, 056111 (2009)], the turbulent particle transport flux of the impurity carbon ion remains radially inward-directed robustly within the wide ranges of radial gradient profiles of the plasma temperatures and densities.

Highlights

Understanding the physical mechanism for the plasma turbulent transport phenomena is one of the most critical issues in the magnetically confined fusion researches because the turbulent transport often strongly influences the plasma confinement performance in the fusion reactors
In the turbulent heat transport, there are slight differences of the plasma gradient profile dependences between each particle species due to the turbulent potential fluctuation which is shared with all species
If the ion temperature gradient increases, the particle transport fluxes for the hydrogen and the helium ions increase while the particle fluxes of the electron and the carbon ion decrease

Summary

INTRODUCTION

Understanding the physical mechanism for the plasma turbulent transport phenomena is one of the most critical issues in the magnetically confined fusion researches because the turbulent transport often strongly influences the plasma confinement performance in the fusion reactors. Of V , and Γs (ρ) and Γs (ρ) are the turbulent and neoclassical contributions of the particle transport fluxes of the species s, respectively. The quasi-linear analyses of the turbulent transport of the impurity ions in the LHD impurity hole plasma indicated that the quasilinear particle fluxes of the carbon impurity are radially inward-directed[6 ]. T s ≡ −dlnTs /dr, Lns is the density gradient scale length for the species s defined by L−1 ns ≡ −dlnns /dr, and fCs is the normalized charge density for the ion species s defined by fCs ≡ ns Zs /ne In this plasma, there are four particle species including electron e− , hydrogen ion H+ , helium ion He2+ , and carbon ion C6+. In order to evaluate the turbulent transport of the multi-species helical plasmas, we employ the local δf flux-tube gyrokinetic code, GKV10–13.

TURBULENT TRANSPORT ANALYSES IN LHD

AGAINST NEOCLASSICAL CONTRIBUTION OF

Findings

SUMMARY AND DISCUSSIONS