Effects of neoclassical toroidal viscosity on plasma flow evolution in the presence of resonant magnetic perturbation in a tokamak

Abstract

Effects of neoclassical toroidal viscosity (NTV) on plasma flow evolution in the presence of resonant magnetic perturbation (RMP) in a tokamak have been evaluated using a cylindrical theory model. Calculations show that the introduction of NTV has almost no effect on the flow on the resonant surface, so the locked or unlocked state on the resonant surface remains unchanged, but it impacts the rotation profile in the core region. The toroidal, poloidal, and parallel flows in the core region are slightly reduced with uniform pressure. For non-uniform pressure profiles, elevated $β$ enhances the global amplitude of NTV torque but suppresses that of electromagnetic (EM) torque. These two driving terms collectively maintain the locked mode state.

Figures (14)

• Figure 1: Radial profiles of perturbed magnetic flux $\psi$, where $\psi_{tot}=\psi_s+\psi_c$, $\psi_s$ (blue) the tearing mode eigenfunction and $\psi_c$ (green) represents the external RMP field (a). Corresponding contour of the perturbed magnetic field strength $|b_{mn}|$ (b). Radial profiles of $T_{\mathrm{NTV},i}$ (blue) and $T_{\mathrm{NTV},e}$ (green) with uniform pressure (c).
• Figure 2: Radial profiles of $-N_{\mathrm{mag}}$ (red) and $-N_{\mathrm{ntv}}$ (blue) at the initial (dashed) and steady state (solid) over the entire range (a) and the zoomed view near the q=2 surface (b), with the vertical axis in logarithmic scale. Here $S=3\times10^5$, $Pr_m=40$, $\Omega_0=2\times 10^2\mathrm{rad/s}$, $W_C/a=0.292$.
• Figure 3: Radial profiles of $\Delta \Omega_\phi$ (a), $\Delta \Omega_\theta$ (b) and $-\mathbf{k}\cdot\mathbf{u}$ (c) at different time slices. Here $S=3\times10^5$, $Pr_m=40$, $\Omega_0=2\times 10^2\mathrm{rad/s}$, $W_C/a=0.292$.
• Figure 4: Radial profiles of $\Delta \Omega_\phi$ (a), $\Delta \Omega_\theta$ (b) and $-\mathbf{k}\cdot\mathbf{u}$ (c) in the steady state with NTV effect (red solid) and without it (red dash-dotted) and their difference (blue dashed). Here $S=3\times10^5$, $Pr_m=40$, $\Omega_0=2\times 10^2\mathrm{rad/s}$, $W_C/a=0.292$.
• Figure 5: The width of magnetic island (red) and $\sin\varphi$ (blue) as function of time with NTV effect (solid), without it (dash-dotted). Here $S=3\times10^5$, $Pr_m=40$, $\Omega_0=2\times 10^2\mathrm{rad/s}$, $W_C/a=0.292$ and $W_0$=0.11.