Influence of driven current on resistive tearing mode in Tokamaks

Abstract

The influence of driven current on the m/n=2/1 resistive tearing mode is studied systematically using a three-dimensional toroidal magnetohydrodynamic code. A uniform driven current with Gaussian distribution in the radial direction is imposed around the unperturbed rational surface. It is found that the driven current can locally modify the profiles of the current and safety factor, such that the tearing mode becomes linearly stable. The stabilizing effect increases with the increase of the driven current Icd or the decrease of its width δcd, unless an excessively large driven current reverses the magnetic shear near the rational surface and drives other instabilities such as double or triple tearing modes. The stabilizing effect can be negligible or becomes reversed if the maximum driven current density is not at the unperturbed rational surface.

Hall effect on tearing mode instabilities in tokamak

“…  JB (21) Where  , p, v, B, E, and J denote the plasma density, the thermal pressure, the plasma velocity, the magnetic field, the electric field, and the current density, respectively. e p is the electron pressure.…”

“…To the best of our knowledge, a toroidal tokamak simulation in the framework of Hall-MHD has not been carried out. In this paper, Hall MHD simulations are performed to investigate the dynamic processes of the m/n=2/1 tearing mode and the m/n=3/1 double tearing mode by the CLT code 20,21 developed at Zhejiang University.…”

Magnetic island suppression by electron cyclotron current drive as converse of a forced reconnection problem

“…Secondary instabilities, plasmoid-like (Lazzaro et al. 2018) or triple tearing modes (Wang, Ma & Zhang 2016), may develop when an intense driven current has a deposition depth narrower than the magnetic island separatrix.…”

Open problems of magnetic island control by electron cyclotron current drive

“…2015; Wang et al. 2016) have established that the stabilizing effect is inversely proportional to the depostion width, , for the same total driven current.…”

“…2006), DIII-D (Petty et al. 2004) and EAST (Wang, Ma & Zhang 2016). The main task of a theoretical study of rf control of these tearing instabilities, in the observable nonlinear phase, is the estimate of the necessary driven current, e.g.…”