Three-Dimensional Nonlinear Modeling of MHD Instabilities for Low-q Plasma on J-TEXT

Abstract

The characteristics of the magnetohydrodynamics (MHD) instabilities for low edge safety factor (low-q) plasma are investigated on J-TEXT with three-dimensional (3D) nonlinear MHD Infrastructure for Plasma Simulation (MIPs) code. The dynamics of m = 2 mode coupling with m = 1 mode is found in the linear growth phase with the initial q axis < 1 equilibrium. And new 3D helical coils are designed for generating additional rotational transform based on the J-TEXT configuration, which is helpful to suppress the amplitude of the MHD instabilities from the modeling result.

A brief review of the development and optimization of the three-dimensional magnetic configuration system in the J-TEXT tokamak

“…For the case with the applied helical coils, the growth rate is far lower than for that without, which implies that the applied helical coils or the externally applied rotational transform have the capability to suppress the MHD modes for the low-q plasma. Further simulation results show that, with the externally applied helical coils, the m=2 mode does not appear and the growth rate of the m=1 mode is much smaller [11].…”

“…The above two kinds of RMP coils can effectively control different TMs in plasma, but cannot effectively increase the stability of the plasma itself. Therefore, in recent years, in order to prevent or avoid the generation and growth of TMs in plasma, a set of helical coils that can provide external rotational transform has been designed on J-TEXT [11]. The helical coils will be put into operation in the near future.…”

“…The safety factor q profiles of the equilibrium in the cases with (red line) and without (black line) the external helical coils. Reprinted from[11], with permission from The Japan Society of Plasma Science and Nuclear Fusion Research.…”

Towards advanced divertor configurations on the J-TEXT tokamak

“…By analyzing the behavior of the kink mode in an external 3D field, it was found that a pair of opposite iota=1 coils can be used to stabilize the kink mode and suppress its growth by adding a small background m=2, n=2 component to the edge magnetic field [53]. Such a coil pair might be used in the near future on J-TEXT to experimentally investigate the stabilization of the low-q regime.…”