Error-field penetration in reversed magnetic shear configurations

Abstract

Error-field penetration in reversed magnetic shear (RMS) configurations is numerically investigated by using a two-dimensional resistive magnetohydrodynamic model in slab geometry. To explore different dynamic processes in locked modes, three equilibrium states are adopted. Stable, marginal, and unstable current profiles for double tearing modes are designed by varying the current intensity between two resonant surfaces separated by a certain distance. Further, the dynamic characteristics of locked modes in the three RMS states are identified, and the relevant physics mechanisms are elucidated. The scaling behavior of critical perturbation value with initial plasma velocity is numerically obtained, which obeys previously established relevant analytical theory in the viscoresistive regime. V C 2013 AIP Publishing LLC. [http://dx.

Penetration of resonant magnetic perturbations in a rotating tokamak plasma with neoclassical poloidal viscosity

“…21 Moreover, in the core regime, Cromb e et al investigated the plasma poloidal rotation velocity across internal transport barriers (ITBs) on JET, revealing a very clear link between the steepest region of the ion temperature gradient and localized spin-up of poloidal velocity. 22 Although the present magnetohydrodynamic (MHD) theories 11,17,23 and modellings [24][25][26][27][28][29] of plasma response to static RMPs have already discovered some significant roles of plasma flows with respect to the mode penetration, they are still far from establishing a self-consistent complete picture concerning the NPV. This drives further physical and numerical improvements of the relevant underlying understanding.…”

Effects of resonant magnetic perturbation on the triggering and the evolution of double-tearing mode

“…-The nonlinear evolution of the DTMs induced by the error field has been shown in ref. [17]. It has been found that the DTMs can be locked by the error field when the rotation is very small [17].…”

“…In these works, the onset of DTMs has been generally considered as a result of the localized initial magnetic perturbation at the rational surfaces. In actual experiments, however, the magnetic perturbation may also appear on the plasma boundary, such as error field, resonant magnetic perturbation (RMP) [12][13][14][15][16][17]. Therefore, studies about the effect of RMP on the DTM are important to well understand the triggering mechanism of the DTM.…”

“…[17]. It has been found that the DTMs can be locked by the error field when the rotation is very small [17]. On the other hand, the RMP may be similar to the error filled which can form a seed island on the rational surfaces [39].…”

“…2, we also find that, in the early stage, the mode is stable with the island width being zero. This suggests that at the beginning of the evolution, the plasmas perhaps cannot respond to boundary perturbation immediately, because it takes times for the infiltration of RMP to propagate from the boundary to the core in tokamak plasmas [17][18][19]. Moreover, since the outer rational surface is much closer to the boundary RMP than the inner one, the outer island first enters the lineargrowth stage.…”