时 间： 2016年04月12日（周二） 14:30

地 点： 三楼会议室313

报告人1： 胡启明（HUST）

题 目1： Study the plasma response to externally applied resonant magnetic perturbations

摘要：

The influence of both static and rotating RMP on plasma response is studied on J-TEXT. It is found that:

(1) For static 3/1 RMP, the 3/1 tearing mode is completely suppressed when the RMP coil current Ic ramps up to 4 kA for phase B; on the other hand, for tearing-stable plasma, 3/1 tearing mode is excited by RMP for phase D.

(2) For static 2/1 RMP and tearing-stable plasma, the plasma parameters change little when the applied RMP doesn’t cause field penetration for tearing stable plasma. When field penetration happens, electron density decreases substantially, the edge toroidal rotation increases in co-Ip direction, the poloidal rotation changes from electron diamagnetic drift direction to ion diamagnetic drift direction, and the density fluctuation decreases.

(3) For static 2/1 RMP and plasma with 2/1 tearing mode, the applied RMP causes strong density pump-out no matter whether mode locking happens, and the density pump rate is the same.

(4) For rotating 2/1 RMP and plasma with 2/1 tearing mode, density pump-in is observed when the frequency of rotating RMP is higher than that of 2/1 tearing mode, being in consistent with previous results.

报告人2： 李达（HUST）

题 目2： Feedback system control tearing mode by RMP

摘要：

The locking of large magnetic islands by error fields or vacuum vessel wall is often observed in both tokamak and reversed-field pinches (RFPs) experiments, leading to severe confinement degradation or even to disruptions. Just as we known, there are exist many magnetohydrodynamic instability of a plasma in tokamaks, (neo) classical tearing mode (NTM) is one of the general instabilities. It is found that neoclassical tearing modes will be locked at a small amplitude by the error field in a reactor plasma, so the mode locking is an important issue for ITER. It is of great importance to investigate active control of locked mode and avoid it, for the purpose of avoiding disruption caused by mode locking. This has led to a discussion on feedback control of the magnetic islands associated with the instability.

RMP is one of two mainstream methods to control MHD instability. RMP could decelerate and stabilize tearing mode holistically. Static RMP contributes a stabilizing (destabilizing) effect on the island when 0.5π < φ < 1.5π(−0.5π < φ < 0.5π), and it also contributes a accelerating(decelerating) effect on island rotation when π < φ < 2π(0 < φ < π),where φ is the phase difference between the ntm and rmp. a new method is investigated for stabilizing the ntm as well as for accelerating the island rotation: to apply static resonant magnetic perturbation (rmp) only when π < φ <2π via feedback control of the rmp amplitude. it is found that the ntm can be effectively suppressed, and the mode frequency is increased with this method by nonlinear numerical modeling based on reduced mhd equations has been carried out.

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