J-TEXT 学术报告第55期

时 间： 2016年10月28日（周五） 14:00

地 点： 二楼会议室

APS预报告

报告人1：彭水涛

题目：Intrinsic toroidal rotation drive by electromagnetic turbulence in high pressure pedestal plasmas

摘要：Intrinsic rotation has long been of interest to researchers in magnetic fusion plasmas field since it may be helpful to suppress micro-turbulence and to stabilize RWMs in ITER, where neutral beam injection (NBI) is of low efficiency and high cost. Kinetic ballooning mode (KBM) can be the dominant electromagnetic instability in pedestal region from GTC simulation. In DIII-D, the high frequency coherent (HFC) modes observed in high pedestal pressure Quiescent H-mode (QH-mode) plasmas may be relevant to KBM as well. We analytically derive the toroidal rotation velocity equation by using electromagnetic gyrokinetic theory in toroidal geometry. Intrinsic rotation drive includes the usual residual stress, cross Maxwell stress, kinetic stress and turbulent acceleration. Quasilinear estimates for these terms are presented for KBM turbulence, and electromagnetic effects on intrinsic toroidal rotation drive are also discussed.

报告人2：李树才

题目：Enhancement of critical electric field for relativistic runaway electrons due to magnetic fluctuation and synchrotron radiation

摘要：The dynamics of relativistic runaway electrons are analyzed using the relativistic Fokker-Planck equation including deceleration due to synchrotron radiation and radial diffusion loss caused by magnetic fluctuations. Unlike [J. Martín-Solís. et al., Phys. Plasmas 6, 3925(1999)] in which magnetic fluctuations are treated as friction force, we think magnetic fluctuations act as a “porter” in configuration space, but not directly affect the runaway electrons (REs) in momentum space. The critical electric field for sustainment of runaway electrons and for avalanche growth onset are enhanced. The avalanche growth rate is significantly reduced by the combined effects of MF and SR as compared to the case with only SR. These results indicate the important effects of synchrotron radiation and magnetic fluctuations on the runaway electrons of tokamak plasmas.

报告人3：刘林子

题目：Observation of Kinetic Alfvén Eigenmodes with RMP Penetration in J-TEXT Tokamak

摘要：Three types of kinetic Alfvén eigenmodes (AE) excited in J-TEXT Ohmic plasmas are observed when the penetration of external applied resonant magnetic perturbations (RMPs) occurs. These modes are identified localized in gaps (20-80kHz) triggered by kinetic thermal ion effect [1] in the Alfvén continuum. One of these three types of modes, which have the highest frequency, is modulated by the RMP intensity, and its frequency converge to the nonlinearly modified beta-induced Alfvén eigenmode (BAE) continuum accumulation point (CAP) [2]. The experimental observation of this type of mode agrees with BAE whose frequency is proportional to the magnetic island half width. Another type of mode with lower frequency（~35kHz） well settled down in the thermal ion transit frequency range () is found that it has no relation with RMP strength and magnetic island width, as indicated in previous work [3]. The investigation of the third type of modes shows that the mode frequency is in the range of diamagnetic drift frequency (~20kHz) and its damping mechanism should involve the fast particle effect. All of the modes above are observed only in low density (~) along with slide-away discharge. With this condition, large amount of fast electrons are generated. With RMP penetration, fast electrons can be accelerated through magnetic line reconnection process. In particular, Alfvén type instabilities have strongly interact with fast electrons and can contribute critically to the radial redistribution of the fast electrons. Experimental results show that fast particles have been expelled from the plasma through their interaction with AE.

实验提案总结汇报

报告人1：黄卓

题目：Summary of the experiment：RMP penetration region searching

摘要：The report gives the parameters on J-TEXT including electron density and safety factor, where static RMP penetration occurs stably. It is observed that there is a larger region for RMP to penetration beyond the expectation, especially at the high density near 4*10¹⁹m^-3. The scaling between the density and penetration threshold is also investigated.

报告人2：李达 (并代丁永华)

题目：Feedback system control tearing mode by RMP

摘要：Interaction of tearing modes with RMP has been known clearly in previous experiments. We want to control tearing mode by applying static resonant magnetic perturbation (RMP) only in particular phase section Φ via feedback control of the RMP amplitude, where Φ is the phase difference between the NTM and RMP. The effect of this method has been confirmed in experiment of last campaign, though the effect is feeble.