地点：4号楼601会议室

　　时间：2023年12月8日（星期五）下午14:00-16:00

　　报告题目：Effect of Toroidal Alfven Eigenmode Nonlinearity on Edge Localized Mode in HL-2A NBI Heated H-mode Plasmas

　　主持人：刘海庆

　　摘要：Prior to ELM crash, shear Alfvenic wave fluctuations are observed in HL-2A NBI H-mode Plasmas. These Alfvenic fluctuations principally come from the contributions of unstable toroidal Alfven eigenmodes (TAEs). There are strong nonlinear mode couplings between dominant TAEs with n=3-4 and low frequency MHD mode (kink or fishbone) with n=1 before the ELM crash. The pitch-fork phenomena of TAEs grow explosively and become an explosive instability. The explosive events have two kind fine structures, i.e., multi-modes and pitch-fork. The two kind structures can coexist, but the strong nonlinear mode coupling induces that the pitch-fork weakens or vanishes and the modes blow-up in finite-time, and this indicates that the nonlinear mode coupling may redistribute energetic-ions, destroy hole-clump pairs in the phase-space, and maybe induce three-wave mixing nonlinearly. As a consequence, we find and identify firstly that the TAE nonlinear dynamics triggers the onset of ELMs and pedestal collapse within several hundred Alfven times, and they are correlated to the irregular shape ELM features. The experimental result manifests that the nonlinear dynamics of Alfven fluctuations may furnish an additional perturbation of the energetic-particle pressure in the pedestal, and this pressure perturbation can move closer to MHD limit, so that the ELM trigger is determined by the nonlinear mode coupling and edge stability. These findings can help to understand the triggering mechanism of an ELM event.

　　报告人简介：

　　陈伟，研究员，核工业西南物理研究院聚变科学所副所长，核聚变产物和快粒子联合实验室主任，国家自然科学基金杰出青年项目获得者，国家重点研究计划首席科学家。本硕毕业于华中科技大学，博士毕业于核工业西南物理研究院，2011—2012年在日本核融合研究所做访问学者。主要研究方向包括磁流体不稳定性、高能量粒子物理、等离子体运行模式、约束与输运及诊断等。在Physical Review Letter 和Nuclear Fusion 等期刊上发表SCI论文百余篇，其中第一和通讯作者论文四十余篇，授权发明专利多项，获国防科学技术进步奖两项。