四川大学物理学一流学科论坛（第25期）

报告题目：Influence of energetic ions on neoclassical tearing modes

报告时间：2019年4月25日（星期四）上午10:00

报告地点：望江校区物理馆103会议室

报告专家：蔡辉山

中国科学技术大学教授，中科院青年创新促进会优秀会员。一直从事核聚变等离子体不稳定性和高能粒子的理论与模拟研究。近年来主要围绕ITER计划面临的关键性物理问题，即对磁流体不稳定性、运行极限和破裂（主要是撕裂模（包括新经典撕裂模）、电阻壁模、逃逸电子）、快粒子物理、磁流体不稳定性与快粒子的相互作用等方面进行了一定的研究。在Phys. Rev. Lett.等SCI 期刊上发表论文二十多篇。主持过科技部国家磁约束专项项目、国家基金委项目等多项。任IPAC（IAEA-EP国际顾问委员会）成员，ITPA-EP（国际托卡马克物理组织-快粒子物理专题）成员。2017年获安徽省自然科学二等奖，第一获奖人。

报告摘要：

Influence of energetic ions on the evolution of magnetic island has been studied systematically for the island width is much smaller than the orbit width of energetic ions, where energetic ions affect magnetic island mainly through the interaction with the outer region of tearing modes. First, the effects of circulating energetic ions (CEI) on the stability criterion have been studied. The stability criterion including the effects of CEI has been derived analytically. These effects depend on the toroidal circulating direction, and are closely related to the momentum of energetic ions. CEI provide an additional source or sink of momentum to affect tearing modes. For co-CEI, tearing modes can be stabilized if the momentum of energetic ions is large enough. On the other hand, the growth of tearing modes can be enhanced by counter-CEI. Based on the above model, the effects of energetic ions on tearing modes are studied by global kinetic/MHD hybrid simulations. The dependence of kinetic effects on energetic ion beta, gyroradius and speed is studied systematically and the results agree in large part with the previous analytic results for the kinetic effects of CEI. For trapped energetic ions, their effects on tearing mode stability are dominated by the adiabatic response due to large banana orbit width and strong poloidal variation of particle pressure.

In addition to the above effects, an uncompensated cross field current is yielded based on quasi-neutrality. It produces a return parallel current, and may compensate the loss bootstrap current in the island, and depends on the island propagation frequency, the density gradient of energetic ions and magnetic shear. For the weak magnetic shear, this effect becomes significant, and cancels partially or overcomes the destabilizing effect of the bootstrap current.

Based on the analysis, a possibility to suppress neoclassical tearing modes by co-CEI for the operation scenario with weak magnetic shear for ITER is provided.

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