HL-2A/2M装置上反剪切阿尔芬本征模的实验研究

Reversed shear Alfvén eigenmode (RSAE) are typical of the discrete shear Alfvén wave (SAW) spectrum in a reversed or weak magnetic shear plasma. They are characterized by frequency sweeping following the minimum safety factor qmin evolution. On one hand, they may induce excessive alpha particle losses and deteriorates fast ion confinement. On the other hand, RSAEs imply the presence of a reversed shear q-profile, and as a result the RSAE phenomenon can serve as a useful plasma diagnostic for the measurement of safety-factor profiles. Therefore it is important to study the properties of RSAEs, such as the stability of the modes, their non-linear behaviors, as well as effect on the plasma transport. Investigation of RSAEs will be carried out on HL-2A/2M in this project. Firstly, basic characteristic of RSAEs during electron cyclotron resonance heating (ECRH) can be measured by relevant diagnostics and the mechanism of ECRH effecting on RSAE will be investigated. Secondly, evolution of nonlinear behaviors will be studied, then compared to the previous theoretical models so that the defining parameters can be found out. Finally, research about influences of RSAEs on the plasma transport will be taken place.

反剪切阿尔芬模（RSAE）是反剪切位形下高能粒子与阿尔芬波相互作用而激发的本征模，其主要特征为频率随着最小安全因子qmin变化而具有扫频行为。RSAE可以排出高能粒子，使得等离子体约束变差；又可以作为诊断工具用来检测等离子体参数，如qmin。因此，深入分析RSAE的激发机制、非线性行为以及对背景等离子体输运影响，对提高ITER等离子体约束具有重要意义。本项目将在HL-2A/2M装置上开展RSAE的实验研究。首先，研究RSAE在电子回旋加热（ECRH）条件下的基本特征，结合相关理论阐述高能电子对RSAE产生作用的机制。其次，从实验上分析诱导RSAE与撕裂模（TM）非线性模模耦合的依赖因素并通过与现有理论模型比较，确定依赖参数信息。最后，阐明RSAE对背景等离子体热输运的影响。

项目通过实验与模拟、理论相结合的方法研究了反剪切阿尔芬本征模（RSAE）的线性和非线性基本特征及其对背景等离子体的影响并取得了重要前沿成果：掌握了RSAE实验激发的基本规律并根据其频率特征获取了最小安全因子的时间演化；利用δf-COBBLES和BOT程序揭示了摩擦项和扩散项对本征模频率快速变化特征的决定性作用；首次从实验和理论上发现了非线性模耦合驱动的高频轴对称模；首次发现了RSAE导致的背景热离子能量输运并利用准线性输运理论解释了其中的物理机制。这些研究成果不仅丰富了对阿尔芬波与高能粒子不稳定性相互作用的认识，还推动了国际托卡马克物理活动及相关技术的发展。在项目执行期间，项目组成员在核聚变顶级期刊《Nuclear Fusion》发表论文4篇；获得亚太等离子体物理会议邀请报告、国际原子能机构聚变能源大会口头报告及全国等离子体技术会议口头报告各1人次。