托卡马克边界磁拓扑改变条件下偏滤器稳态热流控制及相关机理研究

Advanced steady-state operation (non-inductive drive, plasma duration of 3000s and the fusion gain Q≥5) is one of the scientific objectives of ITER, whose high power load on divertor targets and thus the intense plasma-wall interactions is the critical challenge to be overcome. Both lower hybrid wave (LHW) heating and resonant magnetic perturbation (RMP) coils can induce edge magnetic topology distortion in tokamaks, which under certain condition can achieve the splitting of divertor strike point and eventually open new channels for divertor power exhaust. This project, based on EAST’s current capabilities and characteristics, aims at the international front of divertor physics study and focuses on the urgent necessity for the steady-state operation of EAST and ITER. By utilizing the infra-red camera and divertor Langmuir probe arrays at different toroidal locations, along with other key diagnostics and simulation, to study steady-state heat flux control and its physical mechanism with edge magnetic topology change. The integration of 3D magnetic topology change with radiative divertor scenario, the most promising means of steady-state heat flux control in high-performance discharges, or divertor conditions to control steady-state divertor heat flux and its distribution is also planned. These researches are of significant importance for the effective reduction of steady-state divertor heat flux while maintaining the steady-state operations for high-performance plasmas.

先进稳态运行（非感应电流驱动，等离子体持续3000秒，聚变增益Q≥5）是未来ITER的科学目标之一，其引起的偏滤器靶板稳态高热负荷进而等离子体与壁相互作用是ITER实现该目标面临的巨大挑战。低杂波加热与共振磁扰动线圈均可引起托卡马克边界三维磁拓扑结构的改变，在一定条件下可实现打击点撕裂进而打开新的热与粒子排除通道。本项目瞄准偏滤器物理研究的国际前沿，立足EAST全超导托卡马克现有能力与特色，紧紧围绕EAST与未来ITER稳态运行的迫切需要，基于红外相机与具有环向多阵列的偏滤器探针等关键诊断系统并结合理论模拟，研究边界磁拓扑改变条件下偏滤器稳态热流控制及相关物理机制，并计划整合边界磁拓扑改变与辐射偏滤器（高参数放电中控制稳态热流最有前景的方式）、偏滤器运行状态来主动控制偏滤器靶板的稳态热流及其分布。该研究对于有效降低偏滤器稳态峰值热流，进而维持高性能等离子体的稳态运行具有重要意义。

对于EAST长脉冲高性能稳态运行，偏滤器靶板的高热负荷问题一直是急需解决的问题之一。项目依托EAST托卡马克实验平台，利用红外相机、偏滤器探针阵列等主要诊断，结合EMC3-EIRENE、MARS-F等大型理论模拟程序，详细研究了边界磁拓扑结构变化与等离子体电流、加热功率等等离子体主要参数间的依赖关系。系统比较了LHW加热、RMP线圈投入时靶板三维粒子流热流分布的区别以及对靶板稳态热流控制的影响。在打击点撕裂的条件下，通过控制打击点位置，优化等离子体位形，调节杂质气体注入的速度和量，实现了对当前偏滤器区域杂质气体注入的反馈控制，有效屏蔽了杂质聚芯以防止对芯部等离子体污染。此外，分析了边界磁拓扑结构变化对辐射偏滤器、偏滤器脱靶等不同运行状态行为的影响，及物理机制。通过边界和偏滤器区域的杂质气体注入，对偏滤器运行状态的变化以及边界台基区等离子体输运行为变化进行了深入分析，发现边界的E×B电漂移对偏滤器区域粒子和热流分布存在显著影响。在边界磁拓扑结构改变条件下，结合辐射偏滤器或者偏滤器脱靶主动反馈，实现了偏滤器靶板峰值热流的有效降低和对偏滤器靶板稳态热流分布的主动稳定控制，为未来ITER提供有价值的参考。