聚变装置中能量和粒子输运通道退耦合物理机制的研究

It has been known for years that energy and particle transport channels in magnetic fusion plasmas can sometimes response differently to external actions. One example is the decoupling of energy and particle transport channels in the I-mode. I-mode is characterised by a temperature pedestal similar to H-mode, while particle confinement remains as in L-mode level. Since there is no ELMs and impurity accumulation, I-mode is conserved as a strong candidate for operation scenario of the next generation fusion devices. Another example is the response of transport channels to the resonant magnetic perturbations (RMP) used for EML-control in H-mode. It has been observed that when RMP is applied, density profile is strongly modified while temperature profile modification remains modest. Understanding the physical mechanism of the decoupling of energy and particle transport channels is crucial for the extrapolation of present ELM free plasma operation scenarios (e.g. I-mode) and ELM-control technique (e.g. RMP) to the next generation devices, such as ITER and DEMO. In this project, we will study the decoupling of energy and particle transport channels in the RMP ELM control in the EAST tokamak. A dual-Langmuir probe arrays will be used to measure simultaneously fluctuations and their cross-phase, and Long-Range Correlation (LRC) in the edge. This project will clarify the role of interaction between edge turbulence and zonal flow in the decoupling between energy and particle transport channels.

实验发现，能量和粒子输运通道在一定条件下会出现分离（或退耦合）。例如，在I-mode 模式下，能量约束处于H-mode水平（边界有温度台基形成），而粒子约束却处于L-mode水平。由于I-mode中没有边界局域模（ELM）出现和芯部杂质聚集，该模式是未来聚变装置运行的重要候选。另外，输运通道退耦合也出现在共振磁扰动（RMP）控制ELM的实验中；RMP对电子密度剖面有强烈影响，而对温度剖面的影响却很弱。理解输运通道退耦合的物理机制对于探索进入I-mode并保持其稳定运行的阈值条件和将RMP用于ELM控制的技术拓展到未来聚变装置（如ITER、DEMO）至关重要。本课题将在EAST装置上RMP对ELM控制产生退耦合的实验中，利用新设计的探针阵列系统测量边界湍流涨落，各涨落之间的交叉相位和长程相干系数的变化。通过分析带状流、平均剪切流和湍流的相互作用并结合模拟仿真来研究输运通道退耦合的物理机制。

等离子体能量和粒子输运是研究等离子体约束的重要课题。不同输运通道以及不同区域输运的耦合对深入理解等离子体输运的物理机制至关重要。该项目通过TJ-II、HL-2A和Heliotron J上的物理实验从等离子体湍流多尺度相互作用的角度研究了等离子体输运耦合的特性。具体包括如下方面：TJ-II上，发展了基于双朗缪尔探针和偏压电极组合探测磁面的新方法。该方法用于TJ-II中性束离子根等离子体电势不对称性实验研究，发现电势不对称的大小随电子温度（Te）增加可达到15 V。电势差的绝对值以及随Te的变化与新经典蒙特卡洛模拟结果一致。该发现首次提供了仿星器离子根等离子体存在电势不对称的直接实验证据。通过HL-2A和TJ-II实验对湍流扩散对边界等离子体与刮削层等离子体的耦合特性进行了研究。HL-2A上结果显示，当电流增加20%刮削层宽度实现了加倍，并伴随E×B剪切的增强。TJ-II上实验发现，通过外加电极偏压改变边界径向电场，刮削层密度和宽度受明显影响，同时E×B剪切和径向输运也随之变化。这些结果表明刮削层参数不仅受局部参数如碰撞率的影响，还在很大程度上受非局域输运的影响，这对今后磁约束聚变装置热负载的研究有指导作用；提出了偏滤器几何优化和等离子体运行模式集成的必要性。Heliotron J上通过ECRH功率调制改变边界径向电场和湍流涨落，实验观察到等离子体湍流多次度相互作用对等离子体边界耦合性的影响。