EAST上低杂波电流剖面实时反馈控制及实验研究

The advanced scenario provides a potential choice for achieving high confinement and high β plasmas in future fusion reactor. However, as the plasma β increasing, the much steep pressure gradient will trigger various MHD instabilities, leading to the fact that a reversed magnetic shear was sustained only in the resistive diffusion time scale on recent experiments. Consequently, it is crucial to avoid and suppress MHD instabilities actively through real-time control of current profile for the long-pulse advanced scenario operation, which can optimize and balance the relationship among the pressure gradient, current density profile and bootstrap current. In this project, the real-time feedback control of lower hybrid current drive (LHCD) current profiles via HXR diagnostic on EAST will be studied. The real-time control system will be designed and developed, in which the parameters of 2.45/4.6 GHz LHCD systems and the plasma density are the control variables and the LHCD current profile is the control target. Then, related experiments will be performed in order to validate the reliability of the control system, and the algorithm will be optimized to improve the control accuracy and real-time performance. This project can provide a powerful tool for real-time control of MHD instabilities in steady-state advanced scenarios on EAST in future, and make a valuable reference for integrated control in steady-state plasmas.

先进运行模式是未来聚变堆实现高约束、高比压稳态等离子体的一种很有潜力的选择。然而随着等离子体比压不断提高，过陡的压强梯度会引起各种MHD不稳定性，导致目前实验上反磁剪切位形维持的时间仅达到电阻扩散时间尺度。因此，通过实时控制电流剖面来优化和平衡压强梯度、电流密度分布及自举电流之间的相互关系，主动避免和抑制MHD不稳定性，是维持长脉冲先进运行模式的关键。本项目将在EAST上开展根据HXR诊断实时反馈控制低杂波电流剖面的研究。以低杂波电流剖面为控制对象，以2.45/4.6 GHz两套低杂波波参数以及密度等为控制变量，设计和搭建反馈控制系统。然后通过开展相关物理实验研究验证系统的可靠性；同时通过进一步优化算法，提高整个控制系统的实时性和精度等性能。此项目研究为将来EAST稳态先进运行模式中MHD不稳定性实时致稳提供了一个有力工具，同时也为稳态等离子体的综合控制提供很好的借鉴意义。

根据项目研究目标和计划安排，首先，研制了HXR诊断信号的放大和传输等信号调理模块，利用PXI控制器和采集卡，搭建了诊断数据采集的硬件平台；开发了数据采集软件，并设计了一种截止频率为5Hz的低通数字滤波器，很好地去除了原始信号中的噪声，为反演电流剖面提供了准确的数据基础；同时优化了4.6GHz低杂波功率控制算法，使得低杂波系统更为准确地跟随EAST PCS实时调节输出总功率，以上为开展实验研究奠定了良好的工程基础。其次，在EAST上采用ARTAEMIS模型，开展了单独利用LHCD对电流分布实施控制的模拟，仿真结果表明控制q分布的同时βp也在变化。最后，结合仿真结果和EAST参数，设计了实验提案并在EAST上开展了实验研究，实验结果发现在低杂波控制下等离子体内感产生变化，表明通过低杂波实时反馈控制电流分布的可行行，这为EAST提供了一种更为有效的物理研究和实验手段。