低杂波PAM阵列天线的耦合分析与实验研究

Lower Hybrid Current Drive (LHCD) is one of the most efficient means to drive plasma current non-inductively in tokamak. With the power improvement of the EAST auxiliary heating system and the steady state operation, the general used fully active multijunction antenna should be put far away from the high temperature plasma, so as to avoid being damaged by the heat radiation. However, the electron density at the mouth of the antenna will be much lower, and this will lead to bad wave coupling with the plasma, and decrease the current drive efficiency. The Passive-Active Multijunction (PAM) antenna may be the best candidate for EAST in the future because of its good coupling in low edge densities even near the cutoff density. Through establishing the three-dimensional coupling model of the antenna and plasma, this proposal will study the coupling characteristics of the PAM waveguide array antenna in different plasma density models, and explore the method to improve the current drive efficiency of the PAM. Then, we will study the integrated optimization design method of the PAM, considering the plasma load. Finally, combining the physics experiments on EAST, We will analyze and predict the wave coupling with plasma and the performance of current drive of the PAM antenna. The main objective of this research is to master coupling analysis and optimization design method of the PAM antenna and to direct the physics experimental research. The study achievement can be applied to the design of high performance 4.6GHz EAST LHCD antenna in the near future, so that the requirements of high parameters and steady-state operation on EAST can be satisfied.

低杂波是托卡马克等离子体实验中非常有效的非感应电流驱动手段之一。随着EAST辅助加热功率的提高和稳态运行，常用的有源多结波导天线需要与高温等离子体保持较远距离，以避免天线端口被烧坏，但此时会导致天线口密度较低而耦合变差，降低电流驱动效率。PAM类型的低杂波天线在密度较低时也能达到较好的耦合，是EAST装置未来的理想选择。本项目拟通过建立天线与等离子体的三维耦合模型，研究PAM波导阵列天线在不同等离子体密度模型下的耦合，探索提高PAM天线电流驱动效率的方法；考虑等离子体负载，研究PAM天线的综合优化设计方法；结合EAST装置物理实验，分析并预测PAM与等离子体的耦合和电流驱动性能。最终目标是掌握PAM天线的耦合分析和优化设计方法，指导物理实验研究。研究成果可应用于将来EAST装置的高性能4.6GHz低杂波天线的设计，满足未来EAST装置的高参数和稳态运行要求。

在托卡马克低杂波电流驱动实验中，常规有源多结波导天线需要距离等离子体较远，以避免天线端口被烧坏，但此时会导致天线口密度较低，耦合变差，降低电流驱动效率。有源无源多结波导PAM天线在低密度时仍有较好的耦合，是EAST 装置未来的理想选择。本项目针对PAM天线设计中的关键技术进行研究，主要对PAM与等离子体的耦合，波导阵列的优化，水冷设计等问题进行深入计算和研究，具体包括：. 1. 研究了PAM波导阵列与等离子体的耦合。在完善有源波导阵列耦合程序的基础上，利用散射矩阵网络级联方法，建立了PAM与等离子体耦合的微波网络模型，计算得到了PAM的辐射功率谱、方向性和波导内反射等，研究了边界电子密度对天线耦合的影响。结果表明，PAM在边缘密度低至截止密度附近时，仍保持低的反射和较高的方向性系数。这从理论上验证了，PAM在距离等离子体较远时仍能获得较好的耦合和驱动效果。在实验上，开展了4.6GHz多结波导天线与等离子体的耦合和电流驱动实验，验证本项目所发展的耦合程序的正确性。. 2. 研究了PAM波导阵列的优化。对PAM的功率分配结构、微波器件性能、无源波导深度、自匹配效应等进行详细优化，提高耦合效率和n//加权方向性系数。以未来EAST装置4.6 GHz低杂波天线为应用目标，为4.6 GHz低杂波设计了一种PAM结构，满足未来EAST装置的高功率和稳态运行需求。. 3. PAM阵列的水冷设计和研究。仔细研究了PAM的内置水冷结构和实现方法，对比研究了有源多结波导和PAM天线端口的温度分布特性。计算了PAM温度增加随着时间的演化，评估天线面对高温等离子体的安全。计算表明，PAM天线端口温度远低于多结波导天线，天线冷却需求的水流量较少。 . 通过本项目的实施，掌握了PAM天线设计中的关键理论和核心技术，为将来EAST装置发展新型低杂波天线提供了理论指导和技术支持，以满足高功率和长脉冲的实验要求。