Toroidal rotation induced by 4.6 GHz lower hybrid current drive on EAST tokamak

Using a tangentially viewing x-ray imaging crystal spectrometer, substantial co-current rotation driven by lower hybrid current drive(LHCD) at 4.6 GHz is observed on EAST tokamak. This study presents plasma rotation behaviors with 4.6 GHz LHCD injection. Typically, the 10-20 km/s co-current rotation change and the transport of rotation velocity from edge to core are observed. The relationship between plasma parameters and rotation is also investigated, indicating that rotation decreases with increasing internal inductance(l_i) and increases with increasing safety factor(q_0). Hysteresis between rotation and T_e plasma stored energy is observed, suggesting different response times between the electron heating and rotation acceleration by LHCD. A comparison between the rotations driven by 4.6 G LHCD and 2.45 G LHCD on EAST is also presented, in which higher frequency LHCD could induce more rotation changes.     

EAST上基于端口密度测量的低杂波耦合研究

介绍了一套安装在EAST装置低杂波天线端口上方,用来测量端口附近电子密度的Langmuir三探针系统及其初步实验结果。此探针系统由探针、测量电路、数据采集以及数据处理四部分构成。实验结果表明：在低杂波天线端口充气的条件下,低杂波注入后端口密度会有明显的增加。端口密度与反射系数的关系与理论趋势一致,EAST上低杂波耦合的最佳密度出现在4~5×10¹⁷m^-3。     

射频等离子体光源高效固态功率源的设计

针对射频等离子体光源(LEP)开发了一种较高抗负载失配能力的高效驱动功率源。采用三次谐波开 路和偶次谐波短路,并利用集总参数和分布参数相结合的拓扑结构,实现了谐波控制的高效 F 类功率放大器;利 用单片机控制固态源的工作频率,使其与光源谐振频率的变化一致,减小功放输出的驻波比,提高长期可靠性。 对高效固态功率源进行连续波满功率测试和等离子体光源的匹配性测试。结果表明,末级 F 类功放在 435~445MHz 频段内输出功率大于 200W,漏极效率 80.7%以上,功率源在等离子体光源工作频段内整体效率为 77.5%;与等离 子体光源谐振器的联合热测试中,系统光效为 86.21m·W⁻¹。     

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详细介绍了HT-7装置低杂波前级系统的组成、低杂波系统的采集和功率模式控制。实验中通过前级PIN开关控制不同的低杂波输出模式,满足了HT-7装置相应实验对低杂波的要求。     

Design of a TE10-TE30 Rectangular Mode Converter for 4.6GHz LHCD Launcher in the Experimental Advanced Superconducting Tokamak

A compact rectangular TE10-TE30 mode converter is developed for the lower hybrid current drive （LHCD） launcher on the Experimental Advanced Superconducting Tokamak （EAST） at 4.6 GHz. The converter with periodic width perturbation aims to divide the microwave power into three sub-waveguides in the poloidal direction. We present the design and numerical calculation of the mode converter. Calculations are performed on the ripple wall converter by codes based on numerical solving the coupled-mode differential equations and on the simulation of the High Frequency Structure Simulator （HFSS） package. The resulting conversion efficiency from TE10 mode to TE30 mode exceeds 95% within the bandwidth from 4.56 GHz to 4.64 GHz, and the return loss of the oversized transducer can be considerably decreased to 0.068% by means of a capacitive button embedded in the E-plane of the waveguide.     

Investigation of lower hybrid current drive during H-mode in EAST tokamak

H-mode discharges with lower hybrid current drive (LHCD) alone are achieved in EAST divertor plasma over a wide parameter range. These H-mode discharges are characterized by a sudden drop in D_α emission and a spontaneous rise in main plasma density. Good lower hybrid (LH) coupling during H-mode is obtained by putting the plasma close to the antenna and by injecting D₂ gas from a pipe near the grill mouse. The analysis of lower hybrid current drive properties shows that the LH deposition profile shifts off axis during H-mode, and current drive (CD) efficiency decreases due to the increase in density. Modeling results of H-mode discharges with a general ray tracing code GENRAY are reported.     

EAST低杂波电流驱动的数值模拟及分析

介绍了波的射线轨迹程序C3PO和求解三维Fokker-Planck方程程序LUKE的基本计算过程及其物理机制.该程序采用的是反弹平均方法,考虑了相对论效应和捕获粒子效应.利用此程序模拟并分析了EAST偏滤器位形下等离子体电流对低杂波传播以及驱动效率的影响.计算结果表明,随着电流的增大,低杂波射线轨迹在极向的旋转加快,功...     

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结合陶瓷窗设计相关理论,采用电磁场仿真软件(CST)和有限元分析软件(Ansys),仿真计算了低杂波传输线系统新陶瓷窗的电磁和热力学性能。设计的陶瓷窗采用BeO陶瓷作为介质窗体,在中心频率点附近300MHz以上的带宽内,其驻波比小于1.1,窗片中心的最大温升为11.7°C。     

低杂波多结波导阵天线耦合特性的数值分析

通过数值模拟研究了低杂波多结波导阵天线的耦合特性。采用线型耦合理论,用艾黎函数计算了等离子体阻抗,推导出常规波导阵对等离子体的散射矩阵,并利用它和天线自身的散射矩阵研究了HT-7装置低杂波多结波导阵天线的耦合特性;计算了其平均功率反射系数、方向性系数和功率谱与等离子体边缘密度和主波导相位差等参数的关系。结果表明,与常规波导阵相比,由于多结波导阵天线存在自匹配特性,其天线功率反射系数小,且对相位不敏感。但由于存在多余副瓣,驱动效率较低。     

Experimental characteristics of a lower hybrid wave multi-junction coupler in the HT-7 tokamak

A phase-controlled lower hybrid wave (LHW) multi-junction (MJ) coupler (3(rows)×(columns)× (subwaveguides)) has been developed in the HT-7 tokamak. Simulations show that it is more effective for driving plasma current than an ordinary phase-controlled LHW antenna (3(rows)×12(columns)) (traditional coupler). The plasma--wave coupling experiments show that the reflection coefficient (RC) is below 10%, implying that the MJ grill can launch the wave into the plasma effectively. The effect of power spectrum launched by the MJ coupler on RC indicates that an optimal condition is requisite for a better coupling in the lower hybrid current drive (LHCD) experiments. Studies indicate that the drive efficiency of the MJ antenna is higher than that of the traditional one, which is mainly ascribed to the discrepancy in impurity concentration, plasma temperature, and spectrum directivity. An improved confinement with an electron internal transport barrier is obtained by LHCD. The analysis shows that the modified negative (low) magnetic shear and the change of radial electric field profile due to LHCD are possible factors responsible for the eITB formation.