东方超环上低杂波驱动等离子体环向旋转实验研究

旋转和旋转剪切能抑制磁流体不稳定性和增强等离子体约束.低杂波电流驱动作为未来聚变堆上可能的旋转驱动手段,探索低杂波在现有托卡马克装置上驱动等离子体旋转的驱动机制,可以为未来的聚变堆上旋转预测提供重要参考.在东方超环托卡马克装置上,早期发现了2.45 GHz的低杂波能有效驱动等离子体旋转的现象,认为是边界旋转的改变导致芯部旋转的同电流方向的增加造成的.更高频率下4.6 GHz低杂波电流驱动可以更有效地驱动同电流方向的等离子体旋转.本论文分析在欧姆背景等离子体下,不同功率的低杂波对等离子体环向旋转的影响,研究安全因子剖面变化对环向旋转的关系,利用功率调制获得了低杂波驱动旋转实验中的环向动量输运系数变化情况,发现环向动量扩散系数(χφ)、环向动量箍缩系数(Vpinch)的数值大小趋势是从芯部向靠外的区域逐渐变大.这与低杂波驱动环向旋转时,环向旋转速度由靠外的区域向芯部传递的特性吻合.     

托卡马克高场侧低杂波电流驱动模拟研究

利用GENRAY/CQL3D程序研究了EAST装置双零位形下高场侧和低场侧发射低杂波的电流驱动情况。模拟发现,电子密度较小时,高场侧低杂波电流驱动效果不如低场侧。随着电子密度的增加,高场侧低杂波电流驱动的优势逐渐显现,从高场侧发射的低杂波可以将能量沉积在更加靠近等离子体中心的位置。提高环向磁场强度有利于低杂波在高密度条件下传播。增大电子密度时,同比例增大磁平衡位形中的等离子体压强,高场侧低杂波电流驱动效果好于低场侧。     

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.     

Effects of edge-localized mode-induced neoclassical toroidal viscosity torque on the toroidal intrinsic rotation in the EAST tokamak

Intrinsic rotation has been observed in lower hybrid current-driven (LHCD) H-mode plasmas with type-III edge-localized modes (ELMs) on Experimental Advanced Superconducting Tokamak (EAST), and it is found that the edge toroidal rotation accelerated before the onset of the ELM burst. Magnetic perturbation analysis shows there is a perturbation amplitude growth below 30 kHz corresponding to the edge rotation acceleration. Using the filament model, the neoclassical toroidal viscosity (NTV) code shows there is a co-current NTV torque at the edge, which may be responsible for the edge rotation acceleration. For maximum displacement ～1 cm and toroidal mode number n=15, the calculated torque density is ～0.44 N/m², comparable with the average edge toroidal angular momentum change rate ～1.24 N/m². Here, the 1 cm maximum magnetic surface displacement estimated from the experimental observation corresponds to a maximum magnetic perturbation ～ 10^?3–10^?2 T, in accordance with magnetic perturbation measurements during ELMs. By varying n from 10 to 20, the magnitude of the edge NTV torque density is mainly ～0.1–1 N/m². This significant co-current torque indicates that the NTV theory may be important in rotation problems during ELMs in H-mode plasmas. To better illuminate the problem, magnetic surface deformation obtained from other codes is desired for a more accurate calculation.     

Heat Flux on EAST Divertor Plate in H-mode with LHCD/LHCD+NBI

Based on the surface temperature measured by the infrared camera on the experimental advanced superconducting tokamak(EAST), the heat fluxes on the lower outer divertor target plate during H-mode with the lower-hybrid wave current drive(LHCD) only and with the LHCD combined with the neutral beam injection(NBI) are calculated by the DFLUX code and compared. The analyzed discharges are lower single null divertor configuration discharges. In the case with the LHCD only(I_p~400 kA, P_(LHCD)~2 MW), ELM-free appears after L-H transition with the peak heat flux on the lower outer target plate less than 1 MW/m2. However, there is no ELMfree appearing after the L-H transition in the case with the LHCD+NBI(I_P~300 kA, P_(LHCD)+P_(NBI)~2 MW).The results show that the peak heat fluxes on the lower outer target plate in the LHCD+NBI H-mode cases are larger than those in the LHCD H-mode under the similar auxiliary heating power. This is because the heat flux profiles of the lower outer target plate as a function of plate location in ELMing with the LHCD+NBI are narrower than those with the LHCD only. The results are consistent with the results in terms of the scrape-off layer width observed in the EAST.     

低杂波电流驱动中径向扩散效应的数值模拟

应用改进后的程序详细计算了不同径向扩散系数对低杂波电流驱动剖面分布的影响。通过计算发现:考虑径向扩散效应后,驱动电流分布变平展宽,电流驱动的分布随着扩散系数的增大逐渐向外层移动,由局域性分布演化成非局域性分布;驱动电流的大小和效率随着扩散系数的增大而降低。     

低杂波电流驱动中径向扩散效应的数值模拟

应用改进后的程序详细计算了不同径向扩散系数对低杂波电流驱动剖面分布的影响。通过计算发现:考虑径向扩散效应后，驱动电流分布变平展宽，电流驱动的分布随着扩散系数的增大逐渐向外层移动，由局域性分布演化成非局域性分布；驱动电流的大小和效率随着扩散系数的增大而降低。     

EAST中性束反向注入的初步实验研究

对EAST中性束反向注入过程中等离子体加热和电流驱动进行了实验研究,并采用了美国普林斯顿大学等离子体物理实验室开发的TRANSP 程序对高功率中性束注入过程中能量热输运进行了分析。结果表明,中性束注入可有效提高本底等离子体温度,产生束驱动非感应电流,提高等离子体旋转以及有效改善等离子体约束。     

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对EAST中性束反向注入过程中等离子体加热和电流驱动进行了实验研究,并采用了美国普林斯顿大学等离子体物理实验室开发的TRANSP程序对高功率中性束注入过程中能量热输运进行了分析.结果表明,中性束注入可有效提高本底等离子体温度,产生束驱动非感应电流,提高等离子体旋转以及有效改善等离子体约束.     

EAST低杂波电流驱动的数值模拟

应用改进后的低杂波电流驱动程序对EAST进行了低杂波电流驱动的数值模拟。通过模拟发现,波注入位置、功率谱、等离子体温度和密度对低杂波的功率沉积和电流驱动剖面分布有很大影响。通过选取合适的低杂波功率谱、等离子体温度和密度,可以实现对其功率沉积和电流驱动剖面分布的控制。     

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应用改进后的低杂波电流驱动程序对EAST进行了低杂波电流驱动的数值模拟。通过模拟发现,波注入位置、功率谱、等离子体温度和密度对低杂波的功率沉积和电流驱动剖面分布有很大影响。通过选取合适的低杂波功率谱、等离子体温度和密度,可以实现对其功率沉积和电流驱动剖面分布的控制。     

HT-7托卡马克大功率低混杂波电流驱动的实验研究

在HT-7超导托卡马克成功进行了大功率（P_LHW=100—800 kW,f=2.45 GHz）低混杂波电流驱动实验.研究了不同入射功率和等离子体密度下的低混杂波电流驱动效率.获得了以平均电子密度增加、氘阿尔法（D_α）线辐射减少为特征的粒子约束改善;粒子约束时间τ_p增加了约1.5倍.仔细研究了能量约束时间与等离子体密度和低混杂波功率的关系. 关键词： 托卡马克 低混杂波 约束改善 电流驱动效率     

Characteristics of electron cyclotron resonance plasma formed by lower hybrid current drive grill antenna

A 3.7 GHz system, which is meant for LHCD experiments on ADITYA tokamak, is used for producing ECR discharge. The ECR discharge is produced by setting the appropriate resonance magnetic field of 0.13 T, with hydrogen at a fill pressure of about 5 × 10⁻⁵ Torr. The RF power, up to 10 kW (of which ∼50% is reflected back), with a typical pulse length of 50 ms, is injected into the vacuum chamber of the ADITYA tokamak by a LHCD grill antenna and is used for plasma formation. The average coupled RF power density (the RF power/a typical volume of the plasma) is estimated to be ∼5 kW/m³. When the ECR appears inside the tokamak chamber for the given pumping frequency (f = 3.7 GHz) a plasma with a density (n _e) ∼ 4 × 10¹⁶ m⁻³ and electron temperature ∼8 eV is produced. The density and temperature during the RF pulse are measured by sets of Langmuir probes, located toroidally, on either side of the antenna. H_α signals are also monitored to detect ionization. An estimate of density and temperature based on simple theoretical calculation agrees well with our experimental measurements. The plasma produced by the above mechanism is further used to characterize the ECR-assisted low voltage Ohmic start-up discharges. During this part of the experiments, Ohmic plasma is formed using capacitor banks. The plasma loop voltage is gradually decreased, till the discharge ceases to form. The same is repeated in the presence of ECR-formed plasma (RF pre-ionization), formed 10 ms prior to the loop voltage. We have observed that (with LHCD-induced) ECR-assisted Ohmic start-up discharges is reliably and repeatedly obtained with reduced loop voltage requirement and breakdown time decreases substantially. The current ramp-up rates also decrease with reduced loop voltage operation. These studies established that ECR plasma formed with LHCD system exhibits similar characteristics as reported earlier by dedicated ECR systems. This experiment also addresses the issue of whether ECR plasma formed with grill antenna exhibits similar behavior as that formed by single waveguide ECR antenna. Our experimental observations suggest that the characteristics of (LHCD system-induced) ECR-assisted Ohmic start-up discharges show similar properties, reported earlier with normal ECR-assisted Ohmic start-up discharges and hence LHCD system may be used as ECR system at reduced toroidal magnetic field for other applications like wall conditioning.      

HL－1M感应与低杂波组合电流驱动研究

本文结合ＨＬ－１Ｍ的基本参数，利用准线性的低杂波电流驱动理论和等离子体的电回路方程．研究了在控制等离子体总电流不变情形下欧姆感应和低杂波注入组合驱动电流的问题。结果表明，这一组合驱动方案对ＨＬ－１Ｍ装置的运行是可行的，其驱动电流分布可以通过改变低杂波注入功率、波谱形状、等离子体电子温度、密度以及总等离子体电流等加以控制。组合驱动的电流分布将优于欧姆驱动的电流分布，并可能抑制诸如锯齿振荡等一些ＭＨＤ不稳定性。     

用于 EAST 上低杂波平行波数测量的磁探针设计与测试

针对EAST上2.45GHz低杂波，完成了低杂波平行波数测量磁探针的设计、仿真与测试。利用有限元仿真软件COMSOL Multiphysics 5.2对磁探针尺寸进行仿真优化，确定了单匝环、矩形缝以及陶瓷片厚度等影响磁探针耦合性能的关键尺寸。测试结果表明，该磁探针对2.45GHz低杂波有良好的耦合性能和鉴别波极化的能力，与仿真结果一致。研究结果为EAST装置上低杂波平行波数测量诊断系统的建立提供重要的参考依据，从而为进一步开展高密度低杂波电流驱动实验研究提供必要的实验数据。     

HT-6B托卡马克参数下低杂波驱动电流的密度窗口

在简晰的物理模型下,采用数值方法,研究了HT-6B托卡马克参数下的低杂波射线轨迹,波谱移动,功率吸收和驱动电流分布。结果表明,存在着驱动电流的密度窗口,即仅在一定的等离子体密度范围内才能驱动电流(通常在理论和实验上仅注意到驱动电流的密度上限)。文中对这种密度窗口的存在给予了物理解释,并进而讨论了影响驱动电流效率的主要因素。 关键词：     

Compound sawtooth in EAST LHCD plasma:An experimental study

A compound sawtooth with an incomplete relaxation was observed in EAST’s lower hybrid current drive(LHCD)plasma. The sub-crash phase of the compound sawtooth corresponds to a longer-lasting and slower-growing 1/1 mode.Based on the two-dimensional(2D) SXR tomography, the time-dependent 2D image of a compound sawtooth crash is obtained. The island produced during a resistive internal kink mode is observed in the all crash phases of the compound sawtooth. The destabilization of 1/1 long-lasting saturated 1/1 mode is related to the current driven by the LHCD near the q = 1 surface.     

低杂波电流驱动等离子体的电导

本文研究了由于欧姆电场与驱动电流的低杂波场相互作用造成的影响等离子体电导的两个物理机制。重新推导了电子响应方程并求出了低杂波电流驱动场引起的等离子体电导增量。与没有考虑到这两个物理过程的结果相比,电导增量改变了2/(1+D_c)倍。     

低杂波电流驱动阴极高压电源系统的优化与实现

4.6 GHz 低杂波电流驱动（LHCD）是EAST托卡马克装置辅助加热系统的重要组成部分。其阴极高压直流电源基于脉冲阶梯调制（PSM）技术,采用64个直流模块串联输出50 kV直流电压。单模块的调制频率设计为50 Hz,故而系统调节速度有限,面对实际运行中网侧电压波动引起的干扰时,电源无法做出更快速的响应与反馈调节,从而导致输出电压产生大幅波动,影响输出性能。为提高电源调节速度和抗干扰能力,设计了具有1 kHz调制能力的高频整流模块以替代部分原低频模块,利用高频模块的快速调节能力抑制输出电压的波动。实验结果表明,升级后的电源输出电压波动减小了50%,更好地满足速调管对于电压精度和稳定度的控制要求,保障了系统运行的可靠性。     

EAST 装置反剪切放电的数值模拟

利用TSC+LSC 程序对EAST 装置反剪切位形进行了数值模拟,反剪切等离子体由偏轴分布的LHCD 来维持,并做了一系列的模拟来研究辅助加热投入时间对等离子体参数的影响。依据这些模拟,提出了一个新的控制安全因子分布的方案,这对托卡马克实验中的实时控制很有帮助。