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在HT-7装置上建立了一套高速CCD可见光成像诊断,测量了边界等离子体的可见光辐射成像.在HT-7装置放电中,首次观察到在等离子体边界区域存在一条极向旋转的可见光辐射带,由CCD诊断系统得到其极向旋转的频率为858Hz.根据多道Hα阵列测量得到极向旋转频率为952Hz.多道磁探针信号测量发现,等离子体内部存在m/n=3/1的电磁模,该模的旋转频率为972Hz.从电子回旋辐射诊断系统得到的电子温度剖面发现该模的磁岛宽度约为2.5cm.     

HT-7装置电子回旋辐射系统接收天线改进

为了提高HT-7装置上等离子体电子回旋辐射(ECE)超外差诊断系统的极向分辨率,根据高斯光学原理,分析了诊断系统天线的改进方案。优化了天线的圆形角锥喇叭尺寸和凸透镜参数以及在装置上的相对位置,使天线接收到的等离子体ECE异常模二次谐波辐射的高斯光束束半径只有30mm左右,能量的高斯光学性质损失不大于13%。     

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为了提高HT-7装置上等离子体电子回旋辐射(ECE)超外差诊断系统的极向分辨率,根据高斯光学原理,分析了诊断系统天线的改进方案。优化了天线的圆形角锥喇叭尺寸和凸透镜参数以及在装置上的相对位置,使天线接收到的等离子体ECE异常模二次谐波辐射的高斯光束束半径只有30mm左右,能量的高斯光学性质损失不大于13%。     

HT-7装置软X射线诊断系统及锯齿行为研究

利用HT-7装置上建立的多阵列软X射线诊断系统对等离子体放电中的锯齿不稳定性进行研究,发现锯齿的出现及其行为特点与等离子体电子密度N_e、电子温度T_e、边界安全因子q_α、壁条件等放电参数有密切关系。在低杂波电流驱动等离子体放电条件下,观察到m/n=1/1的中间模振荡出现在锯齿的上升阶段,并迅速发展、饱和、衰减,在锯齿塌陷或先兆振荡出现以前消失。分析和讨论了欧姆加热条件下和低杂波加热条件下的锯齿行为。     

HL-2A 装置可见光诊断方法初探

等离子体H_α 径向分布的测量是等离子体实验中的重要内容。在HL- 2A 实验中, 等离子体成像系统中的CCD 图片记录了等离子体辐射信息, 特别是H_α  线辐射信息( 在相机前加H_α 滤光片) 。因为光测量是辐射的线积分, 数据的处理和分析显得十分必要的。利用等离子体可见光成像系统, 采用Abel 变换, 得到H_α  在HL- 2A 装置中的径向分布, 提供了一项可靠的测量手段。     

用于等离子体相干模式自动识别的谱聚类算法实现

高约束模式对改善等离子体约束有着重要意义,但目前主要依赖人工进行模式识别,其效率低、成本高,导致核聚变装置中大量的诊断数据没有得到充分分析.为了解决这个问题,本文将机器学习中的谱聚类算法应用到EAST托卡马克装置上的电子回旋辐射成像、一维诊断系统电子回旋辐射计、磁探针、软X射线和快辐射等不同诊断系统的数据上,在时域及频域上识别出了锯齿模,验证了谱聚类方法的迁移性及准确性,解决了监督学习在数据处理上迁移性差以及需要依赖大量标签数据的问题.此外,本文实现了特定模式的筛选;最后利用电子回旋辐射成像及磁探针数据发现了一种可能的新模式,为新模式探索提供了一种新思路.     

HT-7电子加热实验的软X射线能谱诊断

介绍了HT-7装置上软X射线能谱诊断系统,用软X射线能谱对HT-7托卡马克上电子温度进行了测量。在离子伯恩斯坦波和低杂波协同实验中,观察到了对等离子体的较好的加热效果。     

EAST装置上ERD光谱诊断系统设计

在EAST装置上研制了一套边界旋转测量系统(ERD)用于测量边界等离子体环向/极向旋转速度和离子温度分布。前置收光系统采用了嵌入式(plug-in)结构,便于系统调试与维护。光谱仪设计成多入射狭缝结构,可容纳更多的光纤,提高了其利用率。探测器选用了高灵敏度和高动态范围的电子倍增CCD(EMCCD)探测器。使用了含高OH基浓度的石英光纤,可以承受一定剂量的中子辐射。系统设计的测量波段为350~800nm,最高时间分辨为15ms,空间分辨为1cm。低杂波注入下的实验结果与早期EAST上二维弯晶谱仪与快速往复探针联合实验的结论一致。     

EAST 装置电子回旋辐射二维成像系统的屏蔽优化

介绍了EAST 装置上的384 道(极向24 道径向16 道)的外差混频式电子回旋辐射成像诊断系统及其在EAST 及其复杂的电磁环境中的运行情况。在低杂波电流驱动期间,高灵敏度的电子回旋辐射成像系统受到严重干扰以至于无法提供正确的实验数据。通过优化系统各模块的接地、外加多层铜网屏蔽等措施,使得ECEI 系统屏蔽效能与改善之前相比提高了40dB,基本保障了EAST 装置上电子回旋辐射成像诊断的正常工作。     

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介绍了EAST装置上的384道(极向24道径向16道)的外差混频式电子回旋辐射成像诊断系统及其在EAST及其复杂的电磁环境中的运行情况。在低杂波电流驱动期间,高灵敏度的电子回旋辐射成像系统受到严重干扰以至于无法提供正确的实验数据。通过优化系统各模块的接地、外加多层铜网屏蔽等措施,使得ECEI系统屏蔽效能与改善之前相比提高了40dB,基本保障了EAST装置上电子回旋辐射成像诊断的正常工作。     

HT-7上射频波加热时中子辐射行为的研究

HT-7超导托卡马克进行DD等离子体放电时,中子的辐射与辅助加热射频波的类型(LHW加热、ICRF加热)及功率密切相关.利用BF₃与³He正比计数管组成的快速时间分辨中子注量监测系统,研究了不同类型的射频加热对于中子产生机理及高能离子形成的影响.LHW加热功率较低时,易形成逃逸,产生大量的光中子.特定频率的ICRF(27 MHz,24 MHz)加热时,聚变中子所占份额以及总的中子产额均随波功率的增大而显著增涨. 关键词： 射频加热 中子 托卡马克     

Study of sawtooth oscillations on the HT-7 tokamak using 2D tomography of soft x-ray signal

It is the first time so far as we know that two arrays of multi-channel soft x-ray detectors are used to generate twodimensional （2D） images of sawtooth oscillation on the HT-7 tokamak using the Fourier-Bessel harmonic reconstruction method, and using the singular value decomposition to analyse the data from soft x-ray cameras. By these two arrays, 2D image reconstruction of soft x-ray emissivity can be obtained without assumption of plasma rigid rotation. Tomographic reconstruction of the m=1 mode structure is obtained during the precursor oscillation of the sawtooth crash. The crescent-shaped mode structure appearing on the contour map of the soft x-ray emissivity is consistent with the quasiinterchange mode. The characteristics of the m=1/n=1 mode structure observed in the soft x-ray tomography are as follows： the magnetic surface is made up of the crescent-shaped “hot core” and the circular “cold bubble”. The structure of the magnetic surface rotates in the direction of the electron diamagnetic drift and the rotation frequency is the oscillation frequency of soft x-ray signals.     

Tomographic analysis of the central magnetohydrodynamic oscillations on the HT-7 tokamak

Multi-channel soft x-ray (SX) detectors are applied to generate images of magnetohydrodynamic (MHD) oscillation on the HT-7 tokamak, and the data from SX cameras are analysed by using the Fourier--Bessel harmonic reconstruction method and the singular value decomposition. The image reconstruction of SX emissivity is obtained on the assumption of plasma rigid rotation. One of the important phenomena in the HT-7 discharge is the transition from the sawtooth oscillations to the MHD oscillations when the plasma density grows higher. The MHD structure observed in the SX tomography is featured as follows: the magnetic surface of MHD structure is made up of the crescent-shaped ``hot core' and the circular ``cold bubble'. The structure of the magnetic surface is relatively stable. It rotates in the direction of the electron diamagnetic drift at a frequency being the oscillation frequency of the MHD oscillations.     

Density Profile and Diffusion Coefficient During IBW Heating in the HT-7 Superconducting Tokamak

The electron density coefficient was studied during IBW heating in the HT-7 tokamak. The frequency of IBW was 30 MHz, and the injected power was 130 kW. An improved confinement mode was induced by IBW heating in the HT-7. The peaked density profile was formed gradually, and the Ha radiation intensity was decreased abruptly. A five-channel far-infared (FIR) hydrogen cyanide (HCN) laser interferometer was used to measure the electron density profile. The evolution of the density profile and the soft X ray intensity profile were studied during the improved confinement phase. The electron density diffusion coefficient was studied carefully for IBW heating discharges. The results were compared with Ohmic heating plasma and with different toroidal field Bt (2.0 T and 1.8 T). For 30MHz frequency of IBW heating, the higher Bt leads the lower electron density diffusion coefficient at the region of r/a > 0.6 in the HT-7.     

快速扫描气动式静电探针测量系统

介绍了一种可以对等离子体进行快速扫描的新型气动式静电探针诊断系统,该系统由气动传送杆和一组四探针阵列组成。结合相应的数据采集和分析手段,能够在一次放电中得到边缘等离子体的电子温度Te、电子密度ne以及它们的涨落T^-e/Te、n^-e/ne等参量的径向分布。     

Application of Zernicke polynomials on HT-7 tomography

Zernicke polynomials method was first used in HT-7 tomography. Combining the characteristics of the soft X-ray imaging system in HT-7 tokamak, some of the technical consideration in applicating the tomography method are reported in this Letter. Through analyzing experimental soft X-ray data of a typical discharge with m=1 mode superimposed on sawtooth, it is shown that in the mid-mode and precursor phases, the central magnetic surface structure is composed of a hot core and a small magnetic island. In the crash phase, the hot core is obviously pushed outside and evolves into a crescent. The magnetic island is large. In addition, we compared the reconstructions obtained with Zernicke polynomials method and the Fourier-Bessel expansion method. The comparison result shows that as the magnetic island is large, Zernicke polynomials method seems more suitable to reconstruct the central plasma emissivity distribution on HT-7 tokamak. At last, through analyzing the oscillation amplitude and island size of the m=1 mode superimposed on sawtooth, it is thought that the large oscillation amplitude is due to large pressure gradient at the vicinity of inversion surface.     

Multi-Channel FIR HCN Laser Interferometer on HT-7 Tokamak

A Five-channel far-infrared (FIR) hydrogen cyanide (HCN) laser interferometer was developed to measure plasma electron density profile on the HT-7 superconducting tokamak. The structure of the five-channel FIR laser interferometer is described. The laser source used in the interferometer was a continuous wave glow discharge HCN laser with 3.4 m cavity length and 100 mW power output at 337 m wavelength. The temporal resolution was 0.1 ms and the detection sensitivity was 1/12 fringe. Preliminary experimental results measured by the interferometer on HT-7 tokamak are reported.     

HT-7等离子体密度反馈控制系统的研究

介绍了HT－7等离子体密度反馈控制系统,分析了影响等离子体密度控制的因素,改进了密度反馈控制方式,使控制系统密度反馈更为完整、规范,实现了控制系统从单纯的反馈控制向多功能转化。给出了在HT－7装置上的实验结果,并提出了进一步改进的措施。