HL-1M装置上MHD不稳定性磁扰动的探测和分析

给出了HL－1M装置上的Mirnov磁探针系统的布置及MHD不稳定性磁扰动模式的探测方法，探讨了实验中存在的MHD不稳定性现象。用空间傅立叶变换分析了HL－1M装置上的磁扰动模式，给出了在存在不同极向扰动模式放电条件下的各磁探针信号之间的相位比对关系结果，从而确认实验中所使用的方法的正确性和实用性。     

相关分析法确定HL-1M装置磁流体的扰动模式

采用相关分析法模拟分析了HL-1M装置的磁扰动模式,模拟的结果同预期的结果一致。在具有磁流体不稳定性的典型放电中,探测到独立模m=2、3、4,耦合模m=2、3,以及同时出现的耦合模m=4、5和独立模m=5,给出了用扰动幅度的极向截面图分析磁扰动模式的结果,讨论了相关分析法在实验分析中的优点和局限性。     

COSmθ磁探圈的研制及其在HT-6上的应用

一、引言 观测托卡马克装置中等离子体引起的极向磁场扰动,通常把测得的磁扰动信号用电子学线路进行模拟量处理或计算机系统作数字量处理,如相关分析,空间付利叶分析等,以辨别各种扰动模式及其随时间的演化。用这些方法监测放电准稳阶段的磁流体扰动,已属常     

HL-1M装置撕裂模不稳定性的相位比对法研究

采用相位比对法模拟分析了HL-1M装置的磁扰动模式,模拟结果同预期的一致。在具有撕裂模不稳定性的典型放电中,探测到独立模m=2、3、4,耦合模m=2、3,并与用空间傅立叶分析方法得到的扰动模式的分析结果进行了比较。讨论了这些方法在实验分析中的可行性和有效性。     

J-TEXT托卡马克高速单色成像系统研制

在J-TEXT托卡马克上研制了一套高速单色成像系统用于研究等离子体杂质行为与磁流体力学(MHD)不稳定性之间的关系.用STRAH代码模拟估算了碳杂质(CV227.09nm,CIII464.7nm)辐射强度.采用光纤耦合方法设计了系统光路结构,光路覆盖高场侧区域0.3a～0.95a(a为小半径),其空间分辨率为1.3cm...     

HL-1M装置上MHD不稳定性磁扰动模的传播

对在HL-1M装置放电实验中发现的宏观MHD不稳定性磁扰动模的传播现象进行了研究。通过对实验中发现的各种极向模数m值的MHD磁扰动模特征的观察,以及在不同放电条件,特别是在偏压H模放电下传播方向不同的分析,深入研究了MHD模传播与等离子体旋转的定性关系。     

HL-1装置电流上升段MHD不稳定性

在托卡马克放电的初始阶段,由于存在变化的等离子体电流,一般会出现等离子体电流的趋肤分布,这种分布会导致MHD不稳定性的发展和产生破裂。早期的托卡马克实验,对放电初始阶段的MHD扰动现象做过许多讨论和研究。A1cator-A在电流上升段观测到的大多数破裂发生在q_L=1.6模处,同时观察到MHD扰动模式随时间从高模向低模的发展。电流初始阶段的上升率对平顶段的放电特性也有重大影响,在FT上,只有在等离子体电流上升率为1.2—2.6MA.s~(-1)时,才能实现低q_L的等离子体参数运行。     

非圆截面托卡马克轴对称模的反馈稳定

通过直接解真空区扰动磁面的边值问题,本文解析地研究了非闭合导壳对托卡马克中轴对称MHD模的反馈稳定性。我们取等离子体截面为椭圆,反馈系统由导壳和主动反馈线圈构成。结果表明,两块放在等离子体上下的导体块有很强的稳定作用;电阻壳可用以抑制高频模式,主动反馈线圈可用以稳定低频模式。 关键词：     

傅里叶望远镜大气湍流模拟实验

傅里叶望远术是一种能对深空暗弱目标进行高分辨率成像的技术.为了验证大气湍流对傅里叶望远镜系统的影响,进行了实验室环境下大气湍流模拟实验研究.在三束光傅里叶望远镜实验系统上,通过控制射频驱动器的输出功率来模拟光强抖动,改变射频驱动器的瞬时频率来模拟相位抖动.给出了实验理论依据,推导了湍流强度与实验变量的关系.实验在弱湍流闪烁和相位抖动两种情况下,分别给单束光和三束光加随机扰动并计算其Strehl比.结果表明,只在单束光上加扰动时重建图像影响不大;在三束光上加扰动时,弱湍流光强抖动对傅里叶望远镜系统的成像效果影响具有较大的随机性,而相位抖动会严重影响系统成像质量.因此,消除光强抖动和相位抖动影响是图像重建算法改进应该考虑的一个关键因素.     

干涉条纹的高准确度傅里叶变换分析

提出了一种可用于干涉条纹傅里叶变换分析的空间载波频率估计方法.通过干涉条纹的加窗切趾处理及旁瓣质心坐标的计算,得到空间载波频率的高准确度估计.基于傅里叶变换的位移定理,用估计的空间载波频率实现了载频的移除.模拟和实验结果表明此方法可以有效地抑制传统干涉条纹傅里叶变换分析中的载频移除误差和频谱泄漏误差.     

Identification and Analysis of Magnetic Structures on HL-2A

1 Introduction Tearing modes in tokamak plasmas have been studied for many years In HL-2A tokamak, MHD instabilities are investigated by means of the Mirnov probes. The mode number can be determined by the methods of phase comparison analysis or correlation analysis from the experimental data of Mirnov probes, but the analysis of complicated mode structures is difficult. An identification and analysis method of magnetic islands is presented basing on simulation of the perturbation current and magnetic field in plasmas.     

HL-1装置MHD稳定性的研究

利用傅里叶分析和相关分析方法,研究了HL-1装置等离子体MHD不稳定性的特征和抑制不稳定性的若干方法及结果,给出了HL-1装置的稳定运行区域。     

托卡马克理想磁流体不稳定性的统一描述 (I)

在与平衡磁面相联系的坐标系下，用剪切阿尔芬波近似给出了统一描述托卡马克等离子体理想磁流体线性运动的本征模方程。利用此方程，可以进一步给出大尺度扰动（扭曲模、低模数气球模、阿尔芬模）和小尺度扰动（高模数气球模、Mercier模）的本征模方程。本文详细讨论了小尺度扰动的本征模方程。     

Analysis of tokamak plasma confinement modes using the fast Fourier transformation

The Fourier analysis is a satisfactory technique for detecting plasma confinement modes in tokamaks. The confinement mode of tokamak plasma was analysed using the fast Fourier transformation (FFT). For this purpose, we used the data of Mirnov coils that is one of the identifying tools in the IR-T1 tokamak, with and without external field (electric biasing), and then compared it with each other. After the Fourier analysis of Mirnov coil data, the diagram of power spectrum density was depicted in different angles of Mirnov coils in the ‘presence of external field’ as well as in the ‘absence of external field’. The power spectrum density (PSD) interprets the manner of power distribution of a signal with frequency. In this article, the number of plasma modes and the safety factor q were obtained by using the mode number of q = m /n (m is the mode number). The maximum MHD activity was obtained in 30–35 kHz frequency, using the density of the energy spectrum. In addition, the number of different modes across 0–35 ms time was compared with each other in the presence and absence of the external field.     

Comparison benchmark between tokamak simulation code and TokSys for Chinese Fusion Engineering Test Reactor vertical displacement control design

Vertical displacement event(VDE) is a big challenge to the existing tokamak equipment and that being designed. As a Chinese next-step tokamak, the Chinese Fusion Engineering Test Reactor(CFETR) has to pay attention to the VDE study with full-fledged numerical codes during its conceptual design. The tokamak simulation code(TSC) is a free boundary time-dependent axisymmetric tokamak simulation code developed in PPPL, which advances the MHD equations describing the evolution of the plasma in a rectangular domain. The electromagnetic interactions between the surrounding conductor circuits and the plasma are solved self-consistently. The TokSys code is a generic modeling and simulation environment developed in GA. Its RZIP model treats the plasma as a fixed spatial distribution of currents which couple with the surrounding conductors through circuit equations. Both codes have been individually used for the VDE study on many tokamak devices, such as JT-60U, EAST, NSTX, DIII-D, and ITER. Considering the model differences, benchmark work is needed to answer whether they reproduce each other's results correctly. In this paper, the TSC and TokSys codes are used for analyzing the CFETR vertical instability passive and active controls design simultaneously. It is shown that with the same inputs, the results from these two codes conform with each other.     

Scrape-off-layer current model for filament structure observed during edge-localized modes in the DIII-D tokamak

The plasma in tokamaks often exhibits a relaxation oscillation called the edge-localized mode (ELM), which is generally attributed to MHD instability driven by strong gradients at the plasma boundary. It is shown here that field-aligned currents flowing just outside the boundary may also play a role in the ELM process. The poloidal perturbation magnetic field during ELMs in the DIII-D tokamak calculated from measured currents can reproduce prominent observed features, including a narrow magnetic structure at the outboard midplane similar to filaments observed earlier in DIII-D and NSTX.     

Simplified Ideal MHD Normal Mode Equations for Toroidal Axisymmetric Plasmas

The ideal MHD normal mode equations for general toroidal axisymmetric plasmas can be significantly simplified by properly treating the compressibility team limiting cases: and c_s is the plasma sound velocity.These equations describing the general global modes (the low n, m mode) contain only two scalar functions. For tokamak plasmas, a further simplification, the shear Alfven approkimation, is introduced. It makes possible to describe the global mode by a simplified eigenmode equation with only one scalar function. This eigenequation, similar to the reduced tokamak equations widely used in recent literatures, provides a unified way to analyze the kink, Alfven spectrum and MHD TAE modes.