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1.
Comparative measurements of plasma position using coils,hall probes,and bolometers on CASTOR tokamak
J. Sentkerestiová I. Ďuran E. Dufková V. Weinzettl 《Czechoslovak Journal of Physics》2006,56(2):B138-B144
Plasma position on CASTOR tokamak is measured by several systems based on different experimental methods. Vertical and horizontal plasma displacements are deduced from data of 4 Mirnov coils spaced poloidaly by 45°. Output of the Mirnov coils is routinely used as an input for automatic feed-back control of plasma position on CASTOR. Independently, we used an array of 16 Hall sensors, which measure the required magnetic field directly. Additional information on plasma position is obtained from two arrays of bolometers that measure horizontal and vertical profile of plasma radiation. Principle design of the all used diagnostics is given. Comparison of horizontal and vertical displacements deduced using various experimental methods is presented. 相似文献
2.
托卡马克等离子体的三角形变和拉长比对约束和磁流体稳定性有很强的影响,因此在托卡马克装置极向场设计中,在基于物理和工程考虑所预先选定的等离子体平衡位形几何参数下,如何优化确定外部极向场线圈位置和电流,是一个具有重要实际意义的研究课题.为优化确定托卡马克极向场线圈,给出了一个有效的多变量平衡优化方法,能以事先规定的等离子体平衡位形的一些几何参数为目标函数,优化确定极向场线圈位置和电流.并应用它于HT-7U平衡位形计算,得到了所需的结果.
关键词:
等离子体平衡
极向场线圈
优化 相似文献
3.
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. 相似文献
4.
Maryam Ghasemloo Mahmood Ghoranneviss Ahmad Salar Elahi Mohammad Kazem Salem 《辐射效应与固体损伤》2013,168(1):42-47
In this paper, an emissive-biased limiter (EBL) was designed and fabricated then the magneto hydrodynamic activity was investigated based on Mirnov oscillations and hard X-ray spectroscopy through the tokamak plasma biasing. The EBL is positioned at r/a=0.92, and the biased voltage, which is varied from?250 to 250 V, applied between the head of the emissive limiter and vacuum chamber. Furthermore, the effects of the biased limiter for both negative and positive applied voltages are measured, and the results are compared with cold-biased limiter. As the results of IR-T1 tokamak suggest, in emissive negative polarity, the duration of plasma current is increased, compared with no bias, cold positive and emissive positive polarities. The amplitude of Mirnov fluctuations in emissive negative polarity is larger and more regular, compared with emissive positive polarity. The amplitude of the hard X-ray fluctuation in emissive negative polarity is very low compared with cold negative, cold positive and emissive positive polarities which leads to minimum energy loss. 相似文献
5.
The edge plasma characteristics are studied by both a movable array of
Mach/Reynolds stress/Langmuir 10-probes in the boundary region and the fixed
flush probe arrays on the 4 divertor neutralization plates at the same
toroidal cross-section in the HL-2A tokamak. The dependence of the
Reynolds stress on poloidal flow in the edge plasma is analysed. The result
indicates that the sheared poloidal flow in tokamak plasma can be induced by
the radial gradient of Reynolds stress. In the divertor experiments of
HL-2A, the profiles of the electron temperature, density and floating
potential on divertor plates are measured by the flush probe arrays. The
edge electron temperature in divertor configuration is higher than that in
limiter configuration. The temperature asymmetry between outer and inner
target plates
is observed. The result of magnetic surface reconstructed from 18 Mirnov
coils signals is presented. Both the particle recycling and the impurity
flux in the bulk plasma during divertor discharges are discussed. Neutral
gas pressure in divertor chamber, measured by fast ionization gauge during
divertor discharge, is given. 相似文献
6.
7.
R. M. Castro M. V. A. P. Heller I. L. Caldas R. P. da Silva Z. A. Brasilio 《Il Nuovo Cimento D》1993,15(7):983-994
Summary Electrostatic turbulence and various aspects of magnetic fluctuations have been investigated, in the edge region of the TBR-1
tokamak, by using a set of Langmuir and magnetic probes, and a triple probe. Measurements of plasma parameters such as plasma
potential, density, temperature and magnetic field were taken in order to elucidate, the effect on transport of the electrostatic
and magnetic fluctuations in the edge. The fluctuations levels are found to be higher than in most tokamaks. The particle
flux is outward and slightly higher than that calculated from Bohm diffusion, and occurs in the frequency region typical of
the macroscopic MHD oscillations. The Mirnov-oscillation frequencies in TBR-1 are higher than those observed in other tokamaks
and, consequently, there is an uncommon superposition between the Mirnov and turbulent density fluctuations spectra. This
fact and the presence of high MHD activity may contribute to elucidate the possible influence of the magnetic oscillations
on the electrostatic transport observed in the plasma edge.
Work partially supported by FAPESP and CNPq. 相似文献
8.
9.
The spatial and temporal structures of magnetic signal in the tokamak ADITYA is analysed using recently developed singular
value decomposition (SVD) technique. The analysis technique is first tested with simulated data and then applied to the ADITYA
Mirnov coil data to determine the structure of current peturbation as the discharge progresses. It is observed that during
the current rise phase, current perturbation undergoes transition from m=5 poloidal structure to m=4 and then to m=3. At the time of current termination, m=2 perturbation is observed. It is observed that the mode frequency remains nearly constant (≈10 kHz) when poloidal mode structure
changes from m=4 to m=2. This may be either an indication of mode coupling or a consequences of changes in the plasma electron temperature and
density scale length. 相似文献
10.
Yang T. F. Conn R. W. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1976,4(4):249-254
The MHD equilibrium and stability of noncircular tokamak plasmas limited by a separatrix is studied for reactor size systems. A typical example with a plasma current of 15.8 MA and major radius of 8.1 is presented. The required vertical field is generated by a set of discrete external coils and no conducting shell is included. The detailed equilibrium shape is calculated numerically for a vertical elongated plasma with two stagnation points symmetrically located above and below the midplane as would be required for a system with a poloidal divertor. The plasma height to width ratio is 2, the plasma shape factor is 1.6 and poloidal ? is 2.2. The plasma is locally stable. The general stability criteria with respect to quasi-rigid motions (special kink modes) are calculated numerically and found to be satisfied. Size scaling and the engineering constraints are discussed. 相似文献
11.
In this contribution, we have presented two techniques for the determination of plasma equilibrium position in IR-T1 tokamak: relaxation and optical methods. An analysis method of tokamak plasma equilibrium by a relaxation method with a specified magnetic axis is presented. The degrees of freedom due to designated positions of the magnetic axis are possible by using poloidal field coil currents. Stable steady-state tokamak plasma equilibria are calculated along with the magnetohydrodynamic potential energy. The plasma generates a plasma current which partially or fully cancels the magnetic field from the poloidal field coils. For low-temperature plasmas, the plasma current distribution is centrally peaked; for high-temperature plasmas, the plasma current has a hole. A centrally peaked current distribution in a low-temperature plasma is evolved into a current distribution with a hole by increasing the plasma pressure by Ohmic heating, radio frequency heating, or by neutral beam injection heating. In the second technique, an image-processing technique was used for the output signal of the charge coupled device camera and plasma emission intensity profile and then the plasma position was obtained. Results are compared and discussed. 相似文献
12.
根据实验数据系统地描述欧姆放电情况下的TEXTOR托卡马克等离子体的磁流休动力学(MHD)振荡(Mirnov振荡)特性,主要包括:MHD振荡的主要模式及各模振荡的相关性;MHD振荡的传播方向;m=2/n=1模的电子温度、密度和密度涨落强度等各量振荡之间的相关特性。
关键词: 相似文献
13.
混有干扰的Mirnov信号是一类非平稳,和Fourier变换的方法进行MHD信号的提取不能取得满意的效果,因而提出采用小波变换的方法对Mirnov信号进行处理。理论分析与实验结果表明,利用小波变换的时频分析特怀对Mirrnov信号进行滤波处理,可以有效地去除干扰,提取出有用的MHD信号。 相似文献
14.
HL-2A单零偏滤器的位形特征 总被引:1,自引:1,他引:0
利用积分方法对多种电流剖面下HL2A装置单零偏滤器位形特征进行了计算研究。积分方法的优点是可以在任意电流剖面下求解具有X-点的自由边界的Grad-Shafranov方程。对HL2A装置而言,大体上可以在合理设定的分界面形状下,经几次叠代计算出各组极向场线圈(垂直场,三对多极场和多极补偿场以及水平场)中的电流。HL-2A的单零偏滤器位形基本上是圆截面加上在X-点附近的局部形变。对刮离区和偏滤器靶板区磁力线特性进行了分析以确定偏滤器的品质。 相似文献
15.
JI Xiaoquan YANG Qingwei FENG Beibing ZHOU Hangyu YUAN Baoshan CHEN Wei YANG Zhoujun 《核工业西南物理研究院年报(英文版)》2006,(1):53-54
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. 相似文献
16.
The high-energy current of runaway electrons during a major disruption in tokamak reactors can cause serious damage to the first wall of the reactors and reduce their life time. Therefore, finding a method to minimize runaway electron generation during a major disruption is much needed. Tokamak limiter biasing is one of the methods that can be used for controlling the radial electric field and can induce a transition to an improved confinement state. This paper attempts to examine the effect of limiter biasing on the generation of runaway electrons during a major disruption. To do so, a horizontal biased limiter placed on the tokamak was used. Main parameters such as plasma current, loop voltage, emitted hard X-ray intensity, magnetohydrodynamic (MHD) oscillation and Hα radiation and spectrum of hard X-rays, in the presence and absence of negative and positive limiter biasing, were measured. The results show that the application of limiter biasing during a major disruption can reduce runaway electron generation. 相似文献
17.
讨论了用空间傅里叶分析法确定托卡马克等离子体MHD磁扰动模式的方法。根据托卡马克实验的状况,对不同情况下的MHD磁扰动进行了详细的数值模拟,重点分析了该方法的系统误差,模拟结果与HL-1M装置上的实验结果进行了对比。比较结果表明,用空间傅里叶分析法识别托卡马克中的MHD扰动模式是一种可以行之有效的方法。 相似文献
18.
HL-2A装置MHD不稳定性实时预测破裂系统采用了一种简单有效的方法来预测MHD不稳定性导致的等离子体大破裂。利用Mirnov线圈探测MHD信号,根据信号的振幅或频率特点设定计算方法,来预测等离子体破裂先兆,然后用激光吹气注入杂质来缓解等离子体破裂。研究结果表明,该系统能够实时预测破裂先兆,按量注入杂质后,可达到破裂缓解目的。 相似文献
19.
Castle G.G. Wootton A.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1994,22(4):369-375
To determine whether or not magnetic field lines inside a tokamak plasma are stochastic we need the Fourier coefficients of any perturbing radial field inside the plasma. Usually what is measured with magnetic pick-up coils is the root mean square poloidal field outside the plasma. Although no unique transformation is available, we present a model which allows an interpretation of the measured (external) root mean square field in terms of the internal Fourier harmonics. The results are applied to particular TEXT discharges, and suggest a link between magnetic stochasticity and an increasing (more positive) radial electric field, as measured with a heavy ion beam probe 相似文献
20.
HL-2A 装置的边缘参数测量 总被引:3,自引:3,他引:0
HL-2A 装置中平面边缘的等离子体特性通过磁力传动的马赫/ 雷诺协强/ 朗缪尔10 探针组进行了研究。10 探针组安装在可径向向里和向外移动, 并可绕轴旋转360o 的传动杆上, 用于测量主等离子体边缘的温度、密度、悬浮电位、空间电位、径向和极向电场、湍流的雷诺协强、径向和极向等离子体流速及其径向分布。HL- 2A 装置的实验结果表明, 边缘等离子体扰动诱发的雷诺协强产生了边缘极向流; 雷诺协强的径向梯度驱动带状流抑制了湍流输运。 相似文献