EAST等离子体图像采集与位置识别技术

本工作采用快速CCD相机采集并保存托卡马克等离子体放电时的图像。根据放电时等离子体图像的位置特点,采用改进的主动轮廓模型算法实时获得等离子体边界位置,并通过最小二乘法对其边界进行拟合,以此获得等离子体的中心位置,为进一步进行等离子体的实时控制提供了基础。该方法已成功应用于EAST装置的放电实验中,并取得了良好的效果。     

EAST等离子体图像边界提取算法的改进

本文采用快速CCD相机采集托卡马克装置的等离子体放电图像,根据等离子体放电的位置特点,采用基于Otsu阙值改良的Canny算法对等离子体图像进行等离子体边界位置的提取,并通过最小二乘法进行边界拟合,从而得到准确的等离子体位置。     

Study of electromagnetic noise influence on quench detection system under different discharge conditions for EAST

EAST is the first Tokamak device whose toroidal and poloidal magnet are superconducting. The enormous magnetic field energy stored in the magnet system will transfer into thermal energy and cause the damage of superconducting magnet, if a quench happened. Therefore, reliable quench detection is a key issue for steady-state operation. In addition to electromagnetic noise from poloidal magnet fields and plasma current which will experience fast current ramp rate, radio frequency noise from heating system also have some interference on quench detection system to a certain degree. The most difficult point for quench detection system is required to have more detail evaluation on electromagnetic noise interference.Recently experiments have been carried out successfully in EAST device. The steady-state operation with 1 MA of plasma current and more than 100-s plasma duration has been obtained. In the paper, the electromagnetic noise interference on quench detection system under different discharge conditions are analyzed and relative process methods are also introduced. The technological experience and experimental data are significant for the constructing ITER and similar superconducting device have been mentioned which will supply significant technological experience and experimental data for constructing ITER and similar superconducting device.     

Displacement Measure Research on EAST Magnet

For the safe operation of Experimental Advanced Superconducting Tokamak (EAST) with the higher precise control of plasma, it is important to estimate the displacement of the magnet system. This paper force on the displacement measure method on the EAST magnet system during the device operation. Owing to the complicated constitution and environment of the EAST device, an optical metrology system was built to measure the displacement, and the measure result was also described in the paper.     

A poloidal field control system based on VxWorks in HT-7 Tokamak

The PF (Poloidal Field) control system is one of the most important control systems in HT-7 Tokamak.Most of parameters such as plasma current, plasma horizontal position and plasma vertical position will be monitored.For the purpose of long-pulse discharge and the more precise control to plasma, the real-time operation system VxWorks is applied, instead of the behindhand and unbefitting DOS operation system. This paper describes the development process of HT-7 PF control system based on VxWorks on Intel X86 platforms. The method of using hardware cards in VxWorks, and the network communication with other operation systems are discussed especially. Results of the comparison between VxWorks and DOS operation systems are given too.     

The implementation of magnetics verification in EAST plasma control system

Experimental advanced superconducting tokamak (EAST) is an experimental device aiming at steady state plasma operation for fusion research. The values of many discharge parameters, such as plasma shape, position and current must be directly acquired or indirectly evaluated from the magnetic measurements, so the accuracy of magnetic measurements plays an important role in reliable plasma control performance. A method for verifying the key magnetic measurements in real time for each shot is described in this paper. Such magnetics verification will prevent the discharge from a key magnetic signal failure and ensure the quality of a successful discharge. The diagnostics verification algorithm has been implemented in the plasma control system for the EAST. The implementation details and its application in the recent experiment are presented in this paper.     

J-TEXT-EPICS: An EPICS toolkit attempted to improve productivity

The Joint Texas Experimental Tokamak (J-TEXT) team has developed a new software toolkit for building Experimental Physics and Industrial Control System (EPICS) control applications called J-TEXT-EPICS. It aims to improve the development efficiency of control applications. With device-oriented features, it can be used to set or obtain the configuration or status of a device as well as invoke methods on a device. With its modularized design, its functions can be easily extended. J-TEXT-EPICS is completely compatible with the original EPICS Channel Access protocol and can be integrated into existing EPICS control systems smoothly. It is fully implemented in C#, thus it will benefit from abundant resources in.NET Framework. The J-TEXT control system is build with this toolkit. This paper presents the design and implementation of J-TEXT EPICS as well as its application in the J-TEXT control system.     

Robust control design for the plasma horizontal position control on J-TEXT Tokamak

It is extremely important for tokamak to control the plasma position during routine discharge. However, the model of plasma in tokamak usually contains much of the uncertainty, such as structured uncertainties and unmodeled dynamics. Compared with the traditional PID control approach, robust control theory is more suitable to handle this problem. In the paper, we propose a H_∞ robust control scheme to control the horizontal position of plasma during the flat-top phase of discharge on Joint Texas Experimental Tokamak (J-TEXT) tokamak. First, the model of our plant for plasma horizontal position control is obtained from the position equilibrium equations. Then the H_∞ robust control framework is used to synthesize the controller. Based on this, an H_∞ controller is designed to minimize the regulation/tracking error. Finally, a comparison study is conducted between the optimized H_∞ robust controller and the traditional PID controller in simulations. The simulation results of the H_∞ robust controller show a significant improvement of the performance with respect to those obtained with traditional PID controller, which is currently used on our machine.     

Analysis of ripple and error field due to using the ferritic steel insert in EAST

Chinese Experimental Advanced Superconducting Tokamak (EAST) is ITER-like Superconducting (SC) Tokamak with divertor configuration. However, EAST device has 16 toroidal field coils (TFCs) whose ripple amplitude is 0.67% higher than 0.3% of acceptable level of ITER at separatrix point. In order to improve the plasma control and confinement and have more contribution to ITER Physics, it is expected to reduce the TF ripple to ITER acceptable level. In this contribution, it was preliminarily investigated for installation of the appropriate ferristic steel insert inside EAST vacuum vessel to reducing the ripple based on electromagnetic analyses. Results indicated the ripple amplitude could be achieved to the expected level of less than 0.3%. Simultaneously, the error fields introduced due to installation of the ferristic steel insert was analyzed and not beyond scope of physics requirement.     

Evaluation of Electron Energy Distribution Function in the IR-T1 Tokamak Edge Plasma

Electron energy distribution function (EEDF) in the IR-T1 Tokamak edge plasma is measured. In this paper, application of the first derivative method for processing the electron part of I–V characteristics is report. This method is based on the kinetic theory in a non-local approach. Results show that in the confined plasma EEDF is not strictly Maxwellian and is Bi-Maxwellian. Also proposed procedure allows evaluating additional plasma parameters such as plasma potential in Tokamak edge plasma.     

Reconstruction of the Density Profile for the EAST Tokamak Based on Polarimeter/Interferometer and Microwave Reflectometer Systems

A plasma density profile reconstruction procedure based on the Park matrix method has been developed for both circular and elongated plasma configuration on the Experimental Advanced Superconducting Tokamak(EAST).This method incorporates the line integrated electron density measured by the HCN interferometer and polarimeter/interferometer(POINT) system,the equilibrium fit(EFIT) based on magnetic measurements and the edge electron density profile provided by the microwave reflectometer.It is shown that when the magnetic flux surfaces are slightly corrected,the fitting error is less than 5% in comparison with the measurement data.     

受控核聚变托卡马克等离子体水平位移平衡反馈控制的物理研究

在理论上系统地分析了ＨＴ－６Ｍ托卡马克等离子体水平位移平衡控制器系统的结构及其控制方式，并采用大功率ＧＴＯ斩波器作为反馈场电源和Ｂａｎｇ－Ｂａｎｇ控制模式的技术，取得了较好的成果。     

Experimental study of ELM-induced filament structures using the VUV imaging system on EAST

A high-speed vacuum ultraviolet(VUV) imaging system has been developed on the Experimental Advanced Superconducting Tokamak(EAST), which selectively measures line emission with a central wavelength of 13.5 nm(CVI, n=4–2). It has been employed to study edge/pedestal plasma behavior in EAST. Edge localized mode(ELM)-induced filament structures have been captured by the VUV imaging system during the ELMy high confinement mode discharge with both high temporal and spatial resolutions. The typical features(i.e.poloidal width and pitch angle) of the observed filaments are quantitatively characterized based on the VUV imaging data, and the dependence of these features on basic plasma parameters is analyzed. It is found that the poloidal width is proportional to the heating power, and the pitch angle is inversely proportional to the edge safety factor q.95 The scatterplot shows a positive trend between the poloidal width and the ELM amplitude defined by the relative change in stored energy. These results are based on the condition that the perturbation induced by ELMs is confined to a narrow layer in the plasma.     

Two-dimensional vacuum ultraviolet images in different MHD events on the EAST tokamak

A high-speed vacuum ultraviolet (VUV) imaging telescope system has been developed to measure the edge plasma emission (including the pedestal region) in the Experimental Advanced Superconducting Tokamak (EAST).The key optics of the high-speed VUV imaging system consists of three parts:an inverse Schwarzschild-type telescope,a micro-channel plate (MCP) and a visible imaging high-speed camera.The VUV imaging system has been operated routinely in the 2016 EAST experiment campaign.The dynamics of the two-dimensional (2D) images of magnetohydrodynamic (MHD) instabilities,such as edge localized modes (ELMs),tearing-like modes and disruptions,have been observed using this system.The related VUV images are presented in this paper,and it indicates the VUV imaging system is a potential tool which can be applied successfully in various plasma conditions.     

Application Study of Film Capacitor of DC Link Capacitor in EAST Vertical Stabilization Control Power Supply

A hydrogen cyanide laser interferometer is mostly used to measure the plasma electron density in many Tokamak devices. The real-time calculation system of the plasma electron density based on a field-programmable gate array is proposed in this work. An Altera EP4CE30F23C8 FPGA chip is selected as the master chip, and an AD9238 chip of 10 MSps is employed for analog-to-digital conversion. The FPGA-based adapted Fast Fourier Transform and the proposed processing algorithm are designed to obtain the plasma electron density. The calculated density is stored in the secure digital card and can also be transmitted to the plasma control system via Ethernet. The experimental results show that the proposed system can effectively obtain the plasma density. The maximum error range is from ? 1 to 1 degree and the time resolution is 0.025 ms which is better than that of the convention method 0.1 ms. Meanwhile, this system is highly flexible and reduces design costs to meet the demands of Tokamak devices.

     

A Tangentially Visible Fast Imaging System on EAST

A tangentially visible imaging system has been developed on the Experimental Advanced Superconducting Tokamak(EAST) to record the full cross-section plasma visible radiation with speed up to 7500 frames per second at full resolution or much faster for a limited number of pixels.The edge localized mode(ELM) filaments during ELM eruptions in H-modes are captured.Using these pictures,the current in the filament is estimated.     

A Visible Light Imaging System for the Estimation of Plasma Vertical Displacement in J-TEXT

A wide-viewing-angle visible light imaging system (VLIS) was mounted on the Joint Texas Experimental Tokamak (J-TEXT) to monitor the discharge process. It is proposed that by using the film data recorded the plasma vertical displacement can be estimated. In this paper installation and operation of the VLIS are presented in detailed. The estimated result is further compared with that measured by using an array of magnetic pickup coils. Their consistency verifies that the estimation of the plasma vertical displacement in J-TEXT by using the imaging data is promising.     

Discrete magnetic probes measurement versus analytical method in determining plasma position in IR-T1 Tokamak

One of the analytical solutions to the inhomogeneous Grad–Shafranov equation (GSE) is based on the well-known Solov’ev equilibrium that corresponds to source functions linear in ψ. The GSE has been solved by this method with constraints over plasma current and poloidal beta using rectangular fixed boundary conditions [1]. In this paper a new analytical solution to GSE by imposing constraints on the plasma current and β_p + l_i/2 is presented. This method is used for plasma position determination in IR-T1 Tokamak by considering linear source functions and circular fixed boundary conditions. Plasma position is also measured by discrete magnetic probes and is compared with the analytical technique. Results comparison shows good agreement for a typical discharge in IR-T1 Tokamak.     

EAST-ICRH发射机宽频阻抗匹配网络的研究及实现

EAST(Experimental Advanced Superconducting Tokamak)是我国开展受控核聚变研究的新一代实验装置,离子回旋波加热(ICRH)是在该装置中加热等离子体的重要手段之一。论文介绍了离子回旋发射机中阻抗匹配网络的原理及实现方法,并采用LabVIEW软件和PLC相结合的方式开发了一套阻抗匹配网络调节系统。