Multipulse Nd：YAG Laser Thomson Scattering Diagnostics on HT-7 Tokamak

A multipulse Nd：YAG （Neodym-yttrium aluminium garnet） laser Thomson scattering diagnostic system developed was recently applied on HT-7 tokamak to obtain more accurate electron temperatures. A CAMAC-based real-time computer system for laser control, data acquisition, analysis and calibration was investigated in detail. Furthermore, the reliability and accuracy of this diagnostic system were demonstrated by comparing the results with those of a soft-X ray diagnostic system.     

Design of Amplifier Circuit for the HT-7 Tokamak Thomson Scattering System

Thomson scattering diagnostic is important for measuring electron temperature and density profiles. To improve the signal-to-noise ratio, a silicon avalanche photodiode （APD） with high quantum efficiency, high sensitivity, and high gain up to 100 was adopted to measure the Thomson scattering spectrum. A preamplifier, which has low noise, high bandwidth, and high sensitivity, was designed with suitable transimpedance. Using AD8367 as the post-amplifier, good performance of the APD readout electronics have been obtained. A discussion is presented on the performance of the amplifier using a laser diode to simulate the Thomson scattering light. The test results indicate that the designed circuit has a high amplifying factor and fast rising edge. So reduction of the integral gate of the CAMAC ADC converter can improve the signal-to-noise ratio.     

Analysis and Performance of the Thomson Scattering Diagnostics on HT-7 Tokamak Based on I-EMCCD

A visible light imaging Thomson scattering （VIS-TVTS） diagnostic system has been developed for the measurement of plasma electron temperature on the HT-7 tokamak. The system contains a Nd：YAG laser （A = 532 nm, repetition rate 10 Hz, total pulse duration ≈ 10 ns, pulse energy 〉 1.0 J）, a grating spectrometer, an image intensifier （I.I.） lens coupled with an electron multiplying CCD （EMCCD） and a data acquisition and analysis system. In this paper, the measurement capability of the system is analyzed. In addition to the performance of the system, the capability of measuring plasma electron temperature has been proved. The profile of electron temperature is presented with a spatial resolution of about 0.96 cm （seven points） near the center of the plasma.     

Remote Control for the HT-7 Distributed Data Acquisition System

HT-7 is the first superconducting tokamak device for fusion research in China. Many experiments have been done in the machine since 1994, and lots of satisfactory results have been achieved in the fusion research field on HT-7 tokamak^[1]. With the development of fusion research, remote control of experiment becomes more and more important to improve experimental efficiency and expand research results. This paper will describe a RCS (Remote Control System),the combined model of Browser/Server and Client/Server, based on Internet of HT-7 distributed data acquisition system (HT7DAS). By means of RCS, authorized users all over the world can control and configure HT7DAS remotely. The RCS is designed to improve the flexibility, opening, reliability and efficiency of HT7DAS. In the paper, the whole process of design along with implementation of the system and some key items are discussed in detail. The System has been successfully operated during HT-7 experiment in 2002 campaign period.     

Alternate Data Acquisition and Real-time Monitoring System on HT-7 Tokamak

1 Introduction There are many tokamak devices over the world. Be- cause the tokamak device is based on the principle of a transformer, almost all tokamaks are pulse-operated and most of their discharge duration is within one or two minutes. A conventional data acquisition and anal- ysis system would be good enough for such devices. However, recent lower hybrid current-drive (LHCD) ex- periments such as those on the HT-7 and Tore Supra have generated discharges lasting several hundred sec- …     

HL-2A激光汤姆逊散射实验方案

简要描述了激光汤姆逊散射测量等离子体电子温度的基本原理,较详细阐述了用于HL-2A装置等离子体电子温度时空分布测量的汤姆逊散射系统(TLSS)的设计构思和发展规划。     

Design and development of a synchronized operation control system for Thomson scattering diagnostic on J-TEXT

A Thomson scattering diagnostic system is under construction at the Joint Texas Experimental Tokamak (J-TEXT).A 1064 nm Nd:YAG laser with 50 Hz repetition rate is used as the laser source.We have used a software for careful and precise control of the laser through serial communication.A time sequence operating system has been developed to synchronize the laser control and data acquisition system with the central control system (CSS).The system operates commands from the CSS of J-TEXT and generates triggers for the laser and data acquisition system in the proper sequence.It also measures an asynchronous time value that is needed for accurate time stamping.All functions are served by a field-programmable gate array development platform that is suitable for high-speed data and signal processing applications.Several embedded peripherals,including Ethernet and USB 2.0,provide communication with the CSS and the server.     

Asphericalizing the Light Collection Mirror for the 200-Point Thomson Scattering Diagnostic Installed on the Large Helical Device

Shown is a possibility to make the image of a laser beam over a distance of 2.5 m, formed by the spherical multi-segment mirror installed in LHD, twice sharper ...     

Optical Design of ECEI Diagnostic System for HT-7 Tokamak

Electron cyclotron emission imaging system in the frequency range of 95 GHz ～125 GHz is going to be constructed for a two-dimensional diagnosis of the electron temperature profiles and fluctuations on the HT-7 Tokamak. The optical design for the ECEI diagnostic system is completed. Because of the superconducting technology used in HT-7, the vacuum chamber is rather thick (630 mm), the height of the horizontal windows is limited (maximum 450 mm), which constrains greatly the ECE imaging Gaussian beam that passing through the windows. We here comes to make a design compromise between the number of the beams that can pass through the windows and the spatial resolution (around 1.1 cm). We also find that due to the field curvature of the optical system, the gaussian beams of edge channels are always overlapped. To flatten the field curvature, it is needed to insert a concave made of a material with a low refractive index (compared with the one used in the convex). But the suitable material has not been available so far, therefore the deterioration of the resolution in some channels (e.g. the edge channels) is acceptable.     

The Compression Algorithm for the Data Acquisition System in HT－7 Tokamak

HT-7 superconducting tokamak in the Institute of Plasma Physics of the Chinese Academy of Sciences is an experimental device for fusion research in China. The main task of the data acquisition system of HT-? is to acquire, store, analyze and index the data. The volume of the data is nearly up to hundreds of million bytes. Besides the hardware and software support, agreat capacity of data storage, process and transfer is a more important problem. To deal with this problem, the key technology is data compression algorithm. In the paper, the data format in HT-7 is introduced first, then the data compression algorithm, LZO, being a kind of portable lossless data compression algorithm with ANSI C, is analyzed. This compression algorithm, which fits well with the data acquisition and distribution in the nuclear fusion experiment, offers a pretty fast compression and extremely fast decompression. At last the performance evaluation of LZO application in HT-7 is given.     

基于EPICS的X射线小角散射实验站控制和数据采集系统

上海光源（Shanghai Synchrotron Radiation Facility, SSRF）X射线小角散射（small angle X-ray scattering, SAXS）光束线站的常规样品台、掠入射样品台、变温热台的控制程序及数据采集程序均是在LabVIEW环境下开发的,而基于步进电机的狭缝控制系统等则是在分布式控制的EPICS (Experimental Physics and Industrial Control System)环境下开发的。由于开发和运行环境不同,这些设备在联动控制时不可避免地存在网络延时的缺陷。本工作在EPICS环境下对运动控制、探测器数据采集和光强检测等控制进行集成,形成了统一的用户操作界面,操作简单,能极大提高实验效率,并在SAXS实验站得到了稳定应用。     

CO2 laser collective Thomson scattering diagnostics on the HT-7 tokamak

A CW CO2 laser collective Thomson scattering diagnostics was developed to measure plasma density fluctuations on the HT-7 tokamak. The design and construction of CO2 laser scattering apparatus is described. The laser source is a continuous-wave CO2 laser with a cavity length of 1.9 m and a power output of about 10 W at 10.6 μm. The k-resolution of the system is △k ≈ 3.2 cm^-1. The preliminary data from the diagnostic is presented.     

Measurement of electron density and electron temperature of a cascaded arc plasma using laser Thomson scattering compared to an optical emission spectroscopic approach

As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and electron temperature of the plasma device accurately, a laser Thomson scattering(LTS) system, which is generally recognized as the most precise plasma diagnostic method, has been established in our lab in Dalian University of Technology. The electron density has been measured successfully in the region of 4.5?×?10(19)m~(-3) to7.1?×?10~(20)m~(-3) and electron temperature in the region of 0.18 eV to 0.58 eV. For comparison,an optical emission spectroscopy(OES) system was established as well. The results showed that the electron excitation temperature(configuration temperature) measured by OES is significantly higher than the electron temperature(kinetic electron temperature) measured by LTS by up to 40% in the given discharge conditions. The results indicate that the cascaded arc plasma is recombining plasma and it is not in local thermodynamic equilibrium(LTE). This leads to significant error using OES when characterizing the electron temperature in a non-LTE plasma.     

（e,2e）电子动量谱仪的多参数获取和处理系统

本文介绍研制成功的（ｅ，２ｅ）电子动量谱仪的多参数获取和处理系统。这个系统有几个特点：一是５个数据获取通道并行转换数据；二是在微机支持下，每个通道相当于一个多道；三是根据需要可很方便地分开组合数据获取的通道数，即可作为单通道微机多道分析器使用，又可作为一维或二维位置灵敏探测器的数据获取和处理系统使用；最后一点是系统实时获取时，可在线处理数据并在图形显示上分时显示符合时间谱及电离能谱。     

诊断中性束电源的数据采集与处理系统

文中介绍了一种用于诊断中性束电源系统的数据采集与处理系统(DPAS).在电源系统的运行过程中,系统需要对18路电流/电压信号进行实时采集.DPAS采用网络技术以客户端/服务器模式进行开发.系统引进了一种高效的压缩算法从而大量地节约了数据存储所需的磁盘空间.系统所采用的数据存储格式与EastScope软件(一款用于查看实验数据的软件)兼容,从而使实验操作人员可以很容易对实验结果进行分析和总结.     

Control and acquisition for MAST Thomson scattering diagnostics

The MAST (mega-amp spherical tokamak) Thomson scattering (TS) diagnostics have been radically upgraded and expanded. Eight 30 Hz 1.6 J Nd:YAG lasers have been combined to produce a sampling rate of 240 Hz. The scattered signals are acquired by two spectrometer systems: core and edge. The core system has been built anew: collection optics, polychromators, digitizers, and control computers. It allows measurement of electron temperature and density at 130 spatial points with ∼10 mm resolution across the plasma.The Nd:YAG scattered light signals are registered in 650 channels as polychromator outputs; each channel is registered on two ADCs: at 1 GHz rate in a short interval around each laser pulse and at 100 kHz for background data. The fast ADCs are combined in 26 data acquisition units. Each unit is assembled in a 6 U PXI chassis with embedded controller and six 4-channel 1 GHz ADC cards. Some chassis contain a 96-channel slow ADC card with Ethernet control.The Ruby TS has been rebuilt with a new spectrometer and CCD camera to provide higher spatial resolution - 512 points; the laser has been modified to add double pulse capability.A new control and acquisition system has been developed; it has modular design allowing flexibility and seamless expansion. The system supports event-triggered and real-time operation (will be added in a later stage).A smart trigger device has been developed for TS timing and synchronisation. It provides complex pulse sequences for laser firing with resynchronisation on a number of digital and analogue inputs including plasma events. This device also triggers TS acquisition.The system is integrated by a TS master process running on the dedicated computer; it is represented as a standard MAST data acquisition unit. The Ruby TS is also implemented as a standard MAST unit linked with the Nd:YAG TS by MAST system services.     

位置灵敏探测器的数据获取和处理系统的研制

本文介绍微通道板位置灵敏探测器的数据获取和处理系统的研制，简要描述了它的硬件结构和系统软件，本系统设计成一个ＮＩＭ标准单宽仪器插件，采用ＩＢＭ－ＰＣ／ＡＴ微型计算机作为实验数据读出及数据处理。具有实用、可靠和性能价格比高等特点。     

One-Dimensional Vertical Electron Cyclotron Emission Imaging Diagnostic for HT-7 Tokamak

At the first stage of the electron cyclotron emission imaging （ECEI） diagnostic project on HT-7, a 16-channel vertical-resolved ECEI diagnostic has been developed and installed on HT-7 tokamak to measure electron cyclotron emission with a temporal resolution of 0.5 usec. The system works at a fixed frequency of 97.5 GHz. The sample volumes of the system are aligned vertically with a vertical channel spacing of 11 mm, and can be shifted across the plasma cross-section by varying the toroidal magnetic field. The high spatial resolution of the system is achieved by utilizing a low-cost linear mixer/receiver array and an optical imaging system. The focus location may be shifted horizontally when translating one of the optical imaging elements. The details of the system design and laboratory testing of the ECEI optics are presented together with the preliminary experimental results.     

The Design of the Polychromator for Thomson Scattering Measurements on HT-7 Tokamak

A five-channel polychromator, utilizing high performance interference filters, has been completed for Thomson scattering measurements on HT-7 tokamak. For our instrument, therange of electron temperature varies from 50 eV to 1.5 keV. According to this, the bandpass of the different interference filters are chosen. Unique features of the polychromator are high throughput,easy alignment, flexibility and compact size when compared with other alternatives. In this article,both the method of designing and the measured transmission curves for the polychromator are given.