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.     

The Experiment of Modulated Toroidal Current on HT-7 and HT-6M Tokamak

The Experiments of Modulated Toroidal Current were done on the HT-6M tokamak and HT-7 superconducting tokamak. The toroidal current was modulated by programming the Ohmic heating field. Modulation of the plasma current has been used successfully to suppress MHD activity in discharges near the density limit where large MHD m = 2 tearing modes were suppressed by sufficiently large plasma current oscillations. The improved Ohmic confinement phase was observed during modulating toroidal current (MTC) on the Hefei Tokamak-6M (HT-6M) and Hefei superconducting Tokamak-7 (HT-7). A toroidal frequency-modulated current, induced by a modulated loop voltage, was added on the plasma equilibrium current. The ratio of A.C. amplitude of plasma current to the main plasma current △Ip/Ip is about 12% ～ 30%. The different formats of the frequency-modulated toroidal current were compared.     

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.     

Experimental Results of MHD Suppression with Modulated LHCD on the HT-7 Tokamak

Modulation of lower hybrid current drive was used successfully to suppress MHD activity. This was achieved in discharges with MHD m = 2 tearing modes during the discharge conditions Ip = 110 kA, Bt = 1.75 T, ne0 - 1.1 ×1013 cm-3. The delivering time of LHCD pulse is less then 30 μs. The amplitude, interval and the period of LHCD modulation pulse can be adjusted very conveniently. The modulation LHCD can be delivered very fast at any time during the discharge. The modulation LHCD period was always much shorter than the plasma resistive time (Tη≈100 ms). So the profile of plasma current is changed much faster than the plasma resistive time. The different forms of LHCD modulating can be proved.     

HT-6B托卡马克装置运行水平(英文)

介绍了HT-6B托卡马克装置运行情况,分析其运行区扩大过程,讨论了主要参数的提高情况。在归一化运行图上与国际上几个著名装置对比表明:在欧姆加热条件下,HT-6B的运行区域已达到国际上著名装置的同等水平。     

Data Processing and Acquisition System for the HT-7 Multipulse Thomson Scattering Diagnostic

This article describes the data processing and acquisition system for the HT-7 multipulse Thomson scattering diagnostic. An eight-pulse laser is used in the Thomson scattering system to obtain electron temperature profiles at eight different times throughout an entire plasma discharge. The major components of the diagnostic system consist of a multipulse iNd-glass laser,a photodetector‘‘s subsystem, a calibration set and a CAMAC data processing and acquisition system. The data processing software along with LeCroy 2250L will perform the data acquisition.In order to simplify the operation and extend the capability of its compatibility with other math softwares, the processing software has been improved by the authors. The new software based on the VC easily utilizes some math softwares to calculate the electron temperature. The new software is simpler and more operational than the old one.     

基于PC的HT-6M托卡马克控制系统的设计与实现

本文介绍了中科院等离子体所HT-6M托卡马克装置新的控制系统的设计方法、工程实现及实验运行结果     

EAST汤姆逊散射诊断定位控制系统的设计

设计了一种激光光路定位控制系统,用于EAST汤姆逊散射诊断的光路准直和测量区域的定位,其精确性对于该诊断的测量尤为重要,该诊断用于测量EAST装置放电时等离子体的电子温度和密度;为节约宝贵的实验时间,结合该系统给出一种快捷的激光光路定位方法;重点描述该系统中基于单片机PIC16F874A设计的靶板控制器,与传统步进电机控制器相比,具有故障恢复、支持光纤通信、体积小等优点。该系统已在2010年度的EAST实验中投入使用,运行可靠,定位精确,大幅缩短了光路准直所需时间。     

HT-7 Multipoint Nd Laser Thomson Scattering Apparatus

1. IlltroductionThomson scattering diagnostic has been an important and standard method for measuring temperature and density profiles on all modern toka-maks, such as the TV Thotnson Scattering systemon TFTR [1], the LIDAR system on JET [2] and theNd:YAG laser Thomson scattering system on Dlll--D[3]. It has the attractive characteristics of not per-turbillg the plasma to be investigated and of derivingthe absolute values of electronic temperature Ti anddensity ne' From the knot'.led…     

基于ICCD的高分辨率汤姆逊散射系统分析

本文介绍了一套针对EAST托卡马克上的高分辨汤姆逊散射诊断系统(简称TVTS).设计采用了Littrow型平面光栅谱仪和带三代的像增强器的ICCD相机,同时测量整个等离子体中心弦的电子温度和密度.本文概述了该系统的意义和原理,分析了系统各部分的设计方案并对系统性能进行了估算.可测的电子温度范围和电子密度范围分别是250ev～2key和2×1019 m-3～5×1019 m-3,空间分辨率为10mm,时间分辨率约为几个毫秒.