HT-7等离子体密度反馈控制系统的研究

介绍了HT－7等离子体密度反馈控制系统,分析了影响等离子体密度控制的因素,改进了密度反馈控制方式,使控制系统密度反馈更为完整、规范,实现了控制系统从单纯的反馈控制向多功能转化。给出了在HT－7装置上的实验结果,并提出了进一步改进的措施。     

HT-7U装置位移快控电源及其控制系统设计

针对HT－7U装置等离子体位移快控电源低压大电流控制要求，提出了一种采用双PWM AC／DC变流器拓扑且易于多组并联的新颖控制方案；在分析了PWM AC／DC变流器d-q模型的基础上，设计了三闭环控制系统，特别采用了基于前馈的解耦控制和微分反馈控制，从而使系统获得了优良的动态性能，仿真结果证实了方案的正确性。     

CICC稳定性裕度设计法和HT-7U导体方案

HT－7U装置的超导环向场与极向场磁体将采用导线管多级绞缆导体（CICC）。对于大型超导磁体,稳定性是导体设计中最重要的指标之一,优化铜超比是确保稳定性和获得最大电流密度的关键。根据稳定性裕度原则,给出了CICC稳定性裕度设计法,提出了HT－7U新的导体方案。     

HT-7装置逆磁测量

通过在HT 7装置的内真空室安装一对同心圆逆磁线圈 ,并运用软件补偿的方法 ,对HT 7装置的逆磁通量进行了测量。在杂散场测量与软件补偿实验中 ,发现同心圆逆磁线圈感应的杂散信号主要来自垂直场、涡流电流、等离子体电流和纵场电流的变化。逆磁测量结果表明 ,在等离子体线平均密度 ne 很低时 ( ne <2 .2 ×10 1 3cm- 3) ,HT 7等离子体的总体能量约束时间τE 随 ne 线性变化 ;在 ne 很高时 ( ne >2 .2 × 10 1 3cm- 3) ,τE 则趋于饱和 ,其饱和值约为 2 1ms。并运用计算机统计分析的方法给出了欧姆加热的τE 定标律为τE =1.5 7 ne0 .72±0 .0 4 ×Ip0 .35± 0 .0 2 B0 .31 ± 0 .0 3T 。     

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介绍了HL-2M装置控制系统的静态架构、动态行为、控制理论以及模拟仿真。设计采用通讯网络将各控制子系统有机地连接起来,以实现各子系统的实时通讯和控制。等离子体放电控制系统将保证实验的各种参数达到预定要求,监控系统的故障处理机制可以减少各种实验异常对装置造成破坏,磁场控制系统的各种控制器则用来控制等离子体电流和位形,模拟仿真系统可以实现方便地验证控制器的目的。     

托卡马克LHCD实验中的电子加热

LHCD实验是托卡马克途径为实现稳态运行而进行的重要科研项目。我国的两个主要托卡马克实验装置HL－1M和HT－7已进行多年研究，在建的两大装置HL－2A和HT－7U也将在更高波功率下进行LHCD研究。虽然LHCD实验的主要目的是驱动电流，但波功率平衡问题是一个非常重要的物理问题，因为波功率最终不是被电子或离子吸收，这是通过某种机制损失了。     

HT-7U第一壁材料在HT-7装置中的辐照实验研究

把为HT-7U装置开发的系列碳基面对等离子体材料及其比对样品安装在样品架上，通过磁力传送机构送入HT-7装置刮削层中进行辐照实验研究。经过若干次等离子体放电实验后，取出样品进行表面形貌。表面元素成分及深度分布的X射线光电子能谱分析。结果发展，碳石墨材料的渗杂改性和抗等离子体溅射腐蚀的B4C/SiC梯度功能涂层可以有效地提高其抗待了子体轰击的能力。     

HT-7U超导托卡马克冷质部件支撑结构方案

介绍了用于HT—7U超导托卡马克装置冷质部件支撑的柔性支撑结构，设计了支撑整个纵场系统及极各场系统的结构方案，对支撑结构进行了传热分析、应力分析和稳定性分析。     

LHCD实验中低混杂波传播的解析分析

低混杂波电流驱动是托卡马克反应堆非感应电流驱动的主要选择方案之一,近期已在较高密度下获得好的驱动效率。LHCD也是我国的两个主要托卡马克实验装置HL－1M和HT－7长期研究项目,在建的两大装置HL－2A和HT－7U也将其列为主要研究内容。LHCD理论研究已开展多年,已有多个计算编码可用于确定波功率沉积和驱动电流剖面。但由于波动率是在多次穿越过程中逐渐沉积的,关于平行折射率的波功率谱在传播过程中存在上移或下移,因此波传播过程的解析分析相当困难,影响我们对物理问题的深入理解。文献[1,2]在静电近似下进行了解析分析,同时所分析的问题中等离子体参数限于ω≈ωpi的情形。本文将对更一般条件下的波传播性质进行分析。     

HT-7装置新低杂波相控波导阵天线及其微波特性测量

介绍了HT－7装置新低杂波天线的结构。根据天线波导的特殊结构，设计了一些必要的测量器件（过渡波导和测量多结波导阵的波导－同轴转换器），并提出了新天线的测量方案，给出了测量结果及其功率谱计算结果。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.