多脉冲电子束发射度测量

采用多孔板并结合电子束在石英片相互作用产生的契仑柯夫辐射,对以天鹅绒为阴极发射的强流多脉冲电子束发射度和亮度进行了实验研究和测量。实验观测到了有外加磁场条件下的电子束发生旋转现象。对于电子能量为600 kV左右的电子束,多孔板处的磁场小于2.7 mT时,电子束元的偏离已经小于2°。分别测量了天鹅绒阴极发射的强流四脉冲电子束和双脉冲电子束的积分亮度,分别为7.5×107A/(m.rad)2和4.14×108A/(m.rad)2。结果表明,双脉冲电子束的积分亮度明显优于四脉冲电子束的积分亮度,进而验证了阴极等离子体对多脉冲电子束亮度具有重要影响,降低了电子束的品质。     

天鹅绒阴极产生的强流双脉冲电子束特性

 通过一台2 MeV直线感应型强流电子注入器建立的双脉冲功率源系统,实验研究了天鹅绒阴极产生的相对论性猝发双脉冲强流电子束基本特性,给出了双脉冲电子束的积分发射度、亮度和双脉冲电子束时间分辨包络变化情况。研究结果表明：天鹅绒阴极产生的双脉冲的亮度达到108 A·(m·rad)^-2;实验得到的两个脉冲电子束包络半径不完全一致,这是由于天鹅绒阴极在发射电子束过程中产生的阴极等离子体对真空二极管的影响程度不同所导致的。     

碳纳米管阴极强流脉冲发射特性实验

 在2 MeV直线感应加速器注入器平台上研究了采用浸渍涂覆方法制备的大面积碳纳米管阴极发射体的强流发射特性。研究结果表明：在脉冲高压电场下,碳纳米管阴极具有强流电子束发射能力,发射电流密度较大;碳纳米管阴极发射电子过程为场致等离子体发射。实验过程中,阴极端取样电阻环收集到的最大发射电流达350 A,阳极端法拉第筒收集的发射电流为167 A,最大阴极发射电流密度为19.4 A/cm²。     

多脉冲强流真空电子二极管研究

研究了猝发脉冲串条件下真空强流电子二极管状态和输出电子束参数的变化规律, 建立了阴极等离子体膨胀效应的强流电子二极管参量的方程组, 并提出了阴极等离子体柱状膨胀模型. 实验研究了猝发多脉冲电子二极管输出多脉冲强流电子束的能力和束品质的变化, 给出了以天鹅绒为阴极发射体, 阴极等离子体膨胀速度小于1cm/μs时二极管输出的双脉冲电子束包络的变化和电子束的发射度及亮度.     

光阴极RF腔注入器中激光脉冲的时间抖动

 介绍光阴极RF腔注入器中的驱动激光器,采用二极管泵浦的自锁模激光器,通过锁相,使输出激光脉冲的时间抖动小于2ps,实现激光脉冲同微波相位之间的严格同步,在实验上获得流强70A、能量2MeV、亮度4.4×10¹¹A/(m².rad²)的电子束。     

多晶LaB6阴极的脉冲热发射特性

 采用多晶LaB₆材料制成平板二极管阴极，阳极采用钼材料，阴极采用热传导与热辐射加热，加热体为石墨。实验研究了不同阴极温度、不同真空度下的脉冲发射特性，并对热发射稳定性进行了分析。结果表明： 在动态真空系统中， 阴极发射面积为0.012 1 cm²， 工作真空度为2×10^-4 Pa， 阴极温度分别为1 600， 1 650和1 700 ℃，在脉冲宽度为40 ms、重复频率为107 Hz的条件下，最大脉冲发射电流密度分别为34.0，44.0和53.8 A/cm²; 2×10^-4，5×10^-4和2×10^-3 Pa压强下的发射能力没有明显的差异;脉冲宽度的变化不影响发射电流密度的变化。     

一种YAG投影管及投影响显示系统

 介绍了研制成功的YAG投影管及投影显示系统。在阴极电流为5mA时,绿色投影管亮度大于6.5×10⁵cd/cm², 束斑直径在束流为1mA时小于80 μm。在122cm背投影机中可重现高质时图象,其水平分辨率为1000TVL,峰值亮度为1500×10⁵cd/cm²,对比度达成100。     

基于沉淀工艺制作四脚氧化锌纳米材料场致发射阴极的研究

采用沉淀法制备四脚氧化锌纳米材料场致发射阴极，将阴极和荧光屏封装起来抽真空并对屏施加电压，测试阴极的发射电流和荧光屏的发光亮度.利用沉淀法制备出面积为(13×15) cm²的阴极，测试结果表明，硅酸钾体积百分比在50×10^-3—83×10^-3范围，硝酸钡浓度在50×10^-4—77×10^-4 M范围，四脚氧化锌的浓度在82×10^-4—12×10^{-3相似文献}   

重复脉冲强流电子束源长时间稳定运行实验研究

 简要阐述了脉冲变压器型重复脉冲强流电子束加速器CHP01的组成、主要特点及工作原理,利用设计的重复脉冲强流电子束源进行了长时间运行实验研究,实验结果达到：在100 Hz重复频率下连续运行5 s,脉冲变压器能稳定输出电压1.15 MV,强流束二极管输出电压超过800 kV、束流7 kA、脉冲宽度45 ns,阴极电子发射密度超过10 kA/cm²,且运行稳定可靠。利用该电子束源进行了X波段类周期慢波结构微波器件实验研究,在50 Hz重复频率下连续运行5 s,输出微波功率超过1 GW,脉冲宽度大于25 ns。     

大直径钪酸盐阴极发射特性

 为获得kA级热发射电子束,研制了直径为100 mm钪酸盐热阴极组件,并建立了适应大面积热阴极实验环境的2 MV 注入器试验平台。实验在二极管真空3.7×10^-5 Pa、二极管电压1.95 MV、脉宽120 ns（FWHM）、阴极温度1 120 ℃时,获得最大收集电流1 038 A,发射电流密度约13 A/cm²。实验结果表明,工作状态下阴极发射能力与激活温度、系统真空度关系密切。     

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.     

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.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.