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采用等离子体分层模型,利用WKB近似研究了离子回旋共振加热(ICRH)天线发射谱n||对离子回旋波在托卡马克等离子体的表面功率反射系数、吸收衰减的影响,数值模拟了不同天线发射谱n||条件下快波少数离子加热的效果.模拟结果表明,当其它实验参数一定时,ICRH天线发射合适的n||能提高天线与等离子体的耦合效率,增强少数离子加热的效果.     

HL—1M装置ICRH天线设计及最佳耦合研究

本文对HL-1M装置离子回旋共振加热(ICRH)天线设计及最佳耦合研究所采用的数值计算公式进行了推导。对天线耦合有重要作用的特征电阻R、特征电感L和特征电容C进行了数值计算。讨论了天线几何尺寸,等离子体参数对ICRH的影响,比较了3维和2维数值计算的结果,从中得到了HL-1M条件下最佳功率耦合的天线几何参数和设计的指导原则。     

托卡马克中ICRH天线的优化设计

采用等离子体平板模型和三维天线模型数值模拟了托卡马克中ICRH天线与等离子体的耦合过程, 模拟结果表明在其它实验条件相同的条件下,与反对称电流和馈线端长度短的天线相比,对称电流分布和馈线端长度长的发射天线可获得更有效的功率耦合。     

HL-1M装置的ICRH系统

介绍了HL－1M装置的ICRH系统的主要性能指标。调试获得了频率28－36MHz、脉宽40－60ms、0．8MW的输出功率。测试了RF天线的频率特征。ICRH系统已在HL－1M装置上运动，并获取了初步的实验结果。     

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采用三支节液态调配器使离子回旋加热(ICRH)天线系统达到阻抗匹配,在阻抗匹配的条件下结合频率调制技术来减小由天线输入阻抗变化所引起的反射功率。数值模拟了频率调制前后天线负载与反射系数的变化关系,用来验证频率调制对ICRH天线中阻抗匹配装置的影响。模拟结果表明:三支节液态调配器结合频率调制方法,能更好地降低天线传输系统的反射系数,使得发射机的功率通过天线辐射更加有效地耦合到等离子体中去。     

频率调制对ICRH 天线阻抗匹配的影响研究

采用三支节液态调配器使离子回旋加热(ICRH)天线系统达到阻抗匹配,在阻抗匹配的条件下结合频率调制技术来减小由天线输入阻抗变化所引起的反射功率。数值模拟了频率调制前后天线负载与反射系数的变化关系,用来验证频率调制对ICRH 天线中阻抗匹配装置的影响。模拟结果表明：三支节液态调配器结合频率调制方法,能更好地降低天线传输系统的反射系数,使得发射机的功率通过天线辐射更加有效地耦合到等离子体中去。     

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介绍了EAST装置新型离子回旋加热(ICRH)天线电流带的设计结构。通过对电流带实际工况的计算得出电流带的工作温度分布,以此来模拟实际工作条件下电流带的热载荷承受能力以及对电流带结构的影响。论证了在实际工况热载荷条件(0.2MW)下,电流带辐射面温度及电流带整体结构强度满足设计要求。     

KT-5B托卡马克装置上离子伯恩斯坦波激发条件的实验研究

本文介绍了在KT-5B托卡马克装置上,线性离子伯恩斯坦波的激发与边缘离子密度涨落、托卡马克放电参数以及发射天线位置之间关系的实验研究结果。实验表明,边缘离子密度涨落过大,将使离子伯恩斯坦波激发变得困难;正常的托卡马克运行的放电参数范围与有效激发离子伯恩斯坦波的参数范围一致;对纵环电流天线,可能存在静电模转换激发和直接激发这两种离子伯恩斯坦波激发方式共存的情况。 关键词：     

高功率超宽带脉冲辐射实验装置

对高功率超宽带脉冲辐射实验装置的理论分析、工程设计及实验等分别进行了介绍。高功率超宽带脉冲辐射实验装置主要由脉冲充电电源、超宽带脉冲产生装置及超宽带脉冲发射天线三部分组成。脉冲充电电源为脉冲产生装置提供充足的前级能源；超宽带脉冲产生装置包括高压储能电容、高压开关、充电电感、低阻脉冲形成线、亚纳秒开关和高功率负载等部分；超宽带脉冲发射天线包括阻抗变换、传输线、同轴到平板过渡段、TEM喇叭馈源、透镜及密封腔、4．5m抛物面等部分。     

EAST装置离子回旋加热天线电流带热结构分析

介绍了EAST装置新型离子回旋加热(ICRH)天线电流带的设计结构。通过对电流带实际工况的计算得出电流带的工作温度分布,以此来模拟实际工作条件下电流带的热载荷承受能力以及对电流带结构的影响。论证了在实际工况热载荷条件(0.2MW)下,电流带辐射面温度及电流带整体结构强度满足设计要求。     

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.     

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.     

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.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

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.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.