RIBLL粒子鉴别气体电离室

描述了一种用于兰州放射性束流线粒子鉴别的阳极分别在x,y方向分条共阴极纵向场双叠层电离室.对其性能进行初步测试,得到了坪曲线和能量分辨.在10kPa的P10工作气体(10%CH₄+90%Ar)时,阴极电压为–650V,阳极电压为+120V是较佳的工作点.当工作气压为25kPa时,阴极电压为–1650V,阳极电压为+240V的工作条件较好,此时,对²³⁹Pu α源相对能量分辨约为4.7%.     

一套用于重离子耗散反应测量的电离室望远镜

重离子耗散反应需要鉴别产物的电荷数Z,为此,研制了一套ΔE-E望远镜.ΔE由两个串接在一起的气体电离室ΔE₁和ΔE₂组成,位置灵敏硅半导体测量粒子的剩余能量E.被探测粒子的轨迹与电离室的电场方向平行.该望远镜具有很低的能量探测阈,较小的外尺寸和强的抗电磁干扰能力.重离子耗散反应¹⁹F+²⁷Al产物的激发函数实验测量表明,该望远镜的电荷分辨Z/ΔZ约为30.     

气体比分对RPC在流光模式下工作性能的影响

对不同比分气体对RPC性能的影响进行了大量的实验研究,主要是进行了基于氩、异丁烷和绿色氟利昂F134A(C₂H₂F₄)的实验,保持氩气的比分为20%,30%,40%,改变异丁烷和F134A的比分进行实验,分别测量了探测效率、单计数率、暗电流、信号幅度和多重计数随高压的变化曲线,结果发现,减少氩气的比分,增加异丁烷和F134A的比分可以增加RPC的坪长,探测效率也有所提高,在效率坪区的暗电流也有所减小,但工作高压也需要相应地增加。     

一种多阳极横向场电离室

描述了一种将用于兰州放射性束流线较重离子鉴别的多阳极横向场电离室.对其性能进行了初步测试,得到该电离室有较长的坪区和较好的能量分辨.在10⁴Pa的P10工作气体(10%CH₄+90%Ar)下,坪区长度为700V.对²⁴⁴Cm α放射源,在第4片阳极对应的灵敏区域能量损失为1.30MeV,能量分辨41.1keV,相对能量分辨约3.16%。     

高分辨率初始光电子能谱由真空紫外激光速度——映射图像的方法

通过采用真空紫外(VUV)激光速度-地图成像-TPE(真空紫外VMI-TPE)方法获得了高分辨率初始光电子(TPE)氯苯(C₆H₅Cl(X¹A₁))的光谱,炔丙基自由基(C₃H₃(X²B₁))和烯丙基(C₃H₅(X²A₁)). 观察到的真空紫外VMI-TPE方法的光电子能量分辨率在1~2 cm^-1,可以和在真空紫外激光脉冲场电离光电子(VUV-PFI-PE)的测量媲美. 类似真空紫外PFI-PE测量,真空紫外VMI-光电子(真空紫外VMI-PE)和真空紫外VMI-TPE测量能量分辨率依赖于直流电场在光电离区加速电子. C₆H₅Cl和C₃H₃的电离初始值的降低为F的函数表示Stark偏移校正为VUV-VMI-TPE测量由-3.1√F管辖,这是半经典预测值-6.1√F的一半. 我们还测量C₆H₅Cl和C₃H₅的真空紫外光能量的真空紫外VMI-PE谱接近其电离初始值. 在VUV-VMI-PE测量中观察到的C₃H₅⁺阳离子振动谱和振动级数,nv₇⁺(n=0~3). 真空紫外VMI-TPE可以实现更高的实验灵敏度和类似真空紫外PFI-PE测量的能量分辨率,使真空紫外VMI-TPE法成为高分辨率真空紫外PFI-PE测量一个很好的替代.     

OH+C2H3F的反应机理及产物支化比反应的理论研究

本文对HOC₂H₃F可能解离通道的势能面进行从头算CCSD(T)/CBS//B3LYP/6-311G(d,p)计算,同时对速率常数进行Rice-Ramsperger-Kassel-Marcus计算. 生成主要产物CH₂CHO+HF最有利的反应途径是OHC₂H₃F→i2→TS14→i6→TS9→i3→TS3→CH₂CHO+HF,其中速率决定步骤是HF通过TS11从CO桥接位置解离,能量比反应物高3.8 kcal/mol. 借助中间态TS14,F原子从C_α迁移到C_β位置生成CH₂O+CH₂F,然后通过中间态TS16,H从O迁移到C_α位置;通过中间态TS5,C-C键断裂生成产物,其能量比反应物低1.8 kcal/mol,比TS11低4.0 kcal/mol.     

高浓度氩气稀释对C2H2-2.5O2气体直接起爆临界能量影响的实验研究

 采用高压电点火进行直接起爆,通过放电过程中电流的输出信号确定起爆能量,实验测定了C₂H₂-2.5O₂气体和加入摩尔浓度为70%氩气的C₂H₂-2.5O₂混合气体直接起爆的临界起爆能量,研究了高浓度氩气稀释对C₂H₂-2.5O₂混合物临界起爆能量的影响。实验测得的混合物临界起爆能量实验值与Lee等人的表面积能量理论值基本吻合。研究表明：C₂H₂-2.5O₂气体和加入摩尔浓度为70%氩气的C₂H₂-2.5O₂混合气体的临界起爆能量均依赖于初始压力,并呈反相关指数关系;在相同实验条件下,高浓度氩气稀释极大提高了混合气体直接起爆的临界起爆能量。分析认为,由于临界起爆能量正比于诱导区长度的3次方,因此在相同初始压力下,高浓度氩气的稀释增加了C₂H₂-2.5O₂混合气体爆轰诱导区长度,并最终导致其临界起爆能量的显著上升。     

紧凑的非链式脉冲HF激光器

研究了气体组分和峰化电容对紫外光预电离脉冲HF激光器性能的影响.实验发现最佳气体混合比为SF₆/C₂H₆=20:1,峰化电容和主放电电容的最佳比为C_p/C_s=0.3,在最佳气体混合比时,最大激光脉冲峰值功率和对应的总气压随充电电压的提高而增大.同时得到了E/P值和激光能量的关系.整个器件的最大激光输出为400mJ,脉冲峰值功率为1.5MW,最大电光转换效率约为2.2%.     

多丝室工作于自猝灭流光模式下定位特性的研究

对多丝室运行于自猝灭流光(SQS)模式下的定位性能进行了实验研究.用两种不同的丝室结构,以Ar和CO₂的混合气体作为工作气体,在不同的CO₂含量比例及高压下测试了感应电荷信号在阳极丝周围电极上的分布.以阳极丝相邻电极上感应电荷的比来确定入射粒子在垂直阳极丝方向上的位置,分辨率σ_x好于350μm.由阴极面上感应电荷的分布,用重心法确定入射粒子在沿阳极丝方向上的位置,分辨率好于250μm.     

环戊酮光电离解离的实验和理论研究

本文介绍了真空紫外光电离质谱结合理论计算研究环戊酮单分子的光电离解离过程. 在9.0∽15.5 eV能量范围内,测量了环戊酮离子及其碎片离子的光电离效率曲线. 通过光电离效率曲线,将环戊酮分子的电离能确定为9.23±0.03 eV,并确认碎片离子为：C₅H₇O⁺,C₄H₅O⁺,C₄H₈⁺,C₃H₃O⁺,C₄H₆⁺,C₂H₄O⁺,C₃H₆⁺,C₃H₅⁺,C₃H₄⁺,C₃H₃⁺,C₂H₅⁺, C₂H₄⁺. 利用量子化学计算方法,在ωB97X-D/6-31+G(d,p)理论水平基础上,提出了C₅H₈O⁺的解离机制. 通过对环戊酮解离路径的分析,发现开环和氢迁移过程为环戊酮离子解离的主要路径.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

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.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

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.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.