Taleyarkhan等人是否测到了热核中子

对声致发光这一尚不清楚的非平衡态复杂过程，以平衡态近似作为上限，通过对Taleyarkhan等人实验数据的分析和氘氘聚变反应的反应率的计算，指出Taleyarkhan等人实验中测得的中子不是热核中子，今后实验中如能测到大于－10^8n/s的有效中子产生率才能显示“气泡核聚变”的反应温度达到了10^6-10^7K。     

中子的发现

文章回顾了中子发现以前关于中子存在的假说，科学家们因无“目的”探索而错失良机；介绍了查德威克发现中子的过程以及这一伟大发现的深远意义．     

中子单色化新方法

提出了中子单色化的新想法，并从理论上给出了具体的处理方法．以石墨、硅及锗为例演示了新方法的应用，并得到满意结果．将新方法与三组双晶法作了比较，二者效果相差无几，但是新方法简单易行且节省费用 关键词：     

缅怀中子谱仪的先驱布罗克豪斯

中子谱仪的发明人、1994年度诺贝尔物理奖获得者Bertram Brockhouse于2003年10月13日去逝，享年85岁．     

脉冲中子探测系统的中子灵敏度能量响应

为了获得脉冲中子探测系统的中子灵敏度能量响应，编制了适合裂变中子测量探测系统灵敏度能响的一系列专用程序，研究了相应的实验标定技术，采用理论计算和实验验证相结合的方法，对几套探测系统中子灵敏度能量响应进行了研究，初步解决了标定需要的“单能、脉冲、高强度、多个不同能量的中子源”问题，使不确定度大大提高，满足了测量的要求。     

中子照相数值模拟与实验的对比

 介绍了热中子照相的MCNP数值模拟方法，模拟了300＃反应堆Maxwell谱热中子束穿透样品射到转换屏的过程，给出了热中子对铝、铅、铁、铜的穿透能力，分析了引起模拟与实验结果不同的原因。通过模拟得到了清晰的图像，对比数值模拟与在300#反应堆中子照相装置上的实验结果，数值模拟结果图像与实验结果图像非常相似；散射中子对图像的影响也符合相同的规律，随着样品与转换屏之间的距离的增大，散射中子对结果图像的影响越来越小，当样品与转换屏之间的距离为样品尺寸的2倍时可以忽略散射中子的影响。     

中子相衬层析成像方法

介绍了中子相衬和中子层析的工作原理，提出了中子相衬层析成像方法.这种方法兼备了相衬和层析的各自优点，不采用干涉术，能高分辨率地重构待测样品的三维空间位相分布，能测试和分辨吸收系数非常相近样品的空间结构. 关键词： 相衬 层析 中子相衬 中子层析     

数值模拟高能中子照相

 模拟了14 MeV中子在穿透样品后与闪烁体光纤的作用。对每根光纤中的能量沉积进行了计算，并转换成可见光(496 nm)光子数。在模拟实验中，分析了影响图像质量的因素。计算了散射中子本底与闪烁体和样品(聚乙烯)间距的关系。当间距为cm量级时，散射中子本底对图像的影响很小。计算表明系统对样品的甄别厚度与入射中子总数有关，在一定范围内近似与中子总数的对数成线性关系。通过模拟结果给出了理想平行中子束入射情况下系统的平面分辨率。     

高效率BF3正比探测器阵列探测中子技术

针对中子产额范围宽、下限低，研制4个具有高中子探测效率的正比探测器，由置于慢化体内的BF3正比计数管阵列和电压前置放大器组成。每个探测器内共包括12支BF3正比计数管，并根据不同的数目分为两组。在图l所示的实验中，利用这种多管的正比探测器，可以对产额变化范围宽、下限低的不同脉冲中子源产额进行测量。     

钒球介质内中子能谱和伴生γ能谱测量

因钒具有在D—T中子照射下低活性的特点。同时其（n，2n）中子增殖大于（n，X）反应引起的吸收。所以钒是聚变堆第一壁及结构材料使用的主要竞争者。开展过钒的14MeV中子泄漏能谱测量，而有关钒介质内中子能谱及伴生γ能谱的实验数据国内未见报道，因此有必要开展这方面的工作。     

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.