30MeV/u 40Ar+58,64Ni和115In反应中中等质量碎片的角分布

在5°—140°范围内测量了30MeV/u ⁴⁰Ar束流轰击不同靶核(⁵⁸Ni、⁶⁴Ni、¹¹⁵In)后出射的中等质量碎片(IMF,Z=3—19)的角分布.用指数分布函数dσ/dΩ=N·exp(–θ/α)对出射碎片角分布分角区做了拟合.对3个反应系统分别提取出与相互作用时间有关的衰减因子α和与发射源强度有关的物理量N,讨论了α与N在不同角区与反应系统和出射IMF电荷数的关系.考察了角分布与同位旋自由度和反应系统对称性的关系.     

46.7MeV/u 12C+58Ni、115In、197Au α粒子发射研究

本文报道了46.7MeV/u ¹²C轰击⁵⁸Ni、¹¹⁵In、¹⁹⁷Au反应发射α粒子的角分布和能谱.从速度表象中洛仑兹不变截面等高图中明显看到发射α粒子的三个源.用这三个源的运动源模型成功地拟合了α粒子能谱,所提取的强相互作用源参数符合费米气体模型计算结果,并讨论了能谱及拟合参数对靶的依赖关系.认为快速源实质上来自弹核碎裂或类弹核碎裂.     

30 MeV/u 40Ar+natAg反应中类弹碎片发射的时–空演化

报道了30MeV/u ⁴⁰Ar+^natAg反应中中等质量碎片(IMF)发射时间(τ)随发射源空间大小的演化规律,并对类弹碎片的发射时空进行了讨论.结果表明,IMF的发射时标与中等质量碎片关联函数以及发射源的核物质密度(ρ)有关,而与发射源的质量数的关系不大.对于能量较高的类弹碎片来说,在较小的核物质密度下提取的发射时间也较小,因此,在正常核物质密度参数下提取出的发射时间值可作为碎片实际发射时间的上限值.中速碎片的发射时间随密度大小的变化非常缓慢,提取出的发射时间值即可作为实际的发射时间.     

30MeV/u 40Ar+159Tb反应中中等质量碎片发射的时空演化

报道了30MeV/u ⁴⁰Ar+¹⁵⁹Tb反应中中等质量碎片发射时间随空间大小的演化规律.实验结果表明,发射空间大小对IMF关联函数的影响主要来自于发射源的核物质密度,而几乎不依赖于源的质量数,对于发射时间较短(≤100fm/c)的高能碎片,较小的核物质密度导致提取的发射时间变小.在正常核物质密度参数下提取的发射时间可作为其上限值,对于发射时间较长的中低能碎片,发射时间不随空间大小变化,提取的发射时间值即为其实际值.     

35MeV/u 36Ar+112,124Sn反应中中等质量碎片关联函数的入射道依赖

³⁶Ar+^112,124Sn反应中小角关联出射的中等质量碎片(IMF)约化速度关联函数. 结果表明³⁶Ar+¹²⁴Sn反应系统中的约化速度关联函数在小约化速度处的反关联程度比³⁶Ar+¹¹²Sn反应系统中的强, 表现出明显的入射道依赖性. 考察出射粒子对的单核子总动量时, 发现这种差异主要来自于高动量粒子对的贡献. 用三体弹道理论模型MENEKA分别计算了两个系统的IMF发射时标, 在³⁶Ar+¹¹²Sn反应系统中约为150fm/c, 而在³⁶Ar+¹²⁴Sn反应系统中, 约为120fm/c. 同位旋相关的量子分子动力学计算表明, ³⁶Ar+¹²⁴Sn系统中IMF的发射时间谱比³⁶Ar+¹¹²Sn系统略有前移, 相应地, 其中心密度从最高点随时间的下降亦比³⁶Ar+¹¹²Sn系统略快.     

294MeV 20Ne+159Tb反应发射中等质量碎片的研究

在294MeV ²⁰Ne轰击¹⁵⁹Tb靶的反应中,用△E—E望远镜测量了10°—150°发射的中等质量碎片(290°)这些能谱是钟罩型,峰位接近于出射道的库仑位垒.用运动源模型分析了这些能谱,结果说明这些碎片来自于共同的源—非完全熔合所形成的复合核.用统计模型GEMINI程序拟合了碎片的电荷分布和角分布,计算值和实验值很好的符合证实了中等质量碎片来源于复合核非对称的两体衰变.     

25MeV/u 40Ar+209Bi裂变反应的断点激发能和裂变时标测量

对25MeV/u ⁴⁰Ar+²⁰⁹Bi非完全熔合反应中形成的热核,测量了与裂变碎片相符合的α粒子能谱,用运动源模型分解α粒子能谱得到了裂变断前和断后发射α粒子多重性.由断后碎片发射α粒子多重性得到断点激发能约为172.5MeV.由断前α粒子多重性得到激发能在470—600MeV范围内的热核的裂变时标约为4×10^－21S.     

46.7MeV/u 12C轰击197Au、115In、58Ni靶时产生的复杂碎片

用气体电离室-半导体位置灵敏探测器望远镜测量了46.7MeV/u ¹²C离子轰击¹⁹⁷Au,¹¹⁵In,⁵⁸Ni靶时,在大角区发射的从Li到Mg的复杂碎片能谱;由各碎片的能谱提取了蒸发源的温度和碎片发射的最可几动能Ep,并与=V_coul+2T计算的平均动能进行了比较,发现实验上提取的最可几动能E_p总是低于计算的.用A.Friedman简单的统计公式对复杂碎片的产额进行粗糙拟合,拟合结果令人满意.     

46.2MeV/u 12C+64Ni、58Ni反应中发射的轻粒子和复杂碎片

用光二极管读出的CsI(Tl)闪烁探测器和多叠层硅望远镜,测量了46.2MeV/u ¹²C引起各种靶⁶⁴Ni、⁵⁸Ni、¹²C、¹⁹⁷Au、²⁰⁹Bi反应中所发射的轻粒子和中等质量碎片,这些探测器对轻粒子和中等质量碎片有很好的能量分辨和质量分辨.单举的能谱用运动源模型进行了分析,对各种靶在不同角度的中等质量碎片的产额进行了比较.由单举数据推出同位素产额比随靶质量变化的系统性,讨论了N/Z自由度的平衡.     

30MeV/u 40Ar+natAg反应中中等质量碎片的发射源

在6°─110°范围内测量了30MeV/u的⁴⁰Ar轰击^natAg靶产生的中等质量碎片(3≤Z≤16)能谱,利用运动源模型拟合能谱,并详细讨论了类弹、类靶和中速这三种源的特性及其随角度和中等质量碎片电荷的变化规律.从前角区中等质量碎片的符合测量中得到关联测得的两个中等质量碎片分别来自于两个发射源,即一个来自于类弹源,另一个来自于中速源的几率占绝大多数.     

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.