扁椭球πh9/2⊙νi13/2转动带的低自旋旋称反转

利用标准在束γ谱学方法研究了^188,190Tl的高自旋态结构, 实验建立了基于扁椭组态πh_9/2⊙νi_13/2的强耦合转动带. 重新指定了双奇Tl核中πh_9/2⊙νi_13/2扁椭转动带的带头自旋, 从而揭示了这些转动带在低自旋时存在旋称反转. 首次确定了扁椭πh_9/2⊙νi_13/2带内存在低自旋旋称反转, 并在粒子-转子模型框架内对该现象进行了解释.     

158Tm核中的带结构及电磁跃迁性质

通过融合蒸发反应¹⁴⁴Nd(¹⁹F,5n)E=108, 112MeV对双奇核¹⁵⁸Tm的高自旋态进行了研究. 扩展了原已建立的带结构, 并建立了2条新转动带. 获得了γ射线的相对强度和耦合带的B(M1)/B(E2)比值.观测到了πh_11/2⊙νi_13/2组态带的旋称反转点. 对新建立的转动带进行了自旋-宇称以及组态的讨论.     

质量数在160-180核区形变双奇核高自旋态实验研究

基于在160-180核区形变双奇核高自旋态研究中所取得的研究结果和最近几年陆续发表的双奇核高自旋态核谱学数据,系统地考察和研究了πh_11/2⊙νi_13/2强耦合带和πh_9/2⊙νi_13/2半退耦带旋称反转的特征和规律.指出^182,184Au核素的πh_13/2⊙νi_13/2半退耦带也可能出现旋称反转;有限的实验数据似乎支持这一观点.首次在双奇核^178,180Ir的πh_11/2⊙νi_13/2强耦合带中发现了低转频下的逐渐顺排现象;在¹⁷⁸Ir核中发现了回弯频率反常超前.这些反常现象可能与核形变(或中子对力)的组态依赖性有关.     

形变双奇核178Ir转动带能级的旋称反转

利用¹⁵²Sm(³¹P,5nγ)¹⁷⁸Ir反应产生并研究了双奇核¹⁷⁸Ir的高自旋态.实验中进行了¹⁷⁸Ir核的在束γ测量,包括γ射线的激发函数测量、X–γ和γ–γ符合测量.首次建立了双奇核¹⁷⁸Ir基于πh_9/2νi_13/2和πh_11/2νi_13/2准粒子组态上的转动带能级纲图.发现在低自旋区,两个转动带能级均出现旋称反转.对此核区半退耦带的旋称反转作了简要的分析和讨论.     

双奇核176Ir转动带的旋称反转

利用¹⁴⁹Sm(³¹P,4nγ)反应,通过γ射线的激发函数测量、X-γ和γ-γ符合测量研究了双奇核¹⁷⁶Ir的高自旋态.首次建立了双奇核¹⁷⁶Ir由4个转动带构成的能级纲图.依据从实验数据中提取出的带内B(M1)/B(E2)值与理论计算值的比较,以及相邻双奇核的带结构特征,给出了转动带的准粒子组态.基于本实验建立起的带间跃迁和在I=18h处观测到的旋称交叉,指出¹⁷⁶Ir核基于πh_9/2⊙νi_13/2和πi_13/2⊙νi_13/2组态的两个转动带在低自旋时出现旋称反转现象.     

双奇核172Re高自旋态转动带结构实验研究

利用重离子熔合蒸发反应¹⁴⁹Sm(²⁷Al,4nγ)¹⁷²Re布居了形变双奇核¹⁷²Re的高自旋态,用12套带有BGO反康普顿抑制的高纯锗探测器阵列进行了在束γ实验测量,首次建立了形变双奇核¹⁷²Re由3个转动带构成的高自旋态能级纲图.研究和讨论了3个转动带的结构特征,基于已有的高自旋态核结构知识并通过系统学比较和分析指出它们的准粒子组态分别为πh_11/2⊙νi_13/2,πh_9/2⊙νi_13/2和π1/2^－[541]⊙ν1/2^－[521].发现前两个转动带在自旋小于18.5h时其转动能级呈现反常的旋称劈裂.     

188TL的πh9/2×υi13/2扁椭球转动带的旋称反转研究

利用能量为170MeV的³⁵Cl束流, 通过¹⁵⁷Gd(³⁵Cl,4n)熔合蒸发反应研究了¹⁸⁸Tl的 高自旋态能级结构. 依据实验结果建立了¹⁸⁸Tl基于πh_9/2×υi_13/2组态的转动带. 根据双奇Tl核能级结构的相似性, 指定了¹⁸⁸Tlπh_9/2×υi_13/2扁椭球转动带的自旋值. 结果表明在¹⁸⁸Tl中, πh_9/2×υi_13/2扁椭球转动带在低自旋区具有旋称反转性质. 利用包含了质子-中子剩余相互作用的准粒子-转子模型, 定性地解释了πh_9/2×υi_13/2扁椭球转动带的低自旋区旋称反转现象.     

双奇核中πi13/2 νi13/22－准粒子转动带旋称反转研究

利用重离子熔合蒸发反应和在束γ谱学实验方法研究了双奇核^176,178Ir和¹⁸²Au的高自旋态结构,在这3个双奇核中观测到了基于πi_13/2 νi_13/2准粒子组态下的转动带.以能级间隔系统学为判据,对¹⁸⁴Au核中πi_13/2 νi_13/2转动带能级自旋进行了指定.指出^176,178Ir和^182,184Au 4个双奇核的πi_13/2 νi_13/2转动带在低自旋区均出现旋称反转.对πi_13/2 νi_13/2转动带旋称反转现象进行了定性的讨论.用推转壳模型对πh_9/2 νi_13/2带和πi_13/2 νi_13/2带能级结构进行了理论研究,发现当采用形变和对力自洽计算后,从理论上可以定性地解释两个半退耦带出现的旋称反转现象.     

169Re的转动带结构组态相关性研究

研究了¹⁶⁹Re的高自旋态能级结构,建立了组态为π9/2^－[514]的强耦合带和组态为π1/2^－[541]的退耦合带,推转壳模型(Cranked shell model)计算结果表明组态相关的不同形变能够解释这些转动带的不同带交叉频率,在已知的奇ARe核中,¹⁶⁹Re的9/2^－[514]转动带在低自旋时具有最大的能量旋称劈裂,当一对i_13/2中子顺排后,旋称劈裂发生了反转,并且劈裂的幅度非常显著地减少了,另外,还观测到了一个三准粒子激发带,并指定了它的最可能组态为π9/2^－[514]⊙νAE。     

在182,184,186Au的πi13/2⊙νi13/2带中寻找旋称反转

为了搜寻¹⁸²Au, ¹⁸⁴Au,¹⁸⁶Au核中πi_13/2⊙νi_13/2转动带的旋称反转, 我们通过¹⁵²Sm(³⁵Cl,5n)¹⁸²Au,¹⁷¹Yb(¹⁹F,4n)¹⁸⁶Au和¹⁵⁹Tb(²⁹Si,4n)¹⁸⁴Au反应对¹⁸²Au,¹⁸⁴Au, ¹⁸⁶Au核进行了在束γ谱学研究. 本工作扩展了这3个核πi_13/2⊙νi_13/2带的能级纲图, 特别是确定了¹⁸⁴Au核πi_13/2⊙νi_13/2带的能级自旋宇称, 发现了低自旋旋称反转现象.     

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.     

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.     

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.     

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.