先进光源磁铁支撑基座稳定性的实验研究

基座作为磁铁支架的基础,其制作工艺以及与地面连接固定方式的不同将影响磁铁与支架的稳定性。基于先进光源对磁铁支撑系统稳定性的极高要求,开展了基座安装浇筑实验,选取工程上常用的几种混凝土施工工艺,制作统一外形尺寸的实验件,通过锤击法逐一测试其固有频率,评估其稳定性,得到二次灌浆可有效提高稳定性、环氧基灌浆料获得的稳定性优于水泥基灌浆料等结论。基于固有频率测试结果,以HEPS支撑系统为例分析了不同的基座安装方式对系统模态的影响。     

Polarization in the quasielastic scattering of 1-GeV/c protons on light nuclei

Polarization measurements in the A(p, 2p)B reactions on ⁶Li, ⁷Li, and ²⁸Si nuclei at a proton-beam energy of 1 GeV were performed in a kinematically complete experiment. By using a two-arm magnetic spectrometer, two secondary protons were recorded in coincidence at asymmetric scattering angles of θ₁=15°?26° and θ₂=58.6° for residual-nucleus momenta in the range K _B=0–150 MeV/c. Either arm of the spectrometer was equipped with polarimeters based on proportional chambers. The data coming from this experiment are analyzed within the distorted-wave impulse approximation. It is shown that the polarization of recoil protons formed at angle θ₂ in the interaction featuring a proton from the P shell of the ⁷Li nucleus can be described under the assumption of an effective intranuclear-proton polarization by using the single-particle shell-model wave function of the nucleus. Our data on the polarizations of the two protons from the reaction (p, 2p) on a ²⁸Si nucleus also suggest the effective polarization of the protons in the D shell of the ²⁸Si nucleus. It is found that, for high recoil-nucleus momenta of K _B≥90 MeV/c, the effective polarization of the protons in the P shell of the ⁶Li nucleus—this polarization was discovered in studying the polarization of recoil protons in the reaction ⁶Li(p, 2p)⁵He—cannot be described within the shell model assuming LS coupling. As might have been expected, the polarization of recoil protons knocked out from the S shells of the ⁶Li and ⁷Li nuclei comply well with the predictions obtained in the impulse approximation with allowance for the depolarization effect alone.     

Arc modulator for the TFTR neutral-beam ion source

A discussion is presented of the protection of the tokamak fusion reactor neutral-beam ion source, located at the Princeton Plasma Physics Laboratory. The system design is based on three operational protection requirements that include provisions for ion-source current pulse matching, ion-source fault current extinction, and metallic fault current extinction. A power circuit configuration satisfying these requirements is illustrated and briefly described. Simplified analytical expressions relating the protection requirements to the circuit parameters are developed. Experimental findings are in good agreement with a computer simulation of the circuit model, although several side effects introduced by the circuit configuration have been observed. The side effects observed include ion-source current overshoot and the existence of a negative ion source current. Modifications to counteract these side effects are briefly described     

Neutron production in the interaction of 2-GeV protons with nuclei

The double-differential cross sections for neutron production in the interactions of 2-GeV protons with Be, Al, Cu, Cd, and Pb nuclei were measured by the time-of-flight method in the region of angles larger than 30°. The respective experimental data are analyzed within the phenomenological model of four moving sources, including those associated with neutron emission in primary nucleon-nucleon collisions, the decay of a hot source (fireball), the multifragmentation process, and the deexcitation of nuclear fragments via neutron evaporation. Temperature-parameter values are universal for all sources and are virtually independent of the target nucleus and of the projectile energy in the region above 0.5 GeV. It is found that, for all of the above reactions, the relative contribution to the mean neutron multiplicity from the decay of a hot source and multifragmentation is about 41%.     

Diffractive characteristics of the liquid crystal spatial light modulator

The liquid crystal spatial light modulator (LC SLM) is very suitable for wavefront correction and optical testing and can produce a wavefront with large phase change and high accuracy. The LC SLM is composed of thousands of pixels and the pixel size and shape have effects on the diffractive characteristics of the LC SLM. This paper investigates the pixel effect on the phase of the wavefront with the scalar diffractive theory. The results show that the maximum optical path difference modulation is 41\,$\mu$m to produce the paraboloid wavefront with the peak to valley accuracy better than $\la$/10. Effects of the mismatch between the pixel and the period, and black matrix on the diffraction efficiency of the LC SLM are also analysed with the Fresnel phase lens model. The ability of the LC SLM is discussed for optical testing and wavefront correction based on the calculated results. It shows that the LC SLM can be used as a wavefront corrector and a compensator.     

液晶空间光调制器的调制特性测量

分析了液晶空间光调制器LC2002的工作原理,测量了振幅调制特性和最佳相位调制特性曲线.对经扭曲向列液晶空间光调制后的待测波面进行横向剪切干涉,用CCD记录其干涉图样,采用一维图像分析法得到最大相位调制为0.837π.实验证明液晶空间光调制器可以很好地进行相位调制.     

Progress in spatial light modulator performance: a status report

Spatial light modulators (SLM) developed to date have fallen into one of two categories, optically addressed or electronically addressed. Each approach has its advantages and disadvantages, and successful implementation of optical processing in real world applications may depend upon a combination of the two. This article briefly reviews the concept of optical information processing, discusses the development of SLMs from their early beginnings, and concludes with a discussion of where the field is now, and where it is going in the next few years.     

2Nd international swiss light source (sls) workshop in brunnen

The workshops held in conjunction with the Canadian Light Source's 7th Annual Users' Meeting were extremely well attended, with over 350 registered participants attending sessions in five workshops from November 17 to 19, 2004, at the University of Saskatchewan in Saskatoon. The topics of the workshops highlighted the exciting applications that will be an integral part of the CLS experimental program, including XAFS analytical techniques, SR applications in earth and environmental sciences, protein crystallography, medical imaging, and studies using elliptically polarized SR light. All of the presenters did an outstanding job and excited their audiences with thought-provoking discussion.     

Modulation spectroscopy using the beam-foil light source

When a beam of ions passes through a thin exciter foil, certain radiation emitted by the beam particles can exhibit time-periodic intensity variations. These variations can be induced by external E and H fields, or they can be the result of the field-free atomic structure itself.Intensity modulations observed so far in beam-foil spectroscopy can be divided into three classes: (1) Quantum mechanical interference of fine structure levels. This is a QM resonance arising from time-dependent populations of emitting states having different transition probabilities. The resonance is induced by external constant electric fields. (2) Initial coherent superpositions of radiating states. This results from the creation of M_L alignment at the instant of excitation by the foil. The modulations are field free and are observed in polarized light. (3) Rotating electric dipole in a magnetic field. When alignment occurs, the intensity of the beam radiation after excitation satisfies the relation I(t) = = I₀[1+Acos(2γHt)] e^?αt. The modulation will be a function of the magnetic field H and the gyromagnetic ratio γ.These effects can be used to study Lamb shifts, g-values, fine structure levels, and interaction processes.     

Infrared facility at the Canadian light source

The Canadian Light Source (CLS) is constructing two beamlines for Infrared Spectroscopy using synchrotron radiation (IRSR). One will supply mid-Infrared (2–25 μ) light to a Fourier Transform Infrared (FTIR) spectrometer and microscope for biological applications. The second will have a high resolution FTIR spectrometer for gas-phase and surface spectroscopy in the far-Infrared (beyond 25 μ). The Infrared beamlines will use dipole bending magnet radiation from a special bend magnet port design which provides a 50 mrad square acceptance. Issues with the first mirror and photon mask design, as well as the beamline layout and features are discussed.     

The superconducting magnet system with a cryocooler for the ion source Decris-SC

A superconducting magnet system (SMS) for the multicharged ion source DECRIS-SC was designed and manufactured at the Joint Institute for Nuclear Research. Successful tests of the SMS were conducted in late 2003 and early 2004. The peculiarities of this system are stipulated by the use of a cryocooler 1 W in power for the cryostating of the magnet and also by the special configuration of the magnetic field demanded for the source of ions. Four coils ensure the induction of a magnetic field on the axes of the source of up to 3 T (the stopper ratio of ～6), which considerably extends the possibilities of the ion source from the point of view of producing intense highly charged ion beams. The problem of compensating the large forces of interaction between the coils and surrounding iron yoke in this magnet has been successfully solved, and a reliable suspension of the magnet in a cryostat realized. To compound the windings, which work in vacuum at indirect cryostating, prepreg (thermosetting fiberglass fabric impregnated with epoxide) is used. A new technology of superconducting magnet protection has been applied with the help of sectionalized windings, using passive elements of protection based on “cold” diodes and resistances. A new technology of active protection has also been applied, with normal zone detectors and heaters.     

液晶空间光调制器产生可调三光学势阱

提出了产生三光学势阱的新方案, 在该方案中用液晶空间光调制器制作相位型闪耀光栅, 单色相干光照明, 产生按等边三角形分布的三个光学势阱, 三个光阱光强大小分布相同, 调节空间光调制器的相位分布, 可以改变光阱的相对位置, 实现三光阱到单个光阱、两光阱合并为一个光阱等演变及其反向演变, 调节过程简单、方便. 根据现有空间光调制器性能和尺寸, 模拟设计光栅, 计算三光阱的光强分布和调控过程中光强的变化, 结果表明: 用一般功率的激光照明, 能够得到具有较大峰值光强和较高光强梯度的可调三光阱, 在原子和分子光学实验研究中有多种重要的应用. 关键词： 原子和分子光学 可调三光学势阱 空间光调制器     

Temperature effect on the diffraction efficiency of the liquid crystal spatial light modulator

Temperature effect on the diffraction efficiency of the liquid crystal spatial light modulator is investigated. The birefringence of the liquid crystal as functions of the temperature is measured with and without the power supply. It is shown that the birefringence reduces while the temperature increases. And the change magnitude of the birefringence has an exponential decay relation with the applied voltage for different temperature intervals. The scalar diffractive theory is used to analyze this effect on the diffraction efficiency. It indicates that the diffraction efficiency decreases from 98.7% to 27.2% while the temperature increases from 10 to 90 °C for 16 quantified levels. At last, temperature effect on its applications in optical testing and wavefront correction is discussed. It indicates that it has almost no effect on optical testing, but has an important effect on wavefront correction. And two solutions are given to eliminate this effect.     

用空间光调制器产生三维光阱阵列

本文提出了用液晶空间光调制器制作复合相位光栅、产生三维光阱阵列的新方案．在本方案中,首先将一维矩形光栅转变为能够产生纵向光阱阵列的环形光栅,再把环形光栅和二维矩形光栅组合成复合光栅．根据现有空间光调制器的技术参数,模拟仿真设计了产生5×5×5光阱阵列的光栅,以普通功率的高斯光波为输入光,正透镜聚焦衍射光,计算输出光强分布,结果表明：在透镜焦点附近获得具有很高峰值光强和光强梯度的三维光阱阵列,囚禁冷原子的光学偶极势达到mK量级,对原子的作用力远大于原子的重力．用大功率激光作为输入光波时,产生的光阱阵列也能用于囚禁Stark减速后的冷分子．     

Microfabrication by use of a spatial light modulator in the ultraviolet: experimental results

We report the development of a new microstereophotolithography technique for creation of three-dimensional microcomponents by use of a planar, layer-by-layer process of exposure, in which a spatial light modulator is used as a dynamic lithographic mask. The system operates in the UV to take advantage of the wide supply of commercially available photopolymers designed for conventional stereolithography. With this novel procedure it is possible to build components with feature sizes as small as a few micrometers. The experimental setup is briefly described, and the first microcomponent fabricated by this system is shown.     

读出光光源对液晶光阀实验的影响

液晶光阀实验中一般是用带布氏窗的He-Ne激光器作为读出光光源,本文分析了普通He-Ne激光、半导体激光、卤素灯等常见光源在液晶光阀实验中应用的可能性和各自特点并进行了实验验证.     

Generalized synchronization of spatiotemporal chaos in a liquid crystal spatial light modulator

We demonstrate generalized synchronization in a spatiotemporal chaotic system, a liquid crystal spatial light modulator with optoelectronic feedback.