电子储存环中离子俘获不稳定性和高频清洗的模拟

介绍了用强–弱模型对电子储存环中离子俘获不稳定性和高频清洗机制进行模拟研究的结果.模拟结果可合理地解释在合肥光源(HLS)储存环上观察到的现象.     

利用同步辐射与离子阱研究高电离态离子

近年来,各种形式的离子阱作为“清洁”的离子存储器被应用于低能高电离态离子的碰撞和光谱学的研究.同步辐射作为一种新型光源,其能量范围宽,产生的光子能量高,是高电离态产生、电离和激发的有力手段.把二者的优点结合起来,可开辟新的科学生长点.[1] 研究低能高电离态离子,对于实验室等离子体和天体等离子体中的光电离和碰撞过程;对于量子电动力学的精密检验; 对于研究高电离态离子的能极结构和谱线;对于检验和发展光电离以及其他光与离子相互作用理论,都具有非常重要的意义,是当前原子、分子物理学的重要研究前沿. 利用同步辐射光产生离子…     

电子储存环中离子俘获不稳定性的强-强模型模拟

 电子储存环中,由于被束流势阱俘获的离子会引起束流不稳定性。研究这种不稳定性的产生机制和抑制方法对提高机器的性能有重要理论和现实意义。介绍了用强-强模型对合肥光源（HLS）电子储存环中离子俘获不稳定性产生机制进行的模拟研究。模拟结果可用于理解在合肥光源（HLS）储存环上观察到的离子俘获现象。     

Penning阱中离子谱的优化及Hn^＋离子的分析

根据Penning阱存储离子的探测原理,系统分析了阱内离子信号及信号本身的噪声、实验仪器及探测电路的噪声干扰,采用适当的品质因数和电子束流,得到较高信噪比和分辨率的离子谱.并对Hn+离子的形成机制和结构进行了分析.     

四氯化碳同步辐射光电离的研究离子生成焓与键能的测定

采用ＶＵＶ同步辐射光源，在超声冷却条件了研究四氯化碳，光电离的动力学过程，实验表明，母体离子极不稳定。本文通过对ＣＣｌ４光解离电解碎片出现势的测定，结果有关确认的势力学数据，了该体系中有关离子的标准生成焓、离子型分子自由基中的键能、中性分子及自由其中的键能和母体离子的解离能等一系列热化学数据。详细探讨了ＣＣｌ４及ＶＵＶ光解离电离的通道及其它可能发生的动力学过程。     

高功率单频氩离子激光器

一、前 言 单频氩离子激光器输出的激光不但功率较高,更主要的是单色性非常好,即有很长的相干长度.因此,对于全息术研究和全息术应用来说,它是比较理想的一个光源.人们使用它,可以顺利地制作大体积、大景深目标的全息图.例如,在全息干涉计量中,被测试的物体尺寸甚至可大到几米,这就扩大了全息干涉计量方法的应用范围. 通常的氩离子激光器运转在多谱线、多模和多频状态,要获得单频输出,必须对激光器进行模式选择.选模的方法很多,谱线选择通常是在激光腔内加色散元件(如色散棱镜、布儒斯特棱镜)、横模选择一般是在激光腔内加小孔光栏以抑制高…     

Paul阱中离子运动及稳定性分析

Paul离子阱由于没有外加磁场所引起的塞曼效应的影响,已成为离子存储及研究离子的重要装置.根据在实验中所采用的Paul离子阱结构及电场分布特点,列出阱内离子运动方程并进行求解,对其中各种运动进行分析,同时还分析了离子存储稳定性.最后对所作的研究进行总结,得到如下结论:阱中离子的运动为谐振运动、基频微运动和高阶微振动.     

离子和原子碰撞发射光谱

本实验利用光学多道分析系统(OMA)对He~++Ne,He~++Ar,Ne~++He,Ne~++Ar,Ar~++He和Ar~++Ne六个碰撞体系的发射光谱进行了测量,并对这些离子和原子碰撞过程中所产生的激发态进行了研究。实验证明:在六个碰撞体系中都存在着两个激发过程,一是电子俘获激发过程,另一是直接激发过程。本文还说明了从测量得到的发射光谱,由标准光源定标,可以确定绝对发射截面和激发截面,以及可以研究粒子数反转控制,寻找新的激光光源。     

离子导体薄膜

最近十几年来,发现了一些离子电导率很高的固体材料即超离子导体或快离子导体.然而与液体电解质相比,其离子电导率仍然很低.为了克服这个缺点,在探索电导率更高的离子导体新材料的同时,也开展了离子导体薄膜的研究.本文综述了离子导体薄膜的研究情况. 一、薄膜生长和物理性质1.衬底 通常将薄膜制备在衬底上,以获得适当的机械强度.因而衬底材料的选择和处理就是离子导体薄膜研究中的重要问题. 在离子导体薄膜器件中通常有几个薄膜叠在一起,除了原始衬底外,每一层薄膜又成为下一层的衬底,这样就涉及到膜与衬底和膜与膜之间的相互作用.薄膜与衬…     

离子速度成像技术及其数据处理

从能量守恒的角度论述了离子速度成像技术的基本原理,从"离子透镜"、二维探测、数据处理的原理与方法等方面介绍了离子速度成像技术.将离子速度成像技术与"完全非弹性碰撞"问题及夫兰克-赫兹实验等内容相结合,为学生直观地学习和掌握微观世界的"碰撞"问题及微观世界的能量守恒定律提供了一种实验方法.     

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.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.