RF and field measurements of the SSC-LINAC RFQ

The 53.667 MHz continuous-wave heavy ion RFQ has been designed and manufactured for the SSC-LINAC project.This four-rod RFQ accelerates ions with maximum mass to charge ratio of 7 from 3.728 keV/u to 143 keV/u.Measurements have been carried out to check the RF performance of the cavity and the quality of the electric field.The S11 of the power coupler is adjusted to better than-44 dB,and the Q0 of the cavity is 6440.The quality of the electric field is evaluated by the perturbation method.The measurement procedure and data analysis will be discussed in detail.The error due to gravity of the perturbation bead has been corrected by averaging the fields in different quadrants.As a result,the unflatness of the electric field is±2.5%,and the dipole field component distributes from 0%to 20%in different longitudinal positions,which indicates the asymmetry of the quadrupole field.The unflatness of the quadrupole field distribution represents a good agreement with the simulation results.High power RF test and beam commissioning of the RFQ are on schedule in early 2014.     

用于CARS激发源的全光纤飞秒脉冲谱压缩

进行了基于光纤预啁啾和自相位调制的多模/单模组合式全光纤啁啾谱压缩研究.提出利用多模光纤模式估计群速度色散均值的方法,并将该估计值作为啁啾参量分析的计算参数,仿真计算了50/125μm折射率渐变多模光纤的群速度色散均值及其与单模光纤在不同长度比值下的光谱压缩效果.采用三种折射率渐变多模光纤进行实验,对比分析了折射率渐变多模光纤的芯径大小及其与单模光纤的长度比值对光谱压缩效果的影响.实验结果表明使用50/125μm折射率渐变多模光纤获得光谱最大压缩比为5.796,谱宽为2.243 nm,与理论仿真一致;使用105/125μm折射率渐变多模光纤,可进一步提高压缩比至152.941,输出谱宽为0.085 nm的光脉冲.将此脉冲用于相干反斯托克斯拉曼散射光谱探测,理论光谱分辨率可达1.386 cm~(-1).     

Polarization and Angular Distribution of Ll X-Ray Following Inner-Shell 2p3/2 Photoionization of Magnesium-Like Ions

The inner-shell 2pa/2 photoionization and the subsequent decay of Mg-like Fe^14＋, Cd^36＋, W^62＋ and U^80＋ ions are studied theoretically within the multiconfiguration Dirac-Fock method and the density matrix theory. Special attention is paid to exploring the influence of the non-dipole terms which arise from the multipole expansion of the electron-photon interaction in the photoionization process. The results show that the non-dipole contribution to the total cross section, the magnetic sublevels cross section of the photoionization process, the degree of linear polarization and angular distribution of the subsequent characteristic x-ray radiation become more important with the increase of photons energy and atomic nuclear Z. Especially for the cross section and the degree of linear polarization, the non-dipole contribution arrives at 50% for U^80＋ at four time energy threshold units. However, for the angular distribution, the maximum contribution does not exceed 4%, even for U^80＋ ions.     

Microwave-assisted synthesis of Cu2ZnSnS4 nanocrystals as a novel anode material for lithium ion battery

One-dimensional ordered quantum-ring chains are fabricated on a quantum-dot superlattice template by molecular beam epitaxy. The quantum-dot superlattice template is prepared by stacking multiple quantum-dot layers and quantum-ring chains are formed by partially capping quantum dots. Partially capping InAs quantum dots with a thin layer of GaAs introduces a morphological change from quantum dots to quantum rings. The lateral ordering is introduced by engineering the strain field of a multi-layer InGaAs quantum-dot superlattice.     

食用香料的太赫兹时域光谱

食用香料是人们在烹饪过程中必不可少的调味品,对食用香料的鉴别和食用安全性检测也尤为重要.本文利用太赫兹时域光谱技术对食用香料进行测试,得到了黑胡椒、白胡椒、花椒、大料、姜粉、甘草、香叶以及五香粉、十三香等香料在太赫波段的吸收谱和折射率谱.结果表明,不同种类的香料都有其独特的特征吸收光谱,样品的吸收谱在0.2～1.25THz频段内以不同的斜率单调递增,在1.25～2.0THz频段呈现出不同的吸收峰.样品的折射率值在1.3～1.8之间变化,并且,样品的折射率在其吸收峰所对应的频率处出现了反常色散.通过对吸收系数的斜率、峰值位置以及折射率进行定标分析,太赫兹时域光谱技术可以用于不同种香料的定性检测.实验数据为食用香料的鉴别提供了依据,可以用于建立食用香料的太赫兹波谱数据库.     

Digitalized Mirror Array and Its Application in Large Telescope： Principle and Case Studies

In this article, we report the principle and conceptual design of a fundamentally different technology in fabricating high precision aberration free optical devices. The tip-tilt of facet in a mirror array is produced by digitally controlled line-tilts of rows and columns. It has not only provided a cost-effective designing methodology in optical physics but also led to a much finer precision of 1 mili arc sec or less. As examples of the application of the proposed digitalised optics, two case studies have been given： a 10 m Schmidt telescope （off-axis） and an 8 m Cassegrain telescope （on-axis）.     

Anomalous Pressure Behavior of N-Cluster Emissions in GaAs0.973Sb0.022N0.005

Photoluminescence of GaAs0.973Sb0.022N0.005 is investigated at different temperatures and pressures. Both the alloy band edge and the N-related emissions, which show different temperature and pressure dependences, are observed. The pressure coefficients obtained in the pressure range 0-1.4GPa for the band edge and N-related emissions are 67 and 45meV/GPa, respectively. The N-related emissions shift to a higher energy in the lower pressure range and then begin to redshift at about 8.5GPa. This redshift is possibly caused by the increase of the X-valley component in the N-related states with increasing pressure.     

2-F-环氧丁烷与几种生物小分子间的赝氢键结构

采用密度泛函B3LYP(Becke,three-parameter,Lee-Yang-PaH)/6-311++G**和HF(Hartree Fock)/6-311++G**方法,从理论上探讨了2-F-环氧丁烷分别与几种常见而重要的生物小分子咪唑(Iminazole)、噻唑(Thiazole)和恶唑(Oxazo1e)等分子间的弱相互作用,发现分子间同时存在N…H常规氢键和C-F…H-C赝氢键结构.弱相互作用能计算表明3个复合物的相对稳定性相当.计算结果表明,在C-F…H-C赝氢键结构中,与电子的直接供体F密切相关的共价键C-F键长增大,伸缩振动的频率红移,而作为电子受体的H-C基团,其C-H键伸缩振动光谱蓝移;另外,电子密度拓扑性质表明C-F…H-C赝氢键的共价性及离子性均与常规氢键相当.     

车前草中多酚的抗氧化活性

采用福林-酚法测定车前草60％乙醇提取物和不同极性部位的总多酚含量,应用DPPH法、ABTS法和邻苯三酚法,研究上述提取物对自由基的清除能力.车前草正丁醇相的总多酚的含量最高,正丁醇相对DPPH自由基和ABTS自由基显示了较强的清除能力,其各相的抗氧化活性大小与总多酚的含量高低顺序一致;而乙酸乙酯相对O2-·的清除能力最强.实验结果表明,车前草60％乙醇提取物及其不同极性部位都具有抗氧化作用,其活性部位为正丁醇相和乙酸乙酯相.     

Electric field control of nonvolatile four-state magnetization at room temperature

We find the realization of large converse magnetoelectric (ME) effects at room temperature in a magnetoelectric hexaferrite Ba0.52Sr2.48Co2Fe24O41 single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then reaches up to 0.62μ(B)/f.u. in an electric field of 1.14 MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be approximately described by an effective free energy with a distinct set of ME coefficients.