Upgrade of beamline BL08B at Taiwan Light Source from a photon‐BPM to a double‐grating SGM beamline

During the last 20 years, beamline BL08B has been upgraded step by step from a photon beam‐position monitor (BPM) to a testing beamline and a single‐grating beamline that enables experiments to record X‐ray photo‐emission spectra (XPS) and X‐ray absorption spectra (XAS) for research in solar physics, organic semiconductor materials and spinel oxides, with soft X‐ray photon energies in the range 300–1000 eV. Demands for photon energy to extend to the extreme ultraviolet region for applications in nano‐fabrication and topological thin films are increasing. The basic spherical‐grating monochromator beamline was again upgraded by adding a second grating that delivers photons of energy from 80 to 420 eV. Four end‐stations were designed for experiments with XPS, XAS, interstellar photoprocess systems (IPS) and extreme‐ultraviolet lithography (EUVL) in the scheduled beam time. The data from these experiments show a large count rate in core levels probed and excellent statistics on background normalization in the L‐edge adsorption spectrum.     

Characteristics of Friedel pairs and diffraction contrast tomography with non‐perpendicular rotation axis

The characteristics of Friedel pairs in diffraction contrast tomography (DCT) are studied in the condition that the rotation axis of the sample is not exactly perpendicular to the incident X‐ray direction. For the rotation axis approximately aligned along the vertical direction, the Friedel pairs close to the horizontal plane are insensitive to the non‐perpendicularity of the rotation axis, and can be used to refine the sample‐to‐detector distance and X‐ray energy, while the Friedel pairs close to the vertical direction are sensitive to the non‐perpendicularity of the rotation axis, and can be used to determine the rotation axis orientation. The correct matching proportion of Friedel pairs decreases with increasing non‐perpendicularity of the rotation axis. A method of data processing considering rotation axis misalignment is proposed, which significantly increases the correct matching and indexing proportions of the diffraction spots. A pure aluminium polycrystalline sample is investigated using DCT at beamline 4W1A of Beijing Synchrotron Radiation Facility. Based on the analysis of Friedel pairs, the sample‐to‐detector distance and X‐ray energy are refined to be 8.67 mm and 20.04 keV, respectively. The non‐perpendicular angle of the rotation axis is calculated to be 0.10°. With these refined geometric parameters, the matching proportion of the spatial position of diffraction spots is 90.62%. Three‐dimensional reconstruction of the sample with 13 grains is realised using the algebraic reconstruction technique. It is demonstrated that the precise correction of the orientation of the sample rotation axis is effective in DCT suffering from rotation axis misalignment, and the higher accuracy in determining the rotation axis is expected to improve the reconstruction precision of grains.     

Determination of Thermal History by Photoluminescence of Core‐Shelled Quantum Dots Going Through Heating Events

A kind of novel thermal history nanosensors are theoretically designed and experimentally demonstrated to permanently record thermal events. The photoluminescence (PL) spectrum of core‐shelled quantum dots (QDs) CdSe/ZnS irreversibly shifts with heating histories (temperature and duration) of thermal events. The induced PL shift of the QDs CdSe/ZnS is employed to permanently record thermal histories. We further model a kind of thermal history nanosensor based on the thermal‐induced phenomena of core‐shelled QDs to permanently record thermal histories at microscale and demonstrate to reconstruct temperature and duration of heating events simultaneously from PL spectra of the QDs. The physical mechanism of the sensors is discussed.     

基于超声波和云测试的油井液面测试系统研究

针对目前油井液面深度测试系统测量范围小、误差大、稳定性低的缺点,提出了基于声波法测动液面原理,利用时间序列分析技术、新息自适应卡尔曼滤波技术来实时检测回波信号,进而实现对油井液面深度的高精度测量和噪声处理;选用FPGA和云测试技术成功实现了油井液面深度测量系统的远程化和网络化。基于云测试的油井液面远程监测系统目前已在油田生产现场通过测试,测试结果表明,系统稳定,算法实时、高效,动液面深度测量误差小,测量精度高,能满足实际工程应用。     

高超声速平板边界层流动显示的试验研究

本文在高超声速脉冲式风洞内对基于纳米示踪的平面激光散射技术(nano-based planar laser scattering, NPLS)的应用进行了探索, 并在此基础上对平板边界层流动结构的精细测量进行了研究. 试验来流Ma=7.3, 总压4.8 MPa, 总温680 K. 通过时序的分析和调试, 对各分系统实现了高精度的同步控制; 定量的粒子注入及混合, 实现了粒子的均匀撒播, 对主流获得了均匀的显示效果; 对于边界层流动, 获得了精细的瞬态流动结构图像, 显示了层流到湍流的转捩过程, 并分析了其时空演化特性.     

微液滴在不同能量表面上润湿状态的分子动力学模拟

微小液滴在不同能量表面上的润湿状态对于准确预测非均相核化速率和揭示界面效应影响液滴增长微观机理具有重要意义. 通过分子动力学模拟, 研究了纳米级液滴在不同能量表面上的铺展过程和润湿形态. 结果表明, 固液界面自由能随固液作用强度增加而增加, 并呈现不同液滴铺展速率和润湿特性. 固液作用强度小于1.6的低能表面呈现疏水特征, 继续增强固液作用强度时表面变为亲水, 而固液作用强度大于3.5的高能表面上液体呈完全润湿特征. 受微尺度条件下非连续、非对称作用力影响, 微液滴气液界面存在明显波动, 呈现与宏观液滴不同的界面特征. 统计意义下, 微小液滴在不同能量表面上铺展后仍可以形成特定接触角, 该接触角随固液作用强度增加而线性减小, 模拟结果与经典润湿理论计算获得的结果呈现相似变化趋势. 模拟结果从分子尺度为核化理论中的毛细假设提供了理论支持, 揭示了液滴气液界面和接触角的波动现象, 为核化速率理论预测结果和实验测定结果之间的差异提供了定性解释.     

基于双M-Z干涉仪的光纤周界防护系统

基于光纤双Mach-Zehnder干涉仪(MZI)结构对周界防护系统进行了设计研究。通过对两路经过不同延时的相同信号进行互相关运算,实现了对振动入侵点的定位。提出了一种分段数据处理方法,有效地提高了定位稳定性及准确性。测试结果表明,该双Mach-Zehnder干涉仪周界防护系统可以实时对振动点进行定位,在传感光纤长度为2km、采样率为2MHz时定位精度优于200m,能够长时间连续稳定工作。     

基于HRTEM和Raman分析定向多壁碳纳米管阵列的生长机理

以二茂铁、二甲苯为前驱体,石英为衬底,在850 oC的管式炉内采用化学气相沉积法制备出了定向碳纳米管阵列. 高分辨透射电子显微镜和拉曼光谱的结果表明：碳纳米管阵列具有良好的定向性和多壁管状结构,石墨化程度高,并且只在表面存在少量单壁碳纳米管.定向多壁碳纳米管阵列的生长模式为“底部”生长模式,即在生长的初期,当催化剂颗粒较小时,析出的碳原子生成了单壁碳纳米管或与其性质类似的多壁碳纳米管(一般层数小于5层);催化剂颗粒逐渐长大后,大量的碳原子析出后生成了普通的多壁碳纳米管,从而形成了单壁碳纳米管只存在于碳纳米管阵列膜表面和多层碳纳米管膜表面与界面的现象.     

980nm半导体激光器输出光谱特性的改善

为了改善980nm半导体激光器的输出光谱特性,采用传输矩阵分析法推导了双布喇格光纤光栅谐振腔的传输表达式,对布喇格光纤光栅长度和谐振腔腔长对输出光谱的影响进行模拟仿真,结果表明布喇格光纤光栅长度对输出光谱的影响大于谐振腔腔长对输出光谱的影响,加长布喇格光纤光栅长度能压缩输出光谱线宽.在980nm半导体激光器尾纤上写入不同布喇格光纤光栅长度的双布喇格光纤光栅谐振腔,验证了引入双布喇格光纤光栅谐振腔在压缩980nm半导体激光器输出光谱线宽的同时改善了其输出光谱的稳定性.当环境温度在0~75℃范围内变化时,980nm半导体激光器输出中心波长仅变化0.06nm.     

基于大功率LED扩展光源的均匀光斑光辐射模拟器设计

基于边缘光线原理和光学扩展量守恒思想,结合复合抛物面聚光器和轴对称自由曲面透镜,设计并研制了大功率发光二极管扩展光源的反射/折射准直器.运用Tracepro软件对系统进行光束追迹模拟仿真和实验,研制出均匀光斑的光辐射模拟器.模拟器输出发散角为±12°光束,测量距离出射面50cm处光屏的光斑,在尺寸为14cm×14cm的光照范围内,测得光斑水平方向中心线上的光度均匀度优于4.1%,竖直方向中心线上的光度均匀度优于3.8%.