X光透镜应用于蛋白大分子晶体衍射

采用Ｘ光透镜替代单色仪双聚焦镜应用于生物蛋白大分子晶体衍射分析,照射晶体样品的光强提高１－２个量级,衍射强度的提高远大于５倍,大大缩短了测试时间,分辨能力改善０．０２－０．０６ｎｍ,信噪比也有改善。     

X光透镜在X射线衍射技术中的应用

用整体平行束X光透镜代替常规衍射仪的索拉狭缝和/或附加狭缝,入射和衍射X光强度可提高1.5―3.5倍,分辨率可达0.4°,可用于薄膜、粉末样品和离子束沉积样品的分析。将微会聚X光透镜应用于生物大分子衍射、高压X射线衍射、四圆X射线衍射3个不同的衍射领域,在相同X光源功率条件下,使用X光透镜后的衍射强度提高到原来的3―10倍,信噪比和分辨率有不同程度的改善。     

用于衍射的整体平行束X光透镜

X光透镜是90年代国际上发展起来的新技术。整体平行束X光透镜能把点X光源发出的发散X光束聚焦后转变成准平行X光束。我们使用整体平行束X光透镜和准直管在Si(111)晶体上进行了Cu-Kα辐射的衍射实验。实验结果表明:在X光源同一功率条件下,使用整体平行束X光透镜和准直管比单独使用准直管测量的衍射峰强度提高了近3倍,显示了整体平行束X光透镜用于点光源X射线衍射的优越性。     

整体X光透镜在X射线衍射应用中的新进展

介绍了整体X光透镜的物理性能。使用X光透镜进行了生物大分子晶体衍射实验,结果表明:在相同X光源功率条件下,衍射强度提高了近7倍,大大缩短了测试时间,分辨能力改善0.2×10~(-10)～0.6×10~(-10)m,信噪比也有改善。在粉末衍射仪上,进行了Si(100)衬底上金薄膜的衍射实验,结果表明:在相同X光源功率条件下,使用X光透镜后的衍射强度提高了近2倍,同时改善了衍射仪的角分辨率。     

基于晶体衍射的X射线偏振源

基于X射线的晶体衍射,实验设计并搭建了X射线偏振源.该X射线偏振源主要包括X射线光管和用于起偏的布拉格晶体.当X射线以45°角入射到晶体表面上时,经过布拉格衍射,可以得到线偏振的X射线;当X射线的入射角度偏离45°时,将产生部分偏振X射线.实验中利用微通道铅玻璃板做准直器,很好地保证了入射角的大小和X射线的透过率.实验中使用的晶体是LiF晶体和CaF2晶体,并分别用连续能量的X射线和单一能量的特征X射线入射到晶体上,产生能量分别为6.10和4.54 keV的线偏振源,并利用二次衍射的方法对产生的偏振源进行了测量.     

使用X光透镜的XRF谱仪的研究进展

使用外径为２００μｍ的复合导管组装的Ｘ光透镜。可将发散的Ｘ光束聚成直径为２５０μｍ的微束。测量了透镜的能谱特性，选择不同范围能谱特性的透可改善ＸＲＦ谱对个别元素的探测极限。与最佳几何但不带透镜的ＯＭＩＣＲＯＮ微束荧光谱仪比较表明，带透镜的ＸＲＦ谱仪对中重元素的分析灵敏度提高了近１０倍。     

基于X射线衍射仪的X光晶体参数标定

基于实验室X射线衍射仪,利用其运行稳定性和高精度角度控制能力,通过设计、制作晶体样品架,对X光平面晶体的本征参数晶格常数和积分衍射效率进行了实验标定,并给出其不确定度。该方法快速、高效、方便、灵活,实现了X光晶体的实验室标定,为ICF物理实验线谱诊断设备晶体谱仪的定量化测量提供了数据支撑。     

关于X射线在晶体中衍射的理论研究

对X射线衍射强度公式进行了修正,使其理论计算的结果得到了明显的改善。对简单立方晶体银和铁的衍射相对强度进行计算,并与标准PDF卡片相比较发现:对银和铁而言,未修正公式计算的结果:Ag的偏差范围为84%～165%,Fe的偏差范围为66%～90%。修正后的公式计算的结果则与实验数据符合得比较好,Ag的偏差范围为24%～42%,Fe的误差范围为2%～5%。     

利用背散射方法测量整体X光透镜的性能

为了避免探测系统的死时间问题,采用有机玻璃刀口作为散射体来降低探测系统死时间.通过分析来自有机玻璃散射体的背散射谱,测量了不同能量X射线在透镜会聚光束中的空间分布,为分析"光晕(halo)"现象提供了能谱依据,在此基础上,系统地分析了"halo"现象.在大能量范围内,分别利用轴向扫描法和刀口扫描法测量了透镜出口焦距、发散度及焦斑大小与能量的关系.利用背散射方法测量透镜焦斑直径时的相对误差在3%以内;利用轴向扫描法确定透镜出口焦距时的绝对误差在-120-120μm之间.     

石墨晶体预衍射X射线荧光分析中的基体影响

研究了测量U的过程中,后处理中常见基体元素Na、Al、Ru、Cs、Pd、Nd、Fe、Ce、Sr、Y、Mo、Zr等对U测量的影响。结果表明,基体元素Na、Fe、Al、Ru、Cs、Pd、Nd、Ce质量浓度在1 000 mg/L以下,对U的测量无显著影响。对U测量影响较大的元素为Sr、Y、Mo、Zr,当基体元素Sr、Y、Zr、Mo质量浓度在1 000 mg/L以下时,采用银靶散射线可以在一定程度上校正基体对U的影响;但质量浓度大于1000 mg/L时,校正效果不理想。U的Lα线强度对数和基体元素的质量浓度呈现很好的线性关系。通过数学校正法可以有效校正Sr、Y、Zr、Mo对U的影响。     

Identification of origin of single aerosol particles using polycapillary X-ray lens

A micro X-ray fluorescence (Micro-XRF) spectrometer based on a polycapillary focusing X-ray lens (PFXRL) and a laboratory X-ray source was designed to carry out the XRF analysis of single aerosol particles. The minimum detection limit (MDL) of this Micro-XRF spectrometer was 9 ppm for the Fe-Kα. The percentage of the particles of vehicle exhaust among aerosol particles was studied in Beijing, Chinese capital, during the test of odd-even driving restrictions for Beijing 2008 Olympics Games. This Micro-XRF spectrometer had potential applications in the analysis of single aerosol particles.     

The macromolecular crystallography beamline of SSRF

The macromolecular crystallography beamline BL17U1 at the Shanghai Synchrotron Radiation Facility(SSRF) is the first dedicated macromolecular crystallography(MX) beamline at a third-generation synchrotron in China. It utilizes an in-vacuum undulator as a source and is energy-tunable from 5 to 18 ke V. The beamline was commissioned and opened for users in April 2009. The experimental station was upgraded in 2011 with an advanced detector, a high precision goniometer and an automatic sample exchanger for high efficient and high-throughput data collection of protein crystals. The current set-up allows for remote operation of sample mounting, centering and data collection of pre-frozen crystals. In recent two years, the number of PDB depositions from this beamline exceeds 330 each year. In this paper, we describe the complete BL17U1 beamline with upgraded end station and how it is managed for user community.     

Size-resolved source apportionment of aerosol particles using polycapillary X-ray lens with a plateau in its focal spot

A laboratory micro X-ray fluorescence spectrometer based on a special polycapillary X-ray lens (PXRL) was used to carry out the source apportionment of aerosol particles. In the curve of the distribution of the X-ray intensity in the focal spot of the special PXRL, there was a plateau with a diameter of 21.3 μm in which the distribution of the X-ray intensity was homogeneous. The gain in flux density in the plateau of the PXRL is 1490. The uniformity of this plateau was 2.9%. This was helpful for the quantitative X-ray fluorescence analysis of a single aerosol particle with smaller size than that of the plateau of the PXRL. The fingerprint database of aerosol particles with given sizes from various air pollution sources was established with the single particle analysis method. The size-resolved source apportionment of aerosol particles in haze in Beijing city was performed with this fingerprint database.     

Fine structures of divergence of polycapillary X-ray optics

The divergence of the beam focused by polycapillary X-ray optics (PXRO) varied at different distances from the exit of the PXRO. This distance dependence of the divergence of the PXRO was defined as the fine structures of the divergence of the PXRO. The fine structures of the divergence of the PXRO were presented in order to use them fully. There were main three types of the PXRO, such as polycapillary parallel X-ray lens (PPXRL), polycapillary focusing X-ray lens (PFXRL) and polycapillary slightly focusing X-ray lens (PSFXRL). For the PPXRL, the divergence decreased near its exit. The reason for this might be that the divergence near the exit of the PPXRL depended mainly on the X-rays traversing directly through the monocapillaries in the center of the PPXRL without total reflection. For the PFXRL and PSFXRL, they both had respectively a focal depth over which the beam sizes at different output distances remained acceptably small. For the 8 keV X-rays, the focal depth and divergence over the focal depth of the PFXRL were about 300 μm and 25.0 mrad, respectively. At the same energy of 8 keV, the focal depth and divergence over the focal depth of the PSFXRL were about 500 μm and 12.5 mrad, respectively. The divergence of the PFXRL and the PSFXRL depended mainly on the angles between axes of monocapillaries that composed them.     

External scanning micro-PIXE for the characterization of a polycapillary lens: Measurement of the collected X-ray intensity distribution

We developed a PIXE detection system for the analysis of medium-light elements which exploits a weakly focusing polycapillary lens for the transmission of the X-rays emitted from the target material to a Silicon Drift Detector. The polycapillary lens efficiently collects X-rays, while prevents back-scattered protons from impinging on the detector chip, thus avoiding electronics perturbation and consequent quality loss of PIXE spectra. The system is optimized for the detection of X-rays in the energy range 1–10 keV, when the emission from the target is induced by MeV proton beams with size of the order of a few hundreds of micrometers.This work reports the results of the lens characterization in terms of X-ray collection spot, i.e. the area of the sample actually “seen” by the lens, and its dependence on the X-ray energy. The lens properties have been measured using the external scanning microbeam facility of the Tandetron accelerator at LABEC-INFN in Florence. The detection system was used to detect X-rays from a set of pure elemental standards with an incident 3 MeV proton beam focused to a size of about 30 μm scanning an area of 1.9 × 1.6 mm². By measuring the spatial distribution of characteristic X-rays from each given material, the collection profile of the lens at the corresponding X-ray energy was obtained. Using several standards, the behaviour throughout the range 1–10 keV was examined. The sensitivity of the lens collection profile on the lens-sample out-of-focus distance was also investigated.     

NSRL衍射和散射站在蛋白质晶体学的应用

介绍了国家同步辐射实验室X射线衍射和散射光束线实验站用于生物大分子晶体学的主要设备,利用硫的单波长反常散射法(S-SAD,Sulfur-Single wavelength Anomalous Dispersion)解决蛋白质晶体三维结构,测试结果表明,NSRL(National Synchrotron Radiation Laboratory)X射线衍射与散射实验站能够满足单波长反常散射实验测定蛋白质晶体结构的实验要求.     

In-situ energy calibration of SSRF macromolecular crystallography beamline using powder diffraction

<正>For X-ray powder diffraction spectra collected by an area detector of MarCCD on macromolecular crystallography beamline of SSRF,an energy calibration method was developed using LaB_6(660a) powder diffraction for in-situ rapid energy calibration of the X-rays without changing the experimental conditions.The intensity of each diffraction ring was integrated,and the accurate peak positions were fitted by Pseudo-Voigt function model.The sample's interplanar spacing for XRD analysis and the calibrated energy were obtained by the PCPDFWIN code and by fitting all the energies with the least-square method.The exposure time and the sample-to-detector distance were found no effect on accuracy of the energy calibration,and the in-situ energy calibration could be done with an accuracy of better than 0.4‰in 7-18 keV.This method is applicable to other X-ray beamlines.     

SSRF生物大分子晶体学线站用户数据采集系统

上海光源(SSRF)生物大分子晶体学线站BL17U1是结构生物学研究领域的重要平台,SSRF的高性能和光束线的高性能使得用户能快速采集晶体衍射数据。为了能够最大程度的利用好光束线站的物理性能和硬件配置,必须开发一整套的可靠、用户友好的控制与数据采集系统。根据用户实验需求,BL17U1开发了基于分布式控制系统EPICS及Blu-Ice生物大分子晶体学线站的控制与数据获取系统。该系统稳定可靠、功能完善,宜于用户实验操作。