Hydrogen analysis of mineral samples at University of Tsukuba

This study reports the present status of our work on the hydrogen analysis of mineral and rock samples. The preparation of a standard material by means of ion implantation, a method of its calibration and the application of the method are described. The number of hydrogen atoms per unit volume in the standard material can be determined from the simultaneous observation of -particles, γ rays and –γ coincidence events for the ¹H(¹⁹F,γ) reaction at the 16.44 MeV resonance energy. The hydrogen content in a natural obsidian determined with the method mentioned above is in agreement with that obtained by FTIR. A heavy-ion microbeam system under construction, which consists of a Russian-type quadrupole magnet for beam focusing, a beam defining slit system and a γ-ray detector, is also described.     

大米中矿质元素含量测定及分析

采用粉末压片制样,用波长色散X射线荧光光谱法对湖北、四川和黑龙江产地大米中Mn、Fe、Cu、Zn、Mg、P、S、K、Ca 9种元素含量进行测定,并用主成分和聚类分析对结果进行分析。讨论了各目标元素测量条件,运用经验系数法和散射射线作内标对基体效应进行校正,通过测量国家生物标准物质建立了工作曲线。分析结果表明,该方法检出限较低、精密度较好、准确度较高,不同产地大米样品中目标元素含量差异显著。前4个主成分的累计方差贡献率为89.3%,30份大米样品分布在三个区域,分别来自三个产地。聚类分析在阈值为9时,将大米样品分成三类,与主成分分析结果一致。因此矿质元素可作为大米产地溯源的指标。     

Absolute mass thickness determination of thin samples by X-ray fluorescence analysis

An absolute method for mass thickness determination of thin samples by X-ray fluorescence analysis has been developed. The method is based on the experimental determination of the fluorescence intensities of the sample's constituent elements in reflection and transmission geometries. The samples studied were elemental and compound foils. A set of numerical calculations, Monte Carlo simulations and experimental measurements with thin samples including super-conductor monocrystals were performed with very good results. The range of thicknesses which can be determined by the proposed technique depends on the sample's composition, the excitation energy and the geometrical arrangement.     

Three-dimensional restoration of single photon emission computedtomography images

Restoration of single photon emission computed tomography (SPECT) images is usually performed either on two-dimensional (2-D) projection images (pre-reconstruction restoration) or on SPECT slices (post-reconstruction restoration). This study presents the application of a three-dimensional (3-D) filter in restoring SPECT images. The 3-D filter is shown to perform better than the 2-D methods because it takes into consideration the interslice information in the filtering process and has a relatively space-invariant blur function. To reduce the space-variance of the 3-D point spread function (PSF), conjugate projections were combined by geometric averaging before reconstruction. We investigated the potential of 3-D Wiener and power spectrum equalization (PSE) filters. These filters were applied to SPECT images of a resolution phantom and a large, truncated cone phantom containing two types of cold spots: a sphere, and a triangular prism. The filters were also applied to clinical images of the liver and spleen. The images were acquired on an ADAC GENESYS camera. A comparison was performed between results obtained in this study and those obtained by 2-D pre-reconstruction restoration and 2-D post-reconstruction restoration filters. Quantitative analysis of the 3-D restored images performed through measurement of root mean squared (RMS) errors and contrast ratios showed a considerable reduction in error and increase in contrast over images restored using the two other methods     

Development of a new sample chamber for proton microprobe analysis of mineral samples

We describe a newly developed proton microprobe sample chamber designed for analysis of heterogeneous mineral samples. The instrument features a computer-driven stage and is equipped with novel beam and sample optics, external microscope and filter exchange system. Under the employed optical geometry, axes of beam and sample optics are collinear and normal to the sample surface, an essential aspect allowing high spatial resolution of analyses and accurate micrometer-scale sample and beam positioning. Use of a long working distance in conjunction with integral reflectance mirror are the primary design constraints satisfied for successful development. Based on measurements, the presented proton microprobe is expected to enhance studies requiring effective and easy-to-perform nondestructive microanalytical analysis of minerals.     

Synchrotron radiation X-ray fluorescence analysis on altered mineral muscovite in gold deposit

Synchrotron radiation X-ray fluorescence (SRXRF) microprobe was used to ananlyse altered mineral muscovite and its surrounding feldspar in Yuerya gold deposit. The major, minor and trace elements of the two minerals were detected and analyzed. SRXRF analysis showed that the Yuerya muscovite had a complex chemical composition. containing K, Fe, Ca, Ti, Cr, Mn, Co, Cu, Zn and many trace or ultra-trace elements. Since muscovite resulted from the alteration of hydrothermal ore fluid acting on feldspar (plagioclase), the difference of chemical composition between the two minerals shows the components of ore fluid, which are characterized by the enrichment of alkaline and alkaline-earth metal elements K, Ca and ore-associated elements Fe, Cu, Zn. And gold. silver and platinum, invisible under microscope, were detected in some areas of muscovite but not found in feldspar. Especially platinum, a mantle material is rarely seen in the earth crust but now found in the gold deposit of magmatic sources; its appearance approves the idea of mantle flux participating in the gold mineralization, which suggests that the tectonic event controlling gold mineralization in the Yuerya district is a mantle phenomenon.     

Quantitative energy-dispersive X-ray fluorescence analysis for unknown samples using full-spectrum least-squares regression

The full-spectrum least-squares(FSLS) method is introduced to perform quantitative energy-dispersive X-ray fluorescence analysis for unknown solid samples.Based on the conventional least-squares principle, this spectrum evaluation method is able to obtain the background-corrected and interference-free net peaks, which is significant for quantization analyses. A variety of analytical parameters and functions to describe the features of the fluorescence spectra of pure elements are used and established, such as the mass absorption coefficient, the Gi factor, and fundamental fluorescence formulas. The FSLS iterative program was compiled in the C language. The content of each component should reach the convergence criterion at the end of the calculations. After a basic theory analysis and experimental preparation, 13 national standard soil samples were detected using a spectrometer to test the feasibility of using the algorithm. The results show that the calculated contents of Ti, Fe, Ni, Cu, and Zn have the same changing tendency as the corresponding standard content in the 13 reference samples. Accuracies of 0.35% and 14.03% are obtained, respectively, for Fe and Ti, whose standard concentrations are 8.82% and 0.578%, respectively. However, the calculated results of trace elements (only tens of lg/g) deviate from the standard values. This may be because of measurement accuracy and mutual effects between the elements.     

A method for forward energy-dispersive X-ray fluorescence analysis of thin and intermediate samples

The usefulness of forward geometry in Energy Dispersive X-Ray Fluorescence (EDXRF) analysis has been investigated both experimentally and theoretically. This work relates to milli- and micro-beams, which limits this work to tightly collimated incident X-ray beams (<1 mm). The use of forward geometry also limits the targets to be of thin and intermediate thickness. The advantages and the peculiarities of using a forward geometry for XRF are discussed. Forward X-Ray Fluorescence (FXRF) has features including: (a) high geometrical efficiencies when using tightly collimated primary beams; (b) a minimisation in the uncertainty in the interaction volume; (c) a sample thickness at which the production of characteristic X rays is maximised; and (d) a filtering action by intermediate thickness samples resulting in an enhancement of the sensitivity for higher atomic number elements with respect to lower atomic number elements. For thin and intermediate thickness samples simultaneous forward and backward geometry XRF can be used to correct for self-absorption effect.     

Elemental analysis of agricultural soil samples by particle induced X-ray emission (PIXE) technique

In agriculture, elements essential to vital processes are also called nutrients. A suitable and reliable particle induced X-ray emission (PIXE) methodology for content determination of essential nutrients in soil samples was developed and its effectiveness proved. The PIXE method is applied to intermediate thickness samples, whose mass per area unit are smaller than 1 μg/cm². Precision and accuracy of the method was estimated after repeated measurements of a single reference material: CRM PACS-2 (estuarine sediment) with a matrix quite similar to the soil samples measured. This paper reports the results of elemental measurements in soil samples. A discussion of agricultural soil sample preparation for PIXE analysis is also presented.     

微区X射线衍射在矿物鉴定中的应用实例

介绍了微区X射线衍射仪发展的现状,给出了微区X射线衍射仪鉴定物相的研究实例,并讨论了微区X射线衍射法的优、缺点。通过配置有封闭3kWX射线光管、单毛细管透镜、Pixcel探测器和普通CCD视频的Panalytical X’Pert PRO MPDX射线衍射仪,对光片上的铍矿物进行了微区X射线衍射鉴定,结果确定该铍矿物为羟硅铍石。微区X射线衍射法具有微区、微量、原位和无损等优点,能够进行直径在100～300μm范围内的两种或两种以上矿物集合体的物相鉴定。与电子探针等微区手段相互结合、互相补充,鉴定结果更加可靠。     

Design of a dedicated target chamber for PIXE microanalysis of mineral samples

A target chamber design for the proposed mineralogical PIXE microprobe at Guelph is described. A detailed discussion of the light optics requirements for this particular application is presented and a choice made from existing approaches used in electron microprobes.     

医用直线加速器主要部件对X射线能谱的影响

研究了医用直线加速器的主要部件对X射线能谱的影响。利用蒙特卡罗软件包EGSnrc/BEAMnrc针对Varian600C医用直线加速器,模拟完整及分别去除初级准直器、均整器和次级准直器条件下的相空间文件,通过相空间文件分析程序Beamdp对相空间文件进行分析,分别得到相应条件下的X射线能谱。均整器对能谱的影响非常大,对比于无均整器的情况,有均整器时,平均能量上升了48.9%;但初级准直器、次级准直器对能谱的影响小,平均能量的变化小于1%。在射野内,对比于无均整器的情况,有均整器时,能量注量降低了52.4%,但其空间分布变均匀,非平坦度从15.09%变为1.82%;对比于无初级准直器的情况,有初级准直器时,能量注量上升了1.58%;而对比于无次级准直器的情况,有次级准直器时,能量注量下降了2.00%。均整器对X射线的能谱的影响起主要作用,它能够使X射线的平均能量上升和射野内能量注量的分布变均匀。初级准直器对X射线能谱影响小但对X射线的散射不可忽略,而次级准直器对X射线能谱的影响小而且对X射线的散射作用可以忽略,这些结果对加速器X射线束流模型的建立有一定的参考意义。     

使用X光聚束系统的X射线荧光分析研究

复合光导管组成的Ｘ光透镜可将发散的Ｘ光束聚至直径φ０．５ｍｍ，聚束后的功率密度增加１０＾４倍，这种新型的Ｘ光透镜已用于Ｘ射线荧光分析研究，使用Ｘ光管功率仅２Ｗ，而探测限可达１０＾－９－１０＾１０ｇ．     

Method and portable facility for measurement of trace element concentration in prostate fluid samples using radionuclide-induced energy-dispersive X-ray fluorescent analysis

A facility and method for109 Cd radionuclide-induced energy-dispersive X-ray fluorescent(EDXRF) were developed to determine the Fe,Zn,Br,Rb,and Sr concentrations in the specimens of human prostatic fluid.Specimens of expressed prostatic fluid were obtained from 51 men(mean age 51 years,range 18–82 years) with apparently normal prostates using standard rectal massage procedure.Mean values(M ± SEL) for concentration of trace elements(mg L~(-1)) in human prostate fluid were:Fe 9.04 ±1.21,Zn 573 ± 35,Br 3.58 ± 0.59,Rb 1.10 ± 0.08,and Sr B 0.76.It was shown that the results of trace element analysis in the micro-samples(20 l L) are sufficiently representative for assessment of the Fe,Zn,Br,and Rb concentration in the prostate fluid.The facility for109 Cd radionuclide-induced EDXRF is comparatively compact and can be located in close proximity to the site of carrying out the massage procedure.The means of Zn and Rb concentration obtained for prostate fluid agree well with median of reported means.For the first time,the Fe and Br concentrations,as well as the upper limit of the Sr concentration,were determined in the human prostate fluid.     

细胞样品的高分辨率软X射线接触显微术图像的研究

在建立适于软Ｘ射线接触显微术（ＳＸＣＭ）观察细胞样品制备方法的基础上，以培养的肿瘤细胞为生物样品，应用细聚焦软Ｘ射线光源进行ＳＸＣＭ研究，获得了分辨率优于２８ｎｍ的高质量肿瘤细胞ＳＸＣＭ图像。     

多种矿石多元素X荧光分析技术

介绍了在ＣＩＴ－２０００Ｍ管、源激发Ｘ荧光仪上采用双激发、高精度测量、神经网络解谱、自动分类和多种矿石分析几种关键分析技术后,使多种矿石多元素Ｘ荧光分析取得了良好的效果,分析结果达到验收标准。