X射线荧光分析法测定碳酸锂中稀土氧化物

通过轻元素的非相干散射机制的研究,将非相干散射和特征线以散射归一化相结合计算的表观浓度用于修正Lucas-Tooth和Pyne的强度校正模型,利用线性方程组最小二乘回归分析方法以及实验室标准样品,建立了Li_2CO_3中少量Sc_2O_3,Y_2O_3,La_2O_3,Tm_2O_3,和Lu_2O_3的X射线荧光分析方法。该法的测定精密度均优于4.0％,最佳的可达1.4％。这种定量分析方法具有准确、简便、快速和多元素同时测定等优点。     

X射线荧光分析法测定碳酸锂中稀土氧化物

通过轻元素的非相干散射机制的研究,将非相干散射和特征线以散射归一化相结合计算的表观浓度用于修正Lucas-Tooth和Pyne的强度校正模型,利用线性方程组最小二乘回归分析方法以及实验室标准样品,建立了Li_2CO_3中少量Sc_2O_3,Y_2O_3,La_2O_3,Tm_2O_3和Lu_2O_3的X射线荧光分析方法。该法的测定精密度均优于4.0％,最佳的可达1.4％。这种定量分析方法具有准确、简便、快速和多元素同时测定等优点。     

用于便携式X射线荧光仪的基体效应散射校正模型

本文论证了样品对入射射线的质量吸收系数(μ_O)与康普顿散射强度之倒数呈线性关系,提出并验证了样品对待测元素特征线的质量吸收系数(μ_K)与质量吸收系数(μ_O)以及待测元素含量之间呈线性多项式关系。并且给出了这些关系存在的条件。提出了一种适用于低能量分辨率的携带式X荧光仪的散射校正模型。并成功用于锡矿和某些铜矿分析中。     

EDXRF无标样分析未知样品含量的算法研究

针对未知样品能量色散X射线荧光分析(energy dispersive X-ray fluorescence analysis,EDXRFA)方法开展无标样分析,通过测量Ti、Fe、Ni、Cu、Zn、Sr、Sn、Pb单元素标样,得到Rh靶材原级谱中Kα峰的相干与非相干散射峰强度比值R,并建立R与对应单元素标样有效原子序数的关系,得到Zeff-R的拟合曲线。求解未知样品基体时,测量未知样,得到其R,将R代入Zeff-R拟合曲线得到未知样有效原子序数,再通过基本参数法迭代计算其质量衰减系数。利用Ti、Fe、Ni、Cu、Zn、Sr、Sn、Pb单元素标样刻度仪器获取Gi参数,求解未知样品基体时用于相应元素的基本参数迭代。为验证算法可靠性,采用本算法分析15个国家土壤标准样品,结果表明,Ti、Fe、Ni、Cu、Zn元素的计算含量与标准含量接近,部分低含量元素受到散射本底等因素影响,含量误差较大。结果表明,该方法能够用于现场能量色散X射线荧光分析。     

X射线相干散射与非相干散射强度比的蒙特卡罗模拟

本文对X射线相干散射与非相干散射强度比进行蒙特卡罗模拟,模拟结果与实验测定符合较好。     

EDXRF无标样分析未知样品含量的算法研究

针对未知样品能量色散X射线荧光分析（energy dispersive X-ray fluorescence analysis, EDXRFA）方法开展无标样分析,通过测量Ti、Fe、Ni、Cu、Zn、Sr、Sn、Pb单元素标样,得到Rh靶材原级谱中K_α峰的相干与非相干散射峰强度比值R,并建立R与对应单元素标样有效原子序数的关系,得到Z_eff-R的拟合曲线。求解未知样品基体时,测量未知样,得到其R,将R代入Z_eff-R拟合曲线得到未知样有效原子序数,再通过基本参数法迭代计算其质量衰减系数。利用Ti、Fe、Ni、Cu、Zn、Sr、Sn、Pb单元素标样刻度仪器获取G_i参数,求解未知样品基体时用于相应元素的基本参数迭代。为验证算法可靠性,采用本算法分析15个国家土壤标准样品,结果表明,Ti、Fe、Ni、Cu、Zn元素的计算含量与标准含量接近,部分低含量元素受到散射本底等因素影响,含量误差较大。结果表明,该方法能够用于现场能量色散X射线荧光分析。     

放射性同位素XRF技术中一种与“特散比”法等效的新方法

在一定的条件下,待测元素特征X射线和康普顿散射强度比值,与待测元素特征X射线强度和带吸收滤片所测量的强度比值之间有着简单的双曲函数关系。利用这一函数关系,很容易在单道携带式放射性同位素X射线荧光分析仪上实现“特散比”法改善基体效应。用这种方法所得到的分析结果和用“特散比”法得到的分析结果,二者吻合很好,而且不需要增加任何设备,节省了测量时间和成本。已经测量了几种类型的锡矿样品和某些铜矿样品。     

蒙特卡罗方法在X射线荧光分析中的一些应用

本文给出了荧光过程的蒙特卡罗模拟,着重考虑了几种散射过程对特征X射线强度的影响。对几 种纯元素,计算了单位辐射下特征X射线的强度,与实验值取得了较好的一致。     

新型高灵敏度XRF分析仪的研制与应用

新型高灵敏度便携式X射线荧光(XRF)分析仪基于电致冷Si-PIN半导体X射线探测器和微机多道(2048道)谱仪系统,整机重3.8kg(探头重0.6kg),对铜、锌、砷等元素的分析检出限为10μg·g-1,适用于野外现场的天然岩石、土壤和水系沉积物的多元素含量的定量测定,以及工业原料、半成品、产品快速分析。     

用PIXE法分析较厚样品时元素含量的计算

采用质子激发X射线荧光法(PIXE)分析生物,医学及环境等样品时,都要涉及到厚靶的分析。通常,靶都制得很薄,即所谓的薄靶(对2.0MeV的质子束,靶厚小于1mg/cm~2),这可使对样品中各元素含量的计算简单,但其计数效率太低。为了提高效率而又节省用机时间,希望将靶制得稍厚一些,即所谓厚靶(靶厚大于1mg/cm~2),这时就必须考虑质子束通过靶层时能量损失所引起的特征X射线产生截面的变化,以及靶不同深度处产生的特征X射线穿出靶时因吸收而致的强度减弱。本文主要介绍从理论上对未考虑上述影响的薄靶计算公式的修正问题,并通过对标准桃叶的测量来验证这一计算方法的可靠性。     

Development of Soft X-Ray Sources with Electron Guns of Field Emission- and Thermal Cathode-Types and Their Application to Counter Experiments

Soft X-ray sources have been developed with electron guns of field emission- and thermal cathode-types. Those sources are used mainly to investigate the electron drift and avalanche properties in a gas counter. Thin films of aluminum, titanium, iron, copper and nickel are used as the X-ray targets. Beams of quasi-monochromatic X-rays are obtained with these targets. The emitted X-rays consist of characteristic and bremsstrahlung radiations, which are checked by using a high purity germanium detector. Generation of pulsed X-rays is also tried. As an example of the application of the X-ray source, results of measurements of the SQS (Self Quenching Streamer) phenomenon in a gas counter have been shown.     

PIXE spectrum analysis taking into account bremsstrahlung spectra

Continuous background appearing over the wide region of X-ray energy in the PIXE spectrum is very troublesome presence in the peak fitting. In the usual manner, the spectrum of continuous background is predicted as a function of polynomial and is subtracted from the X-ray spectrum. However, the parameters of the polynomial are determined with difficulty in the case that the continuous background exists under many peaks of characteristic X-rays. We calculated the production cross sections of continuous X-rays for several elements on the basis of the theories of quasi-free electron bremsstrahlung (QFEB), secondary electron bremsstrahlung (SEB) and atomic bremsstrahlung (AB), and obtained the continuous X-ray spectrum as a function of atomic number and X-ray energy. X-ray spectra of a standard sample and of a bovine liver sample were analyzed by a pattern analysis method assuming the reference spectra consisting of characteristic X-rays and continuous X-rays for each element. The results of analysis are quite satisfactory. By the present method, the PIXE spectra can be analyzed under little influence of the background subtraction, and it enables us a full auto-analysis of PIXE spectrum.     

Development of a new X-ray source using backscattered X-ray with the use of a cold cathode

The development of an intense X-ray source using backscattered X-ray produced using an advanced electrode configuration is described. The electrodes were composed of field emitters deposited on a wire mounted on a perforated plate as the cathode and a copper plate as the anode. Electrons from these emitters collided with the copper plate and X-ray was generated at collision points. The backscattered X-ray in the direction normal to the electron trajectory through a hole in the anode escaped from the vacuum chamber through a beryllium window. Continuous and characteristic X-rays were detected at an applied voltage lower than that of a conventional X-ray source from 3.0 to 9.4 kV, respectively. Moreover, the X-ray dosage measured with a survey meter reached 0.95 mSv/h at 5.0 kV of applied voltage. The transmission images of three types of material used as an X-ray source for the X-ray imaging system indicate three advantages; low power consumption, focal point controllable by adjusting applied voltage, and photographable motion picture of X-ray transmission.     

Non-destructive analysis of coins using high-energy PIXE

At the Ionenstrahllabor (ion beam laboratory) a great variety of ions with variable energies up to several MeV/u can be produced. Performing proton induced X-ray emission (PIXE) with protons of 68 MeV, heavy elements can be detected via the K X-rays in addition to their L X-rays. The large proton range and the small absorption coefficients for the K X-rays result in an analysable depth of several millimeters. The L–K line intensity ratio yields further information on the composition of the objects. The objects of the study were so-called “Wiener Pfennige” found in Tulln, Austria. The “hoard of Tulln” contains about 11 000 of these silver coins which were strongly corroded and agglomerated to a single block. After the restoration non-destructive analysis should provide information about the elemental composition. The goal was to show the evolution of the copper content of the coins and the verification of the actual coin classification.     

Influence of resonant Raman scattering in the elemental analysis using X-ray emission based techniques

A tabulation of characteristic X-ray energies across the periodic table are provided where those X-rays are expected to result in a significant fractional resonant Raman scattering (RRS) contribution to the X-ray attenuation from a particular shell/subshell of the same or another element. The tabulations can be considered as guideline so as to know what can be expected due to RRS in typical photon- and particle-induced X-ray emission spectrometry. The RRS contribution is not included in the available theoretical attenuation coefficients, which are generally used in estimation of the matrix corrections in routine quantitative elemental analysis based on various X-ray emission techniques. The radiative RRS peaks can also interfere with normal X-ray spectrum and influence the elemental analysis. The RRS cross-section depends upon the energy difference of the X-ray energy and the shell/subshell ionization threshold taken in the units of the shell/subshell energy width, density of available states near the Fermi level, and the band structure in case the element is in the solid form. Some aspects of the dependence of the RRS contribution on the chemical forms of the elements are also discussed.     

放射性同位素X射线荧光分析仪在中条山铜矿的应用

应用放射性同位素X射线荧光分析仪测定各种元素含量在许多文献中均有报道。在这里主要介绍用单道HYX-1型和XY-1型X射线荧光仪测定中条山铜矿粉末样品和巷道岩壁中铜的含量及其取得的经济效益。     

一次传递样品238U、232Th活度测定比对及对以往一些环境辐射调查的联想

本文报告了一个刻度源及测量对象都是采用传递样品方式进行的实验室间γ分析比对.文中特别对外源性X射线干扰的影响进行了研究和较详细的叙述.此外,本工作还对影响比对结果的其它因素也做了讨论,它明确指出,那些受外源性特征X射线干扰的特征γ峰不应该被用来测定样品的γ放射性活度.最后,本文还对以往的一些环境辐射调查阐述了一些联想.     

The Columbia University proton-induced soft x-ray microbeam

A soft X-ray microbeam using proton-induced X-ray emission (PIXE) of characteristic titanium (K_α 4.5 keV) as the X-ray source has been developed at the Radiological Research Accelerator Facility (RARAF) at Columbia University. The proton beam is focused to a 120 μm × 50 μm spot on the titanium target using an electrostatic quadrupole quadruplet previously used for the charged particle microbeam studies at RARAF. The proton induced X-rays from this spot project a 50 μm round X-ray generation spot into the vertical direction. The X-rays are focused to a spot size of 5 μm in diameter using a Fresnel zone plate. The X-rays have an attenuation length of (1/e length of ∼145 μm) allowing more consistent dose delivery across the depth of a single cell layer and penetration into tissue samples than previous ultrasoft X-ray systems. The irradiation end station is based on our previous design to allow quick comparison to charged particle experiments and for mixed irradiation experiments.     

Determination of L3 subshell X-ray production cross-sections and fluorescence yields of Pb, Th and U

A study of L₃ subshell X-ray production cross-sections and fluorescence yields by using characteristic K X-rays as the exciting radiation is described. Only the L₃ subshells of Pb, Th and U were excited by the characteristic K X-rays of the elements used as secondary sources. The cross-sections for the production of L_l, L and L_β groups of L₃ subshell X-rays of Pb, Th and U have been measured using photoionization by Rb, Nb and Mo K X-rays. The measured L₃ X-ray production cross-section values for Pb, Th and U are in good agreement with the theoretical ones evaluated using L₃ subshell fluorescence yield ω₃, fractions of the radiative width F_3i and L₃ subshell photoionization cross-section σ₃. The L₃ subshell fluorescence yields (ω₃) have also been computed using the presently measured cross-section values and the theoretical L₃ subshell photoionization cross-section values. These results are compared with the theoretically predicted values.     

Homogeneity study of an Fe impurity in unalloyed Zn using PIXE

We have studied the distribution of an Fe impurity in unalloyed Zn material along line scans in spots of 1 mm diameter each using PIXE. In order to achieve the necessary precision (1%) in the determination of this low Fe content (about 100 mg/kg), a sufficient counting rate of Fe X-rays is needed without overloading the counting electronics with Zn X-rays at the same time. Therefore, the development of our PIXE analysis system had to take into account: (a) optimising the thickness of a Ni absorber foil in order to selectively reduce the counting rate of Zn without adding an unproportionally high Ni counting rate, (b) implementing a triggered ion beam deflection system capable of handling very high counting rates (up to 8 kcps), (c) developing the spectrum evaluation code to take account of the selective absorption by the Ni foil. The results of our PIXE measurements showed an inhomogeneity in Fe of up to 10%, considered too high to accept this zinc material as a new reference material.