正电子湮没寿命谱技术应用于聚合物微观结构研究的进展

聚合物的晶区堆砌密度、无定形区自由体积的尺寸和数量、晶区-非晶区的界面等微观结构,对其宏观性能,如渗透性能、力学性能、松弛行为等有重要影响。正电子湮没寿命谱技术是一种强有力的微观结构探测与表征技术,能够灵敏有效地探测聚合物的晶区堆砌密度、无定形区自由体积以及两相界面等信息,从而提供了一种直接、简单的研究聚合物微观结构的途径。文中介绍了该技术的基本原理和应用理论,综述了该技术在聚合物研究领域的应用,如:聚合物本征特性与自由体积之间的关系,应力、辐照、外界压力、物理老化等外界因素对聚合物微观结构的影响,以及聚合物共混物、复合材料的相容性和界面特性等。最后总结了正电子湮没寿命谱技术在聚合物微观结构研究中存在的问题。     

Measurement of Sc and V K—shell ionization cross sections by slow electron impact

Electron-induced Sc and V K-shell ionization cross sections,which are scarce have been obtained from measurement of KαX-ray emission cross sections at energies from near threshold to 25keV.The influence of substrate of thin targets on ionization cross sections has been corrected using the bipartition model of electron transprot.     

加速器氚靶膜厚误差对BIXS方法反演的影响

BIXS(β-ray induced X-ray spectrometry)方法是一种氚β衰变诱发X射线谱的氚无损分析技术，在反演过程中会受到诸多因素的影响，氚靶膜厚误差的影响不可忽略。本文基于蒙特卡罗方法程序PENELOPE模拟和实验验证研究，表明加速器氚靶膜厚误差会对BIXS方法反演有一定的影响，其中对递增分布的影响最大，对递减分布的影响最小；氚在靶膜中的深度分布的斜率越大，膜厚误差对BIXS方法反演的影响也越大。     

Measurement of 8～25keV electron impact K－shell ionization cross sections of Cu and Co elements

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用薄靶厚衬底方法测量电子碰撞引起的K壳层电离截面

用能谱仪测量特征X射线,从而导出元素钛和钒的K壳层电离截面。为克服制靶困难,实验中采用薄靶厚衬底方法。通过电子输运计算,由厚衬底产生的反射电子对计数的影响得以修正。将结果和Green等的半经验公式以及Jessenberger等的测量数据进行了比较。     

用于激光驱动冲击波诊断的成像型VISAR设计

利用激光驱动冲击波是高压状态方程研究的主要手段之一,一般利用扫描光学高温计(SOP)对冲击波进行诊断,但SOP存在的靶场干扰、无法实现弱冲击波测量和状态方程绝对测量等缺陷。为解决这些问题,提出了一种用于激光驱动冲击波诊断的双灵敏度成像型任意反射面速度干涉仪(VISAR)设计,并给出了VISAR各组成部分的技术要求。     

Applying image processing method to treat digital signals

In this paper, we present a novel method for digital nuclear signal processing based on image processing and recognition, which can improve signal-to-noise ratio of digital nuclear signal effectively without changing the signal shape. The digital nuclear signal with a "time-amplitude" series is converted into a grayscale image with adjustable pixel size. Template of the converted image is extracted by means of modern image processing methods, such as spatial digital low-pass filtering, image binary and the skeleton extracting of images. The needed parameters are extracted from the template image. The method of template extracting presented in this paper can be used flexibly to extract template of nuclear signals, whether the whole or even part of that, and got multi templates corresponding to the whole or partial characters of the signals. The results of image processing,along with γ-ray energy spectrum of241 Am acquired by this method, show that the new method provides a way to develop future digital nuclear instruments of high efficiency and flexibility, high density and multi parameters.     

Simulation Study of Quantitative X-Ray Fluorescence Analysis of Ore Slurry Using Partial Least-Squares Regression

X-ray fluorescence (XRF) in combination with partial least-squares (PLS) regression was employed to analyze the ore slurry grade. Using the Monte Carlo simulation code PENELOPE, X-ray fluorescence spectra of ore samples were obtained. Good accuracy was achieved when this method was used to analyze elements with concentrations of several percent or above. It was demonstrated that the more the number of X-ray fluorescence spectra used to calibrate, the better the obtained accuracy. In this method detector resolution was found to have little or no effect on the results of quantitative analysis. The effect of the concentration of water was investigated as well, and it was found to have little influence on the results.     

Measurement of 8—25keV electron impact K—shell ionization cross sections of Cu and Co elements

The influence of substrate of thin targets on ionization cross sections has been corrected by a new method based upon the bipartition model of electron transport.The measured cross sections for Cu element are in good agreement with existing experimental data and those produced by the empirical formula of Green and Cosslett.Cross sections for Co element are measured for the first time.     

Preliminary Measurement of the K-Shell Ionization Cross Sections of Ti by Positron Impact in the Low Energy Region

Measurements were performed of K-shell ionization cross sections of Ti element by 10～30 keV positron impact using the thick-target method. The effects of multiple scattering of incident positron and from bremsstrahlung photons and annihilation photons with the thick-target method are discussed with the Monte Carlo code PENELOPE. Meanwhile, the Monte Carlo method is also applied to determine the detection efficiencies of X-and γ-ray detectors. Our experimental K-shell ionization cross sections for Ti element are compared with the distorted-wave Born approximation (DWBA) theoretical predictions, and it is found that the agreement of the experimental data and theoretical values is good and this indicates that the experimental method adopted in this study is applicable.