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冷中子照相利用穿透样品的中子和荧光屏~6Li反应产生的α带电粒子与荧光材料发光,从而在探测器上记录光强度的分布.本文简单介绍了冷中子照相的特点,给出了铍与钛金属宏观总截面随能量的变化,设计特定的样品采用MCNP模拟不同能量下的中子图像,中子图像显现Bragg吸收限上下两幅图像的对比度差异,采用差分成像对两幅中子图像进行处理,凸现了冷中子照相的优点. 相似文献
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设计了一种多路准直器用于消除中子照相中的散射中子,利用MCNP5对准直器的中子吸收材料、长度进行了优化设计,利用该准直器对不同厚度的水层样品在不同样品探测器距离下进行了中子照相的MC模拟计算。计算结果表明选用25μm的Gd作为准直器的中子吸收涂层,准直器长度为1cm时可消除98%的散射中子,使用该准直器可以有效提高中子照相定量分析的精度。 相似文献
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热中子照相技术在检测含氢材料、重金属样品等方面是X射线等其它无损检测技术的有益补充,热中子层析技术研究在国内尚是空白,实验研究条件欠缺且代价高昂,通过仿真研究再过渡到实验研究,将有效降低研究成本,提高研究效率.文章根据中子层析照相基本原理,设计模拟样品,采用MCNP仿真计算的方法获取了样品中子投影图像,利用C++Builedr研发中子层析数据获取程序和反投影滤波算法层析重建程序,重建了样品二维断面图像,样品二维断面图像与实际样品一致,证明了所采用的仿真研究流程合理可行,为中子层析照相技术的深入研究奠定了基础. 相似文献
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中子照相是十分重要的无损检测方法之一,尤其是针对含氢材料、同位素等的无损检测,中子照相技术具有其他射线成像不可比拟的优势。中国工程物理研究院核物理与化学研究所基于紧凑型D-T中子源,研发了可移动中子成像检测仪,成功实现了热中子照相和快中子照相实验检测。为确定基于该装置开展热中子层析检测的可行性,本文进行了数值模拟计算,利用该仪器开展了针对轻重材料模拟件的热中子层析成像实验,利用采集的181幅投影图像,在图像信噪较低和采集幅数较少条件下,成功重建了铝和聚乙烯材料包裹下的0.2 mm直径的钆丝。 相似文献
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铀材料的辐射探测方法是核查技术研究的重要内容,主动法是铀材料探测的有效方法之一.论文利用MCNP程序计算分析了活化法区分浓缩铀和贫化铀的可行性,研究表明通过铀材料的裂变率-慢化体厚度的关系曲线能够判断是贫化铀还是浓缩铀.计算分析了~(252)Cf和14MeV中子源在铀材料探测中的优缺点,结果表明~(252)Cf中子源优于14Mev中子源.最后从测量的角度,重点分析了探测对象--缓发γ射线和缓发中子,分析表明探测缓发中子优于缓发γ射线. 相似文献
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MCNP程序用热中子散射数据制作和检验 总被引:2,自引:2,他引:0
基于ENDF/B-Ⅶ.0评价库,以前已陆续研制了可供MCNP程序使用的连续截面库,以及多套多个温度、多组邦达连柯背景截面修正的多群参数库。本文采用NJOY程序以及ENDF/B-Ⅶ.0评价库热散射子库,完成了MCNP程序使用热中子散射数据库S(α,β)的制作和检验。比较了自制库与MCNP自带基于ENDF/B-Ⅵ版热散射数据库(sab2002),对改进较明显的重要介质“轻水中氢”和“重水中氘”给出了分析说明。通过48个基准装置keff计算结果可看出,MCNP程序自带热中子散射库sab2002与自制库thb70计算的keff整体上偏差不大,keff平均偏差约65pcm。 相似文献
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中子对Si及GaAs半导体材料位移损伤的数值计算 总被引:1,自引:0,他引:1
概述了中子对半导体材料的位移损伤函数及损伤能力的表征,并选用ASTM标准的E722—94给出的Si及GaAs位移损伤函数,用MCNP粒子输运程序计算了Maxwell裂变谱源、Gaussian聚变谱源对Si及GaAs半导体材料的位移损伤以及相对于1MeV单能中子源的损伤等效系数等。 相似文献
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PENGTai-Ping YANGHong-Qiong YANGJian-Lun YANGGao-Zhao LILin-Bo SONGXian-Cai 《核技术(英文版)》2005,16(1):40-42
We develop a kind of neutron detector, which consists of a polyethylene thin film and two PIN semiconductors connected face-to-face. The detector is insensitive to γ-rays. Its sensitivity to neutron has been calculated with MCNP program and calibrated by experiments, and the results indicate that the neutron sensitivity of the compensation detector will vary with polyethylene convel‘ter. The compensation PIN detector can be employed to measure pulse neutron in neutron and gamma mixture radiation field. 相似文献
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The China Advanced Research Reactor (CARR) is scheduled to be operated in the autumn of 2008. In this paper, we report preparations for installing the neutron radiography instrument (NRI) and for utilizing it efficiently. The 2-D relative neutron intensity profiles for the water-vapor two-phase flow inside the tube were obtained using the MCNP code without influence of γ-ray and electronic-noise. The MCNP simulation of the 2-D neutron intensity profile for the water-vapor two-phase flow was demonstrated. The simulated 2-D neutron intensity profiles could be used as the benchmark data base by calibrating part of the data measured by the CARR-NRI. The 3-D objective images allow us to understand the flow pattern more clearly and it is reconstructed using the MATLAB through the threshold transformation techniques. And thus it is concluded that the MCNP code and the MATLAB are very useful for constructing the benchmark data base for the investigation of the water-vapor two-phase flow using the CARR-NRI. 相似文献
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M.N. Nasrabadi M. Jalali 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,263(2):473-476
In this work thermal neutron self-shielding in aqueous bulk samples containing neutron absorbing materials is studied using bulk sample prompt gamma neutron activation analysis (BSPGNAA) with the MCNP code. The code was used to perform three dimensional simulations of a neutron source, neutron detector and sample of various material compositions. The MCNP model was validated against experimental measurements of the neutron flux performed using a BF3 detector. Simulations were performed to predict thermal neutron self-shielding in aqueous bulk samples containing neutron absorbing solutes. In practice, the MCNP calculations are combined with experimental measurements of the relative thermal neutron flux over the sample’s surface, with respect to a reference water sample, to derive the thermal neutron self-shielding within the sample. The proposed methodology can be used for the determination of the elemental concentration of unknown aqueous samples by BSPGNAA where knowledge of the average thermal neutron flux within the sample volume is required. 相似文献