共查询到16条相似文献,搜索用时 109 毫秒
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透射式微型X射线管是能量色散X射线荧光分析中的主要激发源,在能量色散X射线荧光分析中希望得到谱分布较为单一的X射线管输出谱。采用MC方法,研究了透射式微型X射线管在不同目标靶厚度的情况下输出谱的特征,通过低谱段(<5 keV)和高能谱段(5~50 keV)的分析比较,高能谱段计数随厚度加大先增加而后减小,低能谱段计数则随厚度增加减小,增加目标靶厚度可以有效抑制低能谱段。在入射电子能量为50 keV和目标靶为4 Ag的条件下,X射线管输出能谱具有较高的高能谱段注量,同时有效压制低能谱段注量,适合能量色散X射线荧光分析中使用。 相似文献
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利用C语言对钨反射式X射线管出射的X射线光谱公式编制计算机程序,对模拟计算得到的光谱的形状与理论及实验结果进行比较,对模拟计算结果的正确性加以验证. 相似文献
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微型透射式X射线管广泛应用于能量色散X射线荧光分析领域,具有体积小、功耗低、X射线发射效率高等特点,可作为手持式X射线荧光分析仪器的激发源。目前常用铍(Be)作为出射窗材料,成本高,而且有毒性。同时为减少低能散射射线,在射线管前端放置铝(Al)作为过滤窗。本文拟采用Al为微型透射式X射线管出射窗材料,透射高能射线,屏蔽低能散射射线,降低制作成本和难度。文中采用蒙特卡洛模拟软件MCNP5模拟计算不同银(Ag)靶厚度和Al窗厚度的X射线管输出谱。结果表明,Al窗对低能射线的屏蔽作用强于对高能射线的屏蔽作用,在Al窗厚度超过1.5 mm时,低能射线完全被屏蔽,高能射线有部分透射。通过和已有研究成果[1,5]对比分析,在Ag靶厚度为2 μm,Al窗厚度为0.8 mm时,低能射线所占的比例仅为0.087 8%,高能射线产生率为0.002 73%,既能有效屏蔽低能射线,又能保证高能射线较高的出射率,能够满足野外现场能量色散 X射线荧光分析的需要。 相似文献
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根据端窗透射微型X射线管阳极靶的结构,建立了数理模型,讨论了电子束打靶的平均厚度与光管高压的关系,得到了X光管出射特征光谱强度的角度分布特征。同时利用Monte Carlo方法,对出射光谱在2π方向上的强度分布特征开展模拟研究。结果表明,微型X射线管阳极靶材平均厚度在2 μm左右,在与入射电子束垂直方向几度的范围内获得的出射光谱其单色性较好。这些结论对于微型X射线管的结构设计和出射光谱单色化应用具有一定的理论指导意义。 相似文献
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杰亨与他的学生们已经照出了物体的360°的透射式全息图。我们也成功地造出了360°反射式全息图。并且象DENISYUK类型的平面反射式全息图一样能用白色光源去观察。本文报导了制作优质的360°反射式全息图的两种方法。全息图分为透射式或反射式,取决于图象的重现是用透射光或是用反射光。为 相似文献
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为了抑制激光在线测厚时入射角波动引起的误差,根据几何光学分析了激光透射式和反射式测厚原理,发现激光在特定入射角附近波动时,两种方式的测厚误差一正一负,具有互补性,在此基础上提出基于透射和反射同时测量的互补式测厚方法,该方法可将误差限定在透射式和反射式测量误差之间,抑制在线测厚误差.对于有机玻璃平板,理论计算表明,当激光入射角在67.013°±4°波动时,相对误差绝对值在1%以内,误差抑制率均值大于90%;当入射角为61.536°时,误差抑制率为100%.利用线结构激光器和两个线阵CCD相机搭建互补式测厚实验系统,测量了标称厚度为1~5mm的有机玻璃平板,与透射式和反射式测厚结果进行对照,除厚度为1mm的玻璃外,互补式测厚误差被限制在透射式和反射式之间,最大误差抑制率达61%.实验结果表明,该互补式方法有效抑制了误差,提高了在线厚度测量准确度,解决了在线测量不可重复性导致的无法通过均值法减小误差的问题. 相似文献
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本文叙述了我们正在研制的新型闪光X射线设备的设计方案。其主要特点是:(1)毫微秒脉冲发生器采用组件式结构与美国Hewlett-Pac ard公司的产品相似,(2)减少了Marx发生器回路的电感,可提高闪光X射线设备的输出电压及减少设备的体积,(3)采用多级触发,扩展了球隙开关的触发工作范围,(4)采用多尖阴极的爆炸发射闪光X射线管,增加了闪光X射线管的输出剂量及寿命。 改进后的设备,将达到和部份超过美国Hewlett-Packard公司产品的性能。 相似文献
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V. A. Bushuev 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(1):52-56
The influence of coherent properties of an X-ray source (X-ray tube, synchrotron radiation source, free-electron X-ray laser) on the spatial field distribution and the spatial coherence function of this field has been theoretically considered for Bragg reflection from a single crystal. 相似文献
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In order to improve the measuring precision of complex transmission coefficients in impedance tube, the influence that comes from the transmission-reflection wave in the transmission tube is analyzed, and the modified formulas of complex reflection and complex transmission coefficients are proposed. With the experiment of organic glass, it can be confirmed that the modified formulas are useful and can decrease the demand of the tube end. Through the measurement of the complex transmission coefficients of multilayer acoustical panel, the complex transmission coefficients of multilayer both forward and backward incidences are definitely the same in theory either normal or oblique incidence. When sound wave is normal incidence, the method is also verified to be correct with experiments in impedance tube. 相似文献
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Traveling wave tube measurements for low-frequency properties of underwater acoustic materials 总被引:1,自引:0,他引:1
References: 《声学学报:英文版》2007,26(4):301-312
A traveling wave tube measurement technique for measuring acoustic properties of underwater acoustic materials was developed.Water temperature and pressure environments of the ocean can be simulated in a water-filled tube,and the acoustic parameters of samples of underwater acoustic materials are measured in the range of low-frequency.A tested sample is located at central position of the tube.A pair of projectors is separately located at both ends of the tube.Using an active anechoic technique,the sound wave transmitting the tested sample is hardly reflected by the surface of secondary transducer.So the traveling sound field is built up in the tube.By separately calculating the transfer functions of every pair of double hydrophones in the sound fields from the both sides of the sample,its reflection coefficients and transmission coefficients are obtained.In the measurement system,the inside diameter of the tube isΦ208 mm,the working frequency range is from 100 to 4000 Hz,the maximum pressure is 5 MPa.The reflection coefficients and transmission coefficients of a water layer and a stainless steel layer samples are measured actually and calculated theoretically.The results show that the measured values are in good agreement with the values calculated,and the measurement uncertainty is not greater than 1.5 dB. 相似文献
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利用X射线作为载波实现空间远距离、高速率的信息传输已引起研究者的关注,这项技术的发展将对拓宽电磁波频谱的使用范围具有积极意义.针对X射线通信地面模拟真空实验系统对信号发射源的需求,设计了一种栅极控制X射线源.该X射线源是在传统X射线管的基础上,增加了电压控制栅极,通过改变栅极电压实现X射线的脉冲发射.利用三维电磁场仿真软件CST粒子工作室设计了实验样管,模拟计算了管内的电位分布、电子运动轨迹、实际焦斑大小和打靶电子数.仿真结果表明,实际焦斑大小约为0.4 mm×4 mm,栅极开启电压和截止电压分别为0和-10 V.实验测试了样管特性,测试结果与仿真结果符合得很好,并且在X射线真空实验系统中实现了数字信号传输. 相似文献
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S. V. Salikhov F. N. Chukhovskii A. M. Polyakov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(5):887-899
A solution of the problem of X-ray specular reflection from a statistically rough surface is presented. It is based on using
the Green function formalism. The Kirchhoff formula is used to describe the transmission of the wave field through a rough
interface. Generally, microscopically exact expressions for the coefficients of transmission through a rough surface and reflection
from it are obtained by taking multiple scattering effects into account. Averaging of the obtained expressions over possible
realizations of random roughness of the interface between media allows to obtain rigorous expressions for specular reflection
and transmission coefficients. The behavior of exact solutions in the limiting case of infinite correlation lengths is studied.
It is shown that, in this case, the obtained solution corresponds to the Debye-Waller normalization. Expressions for the reflection
and transmission coefficients making it possible to carry out numerical calculations are obtained in the Bourret approximation
of multiple-scattering theory. 相似文献