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针对点堆动力学理论解释脉冲源法测试原理时存在的问题, 基于无源中子输运方程分析次临界系统总中子数、泄漏γ射线计数率随时间的变化关系。理论分析表明: 脉冲中子源作用结束后(无源条件下), 在一定时间范围内, 泄漏γ射线计数率和总中子数近似成正比, 两者随时间变化服从近似指数衰减规律, 反映系统本身的裂变衰减特性, 可以由总中子数和γ射线计数率求解瞬发中子衰减时间常数。基于蒙特卡罗程序构造类Godiva裸铀球次临界系统, 模拟脉冲中子源作用下中子和γ射线输运过程, 计算总中子数、泄漏γ射线计数率及两者比值随时间的变化关系, 结果与理论分析一致; 利用脉冲源法由总中子数、泄漏γ射线计数率计算瞬发中子衰减时间常数α0, 得到与α-k迭代一致的α0。说明总中子数、泄漏γ射线计数率可以准确反映系统本身的裂变衰减特性。此外, 根据理论分析和模拟计算给出脉冲源法可用数据的时间范围, 分析泄漏γ射线计数率和总中子数比值的影响因素。 相似文献
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放射源的辐射指纹能起到标识和鉴别放射性物体的作用.在涉及核弹头不可逆销毁过程的深度核裁军核查中,核弹头的辐射指纹对标识和鉴别裁减下来的核弹头将起到关键作用.预先研究辐射指纹的有关技术,如识别机理的研究,将有助于深度核裁军的核弹头核查技术发展.以实验室放射源为研究对象,探索了类型γ射线能谱指纹的同一性识别机理.类型γ射线指纹识别机理的研究,就是要找出一种合适的方法,以较高的置信度,描述两个正在进行比较的γ射线指纹是否为同一放射源的指纹.采用了谱形比较法,并用谱相似度概念来描述两个指纹的相似程度.在谱形比较思想的指导下,编制了放射源类型指纹识别软件,并通过放射源同一性的识别实验验证了软件的有效性,同时研究了谱相似度随统计涨落和测量条件,如时间、源强和本底等因素的变化情况.研究结果表明:1)用相似度概念来描述两个指纹的相似程度,回答两个待比较的γ射线能谱是否代表同一类型放射源,是切实可行的;2)该识别机理只具备识别放射源类型的能力,而对同一类型、差异甚微的放射源个体还不能识别
关键词:
γ射线能谱指纹
辐射指纹
识别机理
核查技术 相似文献
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为了在无放射源的前提下开设γ能谱测量实验,本文使用氯化钾样品中的40K代替常规放射源,研究了所需的实验样品含量、实验装置和实验内容,并分析了本实验的辐射危害情况.研究表明:使用氯化钾样品不仅可以满足常规γ能谱测量的实验要求,还比仅使用137Cs放射源丰富了实验内容,且经计算和测量本实验的辐射剂量达不到放射源的下限标准,可以保证学生在安全的前提下完成实验内容.本研究设计的实验方法不受放射源使用手续及环保部门的制约,有利于消除学生的放射性恐惧心理,减少放射源的管理成本及非核类院校的γ能谱测量实验课程的开设. 相似文献
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建造了由九块国产锗酸铋晶体组成的采用光电倍增管读出的阵列式探测器. 应用γ放射源、中子放射源、静电加速器(p,γ)反应以及核反应堆(n,γ)反应得到0.5—21MeV γ射线. 在这个能量范围内进行的测试显示了线性的能量响应. 能量分辨率在低能量下满足预期的E1/2关系, 而能量在4.43MeV以上实际测得的数值较预期为大. 实验中还考察了光子在晶体阵列中沉积能量的横向分布情况, 结果与蒙特卡罗模拟一致. 本工作表明, 采用放射源及低能(p,γ)反应作为锗酸铋电磁量能器定标和监测的手段是实际可行的. 相似文献
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γ能谱仪的教与学──一、能谱仪的线性戴乐山,李白云(复旦大学材料科学系,上海200433)γ能谱仪有两个重要指标:能量分辨率与能量定标曲线的非线性度.如果需要分辨一个放射源中的不同能量的γ光子,则能量分辨率是一个重要的指标;测量γ光子的能量时,γ能谱... 相似文献
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XUE Zhen XU Zi-Zong WANG Xiao-Lian HU Tao WANG Zhi-Yong FU Cheng-Dong YAN Wen-Biao L Jun-Guang ZHOU Li CAI Xiao YU Bo-Xiang FANG Jian SUN Xi-Lei SHI Feng WANG Zhi-Gang AN Zheng-Hua SUN Li-Jun LIU Hong-Bang ZHANG Ai-Wu WANG Xiao-Dong 《中国物理C(英文版)》2011,35(1)
The BEPCⅡLuminosity Monitor(BLM)monitors relative luminosity per bunch.The counting rates of gamma photons,which are proportional to the luminosities from the BLM at the center of mass system energy of the ψ(3770)resonance,are obtained with a statistical error of 0.01% and a systematic error of 4.1%.Absolute luminosities are also determined by the BESⅢ End-cap Electro-Magnetic Calorimeter(EEMC)using Bhabha events with a statistical error of 2.3% and a systematic error of 3.5%.The calibration constant between the luminosities obtained with the EEMC and the counting rates of the BLM are found to be 0.84±0.03(x1026 cm-2·count-1).With the calibration constant,the counting rates of the BLM can be scaled up to absolute luminosities. 相似文献
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P. I. H. Bastiaens E. H. W. Pap J. Widengren R. Rigler A. J. W. G. Visser 《Journal of fluorescence》1994,4(4):377-383
The interaction of protein kinase C with lipids was studied in a mixed micellar system. Two fluorescence spectroscopic methods are presented with a different but complementary information content. Diffusion monitored by fluorescence correlation spectroscopy provides information on the interaction of the protein with the whole lipid aggregate. Resonance energy transfer from tryptophans to pyrene-labeled lipids monitored by time-correlated single-photon counting supplies information on the interaction of the protein with specific lipid cofactors within the micelle. The results can be extended to postulate new mechanisms for the activation of protein kinase C by the signal transduction cascades in the cell. Both fluorescence spectroscopic methods can be easily applied to other protein systems which interact with lipids. 相似文献
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显微光子计数成像系统及其应用 总被引:2,自引:0,他引:2
光子计数成像系统可以探测生物超微弱发光,但是只能探测生物的宏观图像,若要深入到细胞、分子水平,必须有显微光子计数成像系统。二者的区别类于显微光子计数成像系统是噪声受限系统。本文报道的显微光子计数成像系统,采用^14C同位素光源来监测系统的状态,保证实现极限探测。该系统可以用来研究痕量生物分子的分布和功能,显示钙离子在细胞内外的分布,活性氧、基因表达的监测等。由单光子到单分子、组织学图像到功能图像的 相似文献
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M D Srinivas 《Pramana》1996,47(1):1-23
We present an overview of the quantum theory of continuous measurements and discuss some of its important applications in
quantum optics. Quantum theory of continuous measurements is the appropriate generalization of the conventional formulation
of quantum theory, which is adequate to deal with counting experiments where a detector monitors a system continuously over
an interval of time and records the times of occurrence of a given type of event, such as the emission or arrival of a particle.
We first discuss the classical theory of counting processes and indicate how one arrives at the celebrated photon counting
formula of Mandel for classical optical fields. We then discuss the inadequacies of the so called quantum Mandel formula.
We explain how the unphysical results that arise from the quantum Mandel formula are due to the fact that the formula is obtained
on the basis of an erroneous identification of the coincidence probability densities associated with a continuous measurement
situation. We then summarize the basic framework of the quantum theory of continuous measurements as developed by Davies.
We explain how a complete characterization of the counting process can be achieved by specifying merely the measurement transformation
associated with the change in the state of the system when a single event is observed in an infinitesimal interval of time.
In order to illustrate the applications of the quantum theory of continuoius measurements in quantum optics, we first derive
the photon counting probabilities of a single-mode free field and also of a single-mode field in interaction with an external
source. We then discuss the general quantum counting formula of Chmara for a multi-mode electromagnetic field coupled to an
external source. We explain how the Chmara counting formula is indeed the appropriate quantum generalization of the classical
Mandel formula. To illustrate the fact that the quantum theory of continuous measurements has other diverse applications in
quantum optics, besides the theory of photodetection, we summarize the theory of ‘quantum jumps’ developed by Zoller, Marte
and Walls and Barchielli, where the continuous measurements framework is employed to evaluate the statistics of photon emission
events in the resonance fluorescence of an atomic system. 相似文献
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研究了在Hanbury Brown Twiss探测方式下,非平衡探测系统对光子统计测量的影响。通过记录2个单光子计数器响应的单分子光子源输出的每一个事件,分析具有泊松统计背景的实际单分子光子源的光子统计特性,讨论并给出了非平衡探测系统的单分子光子源Mandel参数。研究表明:非理想的50/50分束器、非理想的线性传输效率和非理想的探测器都会使单分子光子源Mandel参数的实际测量结果小于平衡系统的Mandel参数,最后给出了单分子光子源Mandel参数的非理想探测的校正表达式。 相似文献
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The counting systems consisting of electronic devices are used for detection of radiation due to X or gamma rays. The dead time of the counting system is based on time limitations of these electronic devices. The dead time causes counting losses. Determination of counting rate losses in quantitative and qualitative analysis become a vital step for correction of analysis. Therefore, compensating for counting rate losses is of great importance. These counting rate losses are due to piled up reject time, paralyzable or non-paralyzable system dead time or a combination of these mechanisms. Paralyzable and non-paralyzable models are well-known and frequently used for correction of counting rate losses dependent on the system dead time. However, these two models do not provide enough correction at medium and high counting rates. Therefore, the new models for corrections of counting rate losses are needed. For this reason, both an alternative approach is proposed and a simulation program is coded for counting rate losses in this study. A good agreement is obtained between theoretical model and simulation program. 相似文献
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Deconvolution has been used by several workers to reduce or eliminate X-ray and analyzer-induced broadenings of XPS spectra, but there is a 30% limit on the amount of improvement in the FWHM of XPS peaks. Deconvolution algorithms generally used also increase the noise in the spectrum. Monochromatic X-ray sources can give high resolution data directly, but the count rates are generally low. Given these limitations, a comparison has been made to see which method of high resolution data acquisition. can achieve data of a certain quality in the least amount of time, for a given system, namely a Kratos ES300 photoelectron spectrometer. Signal-to-noise ratios are used as a means of comparing spectral quality at a given resolution. Results for the Kratos ES300 show that if the desired resolution could be achieved without deconvolution, an order of magnitude less counting time was needed for the Mg Kα standard source. If deconvolution is necessary, the counting times for both sources to achieve a given S/N ratio were found to depend mainly upon the signal-to-background ratios of the peak measured with each source. These results are illustrated for the S 2p doublet from MoS2 and the Ni 2p peaks from oxidized stainless steel. 相似文献
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Insulation failure is one of the major causes of catastrophic failure of transformers. It is established that partial discharge (PD) causes insulation degradation and premature failure of insulation. In power apparatus, more than one PD source may be active simultaneously. The nature of insulation degradation for multiple PD sources is different from that due to single PD source. Therefore, it will be helpful for severity assessment of insulation degradation, if the number of active PD sources are identified and classified. This paper presents a method for identification and classification of two simultaneously active PD sources using acoustic emission techniques. The acoustic emission (AE) signals are measured for laboratory simulated PD in an oil-pressboard insulation system for three different electrode systems. The measurements of partial discharge acoustic emission (PDAE) signals are carried out for single PD source and for two simultaneous PD sources. The measured signals are analyzed using discrete wavelet transform (DWT), box counting fractal dimension and lacunarity. Box counting fractal dimension and lacunarity are calculated for DWT decomposed signal of major frequency band. Energy distribution in different frequency bands of DWT decomposed signal along with box counting fractal dimension and lacunarity is used for classification of two simultaneous PD sources. 相似文献