共查询到19条相似文献,搜索用时 62 毫秒
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248 Cm和252Cf自发裂变瞬发中子谱测量 总被引:1,自引:0,他引:1
在飞行时间方法测量 2 0 0keV— 1 2MeV能区内2 48Cm和2 5 2 Cf自发裂变瞬发中子谱 ,以国际原子能机构推荐的2 5 2 Cf自发裂变瞬发中子谱为标准 ,可以免去探测器效率刻度的问题并消除系统误差 ,提高测量精度 .实验用一个微型电离室作为裂变碎片探测器 ,两个芪晶体中子探测器测量中子及一套基于微机的距离分别为 3 2 ,50和 1 0 0cm ,经过对数据的处理和分析给出了 2 0 0keV— 1 2MeV的中子能区内的实验数据 .用Maxwell分布对实验数据进行拟合 ,得到的核温度为 (1 4 0 1± 0 0 0 6)MeV . 相似文献
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飞行时间法是精确测量快中子能谱的有效方法。但是在实际应用中,各种中子灵敏探测器同时也对r射线灵敏,中子源的伴随r射线会直接影响中子能谱的求解精度。液体闪烁体BC501具有良好的时间响应特性和n-r分辨本领,广泛适用于r射线场中的快中子参数测量。文中选用液体闪烁体BC501作为快中子探测器,根据中子和丫射线在液体闪烁体中产生的闪烁光退光时间长短的明显差异,应用脉冲上升时间法进行n-r分辨,通过对符合甄别^252Cf自发裂变中子飞行时间谱中的丫射线的效果进行研究,从应用的角度描述了脉冲上升时间法的n-r分辨效果。 相似文献
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瞬发裂变中子谱(prompt fission neutron spectrum,PFNS)是用于核实验诊断过程中十分重要的参数数据,传统的测量主锕系核素(U,Pu)PFNS的技术手段是采用裂变室,利用裂变碎片标识裂变中子,通过中子飞行时间技术获得裂变中子谱.目前出现了一种新的用于PFNS测量的技术,其原理是基于如下的物理事实:在一次裂变过程中,释放中子的同时伴随着释放7–8个γ射线光子,而非弹性散射效应产生的γ射线光子只有1–2个.据此,可以通过裂变γ射线的多重性将裂变中子和其他杂散中子甄选出来,达到测量PFNS的目的.本文建立了基于裂变γ标识技术的PFNS测量实验系统.利用该系统对252Cf中子源的PFNS进行了实验测量,测量结果与传统的裂变碎片标识法及ENDF/B-VⅡ数据库的标准谱进行了比较,对新方法的裂变标识率以及实验不确定度也一并进行了分析. 相似文献
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当密封Cf源寿命超过20年后,其他同位素和子体核素尤其Cf-250和Cm-248的贡献不断增大,使得Cf源中子发射率不能简单按照Cf-252半衰期进行估算。基于Cf源中同位素及其子体核素的衰变和自发裂变规律,提出了一种测定密封Cf源中Cf-252和Cf-250成分的方法,达到快速估算寿命超过20年的Cf源中子发射率的目的。采用长计数器相对测量得到一个使用近30年Cf源在某一时刻的中子发射率,确定了该源初始时刻Cf-252和Cf-250原子核数分别为4.4521016和7.7461015,据此给出了Cf源的中子发射率随时间的变化关系。同时在另外两个时刻的推算结果与长计数器测量结果符合得非常好,相对偏差小于0.3%,进一步验证了该方法的可靠性。此外还对Cf-252,Cf-250和Cm-248对中子发射率的贡献与中子源寿命的关系进行了分析,结果表明当Cf源寿命达到30年时,Cf-252对总中子发射率的贡献已经降至67.65%,而Cf-250和Cm-248的贡献已经达到29.32%和2.94%。 相似文献
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用飞行时间方法测量200keV-12MeV能区内 相似文献
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针对252Cf源驱动核材料产生裂变中子脉冲信号具有脉冲序列特殊的"0,1"稀疏结构之特点,采用压缩感知理论,通过巧妙引入图论中的二分图模型,同时结合二分图的最小覆盖性质,适当添加约束条件,构建了稀疏均匀的观测矩阵。研究结果表明,利用压缩感知理论对"0,1"中子脉冲序列特殊稀疏结构的信号重构算法不仅可行,而且还获得了优于l1范数最小化方法重构结果,这对252Cf驱动核材料的中子脉冲信号分析与处理提供了一种新的途径或方法。 相似文献
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The results of a multiparameter investigation of the 6He emission accompanying the spontaneous fission of 252Cf are presented. The energy spectrum and the yield of the 6He particles are found to be in accord with previous measurements, but their angular distribution is observed to be narrower at 13° ± 3° (FWHM) than the value of ? 32° deduced in a previous investigation.Comparisons of the experimental with published calculated energy spectra and angular distributions for 3H, 4He and 6He particles are shown to provide evidence for a compact scission configuration in ternary fission. 相似文献
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The shape parameters of the multiplicity distribution of prompt gamma rays emitted in spontaneous fission of252Cf were obtained using the multiple coincidence technique. The multiplicity distribution is well represented by a Gaussian
distribution. Assuming the average number of prompt gamma rays emitted per fission to be 10.3, the standard deviation of the
multiplicity distribution was estimated to be 4.2±0.4. The variation of the standard deviation of the multiplicity distribution
has also been obtained as a function of kinetic energy of one of the fragments and was found to exhibit a strong zigzag dependence
on the single fragment kinetic energy. The results have been discussed on the basis of the emission mechanism of prompt gamma
rays in fission. 相似文献
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F. Caïtucoli M. Asghar B. Leroux G. Barreau K. Hamadache A. Sicre T.P. Doan M. Allab 《Nuclear Physics A》1983,394(3):360-368
Fission-fragment mass and kinetic energy distributions and their correlations have been measured for the spontaneous fission of 244Cm. About 3.54 × 105 fission events were collected. The global mass distribution shows shoulders at μH ≈ 134 and μH ≈ 143?144. The peak/valley ratio is 86. The dip ΔEK value at symmetry is 13.4 ± 1.5 MeV. In the yields for high-kinetic-energy selected events, the masses 139 and 144 dominate. The results of 244Cm are compared with the other isotopes of Cm and discussed in terms of the structures present in the potential energy surface of the fissioning system caused by the structures in the nascent fragments. 相似文献
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The prompt fission neutron spectra for the neutron-induced fission of 235U at En < 5 MeV are calculated using nuclear evaporation theory with a semi-empirical model, in which the nonconstant and constant temperatures related to the Fermi gas model are taken into account. The calculated prompt fission neutron spectra reproduce the experimental data well. For the n(thermal)+235U reaction, the average nuclear temperature of the fission fragment, and the probability distribution of the nuclear temperature, are discussed and compared with the Los Alamos model. The energy carried away by γ rays emitted from each fragment is also obtained and the results are in good agreement with the existing experimental data. 相似文献
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The first and the second moments of the multiplicity distribution of prompt gamma rays in spontaneous ternary fission of252Cf have been measured by the multiple coincidence technique. While both these moments were found to be nearly independent
of the energy of the light charged particle accompanying the fission fragments, the width of the multiplicity distribution
was larger than that in the case of normal binary fission by about 20%. 相似文献
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Angular distributions of light charged particles from 252Cf fission in the ranges 0–46° and 134–180°
A.J. Kordyasz E. Piasecki L. Nowicki P. Koczoń J. Sobolewski M. Kisieliński W. Czarnackif 《Nuclear Physics A》1985,439(1):28-44
Alpha particles, tritons, deuterons and protons accompanying 252Cf fission were registered in coincidence with both fission fragments by means of a system containing two-dimensional position-sensitive silicon detectors. Angular distributions, kinetic energy spectra of light charged particles as well as mass distributions of fission fragments in coincidence with light charged particles were measured. The experimental results are compared with some theoretical models. 相似文献
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随着第四代反应堆以及先进核能利用系统的发展,对中子核数据提出了高精度、多核素、宽能区的新要求.目前,中国核数据评价库(CENDL库)中相关核裂变的数据较缺失,不足以满足当前核能发展的需求.因此,建立面向中子核数据需求的可靠计算方法和工具变得极为重要.本文基于Monte-Carlo方法建立了裂变碎片质量动能计算模型,研究了中低能中子诱发232Th(n,f)反应发射中子前裂变碎片的分布特性.对于裂变碎片质量分布,本模型计算结果与实验值最大偏差约1%,与GEF, TALYS程序计算结果 (与实验值最大偏差约2%)相比具有一定优势.对于发射中子前裂变碎片动能分布,本模型计算结果与实验数据一致.结果表明,所发展的计算模型能够较好地预测232Th(n,f)反应发射中子前裂变碎片数据,为中子诱发锕系核裂变反应计算提供一种新思路. 相似文献