High accuracy measurement of the 238U(n,γ) cross section at the CERN n_TOF facility
High accuracy measurement of the 238U(n,γ) cross section at the CERN n_TOF facility
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CERN n_TOF 设施中 238U(n,γ) 横截面的高精度测量
DOI：
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发表时间：
2014
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影响因子：
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通讯作者：
T. Wright
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文献类型：
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作者：
T. Wright
在欧洲核子研究中心中子飞行时间设施n_TOF上，在能量范围0.3 eV-20 keV的185 m飞行路径上，测量了高纯度（99.999%），6.125(2)g （(9.56 μ 05)e-4原子/仓）238U样品的辐射俘获截面。全吸收量热计（TAC）检测系统，40个BaF2晶体阵列，利用全吸收技术，其中所有的？-射线从捕获级联被检测。这些数据经过了仔细的背景减去，特别注意来自238U样品散射的中子的背景。堆积和死区时间的影响已经纠正使用创新的校正方法有效的可变高计数率在一个复杂的检测系统，如TAC。所得捕获率的不确定性在5 keV以下为2.2%，在5至20 keV之间为3.7%，符合NEA高优先级请求列表中要求的精度。用代码SAMMY进行了高达5 keV的共振分析。在5到20 keV之间，截面被视为未解析和平均。结果证实了在引用的不确定度范围内最新核数据评价的优良质量，并提出了一些改进建议。特别是，这些TAC数据表明，在2-9 keV的能量范围内，平均截面增加了2%，在9-20 keV的能量范围内，平均截面减少了5%。
The radiative capture cross section of a highly pure (99.999%), 6.125(2) grams 238U sample ((9.56�05)e-4 atoms/barn) has been measured in the 185 m flight path at the CERN neutron time-of-flight facility n_TOF in the energy range 0.3 eV-20 keV. The Total Absorption Calorimeter (TAC) detection system, an array of 40 BaF2 crystals, was used utilising the total absorption technique, where all the ?-rays from the capture cascades are detected. These data have undergone careful background subtraction, with special care being given to the background originating from neutrons scattered by the 238U sample. Pile-up and dead-time effects have been corrected for using an innovative correction method valid for variable high count rates within a complex detection system such as the TAC. The resulting capture yield has an uncertainty of up to 2.2% below 5 keV and up to 3.7% between 5 and 20 keV, in line with the accuracy requested in the NEA High Priority Request List. A resonance analysis has been performed up to 5 keV with the code SAMMY. Between 5 and 20 keV, the cross section is treated as unresolved and averaged. The results confirm the excellent quality of the most recent nuclear data evaluations within quoted uncertainties and suggest some improvements. In particular, these TAC data suggest a 2% increase in the average cross section in the energy range 2-9 keV and a 5% reduction in the energy range 9-20 keV.