First measurement of the 94 Nb( n , ? ) cross section at the CERN n_TOF facility
First measurement of the 94 Nb( n , ? ) cross section at the CERN n_TOF facility
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在 CERN n_TOF 设施首次测量 94 Nb( n , ? ) 横截面
DOI：
10.1051/epjconf/202327906004
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发表时间：
2023
影响因子：
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通讯作者：
Balibrea-Correa J
中科院分区：
文献类型：
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作者：
Balibrea-Correa J
改进恒星模型的关键因素之一是准确了解S过程、r过程和i过程中不同同位素的中子俘获截面。这些测量可以阐明观测到的和预测的同位素丰度之间存在的差异，并有助于限制这些反应沿着恒星演化的不同阶段发生的物理条件。在放射性⁹⁴Nb的特殊情况下，⁹⁴Nb(n，γ)截面可以在确定S过程在AGB星中产生⁹⁴Mo方面发挥作用，这是目前最先进的恒星模型无法再现的。以前没有关于已分辨和未分辨共振区的⁹⁴Nb(n，γ)实验数据，这主要是由于生产高质量样品的困难，以及在飞行时间实验中常用的常规检测系统的限制。在这种情况下，在欧洲核子研究中心n_TOF首次对⁹⁴Nb(n，γ)反应进行了测量，从而利用了EAR2区的高亮度，并结合了小体积C6D6探测器和高质量⁹⁴Nb样品的新检测系统。后者是基于在伊尔格勒诺布尔高通量反应堆激活的高纯93Nb材料。在捕获样本周围的紧密几何结构中的创新的环形配置检测系统使我们能够显著提高信号与背景的比率。这一装置还补充了两个传统的C₆D₆探测器和一个高分辨率LaCL₃(Ce)探测器，将用于可靠地解决系统效应和不确定性。在目前的数据分析状态下，在从热到10keV的中子能量范围内，首次观察到了⁹⁴Nb+n的18个共振。
One of the crucial ingredients for the improvement of stellar models is the accurate knowledge of neutron capture cross-sections for the different isotopes involved in the s-,r- and i- processes. These measurements can shed light on existing discrepancies between observed and predicted isotopic abundances and help to constrain the physical conditions where these reactions take place along different stages of stellar evolution. In the particular case of the radioactive ⁹⁴Nb, the ⁹⁴Nb(n,γ) cross-section could play a role in the determination of the s-process production of ⁹⁴Mo in AGB stars, which presently cannot be reproduced by state-of-the-art stellar models. There are no previous ⁹⁴Nb(n,γ) experimental data for the resolved and unresolved resonance regions mainly due to the difficulties in producing highquality samples and also due to limitations in conventional detection systems commonly used in time-of-flight experiments. Motivated by this situation, a first measurement of the ⁹⁴Nb(n,γ) reaction was carried out at CERN n_TOF, thereby exploiting the high luminosity of the EAR2 area in combination with a new detection system of small-volume C6D6-detectors and a high quality ⁹⁴Nb-sample. The latter was based on hyper-pure 93Nb material activated at the high-flux reactor of ILL-Grenoble. An innovative ring-configuration detection system in close geometry around the capture sample allowed us to significantly enhance the signal-to-background ratio. This set-up was supplemented with two conventional C₆D₆-detectors and a highresolution LaCl₃(Ce)-detector, which will be employed for addressing reliably systematic effects and uncertainties. At the current status of the data analysis, 18 resonance in ⁹⁴Nb+n have been observed for the first time in the neutron energy range from thermal up to 10 keV.