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中国物理学会期刊

利用激光加速电子源开展152 m, 150 mEu的光核活化产生和152 mEu的同核异能素比研究

Studies on photoactivation of 152 m, 150 mEu and isomeric ratio of 152 mEu using a laser-accelerated electron source

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  • 基于激光加速的电子源, 本工作在巨共振能区和百MeV能区分别实现了同核异能素^152\textm,150\textm\rmEu的光核活化产生, 测量了^153\rmEu(γ, n)^152\textm1,\textm2\rmEu和^151\rmEu (γ, n)^150\textm\rmEu反应的通量加权平均截面(FACS), 以及提取了^152\textm\rmEu的同核异能素比(IR). 进一步地, 采用核反应计算程序Talys计算了^153\rmEu(γ, n)^152\textm1,\textm2\rmEu和^151\rmEu (γ, n)^150\textm\rmEu反应的FACS以及^152\textm\rmEu的IR, 并研究了FACS和IR对核模型的敏感性. 结果表明, ^153\rmEu(γ, n)^152\textm1,\textm2\rmEu和^151\rmEu (γ, n)^150\textm\rmEu反应的FACS以及^152\textm\rmEu的IR曲线均对γ强度函数和核能级密度有显著依赖. 研究发现, ^152\textm\rmEu的IR实验测量值与理论计算值基本吻合, 然而FACS的测量值与理论计算结果尚存在一定的差异, 说明现有的γ强度函数和核能级密度模型在合理描述Eu核素方面尚有提升空间. 上述研究结果不仅丰富了^152\textm,150\textm\rmEu的同核异能素产生截面数据, 还对Eu核素的现有核反应计算模型提供了实验约束.

    Research on photonuclear production of europium (Eu) isomers ^152\textm, 150\textm\rmEu is helpful for understanding the nucleosynthesis process of the p-nuclide ^152\rmGd. Currently, experimental data for photonuclear production of ^152\textm,150\textm\rmEu remain scarce, with significant discrepancies persisting between measured and calculated isomeric ratio (IR) for ^152\textm\rmEu. While nuclear reaction calculations provide an alternative means of obtaining these data, their results are highly sensitive to nuclear model parameters. Therefore, high-quality experimental measurements across a broad energy range are still essential to constrain these theoretical models. Laser-driven electron sources, which are characterized by picosecond to femtosecond pulse duration, ultra-high brightness and high signal-to-noise ratio, provide a novel approach to address the scarcity of photonuclear data for ^152\textm, 150\textm\rmEu and the discrepancies of IR data for ^152\textm\rmEu. In the present study, we utilized both the CLAPA laser facility at Peking University and the XG-III laser facility at the China Academy of Engineering Physics to achieve the photonuclear production of ^152\textm,150\textm\rmEu in hundred-MeV and Giant Dipole Resonance energy region, respectively. The flux-weighted average cross-sections (FACS) for the ^153\rmEu(γ, n)^152\textm1,\textm2\rmEu and ^151\rmEu(γ, n)^150\textm\rmEu reactions were measured. Accordinlgy, the IR value of ^152\textm\rmEu was extracted in a reasonable way. Using the CLAPA facility, the FACS values for the ^153\rmEu(γ, n)^152\textm1, \textm2\rmEu and ^151\rmEu(γ, n)^150\textm\rmEu reactions were measured at E_e = 200±28 MeV to be 12.65±2.37 mb, 0.56±0.09 mb, and 10.83±2.70 mb, respectively. Using the XG-III facility, these values were measured at \langle E_e\rangle = 14 MeV to be 37.71±4.63 mb, 0.92±0.05 mb, and 31.23±6.92 mb, respectively. The resulting IR values for ^152\textm\rmEu were determined to be 0.046±0.006@E_e = 200±28 MeV and 0.023±0.003@\langle E_e\rangle = 14 MeV, respectively. Furthermore, we performed Talys calculations to systematically investigate the sensitivity of the FACS and IR values to nuclear model parameters. It is shown that the FACS curves of the ^153\rmEu(γ, n)^152\textm1, \textm2\rmEu and ^151\rmEu(γ, n)^150\textm\rmEu reactions and the IR curve of the ^152\textm\rmEu exhibit significant dependence on the γ strength function and nuclear level density. It was also found that, despite certain discrepancies between the measured FACS values and theoretical calculations, the overall variation trends remain consistent, indicating that current nuclear reaction models still have room for improvement in accurately describing Eu isotopes. Additionally, the experimentally measured IR values of ^152\textm\rmEu agree well with theoretical predictions. These results not only enrich the production data for ^152\textm, 150\textm\rmEu but also provide experimental constraints on existing nuclear reaction models for Eu isotopes.

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