基于激光等离子体产生的轫致辐射源实现同核异能素^(152m)Eu的高效激发  

Efficient excitation of nuclear isomer^(152m)Eu using a bremsstrahlung radiation source generated by laser plasma

作　　者：罗凯军 樊文茹 袁赟 齐伟[2] 张景丽 张晓辉 邓志刚[2] 罗文[1] LUO Kaijun;FAN Wenru;YUAN Yun;QI Wei;ZHANG Jingli;ZHANG Xiaohui;DENG Zhigang;LUO Wen(College of Nuclear Science and Technology,University of South China,Hengyang 421001,China;Science and Technology on Plasma Physics Laboratory,Laser Fusion Research Center,China Academy of Engineering Physics,Mianyang 621900,China)

机构地区：[1]南华大学核科学技术学院,衡阳421001 [2]中国工程物理研究院激光聚变研究中心,绵阳621900

出　　处：《核技术》2024年第3期93-101,共9页Nuclear Techniques

基　　金：国家重点研发项目(No.2022YFA1603300);国家自然科学基金(No.U2230133,No.U2241281,No.12305270);衡阳市科技项目(No.202150054076);湖南省教育厅项目(No.22B0453);湖南省自然科学基金项目(No.2023JJ40525)资助。

摘　　要：同核异能素在宇宙元素合成中发挥着重要作用,并且在控制核能释放方面有潜在的应用。其中,铕(Eu)在现实中有重要的研究意义,例如152Eu被用来做放射性实验的标准源,并且其同核异能态^(152m1)Eu有73%的概率发生β-衰变产生天体p核素钆(^(152)Gd),因此^(152m1)Eu是产生天体p核素^(152)Gd过程中的重要核素。在本工作中,基于激光等离子体产生的轫致辐射源,我们在实验上实现了^(152m1)Eu(45.6 keV,T_(1/2)=9.31 h)的高效激发,其产额能达到8×10^(4)个粒子/发。此外,进一步通过Geant4-GENBOD程序数值模拟了^(152m1,m2)Eu的产额、产生时间以及峰值激发效率随电子温度的演化情况。研究发现,在入射电子电荷量固定为17.6 nC,且当电子温度达到15 MeV时,^(152m1)Eu和^(152m2)Eu的产额趋于饱和,分别为8×10^(6)和2×10^(5)个粒子/发;^(152m1)Eu和^(152m2)Eu的峰值激发效率分别有望达到约10^(17)和10^(16)个粒子/s,其中^(152m1)Eu和^(152m2)Eu的脉宽几乎不变,均为32 ps。超短超强激光技术能够极大提高同核异能素的激发效率,这将为研究宇宙元素合成问题以及控制核能释放应用研究提供一个重要的研究途径。[Background]Nuclear isomers are crucial in cosmic element synthesis and have potential applications in controlling nuclear energy release.Specifically,Europium(Eu)is significant in fundamental studies.For instance,152Eu is used as a reference source for radioactive experiments,and its isomeric state^(152m1)Eu has a probability of 73%to produce cosmological p-nuclei^(152)Gd withβ−decay.Therefore,^(152m1)Eu is a crucial nuclide in the nuclearsynthesis of p-nuclei^(152)Gd.[Purpose]This study aims to realize the efficient excitation of^(152m1)Eu with a bremsstrahlung source generated by laser plasma.[Methods]Firstly,the laser-plasma bremsstrahlung source was utilized to achieve the efficient excitation of^(152m1)Eu(45.6 keV,T_(1/2)=9.31 h)in the experiment with yields of 8×10^(4)particles/shot by this isotope.Then,numerical simulations of the yield of^(152m1,m2)Eu were performed using the Geant4-GENBOD program to get generation time,and peak excitation efficiency evolution with electron temperature.[Results]The results demonstrate that when the electron temperature reaches 15 MeV,the yield of^(152m1,m2)Eu approaches saturation.When the incident electron charge is 17.6 nC,the yield of^(152m1)Eu is approximately 8×10^(6)particles/shot,and that of^(152m2)Eu is approximately 2×10^(5)particles/shot.The generation time of^(152m1,m2)Eu in the target is approximately 32 ps.When the electron temperature reaches 15 MeV,the peak excitation efficiency of^(152m1)Eu is expected to be~10^(17)particles/s,and that of^(152m2)Eu is expected to be~10^(16)particles/s.[Conclusions]The ultrashort ultrahigh intensity laser technology can significantly enhance the excitation efficiency of isotopes of the same nucleus,and this will provide an important research avenue for the study of cosmic element synthesis and nuclear energy release control applications.

关 键 词：同核异能素^(152m)Eu 激光等离子体 轫致辐射源 (γ n)反应 峰值激发效率 

分 类 号：TL92[核科学技术—核燃料循环与材料] TL99