核天体物理实验中的原位正电子湮灭测量方法  

In situ Measurement Method of Positron Annihilation in Nuclear Astrophysical Experiments

作　　者：林棽 宋路洋 苏俊 陈鑫 谌枳霖 张昊 盛耀德 张立勇 何建军 陈思泽[2] 谌阳平 金仕纶[4] 卢飞 肖丹 章勇 南巍 蒋宇辰 张玉强 张扬 田竣文 江信之 陈银吉 王琳 覃之巍 刘峰成 LIN Shen;SONG Luyang;SU Jun;CHEN Xin;SHEN Zhilin;ZHANG Hao;SHENG Yaode;ZHANG Liyong;HE Jianjun;CHEN Size;SHEN Yangping;JIN Shilun;LU Fei;XIAO Dan;ZHANG Yong;NAN Wei;JIANG Yuchen;ZHANG Yuqiang;ZHANG Yang;TIAN Junwen;JIANG Xinzhi;CHEN Yinji;WANG Lin;QIN Zhiwei;LIU Fengcheng(College of Nuclear Science and Technology,Beijing Normal University,Beijing 100875,China;Institute of Nuclear Energy Safety Technology of Hefei Institutes of Physical Science,Chinese Academy of Science,Hefei 230031,China;China Institute of Atomic Energy,Beijing 102413,China;Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China;Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201210,China)

机构地区：[1]北京师范大学核科学与技术学院,北京100875 [2]中国科学院合肥物质科学研究院核能安全技术研究所,合肥230031 [3]中国原子能科学研究院,北京102413 [4]中国科学院近代物理研究所,兰州730000 [5]中国科学院上海高等研究院,上海201210

出　　处：《原子核物理评论》2024年第1期340-345,共6页Nuclear Physics Review

基　　金：国家重点研发计划项目(2022YFA1603301);国家自然科学基金资助项目(12275026)。

摘　　要：在核天体物理关心的热核反应中,有一些反应可以产生短寿命的正电子放射性产物,这些反应产物发射的正电子会在靶中与电子发生湮灭,继而产生一对能量为511 keV的γ射线,通过测量这一对γ射线来得到反应产额,从而计算出核反应截面以及天体物理S因子。近期有研究提出了在实验终端上原位测量正电子湮灭的方法,该方法主要借助511 keV γ射线对的方向相反特性,利用探测阵列的对向单元进行空间符合测量来压制本底干扰。本工作基于近期自主研发的大型模块化BGO阵列LAMBDA-Ⅱ对这一方法进行了研究。结果显示,LAMBDA-Ⅱ对反应产物原位β^(+)衰变探测效率为(7.6±0.2)%,和蒙特卡罗模拟结果一致。通过原位测量得到^(14)N(p,γ)^(15)O反应259 keV共振产额符合瞬发γ射线测量结果,验证了该方法的可靠性,为将来进一步将该方法应用到核天体物理研究中奠定了良好的基础。In thermonuclear reactions of nuclear astrophysical interest,some can produce short-lived products that emit positrons.These positrons will annihilate with electrons in the target and then produce a pair of 511 keVγ-rays,which can be used to determine the reaction yield and calculate the cross-section as well as the astrophysical S-factor.Recently,an in situ measurement method for positron annihilation on experimental terminals has been proposed.This method takes advantage of the characteristic opposite direction of the 511 keVγ-ray pairs and uses the opposite units in the detection array for spatial coincidence measurements to suppress background.In this study,we investigated this method using the newly developed large modular BGO detector array LAMBDA-II.The results show that the detection efficiency of LAMBDA-II for in situ β+ decay of reaction products is(7.6±0.2)%,which is in good agreement with the value given by Monte Carlo simulations.The yield of the ^(14)N(p,γ)^(15)O 259 keV resonance determined by in situ measurement agrees well with that derived from promptγ-ray measurement,verifying the reliability of this method and providing a solid foundation for its further application in nuclear astrophysics research.

关 键 词：核天体物理 正电子湮灭 原位测量 天然本底 

分 类 号：TL8[核科学技术—核技术及应用]