锦屏深地核天体物理实验BGO探测器的研制

发布时间：2018-04-07 16:29

本文选题：BGO闪烁体　切入点：屏蔽体　出处：《郑州大学》2017年硕士论文

【摘要】：锦屏深地核天体物理实验(Jinping Underground Nuclear Astrophysics lab,简称JUNA)项目将在中国锦屏深地实验室开展恒星平稳氦燃烧阶段关键的(α,γ)和(α,n)反应,以及恒星平稳氢燃烧阶段关键的(p,γ)和(p,α)反应的直接测量。该项目需要一个高探测效率的4π阵列γ探测器和本底极低的实验环境。考虑到锗酸铋(Bi4Ge3O12,简称BGO)的探测效率高,阻止本领强,放射性本底低和不易潮解等优良性能,JUNA项目计划研制一套BGO探测器阵列,用于(α,γ)和(p,γ)反应的γ射线探测。我们为BGO探测器阵列设计了两种方案,然后通过对两种方案的12C(a,γ)16O实验能谱模拟,确定采用由八块梯形组成的阵列方案。然后通过对相对效率的计算,确定将探测器阵列的长度设计为250 mm。为了测试上海硅酸盐研究所生产的BGO晶体是否满足我们的实验要求,我们先组装了一台BGO原型机,并用其进行了能量分辨率测试。测试结果表明硅酸盐研究所生产的BGO晶体能量分辨率和稳定性等性能达到世界先进水平,满足我们要求。由于JUNA项目对实验环境本底的要求极高,我们又用原型机进行了本底测试,并根据测试结果,对实验使用的屏蔽体进行了改善。最终,我们设计出了基本达到实验要求的屏蔽方案。由于BGO晶体的光产额对温度敏感,用BGO探测器探测γ射线时,温度的变化会导致γ能谱峰位的漂移和能量分辨率的变化。国内外针对这一问题的研究所使用的BGO的尺寸都比较小,为了探究温度对大尺寸BGO探测器测量的影响,我们用自己设计并制作了简易制冷系统,先后对尺寸为4 cm×4 cm×3 cm和6 cm×8 cm×25 cm的BGO晶体进行了降温,用137Cs源测量了其γ能谱峰位和能量分辨率,对BGO探测器性能随温度的变化关系进行了研究。结果表明:在我们测试的温度区间内,BGO探测器的γ能谱峰位与温度呈良好的线性关系,能量分辨率随温度的降低而提高。通过这次测试,我们对BGO的温度特性有了一定认识,也为将来研制BGO探测器阵列和地下实验测量积累了数据。
[Abstract]:Jinping Underground Nuclear Astrophysics lab.JUNAproject will carry out direct measurements of the critical (伪, 纬) and (伪 -n) reactions in the stationary helium combustion stage of stars, as well as the key reactions in the stationary hydrogen combustion stage of stars in Jinping Underground Nuclear Astrophysics lab. in China.The project requires a 4 蟺 array 纬 detector with high detection efficiency and a very low background experimental environment.Considering the high detection efficiency, strong blocking power, low radioactive background and low moisture solution of Bi _ 4GE _ 3O _ 12 (BGOA), the Juna project plans to develop a set of BGO detector arrays for 纬 -ray detection of (伪, 纬) and (p, 纬) reactions.We have designed two schemes for BGO detector array, and by simulating the energy spectrum of 12Cna, 纬 ~ (16) O experiments of the two schemes, we have determined that the array scheme is composed of eight trapezoids.Then, by calculating the relative efficiency, the length of the detector array is determined to be 250 mm.In order to test whether the BGO crystal produced by Shanghai silicate Research Institute meets our experimental requirements, we first assembled a BGO prototype machine and tested its energy resolution.The results show that the energy resolution and stability of BGO crystals produced by silicate Institute reach the advanced level in the world and meet our requirements.Due to the very high requirement of the background of the experimental environment for JUNA project, we have carried out the background test with the prototype machine, and according to the test results, we have improved the shield used in the experiment.Finally, we designed a shielding scheme that basically meets the experimental requirements.Because the optical yield of BGO crystal is sensitive to temperature, the change of temperature will result in the shift of peak position of 纬 -ray spectrum and the change of energy resolution when using BGO detector to detect 纬 -ray.In order to explore the effect of temperature on the measurement of large size BGO detectors, we designed and manufactured a simple refrigeration system with our own design.The BGO crystals with sizes of 4 cm 脳 4 cm 脳 3 cm and 6 cm 脳 8 cm 脳 25 cm were cooled successively. The peak position and energy resolution of 纬 spectra were measured by 137Cs source. The dependence of the performance of BGO detectors with temperature was studied.The results show that the peak position of 纬 energy spectrum of BGO detector has a good linear relationship with temperature in the temperature range, and the energy resolution increases with the decrease of temperature.Through this test, we have a certain understanding of the temperature characteristics of BGO, and also accumulate data for the future development of BGO detector array and underground experimental measurements.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P144

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