中国暗物质探测实验液氩反符合探测器闪烁光特性研究

发布时间：2018-01-13 01:04

本文关键词：中国暗物质探测实验液氩反符合探测器闪烁光特性研究　出处：《清华大学》2013年硕士论文　论文类型：学位论文

【摘要】：暗物质探测是粒子物理学、天体物理学和宇宙学的重大前沿课题之一，国际上通常采用直接探测法探测暗物质候选粒子WIMP。中国暗物质实验（CDEX）以高纯锗晶体作为主探测器，液氩作为反符合探测器介质，探测WIMP粒子。辐射与液氩相互作用会产生波长128nm左右的闪烁光，CDEX液氩探测器以此为探测信号。多种因素会影响液氩探测器的特性，进而影响液氩探测器的反符合效率。CDEX实验需要获得液氩探测器的特性参数，寻找相应改进方法。本论文通过设计并建立液氩/氩气探测特性测试平台，进行了相关实验。通过光电倍增管的单光电子响应实验，获得297K和77K温度下，9357KB随高压变化的绝对增益值。验证在聚四氟乙烯表面蒸镀TPB的效果，结果表明TPB实现了波长转换的功能，但由于转换效率影响，峰位计数减少。进行了三种纯度氩气的闪烁光信号对比，纯度分别为99.999%，99.9999%和99.99999%，结果表明氩气的纯度越高，闪烁光产额越大。利用双成分函数和三成分函数对闪烁光信号的平均波形进行拟合，得到在双成分函数情况下：快成分衰减时间11.75-15.62ns，慢成分衰减时间239.34-973.54ns，快慢成分比例0.30-0.11；三成分函数情况下：快成分衰减时间10.09-10.92ns，慢成分衰减时间564.72-1852.27ns，“中间成分”衰减时间75.37-95.09ns，快慢成分比例0.22-0.07。慢成分衰减时间随着氩气纯度的升高而显著提升，具有由于监测液氩纯度的可行性。获得了99.999%纯度液氩的闪烁光信号，在双成分函数拟合情况下：快成分衰减时间19.33ns，，慢成分衰减时间211.40ns，快慢成分比例0.26。解决了因氩气的帕邢定律导致的光电倍增管base板打火损坏问题，为CDEX实验提供了经验。
[Abstract]:Dark matter detection is one of the most important frontier topics in particle physics, astrophysics and cosmology. In the world, we usually use direct detection method to detect dark matter candidate particle WIMP.China dark matter experiment (CDEXX) uses high purity germanium crystal as main detector and liquid argon as anti-coincidence detector medium. Detection of WIMP particles. The interaction between radiation and liquid argon will produce a scintillation laser detector with a wavelength of about 128 nm as the detection signal. Many factors will affect the characteristics of the liquid argon detector. In order to influence the anti-coincidence efficiency of the liquid argon detector, the characteristic parameters of the liquid argon detector should be obtained in the CDEX experiment, and the corresponding improvement method should be found. In this paper, we designed and established the liquid argon / argon gas detection test platform, carried out the related experiments. Through the photomultiplier tube single photoelectron response experiment, we obtained 297K and 77K temperature. The absolute gain value of 9357KB changed with high pressure. The effect of TPB on PTFE surface was verified. The results showed that TPB realized the function of wavelength conversion, but because of the effect of conversion efficiency. The peak counting was reduced. The scintillation signals of three kinds of pure argon were compared. The purity was 99.9999% and 99.9999 9, respectively. The results showed that the purity of argon was higher than that of argon. The larger the yield of scintillation light is, the more the twinkling signal waveform is fitted by using the double component function and the three component function, and the fast component attenuation time is 11.75-15.62ns in the case of double component function. The attenuation time of slow component is 239.34-973.54ns, the ratio of fast and slow component is 0.30-0.11; In the case of three-component function, the fast component decay time is 10.09-10.92 ns, and the slow component attenuation time is 564.72-1852.27ns. The attenuation time of "intermediate component" is 75.37-95.09ns and the ratio of fast and slow component is 0.22-0.07.The attenuation time of slow component increases with the increase of argon purity. Because of the feasibility of monitoring the purity of liquid argon, the scintillation light signal of 99.999% pure liquid argon was obtained. Under the condition of two-component function fitting, the fast component decay time was 19.33ns. The attenuation time of slow component is 211.40 ns and the ratio of fast and slow component is 0.26. The problem of fire damage of photomultiplier tube base plate caused by Paxing law of argon gas is solved. It provides experience for CDEX experiment.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：P145.9

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