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Dark matter search by means of high purity CaF_2 scintillators

利用高纯CaF_2闪烁体搜索暗物质

基本信息

批准号：
15340074
负责人：
OGAWA Izumi
金额：
$ 10.24万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-15340074/
关键词：
Dark Matter Double beta decay calcium fluoride

项目摘要

We have modified the CANDLES III detector system, which was originally constructed for the study of double beta decay of ^<48>Ca, to search for dark matter candidate WIMPs. The difference between two measurements is the energy range to detect. The energy to detect in dark matter search is below 100 keV, while the Q-value of the double beta decay of ^<48>Ca is 4.3 MeV. The requirements to detect low energy signals in this system are better light collection efficiency, low background environment and good detection efficiency.1. We developed a new light-guide system which consists of mirror reflector with high reflectivity to get better light collection efficiency. We employed an optimum configuration of photomultipliers, light-guides, and scintillators based on the photon-transportation simulation program which we developed for modified CANDLES III system to detect low energy WIMP recoil signals.2. We studied the dependence of radioactive impurities density inside the CaF_2 crystals on the raw materials and purchased additional ones which made from selected materials.3. We studied the dependence of the quenching factor of CaF_2 on the density of doped Eu using neutron beam.4. To find the cause of the quenching factor dependence, we measured the scintillation emission spectra with various particle beams (γ, proton, Li). We found that the CaF2 scintillators have two components in wavelength and the strength of them was different depending on the incident particle.5. To detect low energy signals efficiently, we developed an intelligent trigger system which uses photon distribution on time and PMT number.We are currently studying characteristics of the detector we modified at Osaka University. After that study we will move the detector system to underground laboratory and start data taking.

我们已经修改了蜡烛III探测器系统，该系统最初是为研究^&lt；48&gt；Ca的双β衰变而建造的，以寻找暗物质候选WIMP。两种测量之间的区别在于要检测的能量范围。在暗物质搜索中探测到的能量低于100keV，而^&lt；48&gt；Ca的双β衰变的Q值为4.3 MeV。该系统对低能量信号的检测要求有较高的光采集效率、较低的背景环境和良好的检测效率。为了获得更好的光收集效率，我们开发了一种由高反射率的镜面反射器组成的新型光导系统。基于我们为改进的Candles III系统开发的光子输运模拟程序，我们采用了光电倍增管、光导和闪烁体的优化配置来探测低能量的WIMP反冲信号。研究了原料对CaF_2晶体内放射性杂质浓度的影响，并对所选原料进行了补充。利用中子束研究了CaF_2猝灭因子与Eu掺杂浓度的关系。为了找出猝灭因子依赖的原因，我们测量了不同粒子束(γ、质子、Li)的闪烁发射光谱。我们发现，CaF2闪烁体在波长上有两个分量，并且它们的强度随入射粒子的不同而不同。为了有效地检测低能信号，我们开发了一种智能触发系统，它利用光子在时间上的分布和PMT数。我们目前正在研究我们在大阪大学改装的探测器的特性。在这项研究之后，我们将把探测器系统转移到地下实验室，并开始采集数据。