由中子捕获产生的三维氘轨迹测量
3D-Deuteron Track Recoils Produced by Neutron Capture in Hydrogen Measured by MIMAC-35 cm
AI总结：
利用MIMAC-35 cm探测器测量氢中中子捕获产生的氘轨迹，通过三维轨迹和电离能量区分核 recoil 与电子 recoil 背景，发现1.3 keV氘轨迹。
摘要：
中子捕获是大多数用于构建探测器的核素所涉及的过程。该过程产生质子、α粒子和伽马射线，生成背景信号。表征此背景对稀有事件搜索至关重要，如暗物质检测或相干弹性中微子-核散射（CEvNS）。本文介绍了使用新的微型TPC矩阵室（MIMAC-35 cm）探测器直接测量氢中热中子捕获的结果。数据收集超过5天（443519秒），使用30 mbar的气体混合物：70%异丁烷（C4H10）和30%三氟甲烷（CHF3）。我们的鉴别方法基于使用三维轨迹和释放的电离能量，以区分核 recoil（NR）与主导的电子 recoil（ER）背景。该方法使能够清晰识别由核捕获反应1H(n, γ)2H产生的1.3 keV氘轨迹。我们观察到51个中子捕获事件，其中大部分由实验室地面房间中的muons产生。同时我们使用BF3探测器测量了热中子通量，并进行了模拟以估计预期的捕获数量。本工作展示了MIMAC在无任何屏蔽情况下对低能（E < 1 keV）稀有事件的鉴别能力。
英文摘要：
The neutron capture is a process that concerns most of the nuclei used to build our detectors. This process produces protons, alpha particles, and gamma rays which generate background signals. Characterizing this background is important for rare event searches, such as dark matter detection or Coherent Elastic Neutrino-Nucleus Scattering (CEvNS). This paper presents the result of the direct measurement of thermal neutron captures in hydrogen using a new MIcro-TPC MAtrix Chamber (MIMAC-35 cm) detector with a sensitive volume of 35 x 35 x 29 cm3. Data were collected over more than 5 days (443519 sec) with a gas mixture at 30 mbar of 70% isobutane (C4H10) and 30% trifluoromethane (CHF3). Our discrimination method is based on using 3D tracks and released ionization energy, in order to discriminate nuclear recoils (NR) from the dominant electron recoil (ER) background. This method enables the clear identification of 1.3 keV deuteron tracks resulting of nuclear capture reaction 1H(n, γ)2H. We observed 51 neutron capture events among more than 11 million total events mainly produced by muons in the experimental room of our ground laboratory. In parallel we have measured the thermal neutron flux just below the chamber with a BF3 detector and a simulation has been performed to estimate the number of captures expected. This work shows the discrimination power of MIMAC search for low-energy (E < 1 keV) rare event with a huge background without any shielding.
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