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稀有事例探测是近几年热门的粒子物理前沿课题, 如暗物质、无中微子双贝塔衰变、中微子-核子相干弹性散射等实验都在逐渐被规划和实施. 进行稀有事例探测要求探测器有极佳的性能, 同时对环境本底有很高的要求, 因此探测器和相关材料的选择是稀有事例探测的一个重要课题. 液氩因为成本低、闪烁性能好、体积限制较小等优势成为稀有事例探测器的一种重要介质. 经过几十年的发展, 单相液氩闪烁体探测器和两相氩时间投影室成为两种常见的液氩探测器类型, 并开始被国内外各实验组应用于稀有事例探测实验中. 本文首先对两种常见的液氩探测器的原理和特性进行介绍, 然后详细介绍国内外相关稀有事例探测实验组对液氩探测器的研究和应用现状以及未来规划, 最后讨论未来液氩探测器在稀有事例探测中的应用前景和优化方向.Rare event detection is a frontier subject in particle physics and nuclear physics. In particular, dark matter detection, neutrino-free double beta decay and neutrino-nucleon coherent elastic scattering are being planned and implemented gradually. Rare event detection requires not only the detectors to possess excellent performances but also extremely low environmental background, so the selection of detectors and related materials is an important issue in rare event detection. Liquid argon has become an important scintillator material for scintillator detectors because of its low cost, good scintillation performance and large volume. Liquid argon was first studied in the 1940s as a sensitive material for ionizing radiation detectors. The first measurements of high-energy beta particles were obtained by using a liquid argon ionization chamber in 1953. The ICARUS group put forward the idea of constructing liquid argon temporal projection chamber, and made attempt to construct liquid argon temporal projection chamber in 1977. The scintillation light signals were collected for the first time in a liquid argon temporal projection chamber in 1999. Thus, the drift time of the particle can be obtained to determine the particle track. After development, single-phase liquid argon scintillator detector and two-phase argon time projection chamber have become two common types of liquid argon detectors, and have been extensively used in rare event detection experiments in recent years. For dark matter detection, the DEAP group and DarkSide group have achieved good results with single-phase liquid argon scintillation detector and two-phase argon time projection chamber, respectively. For neutrino-free double beta decay experiments, the GERDA group has done a lot of researches of liquid argon anti-coincidence system and applied the said system to experiments. The LEGEND group, which is the combination of GERDA and MAJORANA experimental group, upgraded the liquid argon anti-coincidence system which was applied to the following LEGEND-200 project. For neutrino-nucleon elastic scattering experiments, COHERENT obtained the latest results by using the liquid argon detectors. The Taishan neutrino-nucleon coherent elastic scattering project of the High Energy Institute of Chinese Academy of Sciences has also begun to study the feasibility of liquid argon anti-coincidence system. Finally, this paper discusses the direction of optimizing the liquid argon detector, such as exposure, background level and optical readout scheme, and gives a good prospect of liquid argon detector applied to rare event detection in the future.
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液态惰性气体探测器 高纯锗探测器 极低温量热器 液氩探测器 液氙探测器 优势 成本低, 有粒子甄别能力,
探测效率高有粒子甄别能力,
探测效率高低阈值, 极高能量分辨率 高能量分辨率,
有粒子甄别能力缺点 能量分辨率相对较低 成本较高, 能量
分辨率相对低成本较高, 探测器生产
工艺复杂, 单个晶体
质量增加困难需要极低温环境
(mK量级)
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闪烁特性相关物理量 符号 数值 光产额/(光子·keV–1) Y 41±2 发光峰值波长/nm λmax 128 单态时间常数/ns τs 6 三重态时间常数/μs τt 1.59 β事件快慢成分比 Is/It(e–) 0.3 α事件快慢成分比 Is/It(α) 1.3 裂变碎片事件快慢成分比 Is/It(ff) 3 下载:
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实验组
名称稀有事例
探测类型探测器类型 液氩探测
器质量光读出 运行状态 主要特点 DEAP 暗物质 单相液氩闪烁体 3260 kg PMT+光导 运行中 较早采用液氩为介质探测暗物质 WArP 暗物质 两相氩TPC 140 kg PMT 已结束 最早尝试用TPC探测暗物质 DarkSide 暗物质 两相氩TPC 46.4 kg PMT 运行中 地下氩、中子反符合 GERDA 0νββ 高纯锗探测器+单相液氩
闪烁体(反符合)1400 kg SiPM+光
纤/PMT已结束 系统地研究液氩反符合
系统并应用LEGEND 0νββ 高纯锗探测器+单相液氩
闪烁体(反符合)— SiPM+光纤 建设中 实验组合并, 新的读出方案研究 COHERENT CEνNS 单相液氩闪烁体 79.5 kg PMT 运行中 第一个尝试用液氩探测器探测CEνNS事例 Taishan CEνNS 两相氩TPC+单相液氩闪
烁体(反符合)200 kg PMT 建设中 尝试用液氩探测器作为CEνNS
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实验组名称 39Ar本底抑制 其它本底抑制 氩纯度监测和稳定 光读出方案升级 DEAP 利用液氩的粒子甄别能力扣除 水切伦科夫探测器抑制μ子 氡捕集阱去除放射性杂质 — DarkSide 地下氩生产技术应用 水切伦科夫探测器抑制μ子, 载硼或载钆液闪抑制中子 同时进行去除电负性
杂质和氩同位素分离SiPM低温稳定读出和紫外
波段直接读出技术研究GERDA — 水切伦科夫探测器抑制μ子, 液氩探测器抑制其他本底 — SiPM+光纤读出 LEGEND 地下氩生成技术研究 水切伦科夫探测器抑制μ子, 液氩探测器抑制其他本底 液氩纯度监测仪 SiPM+光纤双端读出 Taishan 地下氩生产技术研究 塑料闪烁体抑制μ子, 液氩探测器抑制其他本底 — SiPM低温稳定读出技术研究 下载:
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