MEASUEEMENT OF MINUTE AMOUNT OF RADON AND TORON CONTAMINATION IN THE CHAMBER GAS FOR USE IN THE DOUBLE BETA DECAY EXPERIMENT

双 β 衰变实验用室气体中氡气和 Toron 污染微量的测量

• 批准号: 14540270
• 负责人: KOBAYASHI Shigeharu
• 金额: $ 2.18万
• 依托单位: SAGA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14540270/
• 关键词: radon; toron detector; half-life measurement; humidity effect; toron in noble gas; 二重ベータ崩壊; ラドン; トロン; 静電捕集; 露点計; ドリフトチェンバー; GEM; 静電捕集型測定機; ラドン・トロン; 湿度計; 短寿命核種; マントル; シンチレーションファイバー; PET; 2重β崩壊; 微量ラドン・トロンの測定; 検出効率と湿度; 水分子の静電付着; ラドンとトロ

The major background source in the underground experiments, such as a search for the double beta decay, is recognized as the radio-active materials, specifically the daughter nucleus of toron, ^<208>T1, in the environment as well as the detector itself. To measure such contamination, a large volume electrostatic collection type detector having radon sensitivity, or the detection limit, of the order of 10 mBq/m^3 is commonly used. In case, for example, of an experimental configuration utilizing a drift chamber, the measurement of radio-active contamination in the filling gas is crucial the present detector seems to be useful in the estimate of minute amount of the radon as well as the toron in the gas. To understand such type of the detector, we have studied a general behavior of the 1 litter volume detector. Its construction was a SUS container capable to let the external air from the bottom and a PIN photodiode held at a negative potential was mounted at the top of the inside containe … More r. The radio-active ions, such as polonium and bismuth, are collected to the diode surface and their alpha decays are detected as dearly separated several peaks.In this measurement the detector was first housed in a large acrylic vessel, and next was isolated from the external air, and the change of counting rate with time was observed Since our measurements are for the natural radon and a weak toron source of the "mantle", the observed half lives to specify the daughter nuclei were less accurate compared with the case for large detector mentioned above and a prepared source. The precision of our measurement was at 3〜4 % level. However, the present detector would be much easier to handle to get various kinds of information related to its performance. The daughter nuclei such as ^<218>Po is likely to ionize positive by reacting with oxygen. These ions also tend to adhere the water molecules and as a result the ions may be lost before being detected due to the lifetime effect. Such behavior was studied in the past by Chu and Hopke, and we have considered this by the decrease in mobility of the ions. Our measurement of the temperature dependence of alpha particle yield was in good agreement with the expected behavior as well as the past result.Although the present result was only for the water vapor, about the same argument may hold for alcoholic vapor, which is a common quenching gas in the drift chamber. A more careful study will be needed for the thorium series contamination in the chamber gas to evaluate the beta decay of short lived ^<208>T1 nucleus. Another observation was for the environment of rare gases. We have performed this by using a mantle. The detection efficiency in argon gas environment was about 1/4 of the helium gas. This result was considered by a charge transfer collision of the ions with the argon gas atoms. The observation was in good agreement with this assumption. Less

地下实验中的主要背景源，例如寻找双贝塔衰变，被认为是环境中的放射性物质，特别是 toron 的子核，^<208>T1，以及探测器本身为了测量这种污染，通常使用具有10 mBq/m^3量级的氡灵敏度或检测极限的大容量静电收集型检测器，例如在使用漂移室的实验配置的情况下。 ，测量填充气体中的放射性污染至关重要，本检测器似乎可用于估计气体中的氡气和氡气的微量。为了了解这种类型的检测器，我们研究了一般行为。 1 升体积探测器的结构是一个 SUS 容器，能够从底部排出外部空气，并在内部容器的顶部安装一个保持负电势的 PIN 光电二极管。如钋铋，被收集到二极管表面，它们的α衰变被检测为明显分离的几个峰。在这个测量中，检测器首先被安置在一个大的丙烯酸容器中，然后与外部空气隔离，并且计数率的变化由于我们的测量是针对天然氡气和“地幔”的弱氡气源，因此与上述大型探测器和准备好的源的情况相比，观察到的指定子核的半衰期不太准确。我们的测量然而，本检测器将更容易处理以获取与其性能相关的各种信息，诸如^<218>Po的子核可能通过与氧反应而电离正电。这些离子也倾向于粘附水分子，因此，由于寿命效应，离子可能在被检测到之前就丢失了。Chu 和 Hopke 过去研究过这种行为，我们通过流动性的降低来考虑这一点。我们的测量。 α 粒子产率的温度依赖性与预期行为以及过去的结果非常一致。虽然目前的结果仅适用于水蒸气，但对于酒精蒸气（一种常见的淬灭气体）也可能存在相同的论点需要对室内气体中的钍系列污染进行更仔细的研究，以评估短寿命^<208>T1核的β衰变。我们已经对稀有气体环境进行了这项观察。通过使用氩气环境中的检测效率大约是氦气中的1/4。这一结果是通过离子与氩气原子的电荷转移碰撞来考虑的，这一结果与这一假设非常吻合。

项目成果

L.Saha: "Study of DOI Resolution and Imaging Resolution of a PET Device"Nuclear Instrument and Methods in Physical Research. A in press. (2004)

L.Saha：“PET 装置的 DOI 分辨率和成像分辨率的研究”物理研究中的核仪器和方法。

NEMO collaboration, Possible background reduction in double beta decay Experiments

NEMO 合作，双贝塔衰变实验中可能的背景减少

• 发表时间: 2003
• 期刊: Nuclear Instruments and Methods in Physics Research A503
• 作者: H.Ohsumi et al.;NEMO collaboration;R.Arnold et al.
• 通讯作者: R.Arnold et al.

NEMO collaboration, Intitial Runs of NEMO 3 Experiment

NEMO 合作，NEMO 3 实验的首次运行

• 发表时间: 2003
• 期刊: Nuclear Physics(Presented by H.Ohsumi) A721
• 作者: H.Ohsumi et al.;NEMO collaboration;R.Arnold et al.;H.Ohsumi et al.
• 通讯作者: H.Ohsumi et al.

Possible background reduction in Double beta decay experiment

双β衰变实验中可能的背景减少

• 发表时间: 2003
• 期刊: Nuclear Instruments and Methods in Physics Research A 503
• 作者: H.Ohsumi et al.;NEMO collaboration;R.Arnold et al.;H.Ohsumi et al.;H.Ohsumi et al.
• 通讯作者: H.Ohsumi et al.

R.Amold: "Possible Background Reduction in Double Beta Decay Experiments"Nuclear Instrument and Methods in Physical Research. A503. 649-657 (2003)

R.Amold：“双β衰变实验中可能的背景减少”物理研究中的核仪器和方法。