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

在环境和检测器本身中，基础实验的主要背景源（例如寻找双β衰减的搜索）被认为是放射性材料，特别是托隆的女儿核心， ^<208> t1。为了测量这种污染，通常使用具有辐射敏感性或检测极限的大体积静电收集型检测器通常使用10 MBQ/M^3的检测极限。例如，例如，使用漂移室进行实验构型，在填充气体中对放射性污染的测量至关重要，目前的检测器似乎在估计ra和ra和气体中的托隆量似乎很有用。为了了解这种类型的检测器，我们研究了1个垃圾量检测器的一般行为。它的构造是一个能够使外部空气从底部放置的SUS容器，并将其固定在负电势的销光电二极管安装在内部容器的顶部……更多r。将放射活性离子（例如polonium和Bismuth）收集到二极管表面，并检测到它们的α衰变，因为该测量值首先将探测器置于大丙烯酸容器中，其次是从外部空气中分离出来的。与上述大型检测器和准备好的源相比，指定子核的准确性较差。我们的测量精度为3-4％。但是，目前的检测器将更容易处理，以获取与其性能相关的各种信息。女儿核（例如 ^<218> po）可能通过与氧气反应来使阳性呈阳性。这些离子还倾向于粘附水分子，因此由于寿命效应而被检测到离子可能会丢失。 Chu and Hopke过去研究了这种行为，我们通过离子的迁移率降低来考虑这一点。我们对α颗粒产量的温度依赖性的测量与预期的行为以及过去的结果非常吻合。尽管目前的结果仅是水蒸气的，但对于酒精蒸气来说，这是驾驶员中常见的淬火气体。腔室。对于室内气体中的thor系列污染，需要更仔细的研究，以评估短寿命 ^<208> t1核的β衰变。另一个观察结果是稀有气体的环境。我们已经使用地幔执行了此操作。氩气环境的检测效率约为氦气的1/4。通过与氩气原子的电荷转移碰撞来考虑该结果。该观察与此假设非常吻合。较少的

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。