Development of the high sensitive radon detector and removement of radon from the pure water at the Kamiokande Experiment

开发高灵敏度氡气探测器并在神冈实验中去除纯水中的氡气

基本信息

批准号：
07454049
负责人：
TASAKA Shigeki
金额：
$ 3.97万
依托单位：
Gifu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07454049/
关键词：
Radon High sensitive radon detector SUPERKAMIOKANDE experiment Solar neutrino Earthquake prediction technique Kobe Earthquake Pre-seismic radon concentration increase 超高感度ラドン検出器 Radon KAMIOKANDE Pure water Radon free air

项目摘要

Radon dissolved in the pure water form a strong background component in the Superkamiokande detector. Low energy background for solar neutrino observation is dominated by beta-decay electrons from ^<214>Bi, being a daughter from ^<222>Rn. Advantage of the Superkamiokande is that the recoil electron energy spectrum can be measured with a threshold of 5 MeV.In order to attain a 5 MeV threshold, the radon concentration in the pure water should be finally decreased to the value of 0.005(Bq/m^2). It is essential to remove the small particles by the water purificatin system, and to monitor continuously the changes of the radon concentration in the pure water and the radon free air. We developed an electrostatic collection of the high sensitive radon detector with PIN photodiode. The new radon detector is capable of measuring radon concentration down to 0.001(Bq/m^3) with high stabitity.The observed results of groundwater radon concentration at a well located in Nishi-nomiya city showed that our technique is valid for earthquake prediction. The observation well is 17m deep and is located about 30km northeast of the hypocenter of the magnitude (M) 7.2 the Kobe earthquake that occurred at 17 January 1995. A significant increase in the radon concentration was reacheded to be about ten times on 7 January. After the earthquake, we repaired the radon monitoring system and started the observation again on 22 January, by which time the radon concentration had returned to the pre-October 1994 level.

溶解在纯水中的氡气在 Superkamiokande 探测器中形成强烈的背景成分。太阳中微子观测的低能背景主要是来自^<214>Bi的β衰变电子，它是^<222>Rn的子体。 Superkamiokande的优点是可以在5 MeV阈值下测量反冲电子能谱。为了达到5 MeV阈值，纯水中的氡气浓度最终应降低至0.005(Bq/m) ^2）。必须通过水净化系统去除微小颗粒，并连续监测纯水中和无氡空气中氡浓度的变化。我们开发了一种带有PIN光电二极管的静电采集高灵敏度氡气探测器。新型氡气探测器能够以高稳定性测量低至0.001(Bq/m^3)的氡气浓度。西宫市地下水井的氡气浓度观测结果表明，我们的技术对于地震预测是有效的。该观测井深17m，位于1995年1月17日发生的神户7.2级地震震源东北约30公里处。1月7日，氡气浓度显着增加，达到约10倍。地震发生后，我们修复了氡气监测系统，并于1月22日重新开始观测，此时氡气浓度已恢复到1994年10月前的水平。