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Study of Neutrino and Dark Matter by means of CaF_2

利用CaF_2研究中微子和暗物质

基本信息

批准号：
06452030
负责人：
KISHIMOTO Tadafumi
金额：
$ 4.67万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06452030/
关键词：
Neutrino Double beta decay Dark Matter 二重ベータ崩壊二重ベータ-崩壊

项目摘要

The purpose of this research project is to study Dark Matter and mass of Neutrino by means of CaF_2 detector. Dark matters are strongly suggested to be new particles interacting weakly wiht nuclei. The ^<19>F in the CaF_2 detector has frequent interaction due to its spin thus the dark matter can be detected by obseving its recoil. Since CaF_2 detector has ^<48>Ca it can also be used to study double beta decay of ^<48>Ca which is one of promising methods to study properties of neutrinos.We constructed CaF_2 detector with active and passive shield. The whole system is in operation now. We had severe damage in our detector system due to the big earthquake last year. It has been recovered and we had minimum delay in our research project.It is essential to have low background system to search for above rare process. We achieved quite low background level which is comparable to other laboratories around the world. It should be noted that our detector system resides on the sea level though others are underground. Our future experiment in a underground laboratory is quite hopeful since usually 1 to 2 orders of magnitude of background level reduction is expected. The result was presented at the international symposium on "Weak and Electromagnetic Interactions in Nuclei" WEIN'95. Our achivement is summarized in the following.(1) The detector system has the lowest energy threshold (-3 keV) among similar systems with well studied efficiency and energy resolution.(2) Central CaF2 (Eu) crystal is viewed by pure CaF_2 crystal which act as active shield as well as light guide. It is a first detector which has 4pi active shield.(3) We studied radioactive contamination in the detector and established a way to reduce the background due to alpha emitters.We will be measuring the background level at the sea level until we reach the limit of the system. The we will move the detector to the underground laboratory and start full data taking.

本课题的目的是利用CaF_2探测器研究暗物质和中微子的质量。暗物质被强烈地认为是与原子核弱相互作用的新粒子。CaF_2<19>探测器中的~（14）F由于其自旋而具有频繁的相互作用，因此可以通过观察其反冲来探测暗物质。由于CaF_2探测器中含有^<48>Ca，因此也可以用来研究^ Ca的双β衰变<48>，这是研究中微子性质的一种很有前途的方法。现在整个系统都在运行。由于去年的大地震，我们的探测器系统受到严重损坏。它已经被恢复，我们的研究项目的延迟最小。这是必要的，有低背景系统，以寻找上述罕见的过程。我们达到了相当低的背景水平，与世界各地的其他实验室相当。应该注意的是，我们的探测器系统位于海平面上，而其他探测器系统位于地下。我们未来在地下实验室的实验是很有希望的，因为通常1至2个数量级的本底水平降低是预期的。这一结果已在1995年WEIN国际核弱相互作用和电磁相互作用研讨会上发表。我们的成就总结如下。(1)该探测器系统在类似系统中具有最低的能量阈值（~ 3 keV），具有良好的研究效率和能量分辨率。(2)中心CaF_2（Eu）晶体由纯CaF_2晶体观察，既起主动屏蔽作用，又起导光作用。它是第一个具有4 π主动屏蔽的探测器。(3)我们研究了探测器中的放射性污染，并建立了一种方法来减少由于α发射器造成的背景。我们将在海平面上测量背景水平，直到我们达到系统的极限。我们将把探测器移到地下实验室，开始全面的数据采集。