Neutrino mass study using 100Mo double beta decay with spectroscopic detector MOON

我们开发了用于下一代双β衰变实验的原型探测器MOON-1。该探测器安装在大阪大学核物理研究中心Ohto地下实验室。MOON-1是由6层塑料闪烁片（53平方厘米）和由闪烁片交错的100Mo箔片组成的。闪烁光由环绕在底片周围的60个感光倍增器收集。开发和测量的过程如下。2003年：测试测量；2004年：月球1号探测器的设计与开发；2005年：在地下实验室安装并开始测量。2006年：继续测量。MOON-1在秋天被卸载。2007年：Thst测量。提出了低背景环境下的标定方法。利用背景伽马射线的康普顿散射来评估能量分辨率。能量分辨率是探测器对无中微子双β衰变灵敏度的关键。它是月球一号探测器最重要的休止点之一。在双β衰变的Q值处获得的分辨率为7%（FWHM）。对于如此大的（53平方厘米）塑料闪烁板来说，这是相当好的分辨率。研究了研制新一代双β衰变探测器的背景。

We have developed prototype detector MOON-1 for the next generation double beta decay experiment. The detector is installed at Ohto underground laboratory, Research Center for Nuclear Physics, Osaka University. MOON-1 is six layers of plastic scintillator plates (53cm square) and 100Mo foils interleaved by the scintillator plates. Scintillation light is collected by 60 photo multipliers surrounding the plates. The developments and the measurements were proceeded as the followings.2003: Test measurements2004: Design and development of the MOON-1 detector2005: Install in the underground laboratory and start the measurements.2006: Continue the measurements. MOON-1 was uninstalled in the autumn.2007: Thst measurements.Calibration method in the low background environment is developed. Energy resolution is evaluated using Compton scattering of background gamma rays. Energy resolution is a key in the detector sensitivity for neutrino-less double beta decay. It is one of the most important points to rest MOON-1 detector. The resolution obtained is 7%(FWHM) at the Q value of the double beta decay. It is quite good resolution for such large (53cm square) plastic scintillator plates. The background is studied for developing the next generation double beta decay detectors.