Influence of neutorons and γ-rays in the underground laboratories for double beta decay experiment

(1)Nemo 3合作正在寻找无中微子双β衰变，以研究亚EV区域的Majorana中微子质量。Nemo 3探测器的建造已经完成，目前该探测器在Frejus地下实验室(实验室，LSM)正常运行。在这项研究中，我们研究了地下实验室中γ射线和中子的通量，这是双β衰变研究的背景。(2)我们报道了用大容量碘化钠(NaI)接种器测量激光测深机中的γ射线通量。由于NaI对γ射线和中子都很敏感，我们使用了不同的屏蔽配置来提取纯γ射线通量。由于期望的计数率很低，目前的实验已经进行了3年多。(3)氡是我们实验最严重的本底来源之一。研制了用于NEMO_3探测器的室内气体等氡浓度测量的高灵敏度测氡仪。

(1) The NEMO 3 collaboration is looking for neutrinoless double beta decays to investigate Majorana neutrino mass in the sub-eV region. Construction of the NEMO 3 detector has been completed, and the detector is now operating normally in the Frejus underground laboratory (Laboratoire de Souterrain de Modane, LSM). In this research, we studied the fluxes of γ-rays and neutrons in the underground laboratory, which are the backgrounds of the double beta decay study.(2) We reported the y-ray flux measurement in the LSM using a large volume sodium iodide (NaI) scitillator. Since NaI is sensitive to both γ-rays and neutrons we used different shielding configurations to extract the pure γ-ray flux. Since the expected counting rate is very low, the present experiment has been carried out for more than 3 years.(3) Radon is known to be one of the most serious origins of background of our, experiment. High sensitive radon detectors are developed for the radon concentration measurement of the chamber gas etc. used for the NEMO 3 detector.