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

点击翻译按钮获取中文摘要

(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.