| 研究実績の概要 |
During the FY2017 we constructed detector systems that will be used to study background in underground Dark Matter experiments. We calibrated the 6LiF:ZnS(Ag) thermal neutron detector and developed the GEANT4 model for it.Since March 2018, the thermal neutron detector is being used to collect physics data at the Kamioka mine observatory. Results of this work were summarized in a full-size paper "A large area detector for thermal neutron flux measurements at the KamLAND site"(8 pages)submitted to the Nuclear Inst. and Methods in Physics Research, A journal.We completed tests of two ion-pulse ionization chambers (Radon detectors). Preamplifier electronics of the Radon detectors was upgraded to improve the energy resolution. The current value (1.9%(FWHM) at 5MeV)allowed to achieve clear separation between alpha-particles emitted by decay of the Rn-222 and its daughters: Po-218, and Po-210. An anti- acoustic shielding that prevents degradation of the data quality during standard operation was built. An air sampling system made of a Pfeiffer Vacuum dry pump controlled by National Instruments modules via the LabVIEW software was prepared. Normal operation of Radon detectors started in April 2018.Since the beginning of year 2018 we collect physics data using a ultra -low background 5-inch NaI(Tl) detector placed into an ultra-low background shielding (15cm of lead and 5cm of the OFHC copper) installed at the Kamioka mine. The fast neutron detector components(a 25L vacuum- tight acrylic tank, liquid scintillator,photomultipliers, CAEN DAQ system, shielding materials) were prepared.
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| 今後の研究の推進方策 |
In accordance with the Research Plan we will continue collection and analysis of physics data using all detectors during the entire FY. We will prepare a full size paper for Nuclear Inst. and Methods in Physics Research, A journal describing the fast neutron detector. The paper will also include a result of the fast neutron flux measurement at the Kamioka mine. In addition, we will start to write one more full size paper that includes results of combined analysis of the physics data. At least one talk will be presented at international conference.
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