2016 Fiscal Year Research-status Report
Search for false signals in underground dark matter detectors
| Project/Area Number |
16K05371
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| Research Institution | The University of Tokyo |
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Principal Investigator |
コズロフ アレキサンドル 東京大学, カブリ数物連携宇宙研究機構, 特任助教 (30528063)
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | Ionization Chamber / Radon Detector / Thermal Neutron Detector |
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| Outline of Annual Research Achievements |
A gas-type Cylindrical Ion-Pulse Ionization Chamber (CIPIC) was constructed during first year of the project (2 units). The CIPIC is made to register α-particles directly from the 222Rn decay in a filled air sample. The energy resolution of a 2.1% (FWHM) was achieved for the 5.49 MeV α-line from the 222Rn decay. It will be further improved after construction of a protective cover against an acoustic noise and vibration. However, already with the currently achieved resolution the 5.49 MeV α-peak is clearly separated from neighbor peaks from decay of 218Po and 210Po. A typical signal amplitude is about 400mV, and duration is about 8ms. Signals from the CIPIC were fed to a 12bit waveform digitizer La-n10-12USB.
The thermal neutron detector was made based on a 0.32mm-thick EJ-426 scintillator sheets (a mixture of LiF and ZnS:Ag ; the Lithium is enriched in 6Li to a 95%; the 6LiF to ZnS:Ag mass ratio is 1:2) produced by Eljen Technology, U.S.A. The thermal neutron detection uses the nuclear reaction 6Li (n,α)3H + 4.78MeV with a cross-section of 941 barns. The light emitted by ZnS:Ag scintillator is detected by a 5-inch Hamamatsu R1250 photomultiplier with wavelength sensitivity that matches well the EJ-426 emission spectrum. Between the EJ-426 sheets and the PMT a light collecting pyramid covered with light reflector sheets (Tyvek paper) was placed. Data acquisition is done using a 14bit CAEN waveform digitizer N6724F.The GEANT4 model of the fast neutron detector (a pseudocumene-based liquid scintillator loaded with 6Li) was prepared.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
All tasks originally listed for FY2016 were accomplished as planned. Furthermore, a second Cylindrical Ion-Pulse Ionization Chamber was assembled and tested ahead of the original schedule. That makes possible to focus on construction of the fast neutron detector and on improvement of algorithms for analysis of the data from the CIPIC radon detectors during FY2017
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| Strategy for Future Research Activity |
All research may continue as originally planned. No essential changes to the Research Plan are needed
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