| Project/Area Number |
15340074
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | Osaka University |
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Principal Investigator |
OGAWA Izumi Osaka University, Graduate School of Science, Assistant Professor, 大学院・理学研究科, 助手 (20294142)
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| Co-Investigator(Kenkyū-buntansha) |
KISHIMOTO Tadafumi Osaka University, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (90134808)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥16,000,000 (Direct Cost: ¥16,000,000)
Fiscal Year 2005: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2004: ¥11,200,000 (Direct Cost: ¥11,200,000)
Fiscal Year 2003: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Keywords | Dark Matter / Double beta decay / calcium fluoride |
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| Research Abstract |
We have modified the CANDLES III detector system, which was originally constructed for the study of double beta decay of ^<48>Ca, to search for dark matter candidate WIMPs. The difference between two measurements is the energy range to detect. The energy to detect in dark matter search is below 100 keV, while the Q-value of the double beta decay of ^<48>Ca is 4.3 MeV. The requirements to detect low energy signals in this system are better light collection efficiency, low background environment and good detection efficiency.
1. We developed a new light-guide system which consists of mirror reflector with high reflectivity to get better light collection efficiency. We employed an optimum configuration of photomultipliers, light-guides, and scintillators based on the photon-transportation simulation program which we developed for modified CANDLES III system to detect low energy WIMP recoil signals.
2. We studied the dependence of radioactive impurities density inside the CaF_2 crystals on the raw materials and purchased additional ones which made from selected materials.
3. We studied the dependence of the quenching factor of CaF_2 on the density of doped Eu using neutron beam.
4. To find the cause of the quenching factor dependence, we measured the scintillation emission spectra with various particle beams (γ, proton, Li). We found that the CaF2 scintillators have two components in wavelength and the strength of them was different depending on the incident particle.
5. To detect low energy signals efficiently, we developed an intelligent trigger system which uses photon distribution on time and PMT number.
We are currently studying characteristics of the detector we modified at Osaka University. After that study we will move the detector system to underground laboratory and start data taking.
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