| Project/Area Number |
04402005
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
核・宇宙線・素粒子
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| Research Institution | The University of Tokyo |
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Principal Investigator |
MINOWA Makoto (1993-1995) School of Science, University of Tokyo, Associate Professor, 大学院・理学系研究科, 助教授 (90126178)
渡邉 隆行 (1992) 東京大学, 理学部, 助手 (80202414)
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| Co-Investigator(Kenkyū-buntansha) |
蓑輪 眞 東京大学, 理学部, 助教授 (90126178)
大塚 洋一 東京大学, 低温センター, 助教授 (50126009)
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| Project Period (FY) |
1992 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥36,200,000 (Direct Cost: ¥36,200,000)
Fiscal Year 1995: ¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1994: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1993: ¥20,000,000 (Direct Cost: ¥20,000,000)
Fiscal Year 1992: ¥12,800,000 (Direct Cost: ¥12,800,000)
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| Keywords | dark matter / bolometer / supersymmetry / neutralino / cryogenic detector / thermistor / fluorine / ボロメータ / 極低温 / 検出器 / 暗黒物質 / 二重ベータ崩壊 |
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| Research Abstract |
A dedicated dilution refrigerator has been constructed. It is capable of cooling the detector material down to 10mK.It is made of specially selected raw materials to reduce natural radiation background from them.
In order to manufacture thermistors with high sensitivities at low temperature, neutron transmutation doping method was adopted.Neutron irradiation has been done at the JRR-3 reactor of the Japan Atomic Energy Reasearch Institute.
Using these building elements, we developed cryogenic particle detectors consisting of 8 pieces of 20-gram lithium fluoride bolometers. The lithium fluoride is known to be the material which has the largest cross section for the detection of spin dependently interacting supersymmetric neutralinos. With these detectors a direct experimental search for supersymmetric particle dark matter has been performed and is still ongoing in the Nokogiri-yama underground cell of the institute for the Cosmic Ray Research, University of Tokyo.
On the basis of a pilot run, limits were obtained on normalized point-like cross section for the spin-dependently interacting neutralino incident on a single proton, although the dark matter is not yet deiscovered.While the shielding against back-ground radiation is not fully optimized yet, our search gave the worls best limits for the spin-dependently interacting neutralino with a mass lower than 5 GeV.It demonstrates the advantages of using the fluorine for the target and the low energy threshold of the bolometer. Thwe search continues with the improved shielding and more efficient veto counters.
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