| Project/Area Number |
04452028
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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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 | TOKYO UNIVERSITY OF INFORMATION SCIENCES |
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Principal Investigator |
WATANABE Tadashi TOKYO UNIVERSITY OF INFORMATION SCIENCES,DEPARTMENT OF INFORMATION SYSTEMS,PROFESSOR, 経営情報学部, 教授 (20030786)
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| Co-Investigator(Kenkyū-buntansha) |
EBISU Takeo KOBE UNIVERSITY,DEPARTMENT OF PHYSICS,ASSISTANT, 理学部, 助手 (50090543)
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| Project Period (FY) |
1992 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥6,200,000 (Direct Cost: ¥6,200,000)
Fiscal Year 1994: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1993: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1992: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Keywords | Cryogenic particle detector / Dark matter / Photoelectric effect / Flip-flop phenomenon / Local heating / Superheated superconduction |
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| Research Abstract |
We have carried out a project of constructiog a cryogenic particle detector, which can be applied for the detection of dark-matter particles in cosmic rays and/or neutrinos, using a collection of superheated superconducting tin micro granules as a target set up in the detector.
1.Responses of tin granules in 200micron diameter to alpha rays at 2 kelvins :
It turned out that the single granule is sensitive to several-million-electron-volt energies deposited by an incident alpha particle.
2.Responses of tin granules in 30micron diameter to gamma rays at 30mK :
We were able to measure spectre lines of the energy absorption due to the photoelectric effect for the K-and L-shell electrons in tin atoms irradiated with gamma rays of 60keV.The absorption rates are consistent with roughly-calculated values. The heat energy induced by ionized electrons in the single granule was detected up to less than lkeV.
3.Measurements of the flip-flop phenomenon :
It is expected that a granule not only flips from a superconduting state to a normal conducting state receiving a sufficient heat energy, but also flops vice versa at a sufficiently low temperature. In this case, the state of a granule traces along a hysteresis curve in the phase diagram in magnetic field-magnetization. Precise measuremets showed that the condition for the phenomenon to take place depends critically on the thermal property of the material of a granule. The phenomenon turned out not to manifest itself in the case of tin of which thermal property is explained on the basis the local-heating picture.
4.A prototype detector :
The detector has a l-gram target consisting of a collection of 30micron tin granules set up set up at a temperature of a dilution refrigerator. A test run will start soon.
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