| Project/Area Number |
07044065
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | University of Tokyo |
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Principal Investigator |
OHASHI Yozo Institute for cosmic Ray Research, Univ.of Tokyo, Associate Professor, 宇宙線研究所, 助教授 (80022599)
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| Co-Investigator(Kenkyū-buntansha) |
LEARNED John Univ.of Hawaii, Professor, 天文物理教室, 教授
UEHARA Sadaharu KEK,Assistant Professor, 助手 (70176626)
FUKAWA Mineo KEK,Associate Professor, 助教授 (40044763)
HAYASHINO Tomoki Tohoku Univ., Assistant Professor, 理学部, 助手 (10167596)
YAMAGUCHI Akira Tohoku Univ., Professor, 理学部, 教授 (60004470)
KITAMURA Takashi Kinki Univ., Professor, 総合理工研究所, 教授 (10013426)
KOBAYAKAWA Keizo Fukui Inst.of Tech., Professor, 教養部, 教授 (00031287)
MITSUI Kiyomi Yamanashi Gakuin Univ., Associate Professor, 経営情報学部, 助教授 (80013340)
OKADA Atsushi Univ.of Tokyo, Assistant Professor, 宇宙線研究所, 助手 (90013341)
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| Project Period (FY) |
1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1995: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | Cosmic Neutrino / Deep Ocean Experiment / Light Detector / Pressure Tank |
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| Research Abstract |
*Assembly and test of strings ;
Deep ocean experiment to construct a neutrino telescope at the site, 4800m deep and 30km off the Big Island of Hawaii has been started. The apparatus will finally consist of nine strings. In each string 24 optical sensors are tied at 10m interval and a string controller is placed at the center. The string controller digitizes parallel signals from the optical sensors and translates them to serial signals. Optical sensor modules were fabricated by Japanese group, and the string controllers were prepared by US group. The first three strings were assembled, and calibration and long-run test was completed with one string.
Two years before the first trial for the string deployment at the site was carried out, and it resulted in failure due to water leak into the housing of the string controller. Learning from the string in question recovered from the site, electrical penetrators were improved and more rigorous conditions were imposed to the test program. The housing was renewed, changing materials from original Al to more corrosion resistant Ti. Leak sensors in the housing were exchanged with higher sensitive ones.
*Simulation ;
Neutrino events are very rare, and it is essential to estimate noise effects and to find out methods to select genuine events. Muon is produced by neutrino interaction, which emits Cerenkov light in the transparent medium. In the deep ocean the most severe fake events are produced by atomspheric muons. Zenith angle rheta of an incident particle is restricted as rheta*80ﾟ to select neturino events. Information on pulse height and timing are used to fit muon tracks. Cascade particles associated with muon track and scattering of light in the sea water might lead to misfitting of the track. Simulation shows that time spread of the event is useful to discriminate signals from cascade, and delay time to pick up signals suffered from scattering.
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