Grant-in-Aid for international Scientific Research
|Allocation Type||Single-year Grants|
|Research Institution||University of Tokyo|
OHASHI Yozo Univ. of Tokyo・ICRR, Associated Professor, 宇宙線研究所, 助教授 (80022599)
LEARNED John University of Hawaii, Professor, 教授
UEHARA Sadaharu National Lab. for HE Phys., Assis. Prof., 助手 (70176626)
SAKUDA Makoto National Lab. for HE Phys., Assis. Prof., 助手 (40178596)
HAYASHINO Tomoki Tohoku Univ. ・Faculty of Science., Assis. Prof., 理学部, 助手 (10167596)
YAMAGUCHI Akira Tohoku Univ. ・Faculty of Science., Assoc. Prof., 理学部, 助教授 (60004470)
TANAKA Sho Tohoku Univ. ・Faculty of Science., Professor, 理学部, 教授 (70004306)
YAMAMOTO Isao Okayama Science Univ. ・Faculty of Engineering., Assoc. Prof., 工学部, 助教授 (50090220)
KITAMURA Takashi Kinki Univ. ・Inst. Sci. & Tech., Professor, 理工学研究所, 教授 (10013426)
KOBAYAKAWA Keizo Kobe Univ. ・College of Liberal Arts, Professor, 教養部, 教授 (00031287)
MITSUI Kiyomi Univ. of Tokyo・ICRR, Assistant Professor, 宇宙線研究所, 助手 (80013340)
OKADA Atsushi Univ. of Tokyo・ICRR, Assistant Professor, 宇宙線研究所, 助手 (90013341)
|Project Period (FY)
1989 – 1990
Completed(Fiscal Year 1990)
|Budget Amount *help
¥6,300,000 (Direct Cost : ¥6,300,000)
Fiscal Year 1990 : ¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1989 : ¥3,000,000 (Direct Cost : ¥3,000,000)
|Keywords||Cosmic neutrino / Neutrino oscillation / Large-size PMT / Deep sea / Bioluminescence|
1. At the international collaboration meetings scientists from Japan, U. S. and Europe have discussed details of the DUMAND II including a construction schedule. The detector consists of one central string and 8 strings arranged in an octagon with 40m separation. Each string has 24 Optical Modules with 10m spacing. Construction of the first 3 strings at depth of 4,800m, off the Island of Hawaii will be finished till 1992.
2. The main goal of the DUMAND is detection of VHE cosmic neutrino from active objects. Mt. Hopkins group has observed VHE gamma-rays from Crab Nebula at a flux level of 7 x 10^<-11>/cm^2・s (*400GeV). If the observed gamma-ray originates from hadron processes, the DUMAND II will be able to detect neutrino signals from the object. Recently, some theorists have calculated flux of HE neutrinos from diffuse sources, such as Cosmic Strings and Active Galactic Neuclei. Both of these diffuse sources are expected to become dominant and distinguishable from atmospheric neutrino
s at energy from about 10TeV. At FNAL, construction of an intense 150GeV booster is under planning. DUMAND group has presented to FNAL a letter of intent, a long baseline neutrino oscillation project. A distance between DUMAND and FNAL, about 6,200km, is suitable for the study of neutrino oscillation in matter.
3. From experimental results using PMT we found background light due to bioluminescence is effective only in a limited area of each optical detector and can be removed by coincidence method. Using a highly sensitive video camera images of luminous objects were recorded in the deep ocean. Observed data confirmed that intensity of biolight depends strongly on mechanical stimulation. Video records tells us that the flux of luminous objects is much smaller at DUMAND site than near Japan Island.
4. Neutrino events are detected by measuring Cerenkov light emitted by secondary particles in the sea water. Considering background light in the deep ocean, characteristics of DUMAND array such as effective area, angular resolution and false event rate were simulated. A method to discriminate parallel muon events against high energy single muon event was also examined.
5. Optical module is composed of 15" PMT, enclosed in a pressure housing made of glass. By optimizing a cathode shape and a dynode structure, PMT is improved on pulse height and timing resolutions. Associating electronics are designed to match with 1ns digitization, and to record both of pulse height and pulse width of output signals. Less