1997 Fiscal Year Final Research Report Summary
DEVELOPMENT OF LOW-BACKGROUND LOW-ENERGY BETA-RAY DETECTOR AND ESTIMATION OF FAST NEUTRON FLUENCE OF ATOMIC BOMB
| Project/Area Number |
08454063
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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 |
素粒子・核・宇宙線
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| Research Institution | HIGH ENERGY ACCELERATOR RESEARCH ORGANIZATION (1997)
The University of Tokyo (1996) |
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Principal Investigator |
SHIBATA Tokushi HIGH ENERGY ACCELERATOR RESEARCH ORGANIZATION(KEK), PROFESSOR, 放射線科学センター, 教授 (80028224)
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| Co-Investigator(Kenkyū-buntansha) |
NOGAWA Norio UNIVERSITY OF TOKYO,ISOTOPR CENTER,RESEACHER, アイソトープ総合センター, 助手 (60208311)
NAKAO Noriaki KEK,RESEARCHER, 放射線科学センター, 助手 (80272524)
ITOH Yutaka KEK,RESEARCHER, 放射線科学センター, 助手 (50300679)
MASUMOTO Kazuyoshi KEK,ASSOCIATE PROFESSOR, 放射線科学センター, 助教授 (60124624)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Beta-ray detector / Low-background detector / Fast neutron for atomic bomb |
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| Research Abstract |
The final of this project is to estimate the fast neutron fluence for the Hiroshima atomic bomb. To accomplish the object we develop a low-background low-energy beta-ray detector and measured the energy dependent cross section of the ^<63>Cu(n, p)^<63>Ni reaction then we measured the copper samples. We got the following results.
(1) Detector development
A low-background low-energy beta-ray detector was developed using small CaF_2(Eu) crystals. The background rate was 2.2*10^<-3>cps and the detection efficiency for ^<63>Ni was 20%. This performance is enough for the detection of ^<63>Ni in samples exposed by the Hiroshima atomic bomb.
(2) Excitation function for the ^<63>Cu(n, p)^<63>Ni reaction
The cross section for the ^<63>Cu(n, p)^<63>Ni reaction was obtained by measuring beta-ray from ^<63>Ni extracted chemically from copper targets irradiated by neutrons. The obtained results agree well calculated values given in GENDL-3 in low-energy region.
(3) Measurement of copper samples
The fast neuron fluence was obtained at 100 m from the hypocenter by measuring ^<63>Ni in electric wire. We get only upper limits which is much smaller fluence given by DS86. This is the first measurements for the fast neutron for the Hiroshima atomic bomb except the early only one measurement of ^<32>P
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