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2000 Fiscal Year Final Research Report Summary

Precise measurement of stellar reaction rate of ^<12>C(α, γ)^<16>O with new experimental methods

Research Project

Project/Area Number 11440077
Research Category

Grant-in-Aid for Scientific Research (B).

Allocation TypeSingle-year Grants
Section一般
Research Field 素粒子・核・宇宙線
Research InstitutionOsaka University

Principal Investigator

SHIMA Tatsushi  Research Center for Nuclear Physics, Osaka University, Research Associates, 核物理研究センター, 助手 (10222035)

Co-Investigator(Kenkyū-buntansha) OHSAKI Toshiro  Research Laboratory for Nuclear Reactors, Tokyo Inst.Tech., Research Associates, 原子炉工学研究所, 助手 (80262327)
IGASHIRA Masayuki  Research Laboratory for Nuclear Reactors, Tokyo Inst.Tech., Assistant Prof., 原子炉工学研究所, 助教授 (10114852)
NAGAI Yasuki  Research Center for Nuclear Physics, Osaka University, Professor, 核物理研究センター, 教授 (80028240)
Project Period (FY) 1999 – 2000
KeywordsNuclear astrophysics / Star / Nucleosynthesis / Helium-burning / ^<12>C(α, γ)^<16>O
Research Abstract

The ^<12>C(α, γ)^<16>O reaction plays crucial roles in stellar He-burning, because it governs ^<12>C/^<16>O ratio after core He-burning, abundances of intermediate-mass nuclei produced in He-burning, and the iron core mass just before the type-II supernova explosion. Therefore it is quite important to determine the reaction rate at the center-of-mass energy Ecm<1 MeV, which corresponds to the temperature of stellar interior.
In order to determine the reaction rate accurately, we developed a new experimental method using a pulsed α beam and the prompt γ-ray detection technique.
In 1999 we developed a measurement system, consisting of a high-sensitivity and low-background γ-ray spectrometer and a 2ns pulsed α beam. We carried out a test experiment to check the performance of the system, and found major background is caused by the fast neutrons, which are produced by the (α, n) reactions on boron isotopes contained in the carbon target.
Therefore, in 2000, we made efforts to reduce the backgrounds due to those neutrons. We changed the material of the target chamber from stainless steel to aluminum, which has a small (n, γ) cross section. Here the λ rays from the (n, γ) reactions occurring near the target is quite dangerous, because the area around the target is directly viewed by the γ-ray detectors. With the above improvement, we could obtain the S/N ratios better than 18 and 360 with a natural carbon target and an enriched ^<12>C target, respectively. With the present result, it is expected that the ^<12>C(α, γ)^<16>O cross section can be measured accurately down to Ecm 〜900keV.
In addition, we designed another new method, which measures the inverse reaction, i.e. the ^<16>O(γ, α)^<12>C reaction. In this method, we will use a laser-Compton backscattered γ-ray beam and a time projection chamber filled with CO_2 gas. We made an experimental plan, and proposed it to U.S.DOE.

  • Research Products

    (6 results)

All Other

All Publications (6 results)

  • [Publications] H.Makii,K.Mishima,T.Shima et al.: "A new experimental system for the ^<12>C(α,γ)^<16>O reaction in the MeV region"Nuclear Instruments and Methods in Physics Research A. (in press). (2001)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Shima,H.Makii,K.Mishima et al.: "New project of the ^<12>C(α,γ)^<16>O experiment"Proceedings of Int.Symp.on Origin of Matter and Evolution of Galaxies. 176-181 (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T.Kii,T.Baba,T.Takahashi et al.: "^<16>O(γ,α)^<12>C reaction using monochromatic gamma ray"Proceedings of Int.Symp.on Origin of Matter and Evolution of Galaxies. 374-377 (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] H.Makii, K.Mishima, T.Shima, Y.Nagai, E.Sano, M.Igashira, T.Ohsaki and K.Tosaka: "A new experimental system for the ^<12>C(α, γ)^<16>O reaction in the MeV region"Nuclear Instruments and Methods in Physics Research A. (in press). (2001)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] T.Shima, H.Makii, K.Mishima, T.Kii, T.Takahashi, T.Baba, Y.Nagai and M.Igashira: "New project of the ^<12>C(α, γ)^<16>O experiment"Proceedings of Int.Symp.on Origin of Matter and Evolution of Galaxies 97, Ed.S.Kubono et al., World Scientific. 176-181 (1998)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] T.Kii, T.Baba, T.Takahashi, T.Shima and Y.Nagai: "^<16>O(γ, α)^<12>C reaction using monochromatic gamma ray"Proceedings of Int.Symp.on Origin of Matter and Evolution of Galaxies 97, Ed.S.Kubono et al., World Scientific. 374-377 (1998)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 2002-03-26  

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