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Oral presentation

Neutron induced reaction and Re/Os cosmochronometer, 3

Segawa, Mariko; Nagai, Yasuki*; Masaki, Tomohiro*; Shima, Tatsushi*; Makii, Hiroyuki; Mishima, Kenji*; Ueda, Hitoshi*; Temma, Yasuyuki*; Igashira, Masayuki*; Osaki, Toshiro*; et al.

no journal, , 

no abstracts in English

Oral presentation

$$sigma$$$$_{E2}$$ and $$sigma$$$$_{E1}$$ of the $$^{12}$$C($$alpha$$, $$gamma$$)$$^{16}$$O reaction obtained at E$$_{cm}$$ = 1.6 and 1.4 MeV

Makii, Hiroyuki; Nagai, Yasuki*; Shima, Tatsushi*; Segawa, Mariko; Ueda, Hitoshi*; Masaki, Tomohiro*; Mishima, Kenji*; Igashira, Masayuki*; Osaki, Toshiro*

no journal, , 

no abstracts in English

Oral presentation

Nuclear astrophysics study with pulsed neutrons

Segawa, Mariko; Nagai, Yasuki*; Masaki, Tomohiro*; Temma, Yasuyuki*; Shima, Tatsushi*; Mishima, Kenji*; Igashira, Masayuki*; Goriely, S.*; Koning, A.*; Hilaire, S.*

no journal, , 

The $$^{187}$$Re nucleus is known to be a good chronometer to derive the stellar duration of the r-process nuceosyntheis and deduce the age of universe. However, there are several problems inherent to this chronometer. In order to solve these problems, one must know both the production and depletion rates (via the excited state as well as the ground state) of $$^{187}$$Os and inelastic scattering cross section off the ground state (J$$^{pi}$$= 1/2$$^{-}$$) of $$^{187}$$Os to its excited 10 keV state (J$$^{pi}$$= 3/2$$^{-}$$) are needed. Hence, in the present study we aimed to accurately measure the neutron capture cross sections of $$^{186}$$Os, $$^{187}$$Os and $$^{189}$$Os, and the inelastic scattering cross section for $$^{187}$$Os for neutrons between 10 and 90 keV by developing a new experimental method.

Oral presentation

Neutron induced reaction and Re/Os chronometer

Segawa, Mariko; Nagai, Yasuki*; Masaki, Tomohiro*; Temma, Yasuyuki*; Shima, Tatsushi*; Makii, Hiroyuki*; Mishima, Kenji*; Ueda, Hitoshi*; Nakayoshi, Akira*; Ota, Takeshi*; et al.

no journal, , 

$$^{187}$$Re-$$^{187}$$Os pair is known as the most promising nuclear cosmochronometer with considerable potential. However, there remains non-trivial problems related to an excited neutron capture reaction of $$^{187}$$Os at a stellar temperature. Firstly, $$^{187}$$Os is produced and depleted by the slow process nucleosynthesis. Hence, it is necessary to obtain both the production and depletion rates of $$^{187}$$Os. Secondly, $$^{187}$$Os is depleted not only by its ground state neutron capture reaction but also by an excited state neutron capture reaction of $$^{187}$$Os in a stellar temperature. In the present study, we have measured the neutron capture reaction cross sections for $$^{186}$$Os, $$^{187}$$Os and $$^{189}$$Os accurately and neutron inelastic scattering reaction cross section for $$^{187}$$Os off the ground state of $$^{187}$$Os to its 9.75-keV first excited statein the neutron energy range from 10 to 100 keV. The measurements of the neutron capture reactions have been carried out by detecting a prompt $$gamma$$-ray by means fan anti-Compton NaI(Tl) spectrometer. The (n, n') reaction cross section for $$^{187}$$Os has been measured with use of four $$^{6}$$Li-glass scintillation detectors. Based on these new capture cross sections, we reestimate on the basis of a careful reaction cross section calculation the correction factor F for the neutron capture on the 9.75-keV first excited state in $$^{187}$$Os as a function of stellar temperature, as required to derive the age of the galaxy within the Re-Os chronology.

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