Y. Temma

62Ni(n, γ)63Ni Reaction and Overproduction of Ni Isotopes

The neutron capture cross section of 62Ni has been measured in the energy range from 5.5 to 90 keV by employing a prompt discrete γ-ray detection method with the use of an anti-Compton NaI(Tl) spectrometer. The Maxwellian-averaged capture cross section at 30 keV is derived as being 37.0 ± 3.2 mbarn, 3 times larger than the value currently used for the nucleosynthetic yield estimations in massive stars. The result could provide crucial information for the long-standing problem of the largest overproduction of 62Ni. The intense discrete γ-ray feeding from a neutron capture state to the ground state of 63Ni was for the first time observed at stellar neutron energy. This observation and the neutron energy dependence of the total neutron capture cross section of 62Ni indicate clearly that the dominant capture process of 62Ni is a nonresonant direct s-wave capture process and not a p-wave capture process as previously predicted.

New Approach for Measuring the (n,γ) Cross Section of a Nucleus by a Few keV Neutron

We have for the first time determined with high precision the energy spectrum of low-energy neutrons ( E n <10 keV) which are produced in the 7 Li( p , n ) 7 Be reaction, by detecting γ-rays of the 197 Au( n ,γ) 198 Au reaction whose cross section is known. An anti-Compton NaI(Tl) spectrometer played an essential role in detecting the γ-rays with a good signal to noise ratio by discriminating large background due to thermalized neutrons in the measurement room. The low energy neutrons thus derived were successfully used to measure the 62 Ni( n ,γ) 63 Ni reaction cross section. The present low energy neutrons could be extensively used for cross section measurements for neutron capture reactions and elastic scatterings from nuclei of nuclear astrophysical interests.

Neutron capture and inelastic scattering cross sections for 186Os, 187Os, and 189Os and the Re‐Os chronology

We measured the neutron capture cross sections of 186,187,189Os taking for the first time their pulse height spectra for neutrons between 5 and 90 keV by means of an anti‐Compton NaI(Tl) spectrometer. The neutron inelastic scattering cross section for 187Os as well as the neutron elastic scattering cross sections for 186,187Os were also observed with use of 6Li‐glass scintillation detectors with a small systematic uncertainty.

Probing universe with fast neutrons

Fast neutrons play crucial roles as a probe to trace the history of the universe. The present paper describes our recent work on the measurement of the neutron capture and neutron inelastic scattering cross sections of various nuclei from primordial and stellar nucleostyntheses point of view, which have been carried out by developing a high sensitive measurement system. The obtained results are compared to previous works and theoretical calculations.

Neutron capture cross sections of {sup 186}Os, {sup 187}Os, and {sup 189}Os for the Re-Os chronology

Discrete as well as continuum

Neutron capture cross sections of Os-186, Os-187, and Os-189 for the Re-Os chronology

\ensuremath{\gamma}

Neutron capture cross sections of 186Os, 187Os, and 189Os for the Re-Os chronology

-ray energy spectra from the neutron capture by

Neutron capture cross sections of Os, Os, and Os for the Re-Os chronology

^{186}\mathrm{Os}

Measurements of the

,

(n,\gamma)

^{187}\mathrm{Os}