09:15 〜 09:30
▲ [18a-D411-2] Neutron Capture Cross-Section Measurement and Resonance Parameter Analysis of 191Ir
キーワード：nucleosynthesis s-process, neutron-induced capture cross-sections, ANNRI/MLF/J-PARC
The neutron capture cross-section for 191Ir plays an important role to improve the accuracy of the s-process model, in particular, at branching point where the neutron capture reaction competes with the decay in the s-process. It is however difficult to explain the late stage of stellar evolution due to lack of data and large discrepancies among the neutron capture cross-section data for 191Ir in past measurements. For this reason, we measured neutron capture cross-section for 191Ir in a neutron energy range from 0.01 eV to 1 keV by applying the TOF method with the ANNRI beamline of MLF at the J-PARC. A sample was a pellet of 99.904% enriched 191Ir metal with a diameter of 5 mm and 90.2 mg in weight. The NaI(Tl) detectors equipped at the ANNRI beamline were used for capture yield measurements. The PHWT was applied to derive the 191Ir(n, γ) reaction cross-sections, where the weighting function was normalized by comparing the experimental thermal cross-section of 197Au with that in JENDL-5. The neutron capture cross-sections of 191Ir were fitted with 1/ν function in a neutron energy from 20 meV to 30 meV, and thermal-neutron capture cross-section of 191Ir was preliminarily determined to be 857.47±38.28 b. When compared with past measurements, the present result agreed with the value by Huang et al. The resonances of 191Ir below 160 eV were examined for the obtained 191Ir(n, γ) cross-sections using the resonance analysis code, REFIT, and the present results were compared with parameters both in past measurements and in JENDL-5. Results showed that the magnitudes of several resonances differed from those in the JENDL-5 data due to the change in the neutron width. I will present detailed results and discuss their impact on astrophysics at the conference presentation.