Empirical Abundance Scaling Laws and Implications for the Gamma-Process in Core-Collapse Supernovae

Analyzing the solar system abundances, we have found two empirical abundance scaling laws concerning the p- and s-nuclei with the same atomic number. The first scaling is s/p ratios are almost constant over a wide range of the atomic number, where the p-nculei are lighter than the s-nuclei by two or four neutrons. The second scaling is p/p ratios are almost constant, where the second $p$-nuclei are lighter than the first p-nucleus by two neutrons. These scalings are a piece of evidence that most p-nuclei are dominantly synthesized by the gamma-process in supernova explosions. The scalings lead to a novel concept of "universality of gamma-process" that the s/p and p/p ratios of nuclei produced by individual gamma-processes are almost constant, respectively. We have calculated the ratios by gamma-process based on core-collapse supernova explosion models under various astrophysical conditions and found that the scalings hold for materials produced by individual gamma-processes independent of the astrophysical conditions assumed. The universality originates from three mechanisms: the shifts of the gamma-process layers to keep their peak temperature, the weak s-process in pre-supernovae, and the independence of the s/p ratios of the nuclear reactions. The results further suggest an extended universality that the s/p ratios in the gamma-process layers are not only constant but also centered on a specific value of 3. With this specific value and the first scaling, we estimate that the ratios of $s$-process abundance contributions from the AGB stars to the massive stars are almost 6.7 for the $s$-nuclei of A > 90. We find that large enhancements of s/p ratios for Ce, Er, and W are a piece of evidence that the weak s-process actually occurred before SNe.Comment: 35 pages, 15 figure

Results of Measurements at the NewSUBARU and HIgS Facilities

ニュースバル放射光施設において開催される核セキュリティワークショップにおいて、米国デューク大学のHIgS施設で稼働中のレーザーコンプトンガンマ線を用いて行った核共鳴蛍光散乱実験の結果について報告する。また、ニュースバル放射光施設で稼働中のレーザーコンプトンガンマ線を用いて行った核共鳴蛍光散乱法による非破壊分析の実証試験の結果についても報告する。Workshop on demonstration of nuclear resonance fluorescence technique for detection of nuclear material hidden in a shiel

Evaluation of neutron capture cross section on

The neutron capture cross section of long-lived radioactive 205Pb is derived by using the nuclear reaction calculation code CCONE, based on photonuclear data. The present result is smaller than that of TENDL-2015 by a factor of 4. The derived Maxwellian averaged capture cross section (MACS) is the smallest compared to the existing data. The produced amount of 205Pb is explored with a simulated neutron flux in the Pb-Bi eutectic (LBE) target. The continuous use of the system in 25 years creates 205Pb with about 6 kg at maximum in the LBE (including natural Pb of 103 kg). The impact of the derived MACS on the stellar nucleosynthesis is investigated. It is found that the abundance of Tl is slightly enhanced due to the increase in the remaining abundance of 205Pb

Calculating off-axis efficiency of coaxial HPGe detectors by Monte Carlo simulation

In beam geometries where a directed γ-ray beam hits the surface of a coaxial high purity germanium detector (HPGe), the detector efficiency is sensitive to the position where γ-rays initially hit the detector surface because the structure of the detector is nonuniform. This may cause inaccuracy of the detector efficiency when measured using standard sources that are point-like sources emitting γ-rays isotropically. Obtaining a precise estimation of the full energy peak efficiency of the coaxial HPGe detector in the beam geometry for on-axis and off-axis measurements requires a Monte Carlo simulation. We performed Monte Carlo simulations that calculate the detector efficiency in the beam geometry. The effects of the off-axis distance and γ-ray beam size on the efficiency are quantitatively analyzed. We found that the intrinsic efficiency in the beam geometry is maximized when the beam hits the detector at specific off-axis distances. Our Monte Carlo calculations have been supported by nuclear resonance fluorescence experiments using laser Compton scattering γ-ray beams

The s-process branching at 186Re revised

info:eu-repo/semantics/publishe

The s-process branching at 186Re revised

Recent experimental data for the 187Re(γ ,n) 186Re reaction are reviewed, and the contribution of the (8 +) isomer in 186Re is discussed. Statistical model calculations are used to derive the 186Re(n,γ)187Re capture cross section from the photodisintegration data, and σMACS = 1070±370mb is obtained at κT = 30 keV. The s-process branching at 186Re remains small. © Copyright owned by the author(s).SCOPUS: cp.pinfo:eu-repo/semantics/publishe