Photo-disintegration cross section measurements on 186^{186}W, 187^{187}Re and 188^{188}Os: Implications for the Re-Os cosmochronology

Cross sections of the $^{186}$W, $^{187}$Re, $^{188}$Os($\gamma,n$) reactions were measured using quasi-monochromatic photon beams from laser Compton scattering (LCS) with average energies from 7.3 to 10.9 MeV. The results are compared with the predictions of Hauser-Feshbach statistical calculations using four different sets of input parameters. In addition, the inverse neutron capture cross sections were evaluated by constraining the model parameters, especially the $E1$ strength function, on the basis of the experimental data. The present experiment helps to further constrain the correction factor $F_{\sigma}$ for the neutron capture on the 9.75 keV state in $^{187}$Os. Implications of $F_{\sigma}$ to the Re-Os cosmochronology are discussed with a focus on the uncertainty in the estimate of the age of the Galaxy.Comment: 11 page

Photodisintegration of 80Se^{80}Se as a probe of neutron capture for the s-process branch-point nucleus 79Se^{79}Se

Photoneutron cross sections were measured for 80Se near the neutron separation energy with the laser Compton scattering γ rays. The stellar neutron capture rate for 79Se was evaluated by using the photodisintegration data as constraints on the E1 γ strength function within the framework of the Hauser-Feshbach statistical model. The result is compared with the model calculation of Bao and Käppeler. © Copyright owned by the author(s).SCOPUS: cp.pinfo:eu-repo/semantics/publishe

s -process branching at W 185 revised

The neutron capture cross section of the unstable s-process branching nucleus 185W has been derived from experimental data of the inverse 186W(g,n)185W photodisintegration taken with monochromatic photon beams from laser Compton scattering. The result of sigma = 553 +- 60 mb at kT = 30 keV leads to a relatively high effective neutron density in the classical s-process of N_n = 4.7 \times 10^8 cm^-3. A realistic model for the s-process in thermally pulsing AGB stars overestimates the abundance of 186Os significantly because of the relatively small neutron capture cross section of 185W.Comment: 10 pages, 3 figure

Spallation and fragmentation cross sections for 168 MeV/nucleon Xe 136 ions on proton, deuteron, and carbon targets

The spallation and fragmentation reactions of Xe136 induced by proton, deuteron, and carbon targets at 168 MeV/nucleon were studied at RIKEN Radioactive Isotope Beam Factory via the inverse kinematics technique. A wide range of isotopic distributions of the reaction cross sections has been obtained and systematically analyzed by using the Particle and Heavy Ion Transport code System (PHITS) including dynamical and intranuclear cascade processes plus evaporation process, the semi-empirical parametrization for residue cross sections in spallation reactions (SPACS) and empirical parametrization of fragmentation cross sections (EPAX), and the deuteron-induced reaction analysis code system (DEURACS) incorporating the deuteron breakup effect. The carbon target has exhibited strong potential to produce light-mass isotopes far away from the projectile, in comparison to proton and deuteron targets. This may be attributed to the possible higher excitation energies of the prefragment induced by heavier target. It is demonstrated that the deuteron target has advantages to produce isotopic chains very close to the projectile and also the neutron-rich nuclei in other isotopic chains far away from the projectile, due basically to its structure property and the effect of the breakup neutron in the peripheral collision processes. The proton target has the advantage of being able to produce isotopes produced via charge-pickup reactions in comparison to other targets. The prediction powers of various calculation codes are examined with respective to the experimental isotopic distributions. The target and energy dependences of the produced mass distributions are also discussed

Towards a More Complete and Accurate Experimental Nuclear Reaction Data Library (EXFOR): International Collaboration Between Nuclear Reaction Data Centres (NRDC)

The International Network of Nuclear Reaction Data Centres (NRDC) coordinated by the IAEA Nuclear Data Section (NDS) is successfully collaborating in the maintenance and development of the EXFOR library. As the scope of published data expands (e.g., to higher energy, to heavier projectile) to meet the needs from the frontier of sciences and applications, it becomes nowadays a hard and challenging task to maintain both completeness and accuracy of the whole EXFOR library. The paper describes evolution of the library with highlights on recent developments.Comment: 4 pages, 2 figure

E1 and M1 strength functions at low energy

We report photon-scattering experiments using bremsstrahlung at the γELBE facility of Helmholtz-Zentrum Dresden-Rossendorf and using quasi-monoenergetic, polarized γ beams at the HIγS facility of the Triangle Universities Nuclear Laboratory in Durham. To deduce the photoabsorption cross sections at high excitation energy and high level density, unresolved strength in the quasicontinuum of nuclear states has been taken into account. In the analysis of the spectra measured by using bremsstrahlung at γELBE, we perform simulations of statistical γ-ray cascades using the code γDEX to estimate intensities of inelastic transitions to low-lying excited states. Simulated average branching ratios are compared with model-independent branching ratios obtained from spectra measured by using monoenergetic γ beams at HIγS. E1 strength in the energy region of the pygmy dipole resonance is discussed in nuclei around mass 90 and in xenon isotopes. M1 strength in the region of the spin-flip resonance is also considered for xenon isotopes. The dipole strength function of 74Ge deduced from γELBE experiments is compared with the one obtained from experiments at the Oslo Cyclotron Laboratory. The low-energy upbend seen in the Oslo data is interpreted as M1 strength on the basis of shell-model calculations

Cross sections for nuclide production in proton- and deuteron-induced reactions on 93

Isotopic production cross sections were measured for proton- and deuteron-induced reactions on 93Nb by means of the inverse kinematics method at RIKEN Radioactive Isotope Beam Factory. The measured production cross sections of residual nuclei in the reaction 93Nb + p at 113 MeV/u were compared with previous data measured by the conventional activation method in the proton energy range between 46 and 249 MeV. The present inverse kinematics data of four reaction products (90Mo, 90Nb, 88Y, and 86Y) were in good agreement with the data of activation measurement. Also, the model calculations with PHITS describing the intra-nuclear cascade and evaporation processes generally well reproduced the measured isotopic production cross sections

Spallation reaction study for fission products in nuclear waste: Cross section measurements for 137

Spallation reactions for the long-lived fission products 137Cs, 90Sr and 107Pd have been studied for the purpose of nuclear waste transmutation. The cross sections on the proton- and deuteron-induced spallation were obtained in inverse kinematics at the RIKEN Radioactive Isotope Beam Factory. Both the target and energy dependences of cross sections have been investigated systematically. and the cross-section differences between the proton and deuteron are found to be larger for lighter fragments. The experimental data are compared with the SPACS semi-empirical parameterization and the PHITS calculations including both the intra-nuclear cascade and evaporation processes