New experimental constraint on the W 185 (n,γ) W 186 cross section

In this work, we present new data on the W182,183,184(γ,n) cross sections, utilizing a quasi-monochromatic photon beam produced at the NewSUBARU synchrotron radiation facility. Further, we have extracted the nuclear level density and γ-ray strength function of W186 from data on the W186(α,α′γ)W186 reaction measured at the Oslo Cyclotron Laboratory. Combining previous measurements on the W186(γ,n) cross section with our new W182,183,184(γ,n) and (α,α′γ)W186 data sets, we have deduced the W186γ-ray strength function in the range of 1<Eγ<6 MeV and 7<Eγ<14 MeV. Our data are used to extract the level density and γ-ray strength functions needed as input to the nuclear-reaction code talys, providing an indirect, experimental constraint for the W185(n,γ)W186 cross section and reaction rate. Compared to the recommended Maxwellian-averaged cross section (MACS) in the KADoNiS-1.0 database, our results are on average lower for the relevant energy range kBT°[5,100] keV, and we provide a smaller uncertainty for the MACS. The theoretical values of Bao et al. [At. Data Nucl. Data Tables 76, 70 (2000)0092640X10.1006/adnd.2000.0838] and the cross section experimentally constrained on photoneutron data of Sonnabend et al. [Astrophys. J. 583, 506 (2003)0004-637X10.1086/345086] are significantly higher than our result. The lower value by Mohr et al. [Phys. Rev. C 69, 032801(R) (2004)0556-281310.1103/PhysRevC.69.032801] is in very good agreement with our deduced MACS. Our new results provide an improved uncertainty estimate for the (n,γ)W186 reaction rate, which is one important ingredient in simulations for investigating the neutron density and the Os186,187 production in the s process.