Background: High-energy neutron cross sections are important for fusion devices, accelerator driven subcritical reactors, nuclear waste transmutation, astrophysics, etc.

Purpose: Neutron cross sections were measured using quasimonoenergetic neutrons produced via ${}^7\mathrm{Li}(p,n)X$ reaction in the high-energy region where available data are scarce or have large uncertainties. Significant discrepancies are also present in theoretical predictions and evaluated nuclear data libraries.

Methods: Natural Nd and Sr samples were irradiated with neutrons produced through ${}^7\mathrm{Li}(p,n)X$ reactions. Neutron flux was measured using the Aluminium and Gold foils neutron activation technique. A correction procedure was applied for the low-energy tail of the dominant neutron peak. The proton flux was recorded by monitoring the beam current. Offline $\gamma$-ray spectroscopy measurements were performed using the HPGe detector for irradiated samples and monitor foils. The neutron-induced cross sections for the ${}^{150}\mathrm{Nd}(n,2n){}^{149}\mathrm{Nd}$ and ${}^{86}\mathrm{Sr}(n,2n){}^{85m}\mathrm{Sr}$ reactions were measured with a detailed study of uncertainty propagation using covariance analysis. Theoretical calculations of the cross sections for the reaction channel were performed using the TALYS-1.96, EMPIRE-3.2.3, and YAHFC-v3.66 codes, and the results were compared with the present experimental data. The contributions of different reaction processes, including direct, pre-equilibrium, and compound reactions, were estimated using TALYS. The experimental data were also compared with the results from evaluated nuclear data libraries, i.e., TENDL-2021, JENDL-5.0, ENDF/B-VIII.0, and EAF-2010.

Results: The ($n$, $2n$) reaction cross sections for ${}^{150}\mathrm{Nd}$ and ${}^{86}\mathrm{Sr}$ were measured and compared with the theoretical estimates. The theoretical estimates reproduce the data for ${}^{150}\mathrm{Nd}(n,2n){}^{149}\mathrm{Nd}$ reaction quite well with specific level density models. Most of the model calculations failed to reproduce the cross sections for the ${}^{86}\mathrm{Sr}(n,2n){}^{85m}\mathrm{Sr}$ reaction, except by the TALYS model.

Conclusions: The cross section of the ${}^{150}\mathrm{Nd}(n,2n){}^{149}\mathrm{Nd}$ and ${}^{86}\mathrm{Sr}(n,2n){}^{85m}\mathrm{Sr}$ reactions were measured at three different neutron energies ranging from 12 to 19 MeV using the neutron activation method. Most of the theoretical models reproduce the cross sections for the ${}^{150}\mathrm{Nd}(n,2n){}^{149}\mathrm{Nd}$ reaction. The cross sections for the ${}^{86}\mathrm{Sr}(n,2n){}^{85m}\mathrm{Sr}$ reaction were higher than those predicted by most models but showed good agreement with TALYS calculations and previously reported experimental values. The results suggest that the existing theoretical models need further improvements.

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• Knockout reactions
• Neutron physics
• Nuclear reactions
• 150 ≤ A ≤ 189
• 59 ≤ A ≤ 89