[en] The (n,2n) threshold reaction cross-sections, available in the literature are analysed for nuclei with 20≤Z≤92 in the neutron energy range of about 14.5 MeV. An empirical formula based on multiple regression technique is proposed for quick estimation of the (n,2n) reaction cross sections. The results obtained are compared with experimental data and those from other empirical formulae as long as by N-Z systematic. The validity of this formula is discussed. (author)

[en] Studies of high-energy nuclear reactions are of great important. It may help in deeper understanding of the reaction mechanisms and in extending of various fields of applications such as astrophysics, radiation physics, intense neutron source production and nuclear waste transmutation. The aim of the present work is to investigate the multineutron photonuclear on "1"9"7Au bombarded by 2.5 GeV Bremsstrahlung. Most of the photodisintegration products of gold with half-lives sufficient for the activity measurement. In this work, the necessary corrections were made in order to improve the accuracy of the experimental results The obtained experimental results are in good agreement with the calculated values. The yields for the "1"9"7Au(γ,xn)"1"9"7-xAu reactions depend not only on the excitation energies but also on the number of neutrons ejected

[en] The thermal neutron capture cross-section (σ₀) and resonance integral (I₀) of the ¹⁰⁸Pd(n,γ)¹⁰⁹Pd reaction have been measured relative to that of the monitor reaction ¹⁹⁷Au(n,γ)¹⁹⁸Au. The measurements were carried out using the neutron activation with the cadmium ratio method. Both the samples and monitors were irradiated with and without cadmium cover of 0.5 mm thickness. The induced activities of the reaction products were measured with a well calibrated HPGe γ-ray detector. In order to improve the accuracy of the results, the necessary corrections for the counting losses were made. The thermal neutron capture cross-section and resonance integral of the ¹⁰⁸Pd(n,γ)¹⁰⁹Pd reaction were determined to be σ_0,Pd = 8.68 ± 0.41 barn and I_0,Pd = 245.6 ± 24.8 barn, respectively. The obtained results are compared with literature values and discussed.

[en] We measured the thermal neutron capture cross sections (σ₀) and resonance integral (I₀) of the ¹⁸⁷Re(n,γ)¹⁸⁸Re reaction relative to that of the ¹⁹⁷Au(n,γ)¹⁹⁸Au monitor reaction using neutron activation with the Cd ratio method. The investigated samples and monitors were irradiated with and without a 0.5-mm-thick Cd cover for the pulsed neutron source based on the 100-MeV electron linac at the Pohang Accelerator Laboratory (PAL). The induced activities for the reaction products were measured using a high-purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results, the necessary corrections were made. The thermal neutron capture cross sections and resonance integral of the ¹⁸⁷Re(n,γ)¹⁸⁸Re reaction were determined relative to reference values of σ_o,Au = 98.65 ± 0.09 barn and I_o,Au = 1550 ± 28 barn from the ¹⁹⁷Au(n,γ)¹⁹⁸Au reaction, respectively. The corresponding values for the ¹⁸⁷Re(n,γ)¹⁸⁸Re reaction were determined to be σ_0,Re = 75.6 ± 3.4 barn and I_0,Re = 317 ± 22 barn, respectively. The obtained results are compared with the literature data and discussed.

[en] The excitation function of the ${}^{nat}$Zr(p,x)${}^{90}$Nb, ${}^{nat}$Zr(p,x)${}^{91m}$Nb and ${}^{nat}$Zr(p,x)(p,x)${}^{92m}$Nb reactions were measured within the incident proton energies range of 10.58 MeV to 43.61 MeV, based on the stacked-foil activation technique. The degradation of proton energy along the sample stack was calculated using the code SRIM-2013, and the proton flux was determined by using the ${}^{nat}$Cu(p,x)${}^{62,65}$Zn monitor reactions. The induced $\mathrm{\gamma <!--\; ??\; -->}$-ray activity needed to determine the reaction cross-section was measured by using an HPGe detector. The measured cross sections are compared with the literature data and with the theoretical predictions based on TALYS-1.95 code. For the theoretical calculations, the effect of different level density models and $\mathrm{\gamma <!--\; ??\; -->}$-ray strength functions was taken into account. Besides the measured excitation functions, the integral yields of ${}^{90}$Nb, ${}^{91m}$Nb and ${}^{92m}$Nb formation were also calculated.

[en] Highlights: • The yield ratios of the ^85m,gSr formed in the ^natSr(γ,xn) reactions were measured using the off-line activation method. • The results with bremsstrahlung end-point energies of 55- and 60-MeV have been measured for the first time. - Abstract: The yield ratios of ^85m,gSr were measured in the ^natSr(γ,xn)^85m,gSr reactions with the bremsstrahlung end-point energies of 55-, 60-, and 65-MeV. The experiment was carried out by the activation method in combination with high resolution HPGe γ-ray spectroscopy. In order to improve the accuracy of the experimental results, appropriate experimental procedure was used to reduce the influence of the strong annihilation peak (511 keV) to the 514 keV γ-ray peak of ^85gSr. The experimental results are compared to theoretical predictions using code TALYS-1.6. The present results for 55-, and 60-MeV bremsstrahlung end-point energies have been measured for the first time.

[en] We measured the isomeric yield ratios for the ^120m,gSb and ^122m,gSb isomeric pairs produced by ^natSb(γ,xn)^{120m,g,122m,g}Sb photonuclear reactions in the bremsstrahlung energy region from 40 to 60 MeV with a step size of ΔE = 5 MeV by the activation method. The induced γ-activities of the irradiated samples were measured by a coaxial high purity germanium detector coupled to a PC-based multichannel analyzer. The necessary corrections were made to improve the accuracy of the experimental results. The experimental results at bremsstrahlung energies of 40, 45, 50, 55, and 60 MeV were 0.045 ± 0.003, 0.046 ± 0.003, 0.048 ± 0.003, 0.050 ± 0.003, and 0.049 ± 0.003 for the ^120m,gSb isomeric pair, and 0.341 ± 0.022, 0.362 ± 0.020, 0.374 ± 0.021, 0.371 ± 0.021, and 0.358 ± 0.022 for the ^122m,gSb isomeric pair, respectively. The present results are the first measurements at bremsstrahlung energies just above the giant dipole resonance region. The obtained results confirm the dependence of the isomeric yield ratios on the incident energy and the reaction channel effect observed in some earlier experiments.