No abstract available

[en] The bremsstrahlung spectra of medium-energy electrons (30…100 MeV) were calculated in GEANT4. Cross sections for photonuclear reactions were calculated in TALYS1.9. A convolution over the energy of the cross sections of one- and many-particle reactions with the bremsstrahlung flux density was performed. The numerical values of the yield of ⁹³Nb(γ,xn)^9-xNb reactions, the activity of irradiated ⁹³Nb targets, and the average reaction cross-sections were obtained. The differences of the bremsstrahlung spectra from electrons with close initial energies were calculated. The shape of the difference spectra was analyzed. The contributions of the quanta of the low energy part of the difference spectrum and the quasi-monochromatic peak of the difference spectrum to the total activity of the targets were compared. An approach for correction of the experimental cross-sections of photonuclear reactions using the method of ''bremsstrahlung spectra difference'' was considered. (author)

[en] Experiments to determine the yields and bremsstrahlung flux-averaged cross-sections ⧼σ(γ_max)⧽ of photonuclear reactions on the natural Mo targets were performed on the beam from the electron linear accelerator LUE-40 with the use of the γ-activation technique. The bremsstrahlung end-point energies were in the range γ_max = 35…80 MeV. The bremsstrahlung quantum flux was calculated with the program GEANT4.9.2 and, in addition, was monitored using the ¹⁰⁰Mo(γ,n)⁹⁹Mo reaction. Calculations of the yields and average cross-sections ⧼σ(_γmax)⧽ for photonuclear reactions on stable Mo isotopes were computed using the σ() cross-sections from the TALYS1.95 code (for the level density model LD1). A comparison of experimental and calculated cross-sections ⧼σ(E_γmax)⧽ for reactions ⁹²Mo(γ, 2n)⁹⁰Mo and ⁹²Mo(γ, pn)⁹⁰Nb was performed. (author)

[en] The bremsstrahlung of accelerated electrons passing through a converter is used to study multiparticle photo-nuclear reactions. The results of calculations, numerical modeling, design, and testing of a special magnetic cleaning system to obtain a “pure” beam of bremsstrahlung quanta when studying the cross-sections of such reactions at the LUE-40 linac are presented. The system is based on commercially available permanent magnets of rectangular cross-sections. The maximum on-axis field is 0.9 T, which provides sufficient separation of the electron beam and gamma rays at a distance of more than 90 mm from the magnet. (author)

[en] Over the past several years various preequilibrium model approaches for nuclear reactions were developed. Diversified detailed experimental data in the medium excitation energy region for nucleus are needed for reasonable choice between these theoretical models. Lack of experimental data in this energy region does essentially limit the possibilities for analysis and comparison of different preequilibrium theoretical models. For photonuclear reactions this energy region extends between bremsstrahlung energies nearly 30 - 100 MeV. Experimental measurements and estimations of isomer ratios for products of photonuclear reactions with multiple particle escape on antimony have been performed using bremsstrahlung with energies 38, 43 and 53 MeV. Method of induced activity measurement was used. For acquisition of gamma spectra we used HPGe spectrometer with 20% efficiency and energy resolution 1.9 keV for 1332 keV gamma line of ⁶⁰Co. Linear accelerator of electrons LU-40 was a source of bremsstrahlung. Energy resolution of electron beam was about 1% and mean current was within (3.8 - 5.3) μA

[en] The gamma decay of the resonance-like structures observed in the reaction of radiative capture of protons by the nuclei ²²Ne, ²⁶Mg, ³⁰Si, ³⁴,³⁶S, and ³⁸Ar in the region of excitation energies of 7…12 MeV was studied. The excitation functions of this reaction were measured. The resonance strengths in the energy range of the accelerated protons Ep = 1.0…3.0 MeV were determined. The obtained discrete distributions of the magnetic dipole γ-transitions on the ground and excited states for the nuclei of the 2s1d-shell have resonance character. Giant M1 resonance on the ground and excited states in the ²³Na, ²⁷Al, ³¹P, ³⁵,³⁷Cl, and ³⁹K nuclei has been identified. The position of the M1 resonance on excited states coincides with that predicted by the Brink-Axel hypothesis for nuclei that are at the beginning of the subshell. (author)

[en] Photonuclear reactions with escape of neutrons for some target nuclei are often accompanied with proton emission. To derive isomer ratios for the products of ⁵⁴Fe(γ, np)^52m,gMg reaction one has to take into account the interfering contribution of beta-decay for products of corresponding photoneutron reactions ⁵⁴Fe(γ, 2n)^52m,gFe and ⁵⁴Fe(γ, n)^53m,gFe. Bremsstrahlung with end-point energies within 32,8 - 43,6 MeV generated by electron linear accelerator LU-40 was used for irradiation of targets. Analytical solution for differential system of 4 equations was derived and used for correct estimation of contribution for all interfering reactions

No abstract available

[en] The energy dependence of the reaction cross-sections A(γ,xn)(A-xn) was studied in the energy range 19...70 MeV, i.e. beyond Great Dipole Resonance (GDR) region. Experimental data were taken from international database EXFOR for range of nuclear masses (55 < a < 209). Theoretical values of cross sections were obtained using TALYS-1.8 code. Several models of level densities with both enabled and disabled pre-equilibrium mechanism were considered in our simulations. Obtained results let us to make conclusions about different mechanisms of photonuclear reactions on certain nuclei, energy dependence of their relative contribution. (author)

No abstract available