Data In Energy Region Research Articles

Isomer ratios for products of photonuclear reactions on Rh

Over the past several years various preequilibrium models for nuclear reaction mechanisms description were developed. Diversified detailed experimental data in the medium excitation energy region for nuclei are needed for reasonable selection among 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 range covers 30-100 MeV. Experimental measurements and estimations of isomer ratios for products of photonuclear reactions with multiple particle escape on antimony were performed using bremsstrahlung spectrum as projectile with end-point energies 74,9 and 85,7 MeV. Method of the induced activity measurement was applied. For acquisition of gamma spectra we used HPGe spectrometer with 20% relative efficiency. Linear accelerator of electrons LU-40 was a source of bremsstrahlung. Energy resolution of electron beam was about 1% and a mean electron current varied within (3.8 - 5.3)μA.

Isomer ratios for products of photonuclear reactions on 121Sb

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 selection among 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 end-point energies 38, 43 and 53 MeV. Method of induced activity measurement was applied. For acquisition of gamma spectra we used HPGe spectrometer with 20% efficiency and energy resolution 1.9 keV for 1332 keV gamma line of 60 Co. 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.

Cross-sections of residual nuclei from deuteron irradiation of thin thorium target at energy 7 GeV

The residual nuclei yields are of great importance for the estimation of basic radiation-technology characteristics (like a total target activity, production of long-lived nuclides etc.) of accelerator driven systems planned for transmutation of spent nuclear fuel and for a design of radioisotopes production facilities. Experimental data are also essential for validation of nuclear codes describing various stages of a spallation reaction. Therefore, the main aim of this work is to add new experimental data in energy region of relativistic deuterons, as similar data are missing in nuclear databases. The sample made of thin natural thorium foil was irradiated at JINR Nuclotron accelerator with a deuteron beam of the total kinetic energy 7 GeV. Integral number of deuterons was determined with the use of aluminum activation detectors. Products of deuteron induced spallation reaction were qualified and quantified by means of gamma-ray spectroscopy method. Several important spectroscopic corrections were applied to obtain results of high accuracy. Experimental cumulative and independent cross-sections were determined for more than 80 isotopes including meta-stable isomers. The total uncertainty of results rarely exceeded 9%. Experimental results were compared with MCNP6.1 Monte-Carlo code predictions. Generally, experimental and calculated cross-sections are in a reasonably good agreement, with the exception of a few light isotopes in a fragmentation region, where the calculations are highly under-estimated. Measured data will be useful for future development of high-energy nuclear codes. After completion, final data will be added into the EXFOR database.

Refractive index and interband transitions in strain modified NaNbO3 thin films grown by MOCVD

The influence of lattice strain on the refractive index and optical band gap of NaNbO3 thin films, deposited by the liquid-delivery spin metalorganic chemical vapor deposition method, was investigated by spectroscopic ellipsometry. Epitaxial growth of coherently strained NaNbO3 films was confirmed by high-resolution x-ray diffraction and transmission electron microscopy. Incorporated lattice strain in the films was varied by the use of the oxide substrates NdGaO3, SrTiO3 and DyScO3, which exhibit lattice mismatches to NaNbO3 with different sign, magnitude and anisotropy. The Sellmeier dispersion was employed to analyze the ellipsometry data in energy region of 1.49–2.75 eV. The refractive index at 632.8 nm of the pseudomorphically grown NaNbO3 films critically depends on the incorporated elastic lattice strain and results in a continuous decrease from 2.46 to 2.18 by varying the in-plane strain from compressive to tensile. Band gap energies for films grown under compressive and tensile lattice strain were determined by collecting spectroscopic ellipsometry data in a larger energy range between 0.73–6.48 eV and evaluating them by the Tauc-Lorentz dispersion. We observed that for tensily strained NaNbO3 films deposited on DyScO3 and SrTiO3, the band gap energies increased to and eV, respectively. For the compressively strained NaNbO3 film deposited on NdGaO3 the band gap is shifted to still higher energies ( eV).