Measurement of fast－neutron capture cross sections for ^75As

The cross sections of the ^75As(n,γ)^76As reaction were measured in the neutron energy range from 0.50 to 1.50 MeV by using the activation technique.Neutrons were produced via the T(p,n)^3He reaction and the cross sections of the ^197Au(n,γ)^198Au reaction were used to determine the absolute neutron flux.Present results are compared with existing measurements and evaluations.     

Deuteron–nucleus total reaction cross sections up to 1 GeV

Total reaction cross sections of deuteron, σ^R_d, are calculated by a microscopic three-body reaction model. The reaction model has no free adjustable parameter and applicable to reactions at various deuteron incident energies E_d and with both stable and unstable nuclei. The predicted σ^R_d are consistent with those evaluated by a phenomenological optical potential for E_d ? 200 MeV in which the potential has been parametrized. A simple formula of σ^R_d up to E_d = 1 GeV, as a function of E_d, the target mass number A and its atomic number Z, is given.     

Measurements of fast—neutron capture cross sections for ^159Tb and ^169Tm

The neutron capture cross sections for ^159Tb and ^169Tm relative to the ^197Au (n,γ)^198Au reaction are measured at neutron energies of 0.57,1.10 and 1.60 MeV by using the activation method.The activities of the products are measured with a high resolution HPGe detector gamma-ray spectrometer.The errors of the present work are 5-6% for Tb,6-7% for Tm.The recommended data in energy region of 0.4-3.0MeV are given as compared with other data published previously.     

0.04–4.0 Mev neutron fission cross section of Pu240

A detailed investigation of the Pu²⁴⁰ nucleus cross section is of interest with regard to an experimental verification of theoretical concepts of the energy dependence of fission probability as well as regarding possible uses of Pu²⁴⁰ as a nuclear fuel in fast neutron reactors.We measured the energy dependence of the fast neutron fission cross section of Pu²⁴⁰ for neutrons with the energy E_n = 0.04–4.0 Mev. The T(p, n)He³ reaction served as the neutron source. The Pu²⁴⁰ fission cross section in the plateau region (1–4 Mev) amounts to ~ 1.6 barn and is equal to only one-half of this value for the neutron energy E_n 0.7 Mev. A sharp decrease in the fission cross section value occurs as E_n decreases to 0.3 Mev; for a further decrease in E_n, the cross section value drops less sharply, and it remains practically constant (~ 0.065 barn) for 0.04 < E_n < 0.15 Mev. The correlation between the irregularities in fission cross section values and the levels of Pu²⁴⁰ nuclei which correspond to inelastic scattering channels is discussed.The authors extend their heartfeltthanks to A. I. Leiptmskii and I. I. Bondarenko for their helpfulness and interest in the work, to L. N. Usachev for the discussion of the results, to Yu. I. Baranov and N. E. Tokmantseva for their help in measurements, and to V. A. Romanov, G. A. Strigin, and Yu. I. Parfenov, who kept the accelerator in good running order.     

Optimization of the steady neutron source technique for absorption cross section measurement by using an 124Sb–Be neutron source

An improved experimental approach has been developed to determine thermal neutron absorption cross sections. It uses an ¹²⁴Sb–Be neutron source which has an average neutron energy of only about 12 keV. It can be moderated in either a water tank or a paraffin filled box and can be used for aqueous or powder samples. This new design is first optimized by MCNP simulation and then benchmarked and calibrated with experiments to verify the simulations and realize the predicted improved measurement sensitivity and reproducibility. The ¹²⁴Sb–Be source device is from 1.35 to 1.71 times more sensitive than the previous method based on the use of a ²⁵²Cf source.     

Theoretical stopping cross sections of CH,CC and C=C bonds for swift protons

Stopping cross sections as a function of projectile velocity are developed for CH, CC and C=C bonds, using the kinetic theory of stopping. The scatterer momentum distributions are obtained from theoretical isotropic Compton profiles for the bonds. The Bragg rule is tested for hydrocarbons and we show that additivity of bond stopping cross sections is superior to the atomic Bragg addition.     

Measurement of thermal neutron and resonance integral cross sections of the reaction V(n,γ)V using a 20 Ci Am–Be isotopic neutron source

The thermal neutron capture cross section (σ_o) and the resonance integral (I_o) of the ⁵¹V(n,γ)⁵²V reaction were measured with an activation method to provide fundamental data for reactor calculation, activation analysis, and other theoretical and experimental uses concerning the interaction of neutron with matter. The vanadium and manganese samples were irradiated within and without a Cd shield case using a 20 Ci Am–Be neutron source. The activities of the samples were measured using gamma-ray spectroscopy. The thermal neutron capture cross section and the resonance integral were determined relative to the reference reaction ⁵⁵Mn(n,γ)⁵⁶Mn and the values obtained are 5.16 ± 0.19 barns and 2.53 ± 0.1 barns respectively. The previous measurements of the σ_o and I_o of the reaction ⁵¹V(n,γ)⁵²V were reviewed and the difference between the present values and the previous results were discussed.     

Calculation of production cross sections of γ-rays fromthermal-neutron captures

The calculation methods of production cross sections of y-rays for thermal-neutron captures are briefly presented. The check of intensity balance is made. The examples are given to illustrate its application.     

Thermal neutron cross section determination of short-to-medium lived nuclides using a 20 Ci Am–Be neutron source

While there are growing demands for the nuclear data at higher energy regions than keV for up-to-date scientific and technological development, accurate capture cross sections at thermal energy are still needed. The thermal neutron capture cross sections for the reactions ¹²⁷I(n,γ)¹²⁸I, ¹⁵²Sm(n,γ)¹⁵³Sm,¹⁵⁴Sm(n,γ)¹⁵⁵Sm, and ²³⁸U(n,γ)²³⁹U were determined by the method of foil activation using ⁵⁵Mn(n,γ)⁵⁶Mn as a reference reaction. The experimental samples with and without a Cd cover were irradiated in an isotropic neutron field of a 20 Ci ²⁴¹Am–Be neutron source facility. A high purity Ge detector was used to measure the induced gamma-rays from the samples and the monitor. The thermal neutron capture cross sections of the reactions ¹²⁷I(n,γ)¹²⁸I, ¹⁵²Sm(n,γ)¹⁵³Sm, ¹⁵⁴Sm(n,γ)¹⁵⁵Sm, and ²³⁸U(n,γ)²³⁹U were deduced from the analysis of obtained gamma-ray spectra. The thermal neutron capture cross section values for ¹²⁷I(n,γ)¹²⁸I, ¹⁵²Sm(n,γ)¹⁵³Sm, ¹⁵⁴Sm(n,γ)¹⁵⁵Sm, and ²³⁸U(n,γ)²³⁹U reactions are (5.93 ± 0.52), (207.3 ± 9.4), (7.7 ± 0.3), and (2.79 ± 0.09) barns respectively. The obtained results have been discussed and compared with the available experimental data and were found to be in agreement with each other.     

A method of analysing experimental data of nuclear reaction cross sections

A method of analysing experimental data of nuclear reaction cross sections σr induced by radioactive beam is described.It can be used in analysis of experimental unclear reaction cross section data obtained by Na-isopope radioactive beams on different targets.Neutron halo has not been found in these nuclei.     

Calculation of production cross sections of γ-rays from thermal-neutron captures

The calculation methods of production cross sections of γ-rays for thermal-neutron captures are briefly presented. The check of intensity balance is made. The examples are given to illustrate its application.     

Nuclear in-medium effects on η dynamics in proton–nucleus collisions

The dynamics of the η meson produced in proton-induced nuclear reactions via the decay of N*(1535)has been investigated within the Lanzhou quantum molecular dynamics transport model.The in-medium modifications of the η production in dense nuclear matter are included in the model,in which an attractive η-nucleon potential is implemented.The impact of the η optical potential on the η dynamics is investigated.It is found that the attractive potential leads to the reduction in high-momentum(kinetic energy) production from the spectra of momentum distributions and inclusive cross sections and increasing the reabsorption process by surrounding nucleons.     

Prediction of synthesis cross sections of new moscovium isotopes in fusion-evaporation reactions

In the framework of the dinuclear system model,the synthesis mechanism of the superheavy nuclides with atomic numbers Z=112,114,115 in the reactions of projectiles ^40,48 Ca bombarding on targets ²³⁸ U,²⁴²Pu,and ²⁴³ Am within a wide interval of incident energy has been investigated systematically.Based on the available experimental excitation functions,the dependence of calculated synthesis cross-sections on collision orientations has been studied thoro...     

Differential elastic scattering cross sections of protons from Al in 2.4–4.8 MeV energy range

Measurement of differential elastic cross section of protons from aluminum was taken at 165° degree in the2.4–4.8 Me V energy range. The results and measured energy resonances were compared with reported measurements.These data will improve the reliability of backscattering analysis of Al with protons in this energy region.     

CdZnTe quasi-hemispherical detector for gamma–neutron detection

Quasi-hemispherical CdZnTe detector was manufactured successfully to fully understand the performance in the mixed gamma–neutron detection field. Together with the software of COMSOL, Geant4, and Matlab, the detector structure has been optimized. The CdZnTe detector performs good energy resolutions for ²⁴¹Am, ⁵⁷Co, and ¹³⁷Cs radiation sources, especially for ¹³⁷Cs (10.91 keV full width at half maximum [FWHM] at 662 keV). A linear relationship between the energy positions and spectrum channels indicates that the detector is effective for the precise energy detection from 59.5 to 662 keV. Finally, neutron and gamma events were detected simultaneously at room temperature using ²⁴¹AmBe neutron source. The spectrum shows good energy resolution for neutron capture gamma ray (14.28 keV FWHM at 558 keV). Our work demonstrates that the quasi-hemispherical CdZnTe detector is promising for simultaneous detection of neutrons and gamma radiation.     

How accurately can we predict synthesis cross sections of superheavy elements?

Synthesis of superheavy elements beyond oganesson is facing new challenges as new target–projectile combinations are necessary. Guidance from models is thus expected for future experiments. However, hindered fusion models are not well established and predictions in the fission barriers span few MeVs. Consequently, predictions are not reliable. Strategies to constrain both fusion hindrance and fission barriers are necessary to improve the predictive power of the models. But, there is no hope to get an accuracy better than one order of magnitude in fusion–evaporation reactions leading to superheavy elements synthesis.