Excitation functions of (n, α) reaction cross-sections for some important isotopes from threshold to 20 MeV

The (n, α) reaction cross-sections from threshold to ∼20 MeV on some important nuclides ⁴²Ca, ^50,53Cr, ^56,57Fe, ^58,62Ni, and ^63,65Cu involved in the reactor shielding design have been calculated using the Hauser–Feshbach statistical model with preequilibrium effects by involving PCROSS option in Empire 2.19. The transmission coefficients for neutrons in the entrance channel are calculated using the optical model potential of Koning. In the exit channel optical model potential of Avrigeanu has been used. The experimental values have been chosen carefully for all the isotopes, from EXFOR data base. The calculations are compared with existing experimental data as well as with evaluated data files (ENDF/B-VI.0 and JENDL-3.3). A good agreement between the calculated and experimental data validates the nuclear model approaches with increased predictive power to supplement and extend the nuclear database that is required for several applications.     

Measurements of activation cross sections for Lu(n, α)Tm,Lu(n, α)Tm and Lu(n, p)Yb reactions induced by neutrons around 14 MeV

The cross sections for the ¹⁷⁵Lu(n, α)¹⁷²Tm, ¹⁷⁶Lu(n, α)¹⁷³Tm and ¹⁷⁵Lu(n, p)^175m+gYb reactions have been measured in the neutron energy range of 13.5–14.8 MeV using the activation technique. The first data for ¹⁷⁵Lu(n, α)¹⁷²Tm reaction cross sections are presented. In our experiment, the fast neutrons were produced via the ³H(d, n)⁴He reaction on K-400 Neutron Generator at Chinese Academy of Engineering Physics (CAEP). Induced gamma activities were measured by a high-resolution (1.69 keV at 1332 keV for ⁶⁰Co) gamma-ray spectrometer with high-purity germanium (HPGe) detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The neutron fluences were determined by the cross section of ⁹³Nb(n, 2n)^92mNb or ²⁷Al(n, α)²⁴Na reactions. The neutron energy in the measurement was by the cross section ratios of ⁹⁰Zr(n, 2n)^89m+gZr and ⁹³Nb(n, 2n)^92mNb reactions. The results were discussed and compared with experimental data found in the literature and with results of published empirical formulae.     

Determination of radiation attenuation coefficients of heavyweight- and normal-weight concretes containing colemanite and barite for 0.663 MeV γ-rays

Accurate measurements have been made to determine radiation transmission of concretes produced with barite, colemanite and normal aggregate by using beam transmission method for 0.663 MeV γ-rays energy of ¹³⁷Cs radioactive isotopes by using NaI(Tl) scintillation detector. Linear and mass attenuation coefficients of thirteen heavy- and four normal-weight concretes were calculated. It was determined that the linear attenuation coefficient (μ, cm⁻¹) decreased with colemanite concentration and increased with barite concentration in both type of the concretes. Mass attenuation coefficient values of our concretes were compared with the values proposed by the United States National Institute of Standards and Technology (NIST).     

Measurement of differential cross-sections and widths of resonances in S(p,p′γ) S reaction in the 3.0-4.0 MeV region

The paper reports the widths and differential cross-sections of resonances at 3.089, 3.379 and 3.717 MeV in the ³²S(p,p′γ)³²S nuclear reaction. The cross-sections are computed at 0° and 90° angles (relative to the beam direction) from thick target excitation curves constructed by measuring 2230 keV γ-rays, characteristic of the reaction. The differential cross-sections of resonances are about 18, 64 and 70 mb/sr respectively at 0° angle and decrease by about half around an angle of 90°. The first resonance, the sharpest among the three, exhibits a width of about 400 eV while those at 3.379 and 3.717 MeV are in 1.0-1.5 keV range. The widths of the resonances are extracted from the respective thick target excitation curves by an interquartile separation method and also by simulating their leading edges. A study of thick target yields in the 3.0-4.0 MeV proton energy region for several sulphide forming elements shows the absence of any significant interference. These resonances, as a result, can be effectively utilised for sensitive and high resolution depth profile measurements of sulphur in films and materials surfaces.     

Energy levels in Ag-like (4d4f, 4d5? (? = 0-3)), Pd-like (4d4f [J = 1], 4d5p [J = 1], 4d5f [J = 1]), and Rh-like (4d [J = 5/2, 3/2]) ions with Z ? 86

Relativistic perturbation theory with a model potential is used for the calculation of energy levels of the states 4f_5/2, 4f_7/2, 5s_1/2, 5p_1/2, 5p_3/2, 5d_3/2, 5d_5/2, 5f_5/2, and 5f_7/2 above the 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰ core, with one vacancy , in the same core, in the silver and rhodium isoelectronic sequences with the maximum nuclear charge Z = 86. The method of extrapolation of the model potential parameter is applied to calculate one-electron and one-vacancy wavefunctions. The wavefunctions of Ag- and Rh-like ions were used to calculate the energies of resonance transitions to the ground state ¹S₀ in Pd-like ions. Good agreement between the theoretical and the experimental energies of the resonance transitions in Pd-like ions indicates the reliability of the results obtained.     

Semi-empirical systematics for the cross-sections of the reactions (n,α), (n,p) and (n,2n) at 14.5 MeV neutrons on the basis of experimental data measured by Lanzhou University

Three new semi-empirical formulae for the calculation of the (n,α), (n,p) and (n,2n) cross-sections at neutron energy 14.5 MeV were obtained on the basis of experimental data measured by Lanzhou University. Derived from the statistical model with consideration of the Q-value dependence, the new formulae include three, three and four parameters for (n,α), (n,p) and (n,2n) reactions, respectively. The obtained relations are compared with other recently proposed systematics based on the statistical model as well as on the asymmetry parameter dependence.     

Measurement of cross sections for (n, 2n), (n, p) and (n, α) reactions on germanium isotopes induced by 14 MeV neutrons

Activation cross sections at the neutron energy about 14 MeV on germanium isotopes have been measured, employing the activation technique and γ-ray spectrometry. The data of the cross section are reported for the (n, 2n), (n, p) and (n, α) reactions. The neutron flux was determined using the monitor reactions ²⁷Al (n, α) ²⁴Na and the neutron energies were measured by the method of cross section ratios for ⁹⁰Zr (n, 2n) ⁸⁹Zr to ⁹³Nb (n, 2n) ^92mNb reactions. The measured results were compared with the other measurements.     

Cross-section measurements for the (n,p) and (n,α) reactions on 23Na and for the (n,p) reaction on 26Mg at the neutron energies from 13.6 to 14.9 MeV

Cross sections were measured at neutron energies from 13.6 to 14.9 MeV for the reactions ²³Na(n,p)²³Ne and ²³Na(n,α)²⁰F, and ²⁶Mg(n,p)²⁶Na leading to short-lived products. The production of short-lived nuclei and the spectra accumulation have been carried out by cyclic activation method. Corrections were made for the effects of gamma ray attenuation, coincidence summing, pulse pile-up, dead time, neutron flux fluctuations and scattered low energy neutrons.