Radiative Capture Of Fast Neutrons Research Articles

Activation measurements of fast neutron radiative capture for 139La

The neutron capture cross section of the neutron magic isotope 139La has been measured relative to that of 27Al by means of the activation method. The fast neutrons were produced via the 3H(d,n)4He reaction on Pd-300 neutron generator. The natural high-purity La2O3 powder was used as target material. Induced gamma activities were measured by a high-resolution 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 new values for En=13.5±0.2, 14.1±0.2, and 14.8±0.2MeV are found to be 1.30±0.08, 1.15±0.08 and 0.99±0.07mb, respectively. Results were discussed and compared with some corresponding values found in the literature.

Fast neutron radiative capture cross-sections in fission product isotopes of neodymium

Fast neutron radiative capture cross-sections for Nd-148 and Nd-150 have been measured at about 10 neutron energies between 0.46 and 3.44 MeV using enriched isotopes and the activation technique. Experimental results are also compared with the theoretical one using FISPRO II computer code.

Integrated cross sections in fast neutron capture in medium weight and heavy nuclei

The fast neutron radiative capture in chromium, iron, strontium, yttrium, cerium, barium and lead was studied using the recently proposed consistent version of the direct-semi-direct capture model. We present the comparison of calculated excitation functions and integrated cross sections with experimental data. The results of this study and the analysis of a previous work indicate that the integrated cross section at neutron energy of 14 MeV is a smooth function of the mass number. For the nuclei studied the calculated integrated cross section is less variant compared to the experimental values. Some of the discrepancies of the experimental nature are pointed out.

Fast Neutron Radiative Capture Cross Sections of Natural Niobium and Molybdenum

The radiative capture cross sections of natural niobium and molybdenum are measured relative to that of gold at four neutron energies between 0.7 and 1.4 MeV, using a large liquid scintillation det...

Radiative capture of fast neutrons in 160Gd

Radiative neutron capture cross sections for 160Gd have been measured at eight different neutron energies: 0.46 ± 0.04, 0.57 ± 0.04, 0.75 ± 0.04, 0.97 ± 0.20, 1.22 ± 0.19, 1.52 ± 0.17, 2.22 ± 0.17, and 3.05 ± 0.18 MeV. The activation technique has been employed in the present measurement. Our experimental values are compared with the theoretical values calculated using the FISPRO II code, using the most recent set of parameters available in the published literatures.

Production of high-energy photons in fast neutron radiative capture

Abstract The differential cross section for the production of high-energy γ-rays (10-50 MeV) due to radiative capture of fast neutrons by 48Ti and Ni, are calculated by means of the direct-semidirect (DSD) model.

Fast neutron radiative capture in silicon

Using the28Si(n, γ)29Si reaction, transitions to the ground state and first excited state in29Si have been studied in the neutron energy range 3–14 MeV with improved neutron energy resolution (of about 100 keV). The 90° cross sections show considerable structure in the entire neutron energy range. Comparison with theoretical calculations shows that compound-nucleus and direct-semidirect processes account for the non-resonant part (smoothly varying part) of the cross section. A microscopic model is, however, required to describe the resonance structure. Continuum shell-model calculations have proven to be a very promising means towards a better understanding of the capture process in, and below, the giant resonance region in light nuclei. The angular distributions of gamma rays in the neutron energy range 8–14 MeV indicate that the capture reaction is mainly of direct character and that the effect of interference between the electric dipole and isoscalar quadrupole resonance is weak.

Radiative capture cross-sections of isotopes of Gd, Sm and V between 1 and 3 MeV

Fast-neutron radiative capture cross-sections have been measured relative to the 127I(n, γ) 128I reaction cross-section using the comparative activation technique for 160Gd, 154Sm and 51V (using enriched isotopes and Specpure samples) at five different neutron energies between 1 and 3 MeV. The cross-section for 160Gd is reported for the first time in the above energy region. Experimental values are compared with the statistical-model calculations.

Radiative capture of fast neutrons by 165Ho and 238U

Radiative capture of fast neutrons by the deformed nuclei 165Ho and 238U was measured over the 7 to 15 MeV incident neutron energy range. The γ-ray detector was a large NaI(T1) anti-Compton spectrometer, and time-of-flight techniques were used to suppress background. The total radiative capture cross section exhibits an energy dependence that clearly indicates the importance of the direct-semidirect reaction mechanism. Theoretical calculations compare favorably with experimental observations. However, the shapes of the observed γ-ray spectra differ from those calculated, indicating problems in estimating the distribution of single-particle strength for these deformed nuclei.

Angular distribution measurements for radiative capture of fast neutrons byCa40

Angular distributions have been measured for neutron energies of 8 and 12 MeV for the $^{40}\mathrm{Ca}(n,{\ensuremath{\gamma}}_{0})^{41}\mathrm{Ca}$ reaction. The extracted ${a}_{2}$ coefficients are in good agreement with recent direct-semidirect calculations. The behavior of ${a}_{2}$ is examined in light of recent results from polarized proton capture measurements on $^{54,56,58}\mathrm{Fe}$.NUCLEAR REACTIONS $^{40}\mathrm{Ca}(n,{\ensuremath{\gamma}}_{0})$, measured $\ensuremath{\sigma}(\ensuremath{\theta})$, ${E}_{n}=8.0, 12.0$ MeV. Compared to direct-semidirect model predictions.

Radiative capture of fast neutrons by 89Y and 140Ce

The γ-ray spectra from the reactions 89Y(n, γ) 90Y and 140Ce(n, γ) 141Ce have been measured in the neutron energy range of 6.2–15.6 MeV. The pulse-height spectra were recorded with NaI(Tl) spectrometers and time-of-flight techniques were used to improve signal-to-background ratio. Capture cross sections were determined for γ-ray transitions to the two 2 d 5 2 levels at 0 and 203 keV of 90Y and to the 2 f 7 2 ground state of 141Ce as well as integrated cross sections to bound states in these nuclei. The observed γ-ray spectra and partial radiative capture cross sections were compared with predictions of the direct-semidirect capture theory. The resonance behaviour with neutron energy of both the ground-state and integrated partial capture cross sections shows the validity of the semidirect model for 89Y and 140Ce in the region of neutron energy encompassing the giant-dipole resonance. The observed symmetry of the cross sections about the peak of the resonance argues strongly for the complex form of the particle-vibration coupling interaction. A detailed comparison of the predictions of the DSD model using the complex coupling interaction shows that the capture cross sections are relatively insensitive to the real part of the interaction.

Radiative capture cross section measurements for fast neutrons using a large Gd-loaded liquid scintillator

A 500 1 gadolinium-loaded liquid scintillator tank, previously employed for measuring neutron multiplicities in fission and (n, 2n) cross sections, has been used for fast neutron radiative capture cross section measurements of both fissionable and non-fissionable nuclei. Specifically measurements for 238U and 197Au around a neutron energy of 2 MeV are presented. The scheme for measurement, data reduction and various corrections is described. Limitations of the method above 10 MeV are pointed out.

Fast-neutron radiative capture cross section for242Pu

Fast-neutron radiative capture cross section for242Pu

Higher order processes in the radiative capture of fast neutrons

A coupled channel treatment of the radiative capture of fast neutrons is presented. The results of the calculation indicate that higher order processes not previously included in the direct and semi-direct theories do not affect significantly the capture cross section. The existence of single particle resonances superimposed on the broad giant resonance and at low energy is predicted in the40Ca(n,γ reaction.

Compound-nucleus and direct-semidirect contributions to radiative capture of fast neutrons

Compound-nucleus and direct-semidirect contributions to radiative capture of fast neutrons

Radiative capture of fast neutrons by 40Ca

The radiative capture cross section for the reaction 40Ca(n, γ) 41Ca has been measured for the neutron energy range of 6.8–18.2 MeV. A NaI(Tl) anti-Compton spectrometer, a pulsed neutron beam, and time-of-flight techniques were utilized. The γ-ray spectra show strong transitions to the 1 f 7 2 ground state and a relatively high intensity of unresolved γ-rays to a group of levels at about 2 MeV, where two 3 2 − states are known to carry the 2 p 3 2 strength, and to levels around 4 MeV, which is the centroid energy of the 2 p 1 2 strength. Absolute cross sections were determined for these γ-ray transitions as well as the integrated cross section for transitions to bound states of 41Ca. Only the cross section for the transition to the f 7 2 ground state of 41Ca shows the resonance behavior predicted by the semidirect (collective) capture theory, but the agreement between the theoretical and measured f 7 2 cross sections is not satisfactory. The measured cross sections for the other γ-ray peaks are almost constant with neutron energy below about 15 MeV, in sharp contrast to the cross sections predicted by the semidirect theory for p 3 2 and p 1 2 transitions.

Isospin effects in fast neutron radiative capture

The effect of isospin splitting of the giant dipole resonance of the final nucleus on neutron capture cross sections in N = Z nuclei is discussed. The 40Ca(n, γ) ground-state transition is taken as an example. The suggested modification of the semi-direct capture model gives an improved description of the energy dependence of the 40Ca(n, γ 0) cross section.

Fast neutron radiative capture crosssections for some important standard from 30 keV TO 1·5 MeV

Neutron capture radiative cross sections for Ta, Ag, In and Au have been measured between 30 keV and 1·5 MeV using time-of-flight technique. The detector used was a large liquid scintillator. Cross-sections are given in relative and absolute units.

Cross sections of Mn55, Ga69, Ga71, and Mo98 for radiative capture of fast neutrons

Cross sections of Mn55, Ga69, Ga71, and Mo98 for radiative capture of fast neutrons

Cross sections for radiative capture of fast neutrons by Cu63, Cu65, and W186

Cross sections for radiative capture of fast neutrons by Cu63, Cu65, and W186