Angular distributions and anisotropy of fission fragments from neutron-induced fission of239Pu,237Np, andnatPb in energy range 1–200 MeV (original) (raw)
Related papers
2020
Angular distributions of fission fragments from the neutron-induced fission of Th, U, U, U, Pu, Np, Pb and Bi have been measured in the energy range 1‒200 MeV at the neutron TOF spectrometer GNEIS based on the spallation neutron source at 1 GeV proton synchrocyclotron SC-1000 of the NRC KI PNPI (Gatchina, Russia). The data in the neutron energy range above 20 MeV for U, Pu, Np, Pb and Bi have been obtained for the first time. Recently, the list of nuclei to be studied within the framework of present investigation was filled with isotope Np. Neptunium is a major component of spent nuclear fuel, therefore an accurate knowledge of the fission cross-section and fragment properties is needed for waste transmutation and advanced nuclear facilities (reactors, ADS, etc.) studies. A description of the experimental equipment and measurement procedure is given. The underlying ideas of the theoretical approach developed for analysis of the obtained experimental data are discussed.
Angular distributions of fission fragments from the neutron-induced fission of 232 Th, 235 U, and 238 U have been measured in the energy range 1–200 MeV at the neutron time-of-flight (TOF) spectrometer GNEIS using position sensitive multiwire proportional counters as fission fragment detector. A short description of the experimental equipment and measurement procedure is given. The anisotropy of fission fragments deduced from the data on measured angular distributions is presented in comparison with experimental data of other authors.
New results of the neutron-induced fission experiments carried out at the neutron time-of-flight spectrometer GNEIS of the PNPI are given. Angular distributions of fission fragments from the neutron-induced fission of U and Bi nuclei have been measured in the energy range 1–200 MeV using position sensitive multiwire proportional counters as fission fragment detector. The recent improvements of the measurement and data processing procedures are described. The data on anisotropy of fission fragments deduced from the measured angular distributions are presented in comparison with the experimental data of other authors.
2017
New results of the neutron-induced fission experiments carried out at the neutron time-offlight spectrometer GNEIS of the PNPI are given. Angular distributions of fission fragments from the neutron-induced fission of Pu and Pb nuclei have been measured in the energy range 1-200 MeV using position sensitive multiwire proportional counters as fission fragment detector. The preliminary data on anisotropy of fission fragments deduced from the measured angular distributions are presented in comparison with the experimental data of other authors.
arXiv: Nuclear Theory, 2020
In recent years, investigations of angular distributions of fragments in neutron-induced nuclear fission have been extended to intermediate energies, up to 200 MeV, as well as to a wide range of target isotopes. Using as an example the latest data obtained by our group for the reaction 237-Np(n,f), we discuss the specific features of fission fragment angular distribution and present a method for their simulation based on the code TALYS. It is shown that a simplified model reasonably describes energy dependence of the angular distribution in the whole range 1-200 MeV. The ways to improve the model are discussed along with the possibilities to use it for obtaining new information on fission and pre-equilibrium processes in neutron-nucleus interaction. We consider also the relevant problems of describing fission fragment angular distributions.
Angular distributions of fission fragments from 235U, 238U and 237Np near the (n, 2nf) threshold.
Acta Physiea Hungarica 64 (1-2), pp. 09-18 (1988) - Springer, 1988
The angular distribution of fission fragments from the fast neutron-induced fission of 235U, 238U and 237Np were measured near the (n, 2nf) threshold by polycarbonate nuclear track detector. A function of the form W(θ) = a0 + a2 cos2 θ has been fitted to the measured data. The anisotropy parameters determined around 14 MeV show a definite energy and Z2/A dependence. The differential cross cross sections were also deduced.
ANGULAR DISTRIBUTION OF FISSION FRAGMENTS FROM 235U, 2~U AND 237Np NEAR THE (n,2nf) THRESHOLD
Acta Physica Hungarica - Springer, 1988
The angular distribution of fission fragments from the fast neutron induced fission of 235U, 238U and 237Np were measured near the (n, 2nf) threshold by polycarbonate nuclear track detector. A function of the forro W(θ) = a0 + a2 cos2 θ has been fitted to the measured data. The anisotropy parameters determined around 14 MeV show a definite energy and Z2/A dependence. The differential cross cross sections were also deduced.
Nuclear Physics A, 2005
Fission fragment angular distributions have been measured for the 232 Th(n, f ) and 238 U(n, f ) reactions in the neutron energy range 20-100 MeV. The fragment angular anisotropy for 232 Th was found to be systematically larger than that for 238 U. The obtained results have been analyzed in the framework of the statistical saddle-point model combined with pre-equilibrium and Hauser-Feshbach calculations of partial fission cross sections. The calculations have revealed that fission following multiple neutron emission takes place in both reactions, resulting in a considerable contribution of high chances to the total fission fragment angular anisotropy. This gives grounds to expect that the observed difference is mainly due to nuclei fissioning at the end of the neutron evaporation chain. calculed σ , fission fragments angular anisotropy. Multichance fission, saddle-point statistical model analysis.
Calculation of Fission Fragment Angular Anisotropy in Heavy-Ion Induced Fission
International Journal of Modern Physics E, 2008
Fission fragment angular anisotropies from 16 O + 232 Th , 12 C + 236 U , 11 B + 237 Np , 14 N + 232 Th , 11 B + 235 U and 12 C + 232 Th systems were calculated by means of the standard saddle point statistical model (SSPSM). The results were obtained with and without neutron emission correction in the reactions, and comparisons were made with the corresponding experimental data. The normal and anomalous behaviors of fission fragment anisotropies are extensively discussed.
Fission Fragment Angular Distribution of 232Th(n,f) at the CERN n_TOF Facility
Nuclear Data Sheets, 2014
in the white spectrum neutron beam at the n TOF facility at CERN. A reaction chamber based on Parallel Plate Avalanche Counters (PPAC) was used, where the detectors and the targets have been tilted 45 • with respect to the neutron beam direction in order to cover the full angular range of the fission fragments. A GEANT4 simulation has been developed to study the setup efficiency. The data analysis and the preliminary results obtained for the 232 Th(n,f) between fission threshold and 100 MeV are presented here.