ANGULAR DISTRIBUTION OF FISSION FRAGMENTS FROM 235U, 2~U AND 237Np NEAR THE (n,2nf) THRESHOLD (original) (raw)
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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.
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.
EPJ Web of Conferences, 2020
This work summarizes some results of a series of experiments aimed at the investigation of energy dependence of anisotropy of fission fragments (FFs) in (n,f) reactions for neutron energies from low to intermediate. Angular distributions of FFs from the neutron-induced fission of239Pu,237Np, andnatPb 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 of the Petersburg Nuclear Physics Institute (Gatchina, Russia). The anisotropies of FFs deduced from the measured angular distributions are presented. In the neutron energy range above 20 MeV the results have been obtained for the first time in our works. The experimental data for FF anisotropy in237Np(n,f) are compared with calculations based on "adapted" TALYS software.
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.
Fission Fragment Angular Distribution measurements of 235 U and 238 U at CERN n_TOF facility
In order to measure the fission fragment angular distributions of neutron-induced reactions, a fission detection setup based on parallel-plate avalanche counters has been developed and successfully used ate the CERN n_TOF facility. In this work we present preliminary results on the analysis of new U-235(n,f) and U-238(n,f) data in the extended energy range up to 200 MeV compared to the existing experimental data.
Physical Review C, 2019
Fission fragment angular distributions can provide an important constraint on fission theory, improving predictive fission codes, and are a prerequisite for a precise ratio cross section measurement. Available anisotropy data is sparse, especially at neutron energies above 5 MeV. For the first time, a three-dimensional tracking detector is employed to study fragment emission angles and provide a direct measurement of angular anisotropy. The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration has deployed the fission time projection chamber (fissionTPC) to measure nuclear data with unprecedented precision. The fission fragment anisotropy of 235 U has been measured over a wide range of incident neutron energies from 180 keV to 200 MeV; a careful study of the systematic uncertainties complement the data.
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.
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.