Angular distributions and anisotropy of fission fragments from neutron-induced fission in intermediate energy range 1–200 MeV

Abstract

Abstract. Angular distributions of fission fragments from the neutron-induced fission of 232 Th, 233 U, 235 U, 238 U and 209 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 of the PNPI (Gatchina, Russia). The multiwire proportional counters have been used as a position sensitive fission fragment detector. A 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, first of all, the recent data from WNR at LANSCE (Los Alamos, USA) and n TOF(CERN).

Fission program at n_TOF

“…A recent measurement up to 200 MeV [19] confirmed our results above 30 MeV, contradicting again [17], and in good agreement as well with modelling [15].…”

Angular distributions and anisotropy of fission fragments from neutron-induced fission of239Pu,237Np, andnatPb in energy range 1–200 MeV

“…The measurements were performed at the 36-meter flight base of the spectrometer GNEIS. The detailed description of the experimental setup, the method of measuring the angular distributions of FFs and the procedures of the data analysis were given in our previous publications [3][4][5]. Here we will focus only on the most principal details and some important moments specific to this series of measurements.…”

“…We began the study of the angular distributions of FFs in neutron induced fission of heavy nuclei at energies up to 200 MeV in 2014 at the neutron time-of-flight spectrometer GNEIS [1,2] of the Petersburg Nuclear Physics Institute. At the previous ND-2016 conference we presented results for target nuclei 209 Bi, 232 Th, 233 U, 235 U, 238 U [3][4][5]. Currently, similar studies are also carried out by the n_TOF (CERN) [6,7] and NIFFTE (LANSCE) [8] collaborations.…”

Theoretical Analysis of Experimental Data on the Angular Anisotropy of Fragments of Nuclear Fission Induced by Neutrons at Energies of up to 200 MeV

“…where are the Clebsch-Gordan coefficients. It is also convenient to use identity (4) where are Legendre polynomials, and give expression (2) the form (5) This includes anisotropy parameters (6) which are nonzero only for even values of Q if = If distribution is smooth, parameters (spin tensors ) decline rapidly as Q grows.…”