Narrow Results

The three-dimensional Langevin equation (LE) and Transition State Model (TSM) are applied to calculate prescission neutron multiplicity and anisotropy of fission fragment angular distribution for ¹⁶O+¹⁸¹Ta and ¹⁶O+²⁰⁸Pb systems. Dynamical calculations were carried out considering one-body dissipation. Theoretical results of pre-scission neutron multiplicity and anisotropy have been compared with experimental data for given systems. Calculations show that the results of anisotropy based on dynamical approach are in better agreement with the experimental data as compared with the TSM (in saddle point).

Photofission of ${}^{232}$Th, ${}^{238}$U, ${}^{237}$Np and ${}^{240}$Pu isotopes are investigated. Modified version of Gorodisskiy approach that is developed to study the neutron-induced fission are employed to simulate fission fragment mass distribution for these isotopes in different energies. The effect of emitted neutron prior to scission point is studied. Peak to valley ratio is also extracted. Obtained results using this approach are compared with original Gorodisskiy model as well as available experimental data. Satisfactory agreement is achieved between theoretical and experimental data especially in medium and low $\gamma$-ray energies than original formalism of Gorodisskiy.

Fission fragments mass distribution of ${}^{237}$Np, ${}^{241,243}$Am and ${}^{239,242,244}$Pu isotopes in proton-induced fission at various energies are studied. In order to simulate fission fragments mass distribution, a semi-empirical formula with some adjustable parameters is developed. Adjustable parameters are obtained by least square fitting of simulated fission fragments mass distribution with experimental data for a isotope at a given energy. This formalism is developed based on Gorodisskiy’s method. This approach with a set of adjustable parameters is used to simulate the fission fragments mass distribution of proton-induced fission for various isotopes at different energies in the actinides region. Predicted results using our approach are compared with the results of the Gorodisskiy method as well as the available experimental data. Good correspondence is achieved between our simulated results with the available experimental data compared with the results of the Gorodisskiy method.

After nearly 80 years of research on nuclear fission, we still do not fully understand the fission process. A combination of new requirements for accurate fission nuclear data, the ability to calculate sophisticated models of fission, and the development of new experimental techniques has re-energized the field. This paper concentrates on recent developments in the experimental realm and what the new results can contribute to the database for applications and to improving the underlying physical models. This overview is intended to be an introduction to fission presentations at this meeting.

A major part of the scientific program of the CERN n_TOF facility involves the study of neutron-induced fission reactions, which is essential for nuclear technology, as well as for the development of the theoretical models of fission. An overview of the fission studies performed and the corresponding detection systems is given, with a short description of the latest highlights.

Fission fragments play an important role in nuclear reactors evolution and safety. However, fragments yields are poorly known : data are essentially limited to mass yields from thermal neutron-induced fissions on a very few nuclei. SOFIA (Study On FIssion with Aladin) is an innovative experimental program on nuclear fission carried out at the GSI facility, which aims at providing isotopic yields on a broad range of fissioning systems. Relativistic secondary beams of actinides and pre-actinides are selected by the Fragment Separator (FRS) and their fission is triggered by electromagnetic interaction. The resulting excitation energy is comparable to the result of an interaction with a low-energy neutron, thus leading to useful data for reactor simulations. For the first time ever, both fission fragments are completely identified in charge and mass in a new recoil spectrometer, allowing for precise yields measurements. The yield of prompt neutrons can then be deduced, and the fission mechanism can be ascribed, providing new constraints for fission models. During the first experiment, all the technical challenges were matched : we have thus set new experimental standards in the measurements of relativistic heavy ions (time of flight, position, energy loss).This communication presents a first series of results obtained on the fission of 238U; many other fissioning systems have also been measured and are being analyzed presently. A second SOFIA experiment is planned in September 2014, and will be focused on the measurement of the fission of ²³⁶U, the analog of ²³⁵U+n.