Abstract
The renewed interest for the study of nuclear fission is mainly motivated by the development of GEN-IV reactor concepts, mostly foreseen to operate in the fast neutron energy domain. To support this development, new high-quality nuclear data are needed. In this context, a new experimental setup, the FALSTAFF spectrometer, dedicated to the study of nuclear fission is under development. Employing the double-velocity (2V) and energy-velocity (EV) methods, the fission fragment mass before and after neutron evaporation will be deduced and the correlation between prompt neutron multiplicity and fragment mass will be determined. The first arm of the spectrometer is achieved. It is composed of two SED-MWPC detectors (a combination of a foil to produce secondary electrons and a Multi-Wire Proportional Chamber to detect them) and an axial ionization chamber. The SED-MWPC give access to the velocity (V) via time-of-flight and position measurements. The ionization chamber measures the fragment kinetic energy (E) and the energy loss profile. Preliminary results for spontaneous fission of 252Cf and from the thermal-neutron induced fission experiment on 235U, performed at the Orphée reactor (CEA-Saclay, France), are presented.
Highlights
Nowadays the fission process still presents a great interest from both theoretical and experimental point of view
The renewed interest for the study of nuclear fission is mainly motivated by the development of GEN-IV reactor concepts, mostly foreseen to operate in the fast neutron energy domain
A new experimental setup, the FALSTAFF spectrometer, dedicated to the study of nuclear fission is under development
Summary
Nowadays the fission process still presents a great interest from both theoretical and experimental point of view. The goal is to determine the neutron multiplicity as a function of the fragment characteristics (pre-neutron mass and kinetic energy) in neutron-induced fission of specific actinides in the MeV range. This experiment is rich as it allows accessing numerous aspects of fission, e.g. the deformation at scission, the influence of single-particle. The 2V method (measurement of both fragment velocities in coincidence) gives access to the pre-neutron mass This method is meaningful only when the mass of the fissioning system is known, namely for incident neutron energies below the threshold of the second chance fission channel opening (En < 5.5 MeV). Results for the spontaneous fission of 252Cf and the thermal neutron-induced fission of 235U will be presented in section 3 and 4 respectively
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