Study of the fission process

Nuclear fission is an excellent laboratory for studying nuclear dynamics and correlations with nuclear structure effects. In particular, the characterization of the final state of the reaction (properties of the fragments and neutron and gamma emissions) provides a very rich set of observables, which strongly constrain the models already available or under development.

In this context, LEARN conducts a program to measure the main characteristics (mass, charge, kinetic energy) of the neutron-induced fission fragments in a wide energy range and for different actinides. In the thermal region, the properties of fission fragments are studied with the LOHENGRIN mass spectrometer (ILL, Grenoble). At higher energy (from a few hundreds keV up to 40 MeV), a new instrument under development, FALSTAFF, will be used in the forthcoming NFS facility (GANIL/SPIRAL2).

Another recent approach is to study the de-excitation of fission fragments by measuring their prompt gamma-rays emission in coincidence and with a very good resolution. This study, initiated with a temporary gamma spectrometer moved to ILL (EXILL), is going on with a new and more efficient ILL instrument (FIPPS).

These measurements are part of collaborations, in particular with IN2P3, CEA/DEN and CEA/DIF.

Finally, DPhN physicists have developed extensive expertise in the measurement of delayed neutrons and gammas from fission fragments. This confers a great deal of coherence to the experimental program on fission, complemented by a modeling activity of the fission process that gave rise to the SPY model. This scission point model, based on ingredients derived from microscopic calculations, allows to calculate the properties of fragments and, in the end, neutrons and gammas.

#4239 - Last update : 12/01 2017

Nuclear Physics Division

Institute of Research into the Fundamental Laws of the Universe