Recent developments of the FALSTAFF experimental setup

The study of nuclear ssion is encountering renewed interest with the development of GEN-IV reactor concepts, mostly working in the neutron fast energy domain. To support the fast reactor technologies, new high quality nuclear data are needed. For this reason, the future Neutrons For Sciences (NFS) installation, built in the framework of the SPIRAL2 project and producing high intensity neutron beams from hundreds of keV up to 40 MeV, will open new opportunities to characterise the actinide ssion fragments. To perform these measurements, the development of an experimental setup called FAL- STAFF has been undertaken. This novel apparatus is meant to provide a simultaneous characterisation of the complementary fragments in terms of mass, kinetic energy and to evaluate the average neutron multiplicity. To reach this goal the spectrometer must present a very good time, energy and space resolutions. The coupling of the Secondary Electron Detectors (SeD) detectors with an ionisation axial chamber seems fulll these conditions. The ssion fragment velocities are measured employing two time-of- ight (SeD), sepa- rated by a distance of 50 cm. Those detectors combine a Mylar foil and a MWPC (multi wire proportional counter) to measure the arrival time and the position of the incoming particle. The fragment energies are measured by an axial ionisation chamber, CALIBER, placed after the SeD Stop detector. Moreover, the axial conguration of the chamber gives access to the energy loss prole, which could be used to identify the light fragment nuclear charge. The FALSTAFF setup and the upgrade of the rst arm prototype with the new ionisa- tion chamber CALIBER will be presented. New tests are performed at CEA-Saclay and the combined measurement obtained from the SeD and the ionisation chamber will be shown. The performances of the experimental apparatus in terms of energy and mass resolution will be discussed.