Inverse kinematics relativistic studies of the 238U reactions induced by 82Pb and 4Be

Experiments described in this paper are inverse kinematics studies of fission and nuclear fragmentation reactions of a 238U primary beam at relativistic energies on Pb and Be targets performed at the GSI Fragment Separator. The fragment isotopic distributions have been measured. The projectile fragmentations has been also studied. The isotopes transmitted by the FRS having a magnetic rigidity (B ρ) lower then 10 % of that of projectile are shown. One finds the back-going fission fragments in the projectile framework (more rich in neutrons) and products of the nuclear collisions having an important dissipation in energy, leading to deficient neutron fragments. The isotopic production cross sections of fragmentation process are compared with results of a simulation with the EPAX code. Results for uranium fragments close in charge and mass of 238U projectile ware obtained. Particularly, the influence of fission in the decay of primary fragments was studied and fission cross section measurements for secondary targets of several actinides revealing the transition of the fission asymmetric mode to the symmetric fission for N = 138, were measured. These two experiments have led to a new collaboration aiming to apply this cross sections measurement method to the study of inverse kinematics induced reactions in heavy targets by high energy protons. These measurements are of great interest for the current developments of the hybrid system concept of coupling an accelerator to a reactor for waste transmutation or electricity productions