LOW-ENERGY FISSION INVESTIGATED IN REACTIONS OF 750-AMEV U-238 IONS WITH PB AND BE TARGETS .1. NUCLEAR-CHARGE DISTRIBUTIONS

Charge distributions of fragments from low energy nuclear fission are investigated in reactions of highly fissile U-238 projectiles at relat ivistic energies (750 A . MeV) with a heavy (Pb) and a light (Be) targ et. The fully stripped fission fragments are separated by the Fragment Separator (FRS). Their high kinetic energies in the laboratory system allow the identification of all atomic numbers by using Multiple-Samp ling Ionization Chambers (MUSIC). The elemental distributions of fragm ents observed at larger magnetic rigidities than the U-238 projectiles show asymmetric break-up and odd-even effects. They indicate a low en ergy fission process, induced mainly by dissociation in the electro-ma gnetic field for the U/Pb-system, or by peripheral nuclear interaction s for the U/Be-system.