PRODUCTION OF MEDIUM-WEIGHT ISOTOPES BY FRAGMENTATION IN 750 A MEV U-238 ON PB-208 COLLISIONS

Projectile fragmentation of U-238 in lead target was investigated at a bombarding energy of 750 A MeV. Isotopic production cross sections of about 250 different projectile fragments in the element range Z = 30- 53 were measured with the FRagment Separator (FRS). The magnetic selec tion and the kinematical analysis of the measured isotopes allowed to disentangle fission and fragmentation residues. The mass loss of these residues indicates a violent collision where a large amount of energy is dissipated. The position of the fragmentation corridor defined by the measured residues aas used to determine an effective proton-evapor ation barrier.