New results on low-energy fission with high-energy RNB

At the fragment separator (FRS) at GSI Darmstadt fission studies with a number of secondary beams produced by fragmentation of a 1 A GeV 238U beam have been performed. Fission-in-flight was induced in a secondary lead target at average secondary-beam kinetic energies of about 400 MeV A. By measuring the velocities and the energy losses of both fission fragments their nuclear charges could be determined. From the data, fission-fragment charge distributions for electromagnetic-induced fission in lead at an average excitation energy of 10 MeV were extracted. Our method offers the possibility to vary the A/Z-ratio of the secondary-beam particle over a wide range and thus to investigate the proton even-odd effect as well as the transition from symmetric fission to asymmetric fission in a region of the chart of the nuclides which was difficult to reach in previous fission studies. (orig.)