Map of the nuclear world

A new experiment at the Laboratory for Heavy Ion Research (GSI) in Darmstadt, Germany, has created and analyzed the largest number of elements (from nitrogen through uranium) and the largest number of isotopes (1385) ever seen in a single nuclear research effort. The only ingredients were a beam of uranium-238 nuclei and a liquid-hydrogen target. Fragment nuclei of all sizes, flying away from the collision point, were accurately identified by GSI’s high-resolution fragment separator with its time-of-flight and energy-loss detectors. The meticulous and comprehensive nuclear experiment produced a set of cross sections, each a measure of the likelihood for creating a particular nuclide in the spallation reaction. The data also revealed a clear separation between the heavy evaporation products and the lighter fission fragments. Altogether, the information is valuable for planning a future accelerator of rare isotopes, for studying how to break down nuclear waste in subcritical reactors, and for studying fundamental aspects of nuclear fission and nuclear viscosity. (P. Armbruster et al., Phys. Rev. Lett. 93, 212701, 2004 http://dx.doi.org/10.1103/PhysRevLett.93.212701 .)