Number 83 (Story #3), June 8, 1992 by Phillip F. Schewe and Ben Stein BEAMS OF RADIOACTIVE NUCLEI help scientists to study short-lived nuclides in a way that was not possible before. A great deal of what we know about nuclei comes from high-energy collisions at accelerators, where necessarily the beam or target particles are themselves stable nuclei. In recent years, however, it has been possible to collect short-lived nuclei (created in reactions involving a primary beam) and re-inject them for acceleration, after which they can participate in high-energy collisions of their own. For example, at the Louvain-la-Neuve cyclotron lab in Belgium, a primary proton beam strikes a carbon-13 target. The nitrogen-13 nuclei produced in the process are extracted and accelerated up to an energy of 8.2 MeV and then shot into a polyethylene target. The ensuing collisions provide an important insight into reactions presumed to take place in certain extreme astrophysical environments, such as white dwarfs and neutron stars. (Physics Today, June 1992.)