Relative merits of projectile fragmentation and ISOL methods for producing radioactive beams

There is a wide range of research in nuclear physics which can be addressed at accelerator facilities which provide high-quality, intense radioactive nuclear beams. The spectrum of possibilities is so broad that a single radioactive beam production mechanism will not be able to satisfy all interests. Radioactive beams produced via the fragmentation of high energy heavy ions have advantages for certain classes of experiments, while beams produced by acceleration of isotopes from on-line mass separators (ISOL) are most useful for others. Fragmentation of heavy ion beams in the 100-1000 MeV per nucleon energy range produces a broad range of secondary beams, both proton- and neutron-rich, with separation times on the microsecond time scale so that beams of very short lifetimes and even isomers are possible. Much progress in the design of fragment separators for purifying such beams has been made in recent years, and methods are currently being developed for increasing their brighness. On the other hand, intense sources of a broad range of iostopes are available via spallation of high-current primary beams in targets coupled to ISOL systems. Although release times from spallation targets and ion sources are in the 100 millisecond range, methods for separating and ionizing many chemical species have been developed, especially at the CERN ISOLDE facility. Methods to accelerate such radioactive beams beams are being developed and proposed. These methods will produce intense, high-quality radioactive beams with energies determined by the choice of accelerator. The relative costs and capabilities of various choices for spallation beams will also be discussed