Radioactive projectile beams

There are a few hundred stable nuclei but several thousand nuclei that are radioactive and have experimentally useful lifetimes. Since 1990, one of the fastest growing areas of research in nuclear science has been the study of nuclear reactions induced by radioactive projectiles. Using either ISOL (/sotope Separator On-Line) or PF (Projectile Fragmentation) techniques, several hundred new radioactive nuclear beams have become available (see Chapter 14). 

ISOLDE at CERN (SC), make it feasible to consider using such secondary ions as projectiles for nuclear reactions. A pressing need for reaction rate data involving radioactive species exists in nuclear astrophysics. This requires having available projectiles (A < 60) in the energy range from about 200 keV/amu to 1.5 MeV/amu. It has been proposed to install an ISOL device at the TRIUMF facility to utilize the available intermediate energy (200-500 MeV), intense (<100 yA) proton beam as the primary production source. The mass analyzed, radioactive beam (RB),... 

In the seven decades since the discovery of nuclear fission, experimental studies on low-energy fission have been restricted to about 80 fissionable nuclei. They represent only about 15% of all known nuclei with Z > 82. However, recently a novel experimental technique has been introduced. The fission of relativistic secondary projectiles has now been studied in flight. The benefit of the radioactive beams for studying the fission process is clear, but no fission probabilities below the fission barrier have been determined so far (Schmidt et al. 1994). 

Evaporation residues arising in complete-fusion reactions between actinide targets and radioactive-beam particles are controlled by the same < r /Ff > and dynamical hindrance effects as are the reaction products from stable-ion beam irradiations. It has been observed that fusion cross sections for reactions with neutron-rich radioactive beam particles can be enhanced over those with stable-isotope beams at the same Z, possibly due to an effective lowering of the fusion barrier with the increasing neutron number of the projectile facilitated by neutron flow in the dinuclear reaction intermediate [226, 454, 458]. It is unclear how dynamical hindrance effects and a reduced resistance to deexcitation by fission at high excitation energies in heavier systems will influence the formation of evaporation residues. It has been suggested that the formation of products at the... 

When not constrained to the stable nuclei, beams of particles with neutron numbers out to the neutron-drip line can be considered as possible reactants. Though the lack of suitable accelerator facilities makes this a hypothetical exercise, there are practical concerns governing production of the radioactive species for acceleration as the secondary beam. Continuous production of large quantities of these nuclides is required for the generation of a radioactive beam that is sufficiently intense for a superheavy element synthesis experiment. This limits our discussions to radioactive species close to the line of stability, because of both primary production rate and half-life. To confine the following discussion, only radioactive ions within four mass numbers of the heaviest stable isotope of each element will be considered as projectiles unless there is a stable isotope of a nearby element at higher neutron number (e.g., " Ar, at the same neutron number as Ca). 

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