Exotic Nuclei and Their Separation, Using Atomic Interactions

Abstract

The discovery of short-lived, exotic nuclei has opened new horizons in subatomic physics and allowed many novel applications in other fields, e.g., the understanding of the evolution of matter and production of the atomic elements in the universe. The effective and highly selective separation of the exotic nuclei produced in these reactions from other more abundant products and the primary beam is critical for the study of exotic species. The high sensitivity of separators can reach single ions produced with sub-picobarn cross sections. Depending on the type of production reaction and the kinematics of the products, different accelerator facilities and separation methods have been constructed and applied. A reaction-product separator is the heart of each such facility. The presentation of fragment separators and their application have been divided here in two parts. A brief overview of the relevant production reactions for modern-day separation techniques and then the ion-optical features of fragment separator design and operation were presented in Part 1. These devices can consist of pure dispersive electromagnetic elements or can incorporate specific atomic interactions of the ions in additional matter along their path through the separator. Extension to systems that incorporate atomic interactions and combinations of these devices with additional high-resolution ion-optical systems to provide unique opportunities to study exotic nuclei immediately after they pass through the system is presented here in Part 2. Nuclear physics laboratories around the world have built reaction-product separators, have plans for new separation facilities, and are constructing new machines with enhanced capabilities that rely on these devices. Finally, the whole presentation concludes with a discussion of key goals, achievements, and limitations in the separation and science of exotic nuclei.