ISOL

ISOL, short for Isotope Separation On-Line, refers to a family of techniques in nuclear physics used to produce and deliver beams of short-lived radioactive isotopes for experiments. In a typical ISOL facility, a high-energy primary beam, usually protons, strikes a thick target material. Nuclear reactions in the target generate a range of isotopes, which then diffuse out of the target material. The produced ions are ionized (commonly by surface ionization or resonant laser ionization), extracted from the target region, and mass-separated, typically by a dipole magnet, to select a specific mass-to-charge ratio. The resulting radioactive ion beam is then accelerated to the desired energy and delivered to experimental stations for studies in nuclear structure, decay spectroscopy, or reaction dynamics. The on-line nature of the method means that production, separation, and delivery occur within a single, integrated system, enabling access to very short-lived nuclides.

ISOL is distinguished from other approaches such as in-flight fragmentation, where nuclides are separated before being slowed and implanted. The ISOL technique offers high chemical selectivity and the potential for high-purity beams, including for elements that are difficult to produce by other means. Variants of ISOL include laser ion sources, such as the Resonant Ionization Laser Ion Source (RILIS), and the Ion Guide Isotope Separator On-Line (IGISOL) approach, which uses a gas-filled ion guide.

Notable facilities using ISOL methods include CERN’s ISOLDE and TRIUMF’s ISAC, among others, which have supported a wide range of nuclear and atomic physics research since the mid-20th century.