Short-lived rare isotopes are a challenge to produce in large quantities. Samples cannot be produced through off-line chemical separation: given their short half-life, they would decay away during the time it takes to extract them. The production and study of new isotopes in the laboratory, at Radioactive Isotope Beams (RIB) facilities, provides a wide variety of information, from fundamental-research studies to the development of isotopes for cancer treatments and applications.
In the Isotope Separation On-Line (ISOL) method, the rare isotopes are being produced during the interaction of a light particle with a thick high-Z target. The process is summarized as follows: Protons from a high-energy driver impinge on an ISOL-target material in an enclosed container that is directly connected to an ion source. Nuclear reactions take place in the target with the production of a large variety of isotopes that come to rest embedded in the target material. Operating the target at high-temperature, these isotopes diffuse through the target lattice (move between the atoms of the material) to the surface where they are evaporated and then effuse from the target container to the ion source where they can be ionized. Afterwards, the ions are extracted by a potential difference of several tens of kV in a radioactive ion beam, which undergoes mass purification through an isotope mass separator.
Worldwide, there are several ISOL facilities under upgrade or being proposed, among which the ISOL@MYRRHA project at SCK•CEN. However, the success of these facilities is highly dependent on the capacity to solve issues related to target materials, which have to be capable to withstand reliably high power deposition by the intense high-energy proton beam over long periods of irradiation time without compromising diffusion efficiency of the created rare isotopes.