At the Facility for Rare Isotope Beams (FRIB), development has been underway to collect radionuclides that are produced as by-products of dumping the unused portion of the primary beam into a flowing-water beam stop. This technique, known as ‘isotope harvesting,’ has been tested in several exploratory studies and demonstrated its capability to collect isotopes from the water system. Isotope harvesting is predicted to be a promising source of isotopes, essential for advancing both basic and applied sciences. However, this method is inherently non-selective, and most isotopes can only be recovered from the water at limited radioisotopic purity. A viable method to improve the purity of the harvested samples is by implementing a mass-separation step. Metal oxides were proposed as potential novel sorbent materials, as their refractory nature makes them compatible with the high-temperature environment of the plasma ion source of the mass separator, a feature that makes the envisioned combined approach possible. In the here-performed research, the feasibility of using metal oxides for isotope collection has been investigated. Simulation studies have been performed with nickel, which represents our main isotopes of interest, and nine other stable elements that are the main co-produced isotopes, under conditions similar to the predicted harvesting environment in the aqueous beam dump. Several of the tested metal oxides demonstrated adequate adsorption abilities for certain elements, while magnesium oxide emerged as the most promising for Ni capture. This was used to produce a sample of magnesium oxide with adsorbed, stable, enriched 61Ni for a proof-of-principle mass-separation experiment. The results showed that mass separation performance with oxide-based samples is highly challenging due to the formation of various, partially refractory, species. In retrospect, it was also observed that the use of certain metal oxides, particularly magnesium oxide, results in the release of ions into the aqueous environment, which is undesirable. Based on these findings, while the insoluble metal oxides could see applications for the adsorption of particular elements, it was decided to consider different targetry options for the mass-separation step. In the second part of this work, research was also done to develop a 73As source material for the low-energy and stopped user beam program at FRIB. The source sample was prepared through precipitation of aqueous 73As, after addition of stable As carrier, as silver arsenate. The 73As source was submitted and used to successfully create a 73As beam. Characterization via Scanning Electron Microscopy-Energy Dispersive X-Ray (SEM-EDS) and X-Ray Photoelectron Spectroscopy (XPS) was done with an analogously prepared stable As source sample.
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