The effort of Isotope harvesting has been of interest because of the massive quantities of radioisotopes that will be produced during routine operation of the Facility for Rare Isotope Beams (FRIB). The harvesting of radioactive isotopes from an aqueous beam stop has been successfully demonstrated in a series of experiments carried out by delivering beams from NSCL (National Superconducting Cyclotron Laboratory) into a dedicated aqueous endstation. Solid isotope harvesting approaches have been probed into to a much lesser extent, but, they have great potential because of the flexibility they offer in collection material, location and time, which can greatly simplify the post irradiation chemistry needed to isolate the radioisotopes. In this work, 0.2 μCi of ⁸⁸Zr (t_1/2= 83.4 d, E_γ= 392.8 keV) was collected when ⁸⁸Zr beam (produced from the fragmentation of a 10-pnA, 140-MeV/u ⁹²Mo primary beam) impinges on a tungsten target. Isotopes of Y, Sr, Nb and Rb were also implanted and ⁸⁸Y and ⁸⁵Sr were used as tracers. The collection of ⁸⁸Zr through solid harvesting approaches was important for comparison to aqueous harvesting results which shows an increase in the collection percentage by three times.

The produced radionuclides ⁸⁸Zr, ⁸⁸Y (t_1/2= 106.6 d, E_γ= 1836 keV, 898 keV) and ⁸⁵Sr (t_1/2= 64.8 d, E_γ= 514 keV) were separated from the tungsten matrix and captured on the columns containing cation exchange resin and extraction chromatography resin with ⁸⁸Zr being collected in a low molarity H₂SO₄. Harvesting these long-lived radionuclides are important because they are otherwise very difficult to produce. Through this experiment, we established radiochemical methodologies for separating Zr, Y, and Sr from the tungsten collector material, and from each other; built a solid isotope harvesting endstation; and completed a solid isotope harvesting experiment at the NSCL.

Jennifer Shusterman

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