The nearly completed Facility for Rare Isotope Beams (FRIB) operated by Michigan State University is expected to deliver beams of exotic nuclei for fundamental nuclear science research. As FRIB fulfills this mission, many other by-product radionuclides will be simultaneously produced that could be collected without interference to the primary experiment. These co-produced radionuclides will be available as both gaseous and dissolved species in various locations throughout FRIB, but particularly in the water-filled primary beam dump just after the production target. By recycling the water through a chemical system, it will be possible to collect the radionuclides through a process known as “isotope harvesting.” In order to access the by-product radionuclides in the FRIB beam dump from both the aqueous and gaseous phases, a water-filled beam blocker and harvesting system have been developed and tested at the National Superconducting Cyclotron Laboratory (NSCL), a heavy-ion fragmentation facility similar to FRIB with less capabilities and lower beam intensities. Previous harvesting experiments at the NSCL focused on the feasibility of aqueous-phase harvesting of various radionuclides from different reaction and chemical systems; however, little research into the feasibility of simultaneously harvesting gaseous radionuclides from the system has been done. To demonstrate gas-phase harvesting capabilities at the NSCL and the future FRIB, a gas processing line was designed to be implemented during a low-intensity 150 MeV/nucleon 78Kr irradiation of water with the intent to collect 76Kr and 77Kr to use as generators for 76Br and 77Br, respectively. Before using the harvesting system in the 78Kr irradiation, the durability of the materials and the chemical and physical behavior of the gas stream were tested during a low-intensity 140 MeV/nucleon 40Ca irradiation. And following the 78Kr irradiation, the chemical state of the gas stream was further analyzed during a high-intensity 140 MeV/nucleon 48Ca irradiation. Through this work, target materials were tested, radiolysis products were measured, and the first true test of the gas-phase harvesting capabilities at the NSCL was demonstrated. The insight gained from the experiments described here will lead to successful gas-phase harvesting experiments at FRIB to produce and collect noble gas generators.
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