Abstract
A flowing-water target was irradiated with a 150 MeV/nucleon beam of 78Kr at the National Superconducting Cyclotron Laboratory to produce 77Kr and 76Kr. Real-time gamma-imaging measurements revealed the mass transport of the krypton radioisotopes through the target-water processing, or “isotope harvesting”, system. The production rates were determined to be 2.7(1) × 10–4 nuclei of 76Kr and 1.18(6) × 10–2 nuclei of 77Kr formed per incident 78Kr ion. Utilizing an off-gas processing line as part of the isotope harvesting system, a total of 7.2(1) MBq of 76Kr and 19.1(6) MBq of 77Kr were collected in cold traps. Through the decay, the daughter radionuclides 76Br and 77Br were generated and removed from the traps with an average efficiency of 77 ± 12%. Due to the differences in half-lives of 76Kr and 77Kr, it was possible to isolate a pure sample of 76Br with 99.9% radionuclidic purity. The successful collection of krypton radioisotopes to generate 76Br and 77Br demonstrates the feasibility of gas-phase isotope harvesting from irradiated accelerator cooling-water. Larger-scale collections are planned for collecting by-product radionuclides from the Facility for Rare Isotope Beams.
Highlights
A flowing-water target was irradiated with a 150 MeV/nucleon beam of 78Kr at the National Superconducting Cyclotron Laboratory to produce 77Kr and 76Kr
As FRIB fulfills its mission of providing rare isotope beams for fundamental nuclear science research, many useful by-product radionuclides will be formed through beam interactions with accelerator components
Once the krypton-specific constants were determined, it was possible to benchmark the Nuclear Physics Imager (NPI) measurements against the calibrated, quantitative, BEGe gamma-ray spectra to find the production rates for 76Kr and 77Kr: 2.7(1) × 10–4 nuclei of 76Kr, and 1.18(6) × 1 0–2 nuclei of 77Kr were formed per incident 78Kr ion
Summary
A flowing-water target was irradiated with a 150 MeV/nucleon beam of 78Kr at the National Superconducting Cyclotron Laboratory to produce 77Kr and 76Kr. The successful collection of krypton radioisotopes to generate 76Br and 77Br demonstrates the feasibility of gas-phase isotope harvesting from irradiated accelerator cooling-water. To test the proposed harvesting system to be used at FRIB, a similar system was designed and implemented in several beam experiments at the National Superconducting Cyclotron Laboratory (NSCL)[3] This system was designed with the same materials on a smaller scale and was tested at lower beam power than planned for FRIB as well as with higher areal power deposition. The motivation for the development was to capture 76Kr and 77Kr and generate medically relevant bromine radioisotopes, 76Br and 77Br, respectively. Radioisotopes of bromine, such as 76Br and 77Br, are uniquely suitable radiolabels for small molecule theranostic radiopharmaceuticals. The advantages and disadvantages for the radiobromines in medical applications are thoroughly discussed in a recent review by Wilbur and Adam[13]
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