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Harvesting krypton isotopes from the off-gas of an irradiated water target to generate ⁷⁶Br and ⁷⁷Br.

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.

SUBMITTER: Clause HK

PROVIDER: S-EPMC8792061 | biostudies-literature | 2022 Jan

REPOSITORIES: biostudies-literature

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Harvesting krypton isotopes from the off-gas of an irradiated water target to generate 76Br and 77Br.

Clause Hannah K HK Domnanich Katharina A KA Kleinfeldt Chloe C Kalman Morgan M Walker Wesley W Vyas Chirag C Abel E Paige EP Severin Gregory W GW

Scientific reports 20220126 1

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 ...[more]

PMID: 35082335

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Project description:IntroductionThe radioisotopes of bromine are uniquely suitable radiolabels for small molecule theranostic radiopharmaceuticals but are of limited availability due to production challenges. Significantly improved methods were developed for the production and radiochemical isolation of clinical quality 76Br, 77Br, and 80mBr. The radiochemical quality of the radiobromine produced using these methods was tested through the synthesis of a novel 77Br-labeled inhibitor of poly (ADP-ribose) polymerase-1 (PARP-1), a DNA damage response protein.Methods76Br, 77Br, and 80mBr were produced in high radionuclidic purity via the proton irradiation of novel isotopically-enriched Co76Se, Co77Se, and Co80Se intermetallic targets, respectively. Radiobromine was isolated through thermal chromatographic distillation in a vertical furnace assembly. The 77Br-labeled PARP inhibitor was synthesized via copper-mediated aryl boronic ester radiobromination.ResultsCyclotron production yields were 103 ± 10 MBq∙μA-1∙h-1 for 76Br, 88 ± 10 MBq∙μA-1∙h-1 for 80mBr at 16 MeV and 17 ± 1 MBq∙μA-1∙h-1 for 77Br at 13 MeV. Radiobromide isolation yields were 76 ± 11% in a small volume of aqueous solution. The synthesized 77Br-labeled PARP-1 inhibitor had a measured apparent molar activity up to 700 GBq/μmol at end of synthesis.ConclusionsA novel selenium alloy target enabled clinical-scale production of 76Br, 77Br, and 80mBr with high apparent molar activities, which was used to for the production of a new 77Br-labeled inhibitor of PARP-1.Advances in knowledgeNew methods for the cyclotron production and isolation of radiobromine improved the production capacity of 77Br by a factor of three and 76Br by a factor of six compared with previous methods.Implications for patient carePreclinical translational research of 77Br-based Auger electron radiotherapeutics, such as those targeting PARP-1, will require the production of GBq-scale 77Br, which necessitates next-generation, high-yielding, isotopically-enriched cyclotron targets, such as the novel intermetallic Co77Se.

Project description:We investigate the presence of complex organic molecules (COMs) in strongly UV-irradiated interstellar molecular gas. We have carried out a complete millimetre (mm) line survey using the IRAM 30 m telescope towards the edge of the Orion Bar photodissociation region (PDR), close to the H2 dissociation front, a position irradiated by a very intense far-UV (FUV) radiation field. These observations have been complemented with 8.5″ resolution maps of the H2CO JKa,Kc = 51,5 → 41,4 and C18O J = 3 → 2 emission at 0.9 mm. Despite being a harsh environment, we detect more than 250 lines from COMs and related precursors: H2CO, CH3OH, HCO, H2CCO, CH3CHO, H2CS, HCOOH, CH3CN, CH2NH, HNCO, [Formula: see text] and HC3N (in decreasing order of abundance). For each species, the large number of detected lines allowed us to accurately constrain their rotational temperatures (Trot) and column densities (N). Owing to subthermal excitation and intricate spectroscopy of some COMs (symmetric- and asymmetric-top molecules such as CH3CN and H2CO, respectively), a correct determination of N and Trot requires building rotational population diagrams of their rotational ladders separately. The inferred column densities are in the 1011 - 1013cm-2 range. We also provide accurate upper limit abundances for chemically related molecules that might have been expected, but are not conclusively detected at the edge of the PDR (HDCO, CH3O, CH3NC, CH3CCH, CH3OCH3, HCOOCH3, CH3CH2OH, CH3CH2CN, and CH2CHCN). A non-thermodynamic equilibrium excitation analysis for molecules with known collisional rate coefficients suggests that some COMs arise from different PDR layers but we cannot resolve them spatially. In particular, H2CO and CH3CN survive in the extended gas directly exposed to the strong FUV flux (Tk = 150 - 250 K and Td ≳ 60 K), whereas CH3OH only arises from denser and cooler gas clumps in the more shielded PDR interior (Tk = 40 - 50 K). The non-detection of HDCO towards the PDR edge is consistent with the minor role of pure gas-phase deuteration at very high temperatures. We find a HCO/H2CO/CH3OH ≃ 1/5/3 abundance ratio. These ratios are different from those inferred in hot cores and shocks. Taking into account the elevated gas and dust temperatures at the edge of the Bar (mostly mantle-free grains), we suggest the following scenarios for the formation of COMs: (i) hot gas-phase reactions not included in current models; (ii) warm grain-surface chemistry; or (iii) the PDR dynamics is such that COMs or precursors formed in cold icy grains deeper inside the molecular cloud desorb and advect into the PDR.

Dataset Information

Harvesting krypton isotopes from the off-gas of an irradiated water target to generate ⁷⁶Br and ⁷⁷Br.

Publications

Harvesting krypton isotopes from the off-gas of an irradiated water target to generate <sup>76</sup>Br and <sup>77</sup>Br.

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