Production of 75Br via the 76Se(p, 2n)75Br reaction at a compact cyclotron

Abstract

Excitation functions were measured by the stacked-foil technique for the reactions ⁷⁶Se(p, n)⁷⁶Br, ⁷⁶Se(p, 2n)⁷⁵Br, ⁷⁶Se(p, 3n)^74mBr, ⁷⁶Se(p, α)⁷³As, ⁷⁶Se(p, αn)⁷²As, ⁷⁶Se(p, α2n)⁷¹As and ⁷⁶Se(p, ³He + 2pn + pd)⁷⁴As on 96.48% enriched ⁷⁶Se up to E_p = 40 MeV. The optimum energy range for the production of ⁷⁵Br via the ⁷⁶Se(p, 2n)⁷⁵Br reaction at our compact cyclotron is E_p = 24 → 21.5 MeV, the calculated thick target yield of ⁷⁵Br amounting to 32 mCi/μ Ah and the expected level of ⁷⁶Br-impurity to 2.0%. A thin layer of metallic ⁷⁶Se on Al-backing was used as target in combination with a water-cooled rotating target head. A dry distillation technique for the separation of radiobromine from irradiated targets was developed; radiochemical yields of about 40–52% were obtained. Using a 50.2 mg/cm² thick target (E_p = 24→21.85 MeV, an irradiation time of 1.25 h at a nominal proton beam current of 15 μA and a distillation time of 30 min at 300°C, about 160 mCi of ⁷⁵Br (at EOB) is produced. The total loss of ⁷⁶Se after irradiation and distillation process is <1%. The levels of ⁷⁶Br and ⁷⁷Br impurities in ⁷⁵Br are <3% and 0.15%, respectively.