Production of the positron emitter 51 Mn via the 50 Cr ( d , n ) reaction : targetry and separation of no - carrier - added radiomanganese

In connection with the production of 46.2 min Mn via the Cr(d, n)-process, several separation techniques such as ion exchange chromatography, solid phase extraction, liquid–liquid extraction and co-precipitation have been investigated; the aim was to separate no-carrier-added radiomanganese from the bulk target chromium. Among the separation systems ∗MnII/CrIII , ∗MnII/CrVI and ∗MnIV/CrVI, the latter applying the co-precipitation of ∗MnIV with Fe hydroxide was found to be the optimum; the removal of chromium was rapid and quantitative (remaining content < 0.05%) and the separation efficiency was high (99.3% radiochemical yield of ∗Mn). For production purposes, a sandwiched pellet of the chemical composition Al4 ·50CrCl3 was developed as a new target. This allowed a quick dissolution after irradiation, thus enabling a fast separation of Mn and its production on a MBq scale. A 1 h irradiation at 3 μA (wobbled beam) over an effective deuteron energy range of Ed = 12.8 → 7.9 MeV yielded 107 MBq Mn. Simultaneously formed nuclides of other elements, such as Cl, Na, V and Cr were quantitatively separated using the proposed procedure. Only the shorter-lived radioisotope Mn, formed via the Cr(d, 2n)Mn reaction, was present at a low level of 2%, if the enrichment of Cr was 95% (with ∼ 5% Cr).