Investigation of Cr-50(d,n)Mn-51 and Cr-nat(p,x)Mn-51 processes with respect to the production of the positron emitter Mn-51

The positron emitter Mn-51 (t(1/2) = 46.2 min, Ibeta+ = 97%) is of potential interest in positron emission tomography (PET). With a view to optimizing its production route, excitation functions for deuteron induced nuclear reactions on isotopically enriched (similar to 95%) Cr-50 were determined radiochemically over the energy range of 3 to 13 MeV and for proton induced nuclear reactions on Cr-nat in the range of 18 to 38 MeV. Cross sections are presented for the reactions: Cr-50(d, 2n)Mn-50m, Cr-50(d, n)Mn-51, Cr-50(d, t)Cr-49, Cr-50(d, p)Cr-51, Cr-50(d, alpha)V-48, Cr-52(d, 2p)V-52, Cr-nat(p, x)Mn-51, Cr-nat(p, x)Mn-52, Cr-nat(p, x)Mn-52m, Cr-nat(p, x)Mn-54, Cr-nat(p, x)Cr-48, Cr-nat(p, x)Cr-49, Cr-nat(p, x)Cr-51, Cr-nat(p, x)V-48 and Cr-nat(p, x)Ti-45. In the case of proton induced reactions on Cr-nat, the isomeric cross section ratio for the isomeric pair Mn-52m,Mn-g was also determined. The results are interpreted in terms of the spins of the two isomers concerned. Theoretical thick target yields were derived from the corresponding excitation functions. The maximum achievable thick target yield of Mn-51 is 1.1 GBq/mu Ah in the case of the Cr-50(d, n)Mn-51 reaction at E-d = 14 --> 3 MeV, and 3.2 GBq/mu Ah in the case of the Cr-nat(p, x)Mn-51 process for E-p = 40 --> 20 MeV. The Cr-50(d, n)Mn-51 process is the favourable production route for Mn-51, since the radioisotopic purity is high and a small-sized medical cyclotron is adequate to produce this positron emitter in sufficient quantities.