201-Tl production for medical use by (p,xn) nuclear reactions on Tl and Hg natural and enriched targets

High-specific activity 201-Tl for biomedical uses might be produced by proton activation on: a) Hg targets by direct (p,xn) nuclear reactions, b) Tl targets via its parent radionuclide 201-Pb, c) Pb targets via its parent radionuclides 201-Bi and 201-Pb. With the Milan University AVF Cyclotron (maximum proton energy 45 MeV) the only nuclear reactions, which can be used for its production are the 203-Tl(p,3n), 201-Pb → 201-Tl and the Hg(p,n/p,2n/p,4n)201-Tl ones. So, thin-target excitation function measurements and thick-target-yield calculations have been carried out in the proton energy range available, for the (p,xn) nuclear reactions on nat-Tl, 81% enriched 203-Tl, nat-Hg and 98.6% enriched 202-Hg targets. The yields and contaminations obtainable with the various methods are discussed in some detail. (Auth.)