Excitation functions of nuclear reactions leading to the soft-radiation emitting radionuclides 45Ca, 49V and 204TI in beam collimator materials used in proton therapy

Cross sections of nuclear reactions leading to the formation of the soft-radiation emitting radionuclides 45 Ca (T 1/2 = 163 d; β - = 260 keV), 49 V (T 1/2 = 330 d; K α = 4.51 keV) and 204 TI (T 1/2 = 3.78 a; β - = 763 keV) in proton induced reactions on titanium and lead, respectively, often used as collimators in proton therapy facilities, were measured for the first time over the energy range extending up to 200 MeV. Use was made of the stacked-foil technique. Elaborate radiochemical separations were performed and the radioactivity of the products was determined via anticoincidence beta counting, liquid scintillation counting or X-ray spectrometry. The experimental data were compared with the results of nuclear model calculations using the codes ALICE-IPPE and TALYS. In general good agreement was obtained. In the case of 204 Tl, however, the calculated values from ALICE-IPPE in the energy region above 80 MeV deviated considerably from the experimental data, possibly due to strong contributions of multiple particle emission reactions.