Summary. Excitation functions were measured by the stacked-foil technique fornat Sr( p, xn)

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Proton induced reaction / Excitation function /Collimator materials Ti and Pb / Activation products 45 Ca, 49 V and 204 Tl / Radiochemical separation / Nuclear model calculation Summary. 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 Tl (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.

Nuclear reaction cross-section measurements via the activation technique are generally made using highresolution γ-ray spectrometry. However, in cases where the radioactive product decays exclusively by EC (without emitting a γ-ray) resort has to be made to the rather subtle technique of x-ray spectrometry. Similarly for characterisation of pure β − emitters, gas-flow proportional or liquid-scintillation counting is applied. In both cases the use of radiochemical methods is most essential. We studied the nat Ti(p,xn) 49 V and 85 Rb(p,4n) 82 Sr reactions via x-ray spectrometry. In each case a clean radiochemical separation was performed and a thin source was prepared. The radioactivity of 49 V was determined using the soft 4.5-keV k α x-rays and that of 82 Sr via the 13.4-keV k α x-rays. In another study, the reactions nat Ti(p,x) 45 Ca, 89 Y(n,p) 89 Sr, and nat Pb(p,x) 204 Tl were investigated. All the products are pure β − emitters and therefore clean radiochemical separations were mandatory. The radioactivity of each of the three products was determined via low-level anticoincidence β − counting. Furthermore, in the case of 45 Ca, liquid-scintillation counting was also used. The results obtained using different techniques are compared.