Excitation functions of72Ge(p,xn)72,71As reactions from threshold up to 45 MeV for production of the non-standard positron emitter 72As

Abstract

Nuclear reaction cross sections for the formation of 72As and 71As in proton-induced reactions on enriched 72Ge targets were measured up to 45 MeV utilizing three different cyclotrons at the Forschungszentrum Jülich. The stacked-thin sample activation technique in combination with high-resolution γ-ray spectrometry was used. The major γ-ray peaks of 72As and 71As formed via the 72Ge(p,n)72As and 72Ge(p,2n)71As reactions, respectively, were analyzed. The incident proton energy and flux on a foil were determined using several monitor reactions. Based on integrated counts, irradiation data and the nuclear decay data, the reaction cross sections were measured. All data describe the first measurements. Theoretical nuclear model calculations were then carried out by using the codes TALYS 1.96, EMPIRE 3.2 and ALICE-IPPE. A very good agreement between the measured data and calculated values was found. The new data enabled us to calculate the thick target yields and estimate the radionuclidic impurities for a given energy range. Over the optimum energy range Ep = 14 → 7 MeV, the calculated thick target yield of 72As amounts to 272 MBq/μAh with no 71As impurity at all. The 72Ge(p,n)72As reaction on the enriched 72Ge is thus very suitable for clinical scale production of 72As at a medical cyclotron.