Activation method combined with characteristic X-ray counting: A possibility to measure (α,γ) cross sections on heavy p-nuclei

For an improved modeling of the astrophysical nucleosynthesis of p-nuclei, low energy cross section data of alpha-induced reactions on heavy isotopes are needed. Technical difficulties hamper the experimental determination of these cross sections, therefore the relevant experimental data are almost completely missing. Here we present a new method for the cross section measurements, the activation technique based on the detection of characteristic X-ray radiation. The feasibility of the method is illustrated through the measurement of the 169Tm(α,γ)173Lu and 169Tm(α,n)172Lu reaction cross sections. Despite the relatively long half-life of the reaction products (T1/2=500 and 6.7 days, respectively) it was possible to measure the cross section of the 169Tm(α,γ)173Lu reaction between Ec.m.=13.16 and 17.08 MeV. The 169Tm(α,n)172Lu reaction cross section was derived from close above the threshold up to Ec.m.=17.08MeV. Details of the new method and the experimental results are presented.