The activation method for cross section measurements in nuclear astrophysics

Abstract

The primary aim of experimental nuclear astrophysics is to determine the rates of nuclear reactions taking place in stars in various astrophysical conditions. These reaction rates are important ingredient for understanding the elemental abundance distribution in our solar system and the galaxy. The reaction rates are determined from the cross sections which need to be measured at energies as close to the astrophysically relevant ones as possible. In many cases the final nucleus of an astrophysically important reaction is radioactive which allows the cross section to be determined based on the off-line measurement of the number of produced isotopes. In general, this technique is referred to as the activation method, which often has substantial advantages over in-beam particle-or γ-detection measurements. In this paper the activation method is reviewed from the viewpoint of nuclear astrophysics. Important aspects of the activation method are given through several reaction studies for charged particle, neutron and γ-induced reactions. Various techniques for the measurement of the produced activity are detailed. As a special case of activation, the technique of Accelerator Mass Spectrometry in cross section measurements is also reviewed. PACS. 26.20.-f Hydrostatic stellar nucleosynthesis -26.30.-k Nucleosynthesis in novae, supernovae, and other explosive environments -24.10.-i Nuclear reaction models and methodsContents

Resonance strengths in the N14 ( p,γ)O15Gyürky1, Halász2, Kiss3 et al. 2019Phys. Rev. CSelf Cite140110View full textAdd to dashboardCite

“…In the present work the E p = 278 keV resonance strength is measured using an independent method, the activation technique [17]. As an additional result, the strength of the E p = 1058 keV resonance in the 14 N(p, γ ) 15 O reaction is also measured.…”

Measurement of the 91Zr(p,γ)92m Nb cross section motivated by type Ia supernova nucleosynthesis

“…As outlined above, the primary aim of the present work was the study of the 91 Zr(p,γ) 92m Nb reaction using the activation method [21]. The cross section was determined based on the off-line detection of the γ-radiation following the β-decay of the reaction product.…”

New measurement of the Sm144(α,γ)Gd148 reaction rate for the

“…Measuring the 144 Sm(α, γ ) 148 Gd reaction cross section via the activation technique [30] is specifically challenging due to several reasons [31]. The reaction product 148 Gd (see Fig.…”

“…1) decays with a half-life of 71.10(12) yr [29]. This is a timescale which is usually quoted as unfeasible using the activation technique due to the small expected activity, which requires very efficient and sensitive detection techniques [30]. The widely used γ -ray spectroscopy of transitions between excited states in the daughter nucleus after the decay is not possible in this case because the α decay populates directly the ground state of 144 Sm, leaving no characteristic γ -ray fingerprint.…”