Measurement of the25Mg(α,n)28Si reaction cross section at LNL

R Depalo,V L Kravchuk,C Rossi Alvarez,G Collanzuol,F Camera,G Montagnoli,O Wieland,R Menegazzo,M Cinausero,S Appannababu,T Marchi,N Blasi,F Gramegna,G Prete,D Fabris,V Rigato,A Lombardi,A Caciolli,P Mastinu,C Broggini,Mario Leone

doi:10.1051/epjconf/20146607002

Abstract

The detection of the 1809 keV emission line associated with the decay of 26 Al in the interstellar medium provides a direct evidence of recent nucleosynthesis events in our galaxy. 26 Al is thought to be mainly produced in massive stars, but in order to have a quantita- tive understanding of the 26 Al distribution, the cross section of all the nuclear reactions involved in its production should be accurately known. A recent sensitivity study demonstrated that the 25 Mg( ,n) 28 Si is the reaction with the strongest impact on the synthesis of 26 Al during explosive Neon and Carbon burning (4). In order to improve the experimental knowledge of the 25 Mg( ,n) 28 Si cross section, a new direct measurement has been performed at Legnaro National Laboratories. The experimental setup, the data analysis and preliminary results are discussed.

Highlights

Analyzing the Doppler shift of the 1809 keV line it has been possible to deduce that 26Al is co-rotating with the Galaxy. All this observational evidence favour the massive stars as the main sources of 26Al [5]
In the energy range Eα = 1 - 6 MeV, the 25Mg(α,n)28Si cross section has been reported by many authors ([7] - [11])
A summary of the currently available experimental cross sections is reported in fig

Summary

Introduction

According to standard models of stellar evolution, massive stars may synthesize 26Al in three different evolutionary phases: C/Ne shell burning, explosive C/Ne burning and, for stars more massive than 30 solar masses, core H burning [6]. In all those phases, 26Al is mainly produced by proton capture on 25Mg. The final abundance of 26Al depends on the rate of all the nuclear reactions that contribute to its production or destruction. 2.5 MeV, the NACRE rate is based on Hauser-Feshbach calculations, disregarding the existing experimental cross sections even in the energy region where they are in good agreement. Van der Zwan & Geiger (1981) Anderson et al (1983) Wieland (1995) Falahat (2010)

Experimental setup

Data analysis and preliminary results