Speaker
Description
The study of Asymptotic Giant Branch star (AGB) nucleosynthesis is fundamental to understand the Galaxy chemical evolution. At the energies of interest for AGB stars direct measurements of the nuclear cross sections are challenging because of the extremely low count rate. A breakthrough in experimental nuclear astrophysics is represented by the Laboratory for Underground Nuclear Astrophysics (LUNA) in Gran Sasso, Italy. Over the last 30 years, the LUNA collaboration has provided cross section data directly at the relevant energies for AGB nucleosynthesis for a number of reactions. The talk provide a summary of the latest LUNA measurements and results with implications on AGB stellar evolution and nucleosynthesis.
Moreover the talk will focus on the more recent measurement performed at LUNA. The 17O(p,g)18F reaction play a key role in AGB nucleosynthesis whose footprint is the oxygen isotopic abundances observed in stellar spectra or in
pre-solar meteoritic grains. The rate of the $^{17}$O(p,$\gamma$)$^{18}$F reaction t temperature of interest, 40-80 MK, is dominated by the poorly constrained 65 keV resonance. Only indirect measurement are reported with an evaluated resonance strength of (1.6$\pm$0.3)$\times$10$^{-11}$ eV. A new high sensitivity setup has been installed at LUNA, where a reduction of the cosmic ray background by several orders of magnitude is guaranteed by the underground location. The residual background was further reduced by a devoted shielding. The high detection efficiency of the 4$\pi$-BGO segmented detector was optimized by installing a devoted target chamber and holder. With more than 300 C accumulated on Ta$_2$O$_5$ targets with nominal $^{17}$O enrichment of 90%, the LUNA collaboration has performed the first ever direct measurement of the 65 keV resonance strength.
In the talk details on the experimental setup and some preliminary results will be provided.
| Session | Experimental Nuclear Astrophysics |
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