Nuclei in the Cosmos (NIC XVII)

The first direct measurement of the 65keV resonance strength of the 17O(p,γ)18F reaction at LUNA

19 Sept 2023, 17:25

5m

Poster Nuclear reaction rates and stellar abundances Poster session (Nuclear reaction rates and stellar abundances)

Speaker

Riccardo Maria GESUÈ (Gran Sasso Science Institute)

Description

The ${}^{17}\mathrm{O}(p,\gamma {)}^{18}\mathrm{F}$ reaction plays a crucial role in Hydrogen burning via CNO cycle. In particular at temperatures of interest for HBB in AGB stars ($20\mathrm{MK}<\mathrm{T}<80\mathrm{MK}$) the main contribution to the astrophysical reaction rate comes from the poorly constrained $E_R=65\mathrm{keV}$ resonance. The strength of this resonance has only been determined through indirect measurements. The LUNA (Laboratory for Underground Nuclear Astrophysics) developed a new high sensitivity setup to measure this resonance directly.

The new setup is located at LNGS, where the cosmic ray background is reduced by several orders of magnitude. The residual background was further reduced by installing a devoted shielding made of $10$ cm lead and $4$ cm borated polyethylene. A $4\pi$ BGO detector was coupled with a target chamber and target holder of Aluminum, to increase the efficiency. The beam induced background contribution was precisely determined by collecting more than $300\mathrm{C}$ on ${\mathrm{Ta}}_2{(}^{18}\mathrm{O}{)}_5$ targets.

With more than $400\mathrm{C}$ accumulated on ${\mathrm{Ta}}_2{(}^{17}\mathrm{O}{)}_5$ targets the LUNA collaboration has performed the first direct measurement of the $65\mathrm{keV}$ resonance strength: this is the weakest resonance ever directly measured. In this contribution the improved experimental setup, the analysis procedure and preliminary results will be presented.