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

Abstract

The 17O(p, γ)18F reaction plays a crucial role in AGB nucleosynthesis as well as in explosive hydrogen burning occurring in type Ia novae. At the temperatures of interest for the former scenario ( 20MK < T < 80MK) the main contribution to the astrophysical reaction rate comes from the poorly constrained ER = 65 keV resonance. The strength of this resonance is presently determined only through indirect measurements, with an adopted value ωγ =(16 ± 3) peV. A new high sensitivity setup was installed at LUNA, located at LNGS. The underground location of the LUNA 400kV accelerator guarantees a reduction of the cosmic ray background by several orders of magnitude. The residual background was further reduced installing a devoted shielding. On the other hand, to increase the efficiency, the 4π BGO detector was coupled with Al target chamber and holder. With more than 400C accumulated on Ta2O5 targets, nominal 17O enrichment of 90%, the LUNA collaboration has performed the first direct measurement of the 65 keV resonance strength.