23Na(p,α)20Ne
PI: Carlo Bruno
Astrophysical Motivation
Globular clusters (GC) offer powerful insight into galactic and stellar evolution, yet their formation and abundance patterns are not completely understood.
A promising scenario suggests that material carrying the signature of previous generation's AGB processing could have polluted the pristine seeds of subsequent stellar generations. However, this model fails to explain the observed O-Na anti-correlation.
A potential solution may come from lower 23Na(p,α)20Ne reaction rate due to a lower strength of the narrow resonance at Ecm = 138 keV, for which only tentative upper limits have been found due to the background limitations of ground laboratories. LUNA will provide unique underground setting for direct measurement of the reaction using a purpose-built silicon detector array. This comprehensive study may help solve the GC puzzle.
Experimental Aim
In the framework of the ERC Starting Grant ELDAR (Burning Questions on the Origins of Elements in the Lives and Deaths of Stars), LUNA aims at observing the unknown resonance for the first time in a direct measurement. This will allow exploring its impact n the reaction rates and consequences for AGB stellar models, thus giving possible new insights in the formation and evolution of Globular Clusters.
Experimental Setup
For the experiment, a new beam line has been mounted at the LUNA-400 accelerator, including an interaction chamber with a detection array specifically designed for detecting charged-particles.
The array comprises twenty-four Hamamatsu Si PIN diodes and three Micron Semiconductor PADs 1x5. Both these silicon detector types are double sided, with the possibility of acquiring signals from both p+n and n+n sides.
The sodium targets used in the experimental campaign have been produced with two techniques: evaporation of Na2WO4 or sputtering of the NaNbO3 on Ta backings. The latter technique can produce stable reliable targets that can be irradiated for the long time necessary to study weak resonances in the 23Na(p,α)20Ne reaction.
