New Avenue of Transfer Reactions with Active and Cryogenic 3He Targets – ATRACT

Direct reactions are a cornerstone of our understanding of nuclear structure, providing experimental information on the single-particle and collective properties of nuclear states. While neutron transfer reactions revealed a plethora of new information on nuclear structure, the proton transfer reactions are practically stopped, mostly due to the difficulties in implementing 3He targets. Surprisingly, the question of whether the proton shell closures remain stable far from stability or collapse remains open whereas the disappearance of neutron shell closures and the emergence of new sub-shell closures are extensively studied. Also, key reactions for the understanding of the light curve of Type I X-ray bursts could be tackled via (3He,d) measurements. Finally, the long standing question of the role of neutron-proton pairing along the N=Z line could be addressed with (3He,p) neutron-proton transfer.
This proposal aims at implementing 3He targets tailored to such measurements. We focus on two types of targets, active and cryogenic, that will increase the thickness of the available implanted 3He targets by at least two orders of magnitude. First, a new cryogenic target cooled down by a pulse tube cryocooler will be designed to be coupled with new generation of Silicon and Germanium arrays. New window material will be investigated and an efficient de-icing protocol will be developed. Second, the active target ACTAR will be converted for using 3He gas and tested under beam conditions. The experimental capaign is foreseen at GANIL in 2026.