Nuclear reactions in the storage ring ESR with EXL

EXL (EXotic nuclei studied in Light-ion induced reactions) is a project within NUSTAR at FAIR that aims to investigate nuclear structure at storage rings with direct reactions in inverse kinematics. The programme is focussed on reactions with very low momentum transfers. The existing storage ring ESR at GSI provides a unique opportunity to perform part of the programme already now. We successfully performed experiments with stable ²⁰Ne and ⁵⁸Ni as well as radioactive ⁵⁶Ni beams. The beams hit the internal gas-jet target (H₂ or ⁴He) and the respective target recoils were measured by a newly developed UHV compatible Si detector setup.
The first physics goal was to deduce the nuclear matter radius of ⁵⁶Ni from elastic proton scattering at 390 MeV/u. This experiment can be considered as the first successfully observed nuclear reaction with a stored radioactive
beam ever.
As a proof of principle experiment, a ⁵⁸Ni beam at 100 MeV/u was impinged on a ⁴He target. In inelastic scattering the excitation of the isoscalar giant monopole resonance was observed. During commissioning with a ²⁰Ne beam also a (p,d) transfer reaction was measured.
This first experimental campaign has successfully demonstrated the feasibility of the EXL concept and first physics results are on the way. In my talk, I present the status of the project and discuss the possibilities for an upgraded detector setup covering a larger solid angle and further reaction experiments in the storage rings - CRYRING, ESR and HESR - at FAIR.