CODE BENCHMARKING STUDIES WITH THE ESR INTERNAL TARGET

Nuclear physics and fundamental interaction studies in collisions of rare isotope or antiproton beams with dense targets play a central role in the NESR and HESR storage rings of the future FAIR facility [1]. For instance, high luminosities are expected in experiments with a hydrogen pellet target in the HESR. Therefore, it is important not only to understand but also to predict the influence of a dense target on the stored beam and to investigate the interplay between phase space cooling, intrabeam scattering (IBS) and target effects. Some experiments with gas targets in light ion storage rings were carried out earlier [2]. Measurements of equilibrium horizontal emittance ex and momentum spread Δp/p were performed before at the ESR [3]. The new experiments were carried out with a stored coasting beam of bare lead ions (Pb) with an intensity of about 10 particles and a kinetic energy of 400 MeV/u. The ESR electron cooler was used to reduce the phase space density of the injected beam, to provide a high quality, dense stored beam and to compensate heating by the target. Four target gases (N2, Ar, Kr, Xe) were used in the gas-jet, with densities in the range 2.5−8×10 atoms/cm (gas-jet diameter ≈ 5 mm).