MC Simulations for the PreSPEC campaign of AGATA at GSI

The next campaign of in-flight γ-ray spectroscopy experiments at the GSI Fragment Separator (FRS) will be performed, in the framework of the PreSPEC project [1], using the advanced γ-tracking array AGATA [2]. In order to exploit best its γ-efficiency and high intrinsic energyand spatial-resolution, the geometry and the physical arrangement of this multidetector needs to be optimized according to the characteristics of the ion beam at the final focal plane of the FRS. To this aim we have performed systematic Monte Carlo calculations using the GEANT4-based AGATA code [3]. One of the main experimental constraints is the transversal spatial distribution of the FRS ion beam at the focal plane (approx. 6 × 4 cm FWHM). Thus, the secondary beam covers an area larger than the standard AGATA pentagon holes, commonly used for the beam-pipe at other facilities like LNL [4]. According to our MC calculations, it became clear that a remarkable improvement in γ-ray sensitivity can be achieved for the setup at GSI when the standard AGATA triple cluster detectors are complemented with double cluster detectors (see Fig. 1). This conclusion has triggered the development and production of 5 AGATA double cluster detectors, which will be used for the experiments at GSI, and probably also later at GANIL.