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HK: Fachverband Physik der Hadronen und Kerne

HK 51: Instrumentation 16

HK 51.6: Talk

Thursday, March 26, 2015, 16:00–16:15, M/HS2

Monte-Carlo studies of BGO Compton-suppression shields for the MINIBALL spectrometer — •Dawid Rosiak, Peter Reiter, and Michael Seidlitz — Institut für Kernphysik, Universität zu Köln

An enhanced detection sensitivity of the high-resolution MINIBALL spectrometer is required for future experiments at the HIE-ISOLDE accelerator at CERN. Beam energies up to 10 MeV/u will allow for direct reactions and fusion-evaporation reactions, populating excited nuclei at higher excitation energy than the existing REX-ISOLDE facility. Moreover, high angular-momentum transfer will cause events with higher γ-ray multiplicities. The existing MINIBALL spectrometer with its closely packed eight triple cluster detectors was designed for highest solid-angle coverage, causing best γ-ray efficiency for low-multiplicity events. In future the triple-cluster detectors will be optionally surrounded by BGO Compton-suppression shields in order to cope with the scattering between detectors from high energetic γ-rays and with double hits from high multiplicity. A detailed Monte-Carlo study, based on the GEANT4 simulation toolkit [1], was performed for the full spectrometer by varying the geometry of the BGO detectors. The final result is a detector configuration with improved peak-to-total ratio of up to 55% and a reduced efficiency, which will be the basis of a first prototype detector.

[1] S. Agostinelli et. al., Nucl. Instrum. Methods A 506, 250 (2003).