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HK: Fachverband Physik der Hadronen und Kerne
HK 4: Instrumentation 3
HK 4.5: Vortrag
Montag, 23. März 2015, 15:30–15:45, M/HS4
Optimization of the nonuniformity in light collection of tapered PbWO4 crystals and its influence on the energy resolution of the PANDA barrel EMC* — •Stefan Diehl1, Peter Drexler1, Valery Dormenev1, Myroslav Kavatsyuk5, Svetlana Nazarenko1, Till Kuske1, Rainer W. Novotny1, Christoph Rosenbaum1, Philippe Rosier2, Andrej Ryantsev3, Peter Wieczorek4, Andrea Wilms4, and Hans-Georg Zaunick1 — 1II. Physics Institute, University Giessen — 2IPN Orsay, France — 3IHEP Protvino, Russia — 4GSI Helmholtzzentr. für Schwerionenforsch., Darmstadt — 5KVI-CART Groningen, The Netherlands
The barrel part of the electromagnetic (EM) calorimeter of the PANDA detector at the future FAIR facility will consist of 11 crystal geometries with a different degree of tapering. Due to tapering the crystals show a nonuniformity (NUF) in light collection. For the most tapered crystals the light detected by the photosensor is enhanced by a factor 1.4, if the scintillation light is created in the front part of the crystal. Due to the spread and the fluctuations of the EM shower within the crystal, this effect causes a smearing of the response, resulting in a reduced energy resolution. Therefore one lateral side has been depolished for 9 crystals, decreasing the NUF down to < 5%, with only a slighty reduced light yield. The contribution will compare the response of a 3x3 matrix of crystals with one depolished side, with an identical matrix of polished crystals using a tagged photon beam with energies < 1 GeV and the results from GEANT4 simulations, which indicate a significant improvement of the energy resolution. *Supp. by BMBF, GSI, FAIR