Darmstadt 2016 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 22: Instrumentation VI
HK 22.6: Talk
Tuesday, March 15, 2016, 15:30–15:45, S1/01 A3
Influence of the Light Collection Non Uniformity in Strongly Tapered PWO Crystals on the Energy Resolution of the PANDA EMC — •Stefan Diehl1, Peter Drexler1, Valery Dormenev1, Till Kuske1, Rainer W. Novotny1, Christoph Rosenbaum1, Peter Wieczorek2, Andrea Wilms2, and Hans-Georg Zaunick1 — 12nd Physics Institute, JLU Giessen — 2GSI Helmholtzzentr. für Schwerionenforsch., Darmstadt
The barrel part of the target EMC of the PANDA detector at the future FAIR facility will consist of 11 crystal geometries with a different degree of tapering. Due to the tapering the crystals show a non uniformity in light collection. For the most tapered crystals the light detected by the photo-sensor is enhanced by a factor 1.4, if the scintillation light is created in the front part of the crystal. This effect causes a smearing of the response, resulting in a reduction of the energy resolution. Therefore, one lateral crystal side face has been de-polished for a set of test crystals, decreasing the non uniformity from around 40% to less than 5%. The present contribution will compare the response of a 3x3 matrix of crystals with one de-polished side in the final PANDA EMC configuration, with an identical matrix of polished crystals using a tagged photon beam in the energy range from 50 MeV up to 1 GeV and the results from GEANT4 simulations. A significant improvement of the energy resolution can be observed for the matrix with de-polished crystals in the energy range above 200 MeV, while the resolution stays at the same level between 50 MeV and 200 MeV. *The project is supported by BMBF, GSI and HIC for FAIR.