Bochum 2018 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 35: Instrumentation XI

HK 35.5: Vortrag

Mittwoch, 28. Februar 2018, 15:00–15:15, Audimax H1

An approach to optimising the geometry of the Gas Electron Multiplier — •Jonathan Ottnad, Markus Ball, and Bernhard Ketzer for the CBELSA/TAPS collaboration — Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, Bonn, Germany

Gas Electron Multipliers (GEM) are a sophisticated technology for the multiplication of charges in gaseous detectors. They are used in experiments like COMPASS, LHCb, and for the upgrades of the CMS muon system and the ALICE TPC at CERN. They will also be used for the CBELSA/TAPS TPC at Bonn. Multi-GEM systems provide stable operation, even at high incoming particle rates. Typically a spatial resolution of the order of 50 µ m and an energy resolution of the order of 10 % for ⁵⁵Fe X-rays are reached. Stacking several GEM foils opens a wide parameter space for optimization with respect to experiment-specific demands.

The performance of GEMs is characterized by their ability to collect, multiply, and extract charges. While for a fixed GEM geometry the multiplication of charges (gain) mostly depends on the voltage settings across the GEM, the transfer properties depend on the complete electric field configuration on both sides of the GEM electrodes. Different geometric parameters of the foil, including the pitch of holes and the hole dimensions, modify these characteristics. We measured these properties for various different GEM geometries and compared them to the results of microscopic simulations. As a next step, an attempt to optimise the geometry of GEMs with respect to the transfer properties is made, utilising the same simulation framework.