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HK: Fachverband Physik der Hadronen und Kerne

HK 54: Poster

HK 54.53: Poster

Donnerstag, 21. März 2019, 16:30–19:00, Foyer Theresanium

Investigation of ion backflow and energy resolution in four GEM systems with Ar-CO2 for the Upgrade of the ALICE TPC — •Christoph Weidlich for the ALICE collaboration — Institut für Kernphysik, Goethe-Universität Frankfurt

The Time Projection Chamber (TPC) of the ALICE experiment will be upgraded during the LHC long shutdown 2 (2019-2021). The upgrade includes a replacement of the MWPC-based readout chambers by stacks of Gas Electron Multipliers (GEMs). Two key parameters of the GEMs are ion backflow (IBF) and energy resolution. These parameters are anti-correlated and an ideal working point where both parameters are as low as possible has to be achieved. The phase-space of these parameters has already been measured in detail in the baseline gas mixture Ne-CO2-N2 (90-10-5).

During run1 and run2 operation the MWPCs showed instabilities with the Ne-based gas mixture which were not present in an Ar-based mixture. Such instabilities are not expected with a GEM-based readout. However, for completeness IBF and energy resolution were investigated in Ar-CO2 (90-10). Here we present the results of these measurements.

Supported by BMBF and the Helmholtz Association.