Heidelberg 2015 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 22: Instrumentation 8

HK 22.1: Talk

Tuesday, March 24, 2015, 14:30–14:45, M/HS2

Development of GEM-based readout chambers for the upgrade of the ALICE TPC — •Alexander Deisting for the ALICE collaboration — Universität Heidelberg/Gesellschaft für Schwerionenforschung GmbH

The ALICE experiment at the LHC is designed to examine lead-lead (Pb-Pb) collisions in order to probe genuine multi-particle aspects of QCD. Its main tracking detector is a time projection chamber (TPC), being equipped with a multi wire proportional chamber (MWPC) based readout. Since the rate in Pb-Pb collisions will increase to up to 50kHz in LHC Run3 it is necessary to adapt the TPC to this new environment. A change from the current measurement mode with a gating grid and MWPCs to a continuous readout with new readout chambers is hence forseen.

To match the requirements for Run3 the new chambers should be able to cope with the higher rates and thereby preserve the momentum and dE/dx resolution of the current chambers. In addition the ion back flow (IBF) from the amplification stage into the drift volume should be less then 1%. A solution has been found based on 4 gas electron multiplier foils (GEMs) stacked onto each other.

Extensive R&D studies of 4 GEM stacks were performed. In this talk different experimental setups to examine the performance of quadruple GEM stacks in terms of IBF, energy resolution and dE/dx will be presented. Emphasis will be put on the simultaneous optimisation of the energy resolution and the IBF while studying different kinds of GEM foils in a stack.