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T: Fachverband Teilchenphysik

T 68: Poster

T 68.5: Poster

Tuesday, March 25, 2014, 16:45–19:00, ReWi EG

Discharge probability studies in GEM detectors for the ALICE TPC upgrade — •Jacopo Margutti for the ALICE TPC-Collaboration — TU München, Boltzmannstr. 2, 85748 Garching, Germany

The ALICE experiment at CERN is planning a major upgrade of its Time Projection Chamber (TPC) for the upcoming RUN 3 at LHC. The TPC now uses Multi-Wire Proportional Chambers (MWPCs) with pad readout to amplify and read out the signal. A gating grid is necessary to prevent the ions created in the amplification process to flow back into the drift volume, which would eventually lead to distortions of the reconstructed tracks. The gating limits the TPC readout rate to around 3 kHz, whereas for RUN 3 Pb-Pb collision rates of 50 kHz are expected. We are therefore planning to substitute the MWPCs whit Gas Electron Multiplier (GEM) detectors, which feature an intrinsic suppression of the ion back-flow, allowing to operate in a continuous, trigger-less readout mode. A common issue with micro-pattern gas amplification, such as GEM, is stability against discharges, that are thought to be triggered by events with high local charge-density. We will present the results of the stability tests carried out on a prototype of GEM Inner ReadOut Chamber (GEM-IROC) with highly ionizing particles, i.e. low energy protons. We will also present results from a parallel R&D program on smaller prototypes which aims to understand the influence of gas mixture and field configuration on discharges inside multi-GEMs detectors. This work is supported by BMBF and DFG Cluster of Excellence "Universe" (Exc 153).