Frankfurt 2014 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 43: Instrumentierung

HK 43.4: Talk

Thursday, March 20, 2014, 15:00–15:15, HZ 8

Discharge probability studies in GEM structures for the ALICE TPC upgrade — •Piotr Gasik for the ALICE collaboration — TU München, Boltzmannstr. 2, 85748 Garching, Germany

A large Time Projection Chamber (TPC) is the main device for tracking and charged particle identification in the ALICE experiment at the CERN LHC. After the second long shutdown in 2018, the LHC will deliver Pb beams colliding at an interaction rate of about 50 kHz, which is about a factor of 100 above the present readout rate of the TPC. In order to make full use of this luminosity, a major upgrade of the TPC is required. It is foreseen to replace the existing MWPC-based readout with Gas Electron Multiplier (GEM) foils.

The GEM foils are commonly known structures used as proportional counters, which permits to obtain high gains at very high radiation rates. However, highly ionizing particles, which may be produced during heavy ion collisions, may trigger an electrical breakdown which may result in damage of the foils or readout electronics.

The key parameter for a long-term operation of the GEM-based TPC is the stability against electrical discharges. We performed discharge probability studies in triple and quadruple GEM structures in Ne- and Ar-based gas mixtures to find operational conditions for the upgraded ALICE TPC. Preliminary results from these measurements will be discussed in this contribution.

This work is supported by BMBF and DFG Cluster of Excellence "Universe" (Exc 153).