München 2019 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 7: Instrumentation I

HK 7.2: Talk

Monday, March 18, 2019, 14:30–14:45, HS 11

Discharge studies in a double-GEM detector — •Bogdan-Mihail Blidaru for the ALICE collaboration — GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany

The Large Hadron Collider will provide Pb-Pb collisions at an interaction rate of 50 kHz after 2021, following its Long Shutdown 2.

The ALICE TPC Upgrade project developed a continuous readout based on Gas Electron Multiplier (GEM) technology. The final design will feature a stack of four GEMs at the amplification stage. After installation in the ALICE cavern, the GEM chambers will be inaccessible. Thus, long-term stability and reliable readout over a time span of about 10 years is mandatory.

This talk is focused on one of the major challenges the GEMs must overcome, i.e. discharges: primary discharges that lead to a breakdown of the potential between both sides of a GEM foil and secondary discharges where the potential breaks down in the gap region between two foils. These events can short-circuit a GEM segment and render it inactive.

A small 10×10 cm² detector model with two GEM foils is used to study the evolution of the GEM potentials during and after discharges. Particular emphasis is put on mitigating the appearance of secondary discharges by using decoupling resistors that substantially reduce the propagation probability.