Darmstadt 2016 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 69: Instrumentation XIX
HK 69.2: Talk
Friday, March 18, 2016, 14:30–14:45, S1/01 A2
Space-charge distortion studies in the ALICE TPC — •Ernst Hellbär1, Jens Wiechula1, and Marian Ivanov2 for the ALICE collaboration — 1Institut für Kernphysik, Goethe-Universität Frankfurt — 2GSI - Helmholtzzentrum fur Schwerionenforschung GmbH
The Time Projection Chamber (TPC) is the main particle identification detector of the ALICE experiment at the CERN LHC. For Run 3 starting in 2020, interaction rates of 50 kHz in Pb-Pb require a major upgrade of the TPC readout. The Multiwire Proportional Chambers (MWPCs) will be replaced by stacks of four Gas Electron Multiplier (GEM) foils, introducing an ion backflow of about 1%. In the high-luminosity environment, the back-drifting ions are the dominant source of space-charge, implying significant drift field distortions. In order to study the space-charge effect due to ion backflow, pp collision data was taken during Run 1 with the gating grid of the MWPCs operated in transparent mode. The measured space-charge distortions in the open gating grid data will be presented and compared to expectations for Run 3. The observed distortions in the latest Run 2 data as well as an efficient calibration scheme will be discussed.
Supported by BMBF and the Helmholtz Association.