SMuK 2023 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 3: Instrumentation II

HK 3.1: Gruppenbericht

Montag, 20. März 2023, 16:30–17:00, SCH/A.101

Space-point distortion calibrations for the ALICE TPC in LHC Run 3 — •Matthias Kleiner for the ALICE Germany collaboration — Institut für Kernphysik, Goethe-Universität Frankfurt

The Time Projection Chamber (TPC) is the main tracking and particle identification detector of the ALICE experiment at the CERN LHC. In order to cope with the high interaction rates of up to 50 kHz in Pb-Pb collisions during Run 3, the Multi-Wire Proportional Chambers (MWPCs) were replaced by stacks of four Gas Electron Multiplier (GEM) foils to allow for continuous data acquisition. Despite the intrinsic ion-blocking properties of the 4-GEM system, a residual amount of ions produced during the electron amplification drifts into the active volume of the TPC, leading to space-point distortions of the nominal drift field. Various effects, such as variations in the number of collisions for a given time interval, cause fluctuations of the distortions due to space-charge on very short time scales. Additional effects such as charging up of the GEM frames contribute to the space-point distortions. The average space-point distortions as well as the fluctuations have to be corrected to preserve the intrinsic tracking precision of the TPC.

In this talk, an overview about space-point distortions and distortion fluctuations in the ALICE TPC in Run 3 will be presented, along with procedures developed for the calibration of the space-point distortions.

Supported by BMBF and the Helmholtz Association