The ALICE TPC Upgrade with GEMs
40-S2-A01 - Salle Anderson (CERN)
40-S2-A01 - Salle Anderson
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The ALICE TPC performs tracking of all charged particles produced in pp and Pb-Pb collisions at the LHC, together with particle identification via dE/dx. The gas amplification and readout is done with gated multi-wire proportional chambers with pad readout. In RUN 3 the expected heavy-ion collision rates will reach 50 kHz and the ALICE program includes measurement of non-triggerable events, thus making it mandatory to run the TPC in a continuous readout mode. In this situation, the present gating grid electrode becomes unusable and the space-charge distortions due to Ion Back Flow (IBF) into the drift volume would reach unmanageable levels (order of 1 m). In addition, space charge in the avalanche region would affect the dE/dx measurement. For this reasons it is planned to replace the existing wire chambers with quadruple GEM stacks installed on similarly patterned pad planes. Although GEMs feature intrinsic ion blocking, further R&D is needed to reach values well below 1%. In this Detector Seminar the status of the R&D and current design of the upgraded ALICE TPC will be presented.