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The Time-Projection-Chamber (TPC) is the main tracking and particle identification (PID) device in the central barrel of ALICE. In order to make full use of the increased Pb-Pb luminosity for Run3 and beyond, the TPC needs to be able to cope with a minimum-bias interaction rate of up to 50 kHz. During Run1 and Run2, the operation of the MWPC-based TPC was limited to 3 kHz due to an active ion gating grid. To overcome this limitation, the front-end and readout electronics have been completely re-designed. The MWPC-based chambers have been replaced by GEM-based chambers, allowing for fully continuous readout. The signals from the 524160 channels are amplified, shaped, and digitized with 5 MHz by 16380 SAMPA chips. The raw ADC data is then sent out directly via 6552 optical links using the CERN GBTx and Versatile link system, resulting in a raw data rate of more than 26 Tb/s. All data processing is done off-detector by 360 FPGA-based readout cards (Common Readout Unit, CRU).
This seminar will present the design and performance of the Front-End-Electronics, the special requirements for the TPC readout system and the FPGA processing, and the challenges and difficulties that were overcome to bring the system from a concept to a fully operational system.