Performance of the ALICE TPC Readout Electronics

Abstract

The Readout Electronics for the Time Projection Chamber (TPC) of the ALICE experiment at the CERN LHC consists of 557578 readout channels, each comprising a shaping-amplifier circuit, a 10-bit 10-MSPS ADC, and a digital circuit for the baseline subtraction, tail cancellation, zero suppression and data buffering. The complete readout chain is contained in Front End Cards (FEC), with 128 channels each. A number of the FECs (up to 25) are controlled by a Readout Control Unit (RCU), which interfaces the FECs to the Data Acquisition system DAQ, the Trigger, and the Detector Control System (DCS). The ALICE TPC readout electronics is running successfully since the start of the LHC in November 2009 both with p-p and Pb-Pb collisions. While recording zero suppressed data from p-p collisions at an interaction rate of up to 100 kHz, the TPC readout featured a maximum readout rate of 1 kHz. It is capable to achieve a readout rate of 3:3 kHz for empty events, which is unprecedented for large TPCs. For Pb-Pb collisions, the TPC readout electronics is capable of recording the zero suppressed data at the maximum rate of 250 Hz for central collisions, whereas empty events can be read out at a maximum rate of 1.25 kHz. This performance is presented for the first time in this paper.