The ALICE TPC Readout Electronics: Design, performance optimization and verification of the DAQ circuit

ALICE (A Large Ion Collider Experiment) is a dedicated heavy-ion experiment at CERN’s LHC (Large Hadron Collider). It is designed to study the physics of strongly interacting matter and the quark-gluon plasma in heavy-ion collisions. It contains a large volume Time Projection Chamber (TPC) as its main tracking device. The ALICE TPC is the largest ever built gaseous TPC, both in terms of dimensions and number of read-out channels (557,578). A total number of 128 channels are packed in one TPC Front End Card (FEC) and 4,356 FECs are distributed over 216 independent readout partitions. Each readout partition steered by a single Readout Control Unit (RCU) functions as an independent unit in the data acquisition system of the TPC. The RCU functions as an interface between the FECs, Data AcQuisition system (DAQ), the Trigger and Timing Circuit (TTC) and the Detector Control System (DCS). The ALICE TPC readout electronics is in operation since the start of the LHC in November 2009. The primary objectives of the work carried out for this thesis includes the design and implementation the RCU firmware. The RCU firmware is used by four different ALICE detectors including TPC, PHOS, FMD and EMCAL. Design and implementation of the RCU firmware required flexibility and configurability as a key challenge to meet the requirements of these different detectors. Novel techniques to verify the integration of the RCU firmware with other components of the readout system are developed and set as standard procedures for its commissioning to be used at the ALICE experiment. The optimization of the readout electronics to meet the required performance of the TPC data acquisition system was the second key objective of this thesis. Several techniques and methods to improve the readout rate were implemented in the RCU firmware and its interface to FECs. The performance of the TPC readout electronics is characterized and evaluated. The measured performance of the ALICE TPC during p-p and Pb-Pb collisions is presented in this thesis. Robustness and reliability of the TPC readout system is addressed as the third main objective of this thesis. The RCU firmware is featured to monitor and detect erroneous situations of all its interfaces involved in an event readout, throughout all their transactions. These features and error handling mechanisms are verified and presented along with their results. The RCU firmware was subjected to fault injection test to characterize the effects of SEUs during the event readout. A new technique to correct the SEU effects in any readout partition was developed, implemented and verified as a part of the work carried out for this thesis. This technique ensures that the TPC FEE does not cause an unplanned termination of the data taking session in the ALICE experiment.