The Readout Control Unit of the ALICE TPC

The ALICE Time Projection Chamber (TPC) is the main tracking detector of the central barrel of the ALICE (A Large Ion Collider) Experiment at the Large Hadron Collider (LHC), being constructed at CERN, Geneva. It is a 88 m$^{3}$ cylinder filled with gas and divided into two drift regions by the central electrode located at its axial center. The readout chambers of the TPC are multi-wire proportional chambers with cathode pad readout. About 570 000 pads are read-out by an electronics chain of amplification, digitalization and pre-processing. One of the challenges in designing the TPC for ALICE is the design of Front End Electronics (FEE) to cope with the data rates and the channel occupancy. The Readout Control Unit (RCU), which is presented in this work, is designed to control and monitor the Front End Electronics, and to collect and ship data to the High Level Trigger and the Data Acquisition System, via the Detector Data Link (DDL - optical fibre). The RCU must be capable of reading out up to 200 Mbytes/s from the Front End Electronics, operating at a maximum of 40 MHz. The handling and distribution of the central trigger and clock signals are done with an incorporated TTCrx chip. Interfacing the front-end electronics with the Detector Control System (DCS) is done via a Slow Control bus. The DCS itself communicates with the control layer via high level protocols running on an Ethernet fieldbus. For the prototype of the Readout Control Unit (RCU) the Altera EP20K400 Field Programmable Gate Array (FPGA) has been used for application specific system integration. Chapter 1 gives an overview of the physics observables and thus defines the requirements for the performance of the ALICE TPC and its FEE. In chapter 2 TPC technologies and their development and use in selected heavy ion experiments are discussed. At the end of the chapter the TPC of the ALICE experiment is presented. Chapter 3 gives an overview of the other detectors and the Trigger and Data Acquisition of the same experiment. Details of the readout chain of the ALICE TPC, including the Front End Electronics and the RCU, is the subject of chapter 4. Chapter 5 is a presentation of the first conceptual design of the logic of the RCU. This formed the basis for the development of the RCU, and is a major part of the work of this thesis. It is presented here in detail, even though a number of changes were made during later stages of the development cycle. A number of prototypes of the RCU have been developed, and are presented in chapter 6, along with their use in different test setups of other equipment of the ALICE detector. The work of this thesis includes the development of the first two prototypes, but some results from the ongoing RCU development are also presented. A summary and outlook is given in chapter 7. Two conference contributions originating from this work are included as appendices.