The ALICE detector at the Large Hadron Collider (LHC) at CERN will be used to observe
a new state of matter, the quark gluon plasma. Consisting of several sub detectors including the ITS, TPC and TRD detector this particle detector is able to detect particles at high multiplicities. The transition radiation detector (TRD) is used to extend the particle tracking range of the TPC and differentiates between electrons and pions. The read-out electronics of the TRD is controlled by the Detector Control System (DCS) board. This compact board hosting an embedded LINUX system is based on the ALTERA Excalibur device, a FPGA with embedded ARM processor core. Due to the critical role of the DCS board in the TRD, it is powered separately from the
front end electronics. Each of the eighteen TRD super-modules is equipped with a power istribution box which distributes the common DCS power to the modules' thirty DCS oards. The PDB enables independently switchable power for each DCS board. The control of the power distribution box was realized by two power distribution control boards (PDC) hich are located inside the PDB. Due to the high requirements in reliability the PDC is based on an Actel anti fuse FPGA which provides outstanding radiation hardness and is independent from external memory. The PDC units of the TRD are controlled by four PCU units which are based on the DCS
board. Since these devices are located outside the magnet, the requirements in radiation hardness and reliability are lower. Hosting a DIM server, these devices are the link between the low level PDC units and the high level detector control system. The data transmission between PDC and PCU is implemented as a proprietary optocoupler based serial data transmission line which operates at low speed. Using an error tolerant data encoding scheme as well as two independent data transmission systems per PDB the transmission is considered to be highly reliable. The DCS power supply control system had been excessively tested during the construction and testing phase of the first ALICE TRD module in Heidelberg. Further tests had been done after shipping in CERN. Several modification on the existing power distribution box as well as on software improved stability and reliability of this system.
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