Berlin 2005 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 22: Postersitzung

HK 22.54: Poster

Monday, March 7, 2005, 16:30–18:00, TU MA141

A 2.5 TBit/s Readout Scheme for the ALICE TRD — •Rolf Schneider and Volker Lindenstruth — Kirchhoff-Institut für Physik, Universität Heidelberg

The Transition Radiation Detector (TRD) of the ALICE experiment at CERN serves as trigger, tracking and electron identification detector. All of these functions make particular demands on the readout scheme.

About 65 000 multi chip modules (MCM), each equipped with an amplifier, an ADC and a four-fold processor, preprocess and store the event data. To perform the Level-1 trigger, the preprocessed data has to be shipped off the detector to the next processing stage, the Global Tracking Unit (GTU), within 600 ns. As a result of accurate detector simulations and analyses to qualify the amount of preprocessed data, only a latency of a few clock cycles and a data bandwidth of ∼2.5 TBit/s fulfill these requirements. In contrast the readout of the full event data of ∼30 MByte is less time-critical and a handshaking protocol is used.

Taking into account the specifications like the number of pads, routing area, fault tolerance and power consumption, a readout scheme and corresponding Network Interface (NI) has been developed and tested. The resulting 4-to-1 readout trees which collect the data of 64 MCMs each, end in 1 080 optical links which are connected to the GTU. The NI consists of four 10 Bit wide input ports, one output port, FIFOs, interfaces to the processor, and control logic. The data transfer is performed with 120 MHz DDR. In order to save power the NI is capable of operating stand-alone and dynamically switching off unused LVDS ports. This project is supported by the BMBF (06HD9551).