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CARLOSrx : an online Data Acquisition system for ALICE ITS SDD
| Content Provider | Semantic Scholar |
|---|---|
| Author | Antinoria, S. Costaa, Ferreira Falchieria, D. Gandolfia, E. Masettia, M. |
| Copyright Year | 2008 |
| Abstract | CARLOSrx is part of the Silicon Drift Detector (SDD) readout chain for the ALICE experiment to be held at CERN. CARLOSrx consists of two 9U x 400 mm VME64 printed circuit boards with the main purposes of receiving data from 12 SDDs and send them towards the ALICE data acquisition system (DAQ), configure all the FEE (Front End Electronics) connected to SDD. The paper presents the features of the latest firmware installed on CARLOSrx, the results of tests performed at CERN with the SDD readout chain and gives a little description of software tools used during the debugging phase of the board. I. Overview The ITS (Inner Tracking System) of the ALICE experiment [1,2] is composed by six cylindrical layers. The SDDs occupy the third and fourth layer of the ITS. The detectors are installed on linear structures called ladders. There are 260 SDDs organized in 36 ladders: • 14 ladders for layer 3, each one contains 6 SDDs; • 22 ladders for layer 4, each one contains 8 SDDs. At both ends of each ladder are placed the end ladder boards, one for each detector. They host a chip called CARLOS [3] (Compression And Run Length encOding Subsystem) whose purpose is to perform a bi-dimensional compression of data coming from FEE (Front End Electronics) using double threshold cluster finding algorithm [4]. CARLOS board, after performing compression, sends data to CARLOSrx board, via 100 meters long single mode optical fibers by means of the Gigabit optical link [5]. Each end ladder boards hosts three optical fibers: • one for sending data, • one for receiving the 40.08 MHz LHC system clock, • one for receiving a serial link signal with encoded configuration and trigger informations. CARLOSrx is placed in counting room and it receives data coming from 12 CARLOS and provides the clock and configuration signals to all end ladder boards; so CARLOSrx has to deal 36 optical fibers, plus the interfaces towards the DAQ, trigger system and VME bus. II. CARLOSrx Board Design We were forced to break the design of CARLOSrx in two boards because in due time there were no commercial parallel optical transceivers for single mode 1310 nm. For that reason CARLOSrx boards consists of: • a data processing board called CARLOSrx (fig. 1.1), it contains 12 single optical transceivers for receiving data from 12 detectors and for sending configuration informations to 12 CARLOS, at the same time. It also handles the interface towards the trigger, DAQ and VME systems; • a clock distribution board called CARLOSrx clock (fig. 1.2), it receives the clock from data processing board and distributes it through 12 optical fibers to CARLOS boards. To receive data from all 260 SDDs modules we need 24 CARLOSrx board pairs, they will be hosted in 3 VME64 crates located in ALICE counting room. fig. 1.1 CARLOSrx data processing board fig. 1.2 CARLOSrx clock distribution board |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://cds.cern.ch/record/1091501/files/p416.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
