Project Overview

The "CMS-FED" project will provide the off-detector readout electronics system used to digitize and zero suppress the data from the (10 Million channel) Silicon Strip Tracker detector of the CMS experiment at CERN.

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The CMS experiment is due to begin operating at the Large Hadron Collider facility (LHC) at CERN in Geneva Switzerland in 2008. A key component of the CMS detector is the silicon micro-strip tracker which is designed to provide robust particle tracking and vertex reconstruction within a strong magnetic field in the high luminosity environment of the LHC.

The microstrip tracker readout system consists of over 10 million detector channels and, at expected track occupancies, will generate up to 70% of the final data volume at CMS. The tracker readout system is clocked at the LHC bunch crossing rate of 40.08 MHz and is designed to operate at Level 1 trigger rates of up to 100 kHz.  Microstrip signals are amplified and stored in analogue pipeline memory chips (APV25) located on the detector. After some initial signal processing and multiplexing the signals are transferred (over approx 60m) to the experimental counting room via analogue optical links.

In the counting room the analogue optical data are converted back to electrical signals and digitized on Front End Driver (FED) cards. Each ADC channel processes data serially from a total of 256 microstrips (constituting an APV frame). The FEDs provide digital signal processing, including cluster finding to drastically reduce the data rate, before storing the data in local memory buffers until required by the higher levels of the CMS Data Acquisition system.

FED Project Status

The Final FED which will be installed at CMS will be a 9U format VME card comprising 96 ADC channels with optical inputs. There will be about 450 FED's in the final system. Several prototype boards FEDv1 are now being tested at RAL, Imperial College and CERN.
The Final FED project is in the Implementation phase within the QA system.

An early FED prototype was implemented as an 8 ADC channel PCI Mezzanine Card (PMC). The design of the FED-PMC has been optimized for use in laboratory set-ups and for test beam work. This prototype has all electrical inputs and reads out raw data. More than 100 FED-PMC's are now in use by the tracker community. The FED-PMC project is in the Maintenance phase within the QA system.


9U Final FEDv2 primary side 

FED-PMC Prototype