The CMS Tracker: Front End Readout and Control Systems & DAQ

The CMS Silicon Strip Tracker front-end readout system utilises 73,000 APV25 ASICs to provide low noise signal amplification, analogue buffering and proc essing in a harsh radiation environment on-detector and 440 Front End Drivers (FEDs) to digitise, buffer and process the signals off- detector so that the data rate is reduced. The APV buffers cannot be monitored directly on-detector so an APV Emulator (APVE) has been designed and built to calculate the exact buffer occupancies of the APV25s for preventing buffer overflows. The APVE is als o able to provide information to the FEDs in order to check that synchronisation between the APVE and the APV25s has been maintained. The majority of the authors work concerns the commisioning of the APVE within the final Data Acquisition (DAQ) System. The APVE has been fully tested and integration with the tracker readout and DAQ is almost complete. The author has written an application based on the integrated CMS DAQ framework (XDAQ) for the purpose of monitoring the APVE during the testing and operational phases of the CMS detector.