CERN Accelerating science

CMS Note
Report number	CMS-CR-2007-020
Title	The Terabit/s Super-Fragment Builder and Trigger Throttling System for the Compact Muon Solenoid Experiment at CERN
Author(s)	Bauer, Gerry (MIT) ; Varela, Joao (LIP, Lisbon ; CERN) ; Boyer, Vincent (CERN) ; Branson, James (UC, San Diego) ; Brett, Angela (CERN) ; Cano, Eric (CERN) ; Carboni, Andrea (CERN) ; Ciganek, Marek (CERN) ; Cittolin, Sergio (CERN) ; Erhan, Samim (CERN ; UCLA) ; Gigi, Dominique (CERN) ; Glege, Frank (CERN) ; Gómez-Reino, Robert (CERN) ; Gulmini, Michele (INFN, Legnaro ; CERN) ; Gutíerrez-Mlot, Esteban (CERN) ; Gutleber, Johannes (CERN) ; Jacobs, Claude (CERN) ; Kim, Jin Cheol (Kyungpook Natl. U.) ; Klute, Markus (MIT) ; Lipeles, Elliot (UC, San Diego) ; Lopez-Perez, Juan Antonio (CERN) ; Maron, Gaetano (INFN, Legnaro) ; Meijers, Frans (CERN) ; Meschi, Emilio (CERN) ; Moser, Roland (Vienna, Tech. U. ; CERN) ; Murray, Steven (Fermilab) ; Oh, Alexander (CERN) ; Orsini, Luciano (CERN) ; Paus, Christoph (MIT) ; Petrucci, Andrea (INFN, Legnaro) ; Pieri, Marco (UC, San Diego) ; Pollet, Lucien (CERN) ; Rácz, Attila (CERN) ; Sakulin, Hannes (CERN) ; Sani, Matteo (UC, San Diego) ; Schieferdecker, Philipp (CERN) ; Schwick, Christoph (CERN) ; Sumorok, Konstanty (MIT) ; Suzuki, Ichiro (Fermilab) ; Tsirigkas, Dimitrios (CERN)
Affiliation	(CERN) ; (Fermilab) ; (INFN Legarno, Italy) ; (Kyungpook National Univ., South Korea) ; (LIP, Lisbon, Portugal) ; (Massachusetts Inst. Technol., Cambridge, MA, USA) ; (UCLA) ; (Univ. California, San Diego, CA, USA) ; (Vienna, Tech. U.)
Submitted to	15th IEEE Real Time Conference 2007, Fermilab, Batavia, IL, USA, 29 Apr - 4 May 2007
Submitted by	11 May 2007
Subject category	Detectors and Experimental Techniques
Accelerator/Facility, Experiment	CERN LHC ; CMS
Free keywords	ACQUISITION
Abstract	The Data Acquisition System of the Compact Muon Solenoid experiment at the Large Hadron Collider reads out event fragments of an average size of 2 kilobytes from around 650 detector front-ends at a rate of up to 100 kHz. The first stage of event-building is performed by the Super-Fragment Builder employing custom-built electronics and a Myrinet optical network. It reduces the number of fragments by one order of magnitude, thereby greatly decreasing the requirements for the subsequent event-assembly stage. By providing fast feedback from any of the front-ends to the trigger, the Trigger Throttling System prevents buffer overflows in the front-end electronics due to variations in the size and rate of events or due to back-pressure from the down-stream event-building and processing. This paper reports on new performance measurements and on the recent successful integration of a scaled-down setup of the described system with the trigger and with front-ends of all major sub-detectors. The on-going commissioning of the full-scale system is discussed.
Copyright/License	Preprint: (License: CC-BY-4.0)

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