Dr
Rainer Stamen
(University of Heidelberg)
The ATLAS Level-1 Calorimeter trigger is a hardware-based system which aims to identify high-pt objects within an overall latency of 2.5us. It is composed of a Preprocessor system which digitises 7200 analogue input channels, determines the bunch crossing of the interaction, and provides a fine calibration; and two subsequent digital processors.
The Preprocessor system needs various channel dependent parameters to be set in order to provide digital signals which are aligned in time and have proper energy calibration. The different techniques which are used to derive these parameters are described along with the quality tests of the analogue input signals.
Results from first collision data are expected.
Summary
The high luminosity and bunch-crossing rate of the LHC poses an immense challenge for triggering. The ATLAS Level-1 calorimeter trigger processes 7200 trigger towers within a fixed latency of 2.5 us, reducing the event rate from 40 MHz to below 100 kHz. It is realised completely in hardware, including ASICs and FPGAs, in a VME-based system.
The Preprocessor of the Level-1 calorimeter trigger is a compact system which digitizes the detector signals, determines the bunch crossing number of the interaction and provides a fine energy calibration. The results are sent to two digital processors, the Cluster Processor (CP) and the Jet/Energy Processor (JEP). The CP searches for electron/photon and tau candidates. The JEP identifies jets and computes total and missing transverse energy sums. Both digital processors provide the information to the Central Trigger Processor which makes the overall Level-1 decision.
The Preprocessor is a highly modular system consisting of eight crates hosting a total of 124 preprocessor modules (PPMs). Each of these modules handles 64 channels in parallel. The main signal processing is done by the custom-built Preprocessor ASIC. It is placed on the multichip modules (MCMs) hosted on a PPM. Each MCM handles four input channels.
The Preprocessor system needs various channel dependent parameters to be set in order to provide digital output data which are aligned in time and have proper energy calibration. The analogue cables from the detector frontend have length differences which amount to channel-to-channel timing differences of up to 10 bunch crossings which is corrected for by means of input shift registers. In addition to this, the fine timing of the FADC clock needs to be set with ns accuracy in order to sample the analogue pulses on their maximum which guarantuees proper signal reconstruction and the maximum dynamic range. The energy of the pulses is determined by means of a FIR filter in combination with a look up table for which the corresponding coefficients and values have to be determined in order to increase the signal to noise ratio and to achieve proper calibration.
During the commissioning phase of the experiment the Preprocessor system is also used to test the signal quality of the analogue input signals since it provides independent readout for all trigger towers in parallel.
This talk gives an introduction to the Level-1 Calorimeter Trigger with a focus on the preprocessor system. The different calibration methods are described along with the quality tests of the analogue input signals. Results from cosmic muon data are presented and if possible first results from proton collisions.
Mr
Adam Davis
(STFC, Rutherford Appleton Laboratory)
Dr
Alan Watson
(University of Birmingham)
Dr
Alvin Tan
(University of Birmingham)
Ms
Andrea Neusiedl
(University of Mainz)
Mr
Attila Hidvegi
(Stockholm University)
Prof.
Barbro Asman
(Stockholm University)
Ms
Birgit Oltmann
(University of Mainz)
Dr
Bruce Barnett
(STFC, Rutherford Appleton Laboratory)
Mr
Bruno Bauss
(University of Mainz)
Prof.
Christian Bohm
(Stockholm University)
Mr
Christian Goringer
(University of Mainz)
Mr
Christian Ohm
(Stockholm University)
Mr
Christopher Curtis
(University of Birmingham)
Dr
Damien Prieur
(STFC, Rutherford Appleton Laboratory)
Prof.
David Charlton
(University of Birmingham)
Mr
David Hadley
(University of Birmingham)
Dr
David Sankey
(STFC, Rutherford Appleton Laboratory)
Prof.
Eike-Erik Kluge
(University of Heidelberg)
Prof.
Eric Eisenhandler
(Queen Mary, University of London)
Mr
Felix Muller
(University of Heidelberg)
Dr
Florian Fohlisch
(University of Heidelberg)
Mr
Frederik Ruhr
(University of Heidelberg)
Dr
Gilles Mahout
(University of Birmingham)
Prof.
Hans-Christian Schultz-Coulon
(University of Heidelberg)
Dr
Ian Brawn
(STFC, Rutherford Appleton Laboratory)
Ms
Johanna Fleckner
(University of Mainz)
Dr
John Morris
(Queen Mary, University of London)
Mr
Jorgen Sjolin
(Stockholm University)
Mr
Joseph Lilley
(University of Birmingham)
Dr
Juergen Thomas
(University of Birmingham)
Dr
Juraj Bracinik
(University of Birmingham)
Dr
Kambiz Mahboubi
(University of Heidelberg)
Prof.
Karlheinz Meier
(University of Heidelberg)
Dr
Klaus Schmitt
(University of Heidelberg)
Ms
Marianne Johansen
(Stockholm University)
Dr
Marius Groll
(University of Mainz)
Mr
Mark Stockton
(University of Birmingham)
Mr
Markus Bendel
(University of Mainz)
Mr
Martin Gallacher
(University of Birmingham)
Dr
Martin Wessels
(University of Heidelberg)
Mr
Martin Wildt
(University of Mainz)
Dr
Mohammed Aharrouche
(University of Mainz)
Dr
Murrough Landon
(Queen Mary, University of London)
Mr
Neil Collins
(University of Birmingham)
Dr
Norman Gee
(STFC, Rutherford Appleton Laboratory)
Mr
Paolo Adragna
(Queen Mary, University of London)
Dr
Paul Hanke
(University of Heidelberg)
Dr
Paul Thompson
(University of Birmingham)
Mr
Pavel Weber
(University of Heidelberg)
Dr
Peter Faulkner
(University of Birmingham)
Prof.
Peter Watkins
(University of Birmingham)
Dr
Rainer Stamen
(University of Heidelberg)
Dr
Ralf Achenbach
(University of Heidelberg)
Mr
Richard Booth
(University of Birmingham)
Dr
Richard Staley
(University of Birmingham)
Dr
Robin Middleton
(STFC, Rutherford Appleton Laboratory)
Dr
Sam Silverstein
(Stockholm University)
Mr
Sebastian Eckweiler
(University of Mainz)
Mr
Stefan Rieke
(University of Mainz)
Prof.
Stefan Tapprogge
(University of Mainz)
Dr
Sten Hellman
(Stockholm University)
Dr
Stephen Hillier
(University of Birmingham)
Dr
Taylor Childers
(University of Heidelberg)
Dr
Thorsten Kuhl
(University of Mainz)
Dr
Tony Gillman
(STFC, Rutherford Appleton Laboratory)
Dr
Torbjorn Moa
(Stockholm University)
Dr
Ulrich Schafer
(University of Mainz)
Mr
Victor Andrei
(University of Heidelberg)
Dr
Victor Lendermann
(University of Heidelberg)
Dr
Viraj Perera
(STFC, Rutherford Appleton Laboratory)
Dr
Weiming Qian
(STFC, Rutherford Appleton Laboratory)
