ATLAS Level-1 Calorimeter Trigger Processor

1
Detector Electronics Division
ATLAS Level-1 Calorimeter Trigger Processor
Introduction The ATLAS Level-1 Trigger
algorithms are carried out by a Calorimeter
Trigger processor (electrons and photons, jets,
taus, missing and total transverse energy) and a
Muon Trigger processor (high transverse-momentum
muons in barrel and end-caps). The results of
these two processors are combined in the Central
Trigger Processor (CTP) to produce the level-1
trigger.

• Technical Specification
• The "real time" first-level trigger must reject
  999 crossings out of 1000.
• The first-level trigger must be active for each
  crossing every 25 nanosecs.
• While the trigger is making its decision,
  detector data from all subsequent beam crossings
  must be retained in buffers on the detector.
• Since these buffers are expensive they are kept
  as small as possible. In ATLAS it is set to 100
  beam-crossings (2.5?s) of which only about 1 ?s
  is available for the first-level trigger
  processor.
• It also provides Region of Interest (RoI)
  information to the Level-2 trigger system as well
  as data for monitoring and diagnostics to the DAQ
  system

ATLAS Level-1 Calorimeter Trigger
CPM, CMM, ROD many support modules such as
the Timing, CanBus monitoring system were UK
responsibility

• Technical Achievements
• Processing and moving large amount of data at
  high rates requires a great deal of
  sophistication
• A custom-built pipeline processor operating at
  frequency of 40MHz and multiples of it
• High-speed serial links
• 160Mbit/s backplane data transfers
• 1-3 Million gate FPGAs performing trigger
  algorithms
• High density and complex PCB designs.

Testing Read-out Module
This work as part of the ATLAS-Level-1
Calorimeter Trigger Collaboration from UK,
Germany and Sweden For further information
contact Viraj Perera at v.perera_at_stfc.ac.uk