Abstract

The central part of the ATLAS level-1 trigger system consists of the central trigger processor (CTP), the local trigger processors (LTPs), the timing, trigger and control (TTC) system, and the read-out driver busy (ROD/spl I.bar/BUSY) modules. The CTP combines information from calorimeter and muon trigger processors, as well as from other sources and makes the final level-1 accept decision (L1A) on the basis of lists of selection criteria, implemented as a trigger menu. Timing and trigger signals are fanned out to about 40 LTPs which inject them into the sub-detector TTC partitions. The LTPs also support stand-alone running and can generate all necessary signals from memory. The TTC partitions fan out the timing and trigger signals to the sub-detector front-end electronics. The ROD-BUSY modules receive busy signals from the front-end electronics and send them to the CTP (via an LTP) to throttle the generation of L1As. An overview of the ATLAS level-1 central trigger system will be presented, with emphasis on the design and tests of the CTP modules.

Highlights

  • Abstract-- The central part of the ATLAS Level-1 trigger system consists of the Central Trigger Processor (CTP), the Local Trigger Processors (LTPs), the Timing, Trigger and Control (TTC) system, and the Read-out Driver Busy (ROD_BUSY) modules

  • The TTC system proper encodes the signals received from the CTP, converts them into optical signals and fans them out to the detector front-end electronics, where they are recovered by a dedicated ASIC chip

  • The CTP has many functions that can be divided into three groups: it synchronizes and aligns in time trigger information coming from different sources; it forms the Level-1 trigger decision and distributes it to the TTC partitions; it provides readout data to, and is controlled by the Data Acquisition system

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Summary

THE CENTRAL TRIGGER SYSTEM

The ATLAS Level-1 trigger [1] is a synchronous system operating at the bunch crossing (BC) frequency (40.08 MHz) of the LHC (Large Hadron Collider) accelerator. It uses information on clusters and global energy in the calorimeters and from tracks found in dedicated muon trigger detectors. The CTP itself forms the Level-1 Decision (accept or not) every 25 ns, and distributes it to the TTC partitions. It receives the timing signals from the LHC and fans them out to the TTC partitions. On October 2004, the system has been tested at CERN in a combined test-beam with 25 ns bunch structure

OVERVIEW OF THE CENTRAL TRIGGER PROCESSOR
Trigger inputs
Trigger Formation
Data Acquisition
DESIGN AND STATUS OF THE CTP
The CTP backplanes
C OM bus HPT D C

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