The ATLAS Level-1 Calorimeter Trigger

The ATLAS Level-1 Calorimeter Trigger uses reduced-granularity information from all the ATLAS calorimeters to search for high transverse-energy electrons, photons, tau leptons and jets, as well as high missing and total transverse energy. The calorimeter trigger electronics has a fixed latency of about 1 microsecond, using programmable custom-built digital electronics. This paper describes the Calorimeter Trigger hardware, as installed in the ATLAS electronics cavern

Test results for the Jet/Energy Processor of the ATLAS Level-1 Calorimeter Trigger

The Jet/Energy-sum Processor is one of three processing units of the ATLAS Level-1 Calorimeter Trigger. It identifies and finds the location of jets, and sums total and missing transverse energy information from the trigger data. The Jet/Energy Module (JEM) is the main module of the Jet/Energy-sum Processor. The JEM prototype is designed to be functionally identical to the final production module for ATLAS. Three JEM prototypes have been built and successfully tested. Various input test vector patterns were used to check the performance of the jet and energy summation algorithm. Data communication between adjacent Jet/Energy Modules and all relevant modules of the Jet/Energy-sum Processor has been tested. We present a description of the architecture, required functionality, and jet and energy summation algorithm of the Jet/Energy Module. Recent test results using the JEM prototypes are presented and discussed

ATLAS Level-1 Calorimeter Trigger: Subsystem Tests of a Prototype Cluster Processor Module

The Level-1 Calorimeter Trigger consists of a Preprocessor (PP), a Cluster Processor (CP), and a Jet/Energy-sum Processor (JEP). The CP and JEP receive digitised trigger-tower data from the Preprocessor and produce trigger multiplicity and Region-of-Interest (RoI) information. The trigger will also provide intermediate results to the data acquisition (DAQ) system for monitoring and diagnostic purposes by using Readout Driver (ROD) Modules. The CP Modules (CPM) are designed to find isolated electron/photon and hadron/tau clusters in overlapping windows of trigger towers. Each pipelined CPM processes 8-bit data from a total of 128 trigger towers at each LHC crossing. Four full-specification prototypes of CPMs have been built and results of complete tests on individual boards will be presented. These modules were then integrated with other modules to build an ATLAS Level-1 Calorimeter Trigger subsystem test bench. Realtime data were exchanged between modules, and time-slice readout data were tagged and transferred to the ROD at a trigger rate up to 100 kHz. Tests results have been successful and the CPM's present design is close to the final production design

ATLAS level-1 calorimeter trigger: subsystem tests of a Jet/Energy-sum Processor module

The ATLAS Level-1 Calorimeter Trigger consists of a Preprocessor, a Cluster Processor (CP), and a Jet/Energy-sum Processor (JEP). The CP and JEP receive digitised trigger-tower data from the Preprocessor and produce trigger multiplicities and total and missing energy for the final trigger decision. The trigger will also provide region-of-interest (RoI) information for the Level-2 trigger and intermediate results of the data acquisition (DAQ) system for monitoring and diagnostics by using readout driver modules (ROD). The Jet/Energy-sum Processor identifies and localises jets, and sums total and missing transverse energy information from the trigger data. The Jet/Energy Module (JEM) is the main module of the Jet/Energy-sum Processor. The JEM prototype is designed to be functionally identical to the final production module for ATLAS, and have the full number of channels. Three JEM prototypes have been built and successfully tested. Various test vector patterns were used to test the energy summation and the jet algorithms. Data communication between adjacent Jet/Energy Modules and all other relevant modules of the Jet/Energy-sum Processor has been tested. Recent test results using the Jet/Energy Module prototypes are discussed