D. G. Charlton

The trigger system of the OPAL experiment at LEP

Abstract A pretrigger system is described for running the OPAL detector at the LEP e + e − collider with more bunches than originally foreseen. A large number of low threshold pretrigger signals are formed by several independent components of the detector, and combined by a custom-built VME-based central pretrigger logic. Flexibility, high efficiency and high redundancy in all physics channels are all achieved with low additional deadtime, without any compromise to the trigger performance.

The data acquisition system of the OPAL detector at LEP

Abstract This report describes the 1991 implementation of the data acquisition system of the OPAL detector at LEP including the additional services and infrastructure necessary for its correct and reliable operation. The various tasks in this “on-line” environment are distributed amongst many VME subsystems, workstations and minicomputers which communicate over general purpose local area networks and special purpose buses. The tasks include data acquisition, control, monitoring, calibration and event reconstruction. The modularity of both hardware and software facilitates the upgrading of the system to meet new requirements.

The on-line event filter of the OPAL experiment at LEP

Abstract The on-line event filter of the OPAL experiment at LEP is described. It acts as the second-level software trigger, following the first-level hardware trigger and is implemented on a workstation fully integrated into the data acquisition system. In addition to background rejection and event classification it provides detailed monitoring of the detector status and data quality, event visualisation and data compression. The partial event reconstruction and the selections based on physics quantities used for the event classification are described, and the performance of the system as used for data taking in 1991 is discussed.

Production Test Rig for the ATLAS Level-1 Calorimeter Trigger Digital Processors

R. Achenbach b , V. Andrei b , B. Bauss , B.M. Barnett . C. Bohm , J.R.A. Booth , I.P. Brawn , D.G. Charlton , C.J. Curtis , A.O. Davis , J. Edwards , E. Eisenhandler , P.J.W. Faulkner , F. Fohlisch , C. N. P. Gee , C. Geweniger , A.R. Gillman , P. Hanke , S. Hellman , A. Hidvegi , S. Hillier , E-E. Kluge , M. Landon , K. Mahboubi , G. Mahout , K. Meier , V.J.O. Perera , W.Qian , S. Rieke , F. Ruhr , D.P.C Sankey , R.J. Staley , U. Schafer , K. Schmitt , H.C. Schultz-Coulon , S. Silverstein , R. Stamen , S. Tapprogge , J.P. Thomas , T. Trefzger , D. Typaldos , P.M. Watkins , A. Watson , P. Weber , E.E. Woerhling a

Analysis of the initial performance of the ATLAS level-1 calorimeter trigger

The ATLAS first-level calorimeter trigger is a hardware-based system designed to identify high-pT jets, electron/photon and tau candidates and to measure total and missing ET in the calorimeters. The installation of the full system of custom modules, crates and cables was completed in late 2007, but, even before the completion, it was being used as a trigger during ATLAS commissioning and integration. During 2008, the performance of the full system has been tuned during further commissioning and cosmic runs, leading to its use in initial LHC data taking. Results and analysis of the trigger performance in these runs will be presented.

Commissioning of the Jet/Energy-sum and Cluster Processors for the ATLAS Level-1 Calorimeter Trigger System

The ATLAS first-level calorimeter trigger is a hard warebased system designed to identify high-p T jets, electron/photon and tau candidates, and to measure total and missing E T. The trigger consists of a Preprocessor system which digitises 7200 analogue inputs, and two digit al multicrate processor systems which find jets, measure en ergy sums, and identify localised energy deposits (electron/ph oton and tau candidates). In order to provide a trigger quic kly enough, the hardware is parallel and pipelined. Experience so far of the Jet/Energy-sum and Cluster Processor system production, commissioning, and integration into ATLAS will be described.

Fast two dimensional cluster finding in particle physics

The cluster finding module (CFM) is part of the UA1 trigger processor. The CFM detects and counts two-dimensional clusters of electromagnetic particles. This process requires 75 ns for detection of either isolated or nonisolated clusters and 75 ns to count them. This is equivalent to a peak computational rate of 11000 MIPS (million instructions per second) per module (3000 MIPS average). The required high logic density and speed are achieved by using programmable array logic devices within a pipelined system. The design has been strongly influenced by the need for in-situ computer testing. >

The new UA1 calorimeter trigger processor

The UA1 first level trigger processor (TP) is a fast digital machine with a highly parallel pipelined architecture of fast combinational and programmable transistor-transistor logic controlled by programmable microsequencers. The TP uses 100000 ICs (integrated circuits) housed in 18 crates each containing 21 FASTBUS-sized molecules. It is hardwired with a very high level of interconnection. The energy deposited in the upgraded calorimeter is digitized into 1700 bytes of input data every beam crossing (3.8 mu s). The processor selects in 1.5 mu s events for further processing (1 in 30000). The trigger has improved hadron jet rejection, achieved by requiring low-energy deposition around the electromagnetic cluster. A missing-transverse-energy trigger and a total-energy trigger have also been implemented. >

Testing and calibrating analogue inputs to the ATLAS Level-1 Calorimeter Trigger

The ATLAS Level-1 Calorimeter Trigger is a hardwarebased system which aims to identify objects with high transverse momentum within an overall latency of 2.5μs. It is composed of a PreProcessor system (PPr) which digitises 7200 analogue input channels, determines the bunch crossing of the interaction, applies a digital noise filter, 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.

Control, test and monitoring software framework for the ATLAS level-1 calorimeter trigger

The ATLAS first-level calorimeter trigger is a hardware-based system designed to identify high-pT jets, electron/photon and tau candidates and to measure total and missing ET in the ATLAS calorimeters. The complete trigger system consists of over 300 custom designed VME modules of varying complexity. These modules are based around FPGAs or ASICs with many configurable parameters, both to initialize the system with correct calibrations and timings and to allow flexibility in the trigger algorithms. The control, testing and monitoring of these modules requires a comprehensive, but well-designed and modular, software framework, which we will describe in this paper.