Abstract
The PreProcessor of the ATLAS Level-1 Calorimeter Trigger prepares the analogue trigger signals sent from the ATLAS calorimeters by digitising, synchronising, and calibrating them to reconstruct transverse energy deposits, which are then used in further processing to identify event features. During the first long shutdown of the LHC from 2013 to 2014, the central components of the PreProcessor, the Multichip Modules, were replaced by upgraded versions that feature modern ADC and FPGA technology to ensure optimal performance in the high pile-up environment of LHC Run 2. This paper describes the features of the new Multichip Modules along with the improvements to the signal processing achieved.
Highlights
This paper describes the new MCMs (nMCMs) as operated in Run 2, focussing on the improved performance achieved relative to the Run 1 PPr
The nMCM allows for the minimisation of effects originating from the coupling between analogue and digital ground planes on the PPr Modules (PPMs) by reducing the number of digital signals required by the Multichip Modules (MCMs): (a) Only a single clock signal is transmitted from the Readout Merger (ReM) FPGA to the Calorimeter Information PreProcessor (CALIPPR) FPGA
To continue operating with as high efficiency as achieved during Run 1, the L1Calo Trigger of the ATLAS experiment was upgraded during the first long shutdown of the LHC
Summary
ATLAS is a multipurpose particle detector utilising a forward-backward symmetric cylindrical geometry to achieve near 4π coverage in solid angle. Consisting of silicon pixel, silicon microstrip and transition radiation tracking detectors, the inner tracking detector allows the trajectories of charged particles produced in the proton-proton (p p) interactions to be reconstructed with high efficiency It is embedded in a superconducting solenoid providing a 2 T axial magnetic field. The muon spectrometer is located outside of the calorimeter systems and is based on three large air-core toroid superconducting magnets with eight coils each It includes precision tracking chambers providing accurate muon tracking for |η| < 2.7 and fast-triggering detectors covering |η| < 2.4. The HLT uses fine-granularity calorimeter information, precision measurements from the muon spectrometer and tracking information from the inner detector, in. Events passing the HLT are permanently stored for offline analysis, for Run 2 with an average rate of 1 kHz and event sizes of approximately 1.5 MB
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