Abstract
The ATLAS detector has been designed for operation at the Large Hadron Collider at CERN. ATLAS includes electromagnetic and hadronic liquid argon calorimeters, with almost 200,000 channels of data that must be sampled at the LHC bunch crossing frequency of 40 MHz. The calorimeter electronics calibration and readout are performed by custom electronics developed specifically for these purposes. This paper describes the system performance of the ATLAS liquid argon calibration and readout electronics, including noise, energy and time resolution, and long term stability, with data taken mainly from full-system calibration runs performed after installation of the system in the ATLAS detector hall at CERN.
Highlights
The LAr calorimeters are read out via a system of custom electronics
In the case of the hadronic endcap (HEC) [11], cryogenic preamplifiers mounted on the detector inside the cryostat provide some amplification of the signals before they reach the Front End Boards (FEBs), and the preamplifiers on the FEB are replaced by preshapers that provide a pole-zero cancellation to adapt to the widely varying HEC detector capacitance in order to equalize the pulse shapes before the analog summing that is done for the Level 1 (L1) trigger system
A system of custom electronics has been developed for the readout of the ATLAS LAr calorimeters
Summary
The electronic readout of the ATLAS LAr calorimeters, depicted schematically in figure 1, is divided into a Front End (FE) system [4] of circuit boards mounted in custom crates directly on the detector cryostats, and a Back End (BE) system [5] of VME-based boards located off the detector, outside the detector hall. The FEBs sample the LAr calorimeter signals at the LHC bunch crossing frequency of 40 MHz and store the samples during the latency of the ATLAS L1 trigger system. The largest of which corresponded to the setup required to read out one “half-crate” of the EMB (including 14 FEBs, one calibration board, and the associated trigger and control boards). This configuration included 1792 readout channels, corresponding to ∼1.6% of the channels in the entire EMB, or ∼0.9% of the total LAr calorimeter system. A similar partial system test of the BE electronics was performed at CERN in 2004
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