21 research outputs found
Laser calibration of the ATLAS Tile Calorimeter during LHC Run 2
This article reports the laser calibration of the hadronic Tile Calorimeter
of the ATLAS experiment in the LHC Run 2 data campaign. The upgraded Laser II
calibration system is described. The system was commissioned during the first
LHC Long Shutdown, exhibiting a stability better than 0.8% for the laser light
monitoring. The methods employed to derive the detector calibration factors
with data from the laser calibration runs are also detailed. These allowed to
correct for the response fluctuations of the 9852 photomultiplier tubes of the
Tile Calorimeter with a total uncertainty of 0.5% plus a luminosity-dependent
sub-dominant term. Finally, we report the regular monitoring and performance
studies using laser events in both standalone runs and during proton
collisions. These studies include channel timing and quality inspection, and
photomultiplier linearity and response dependence on anode current
The High Voltage distribution system of the ATLAS Tile Calorimeter and its performance during data taking
International audienceThis article documents the characteristics of the high voltage (HV) system of the hadronic calorimeter TileCal of the ATLAS experiment. Such a system is suitable to supply reliable power distribution into particles physics detectors using a large number of PhotoMultiplier Tubes (PMTs). Measurements performed during the 2015 and 2016 data taking periods of the ATLAS detector show that its performance, in terms of stability and noise, fits the specifications. In particular, almost all the PMTs show a voltage instability smaller than 0.5 V corresponding to a gain stability better than 0.5%. A small amount of channels was found not working correctly. To diagnose the origin of such defects, the results of the HV measurements were compared to those obtained using a Laser system. The analysis shows that less than 0.2% of the about 10 thousand HV channels were malfunctioning
The ATLAS detector control system
The ATLAS experiment is one of the multi-purpose experiments at the Large Hadron Collider (LHC) at CERN, constructed to study elementary particle interactions in collisions of high-energy proton beams. Twelve different sub detectors as well as the common experimental infrastructure are controlled and monitored by the Detector Control System (DCS) using a highly distributed system of 140 server machines running the industrial SCADA product PVSS. Higher level control system layers allow for automatic control procedures, efficient error recognition and handling, manage the communication with external systems such as the LHC controls, and provide a synchronization mechanism with the ATLAS data acquisition system. Different databases are used to store the online parameters of the experiment, replicate a subset used for physics reconstruction, and store the configuration parameters of the systems. This contribution describes the computing architecture and software tools to handle this complex and highly interconnected control system