The High Voltage distribution system of the ATLAS Tile Calorimeter and its performance during data taking

TL;DR

This paper describes the high voltage system of the ATLAS Tile Calorimeter, demonstrating its reliable performance and stability during data collection periods, with minimal malfunctioning channels.

Contribution

It provides a detailed characterization of the HV system's performance and compares HV measurements with Laser diagnostics to identify malfunctioning channels.

Findings

Voltage instability <0.5 V for most PMTs

Gain stability better than 0.5%

Less than 0.2% of channels malfunctioning

Abstract

This 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.