Abstract

Abstract Muon detection plays a key role at the Large Hadron Collider. Resistive plate chambers (RPC) provide the barrel region of the ATLAS detector with an independent muon trigger as well as a two-coordinate measurement. The chambers, arranged in three concentric layers, are operated in a strong magnetic toroidal field and cover a surface area of about 4000 m 2 . The RPC detector control system (DCS) is required to monitor and safely operate tens of thousand of channels, distributed on several subsystems, including low and high voltage power supplies, trigger electronics, currents and thresholds monitoring, environmental sensors and gas and electronic infrastructure. The DCS is also required to provide a level of abstraction for ease of operation as well as specific tools allowing expert actions and detailed analysis of archived data. The hardware architecture and the software solutions adopted are shown in detail along with a few results from the commissioning and first running phases. The material presented here can be used in future test facilities and projects.

Highlights

  • With a surface area of about 4000 m2, an active detector gas volume of about 18 m3, and several tens of thousand of power and control items, all to be operated in strong magnetic field and radiation area, the Detector Control System (DCS) of the ATLAS Resistive Plate Chambers (RPC) belongs to the state of the art Detector Control Systems in High Energy Physics

  • These signals are passed to the on-detector trigger electronics (PAD)[6] which, by requiring appropriate coincidences in η and φ detector layers, provide ATLAS with a Level 1 trigger decision as well as with the detector data

  • The above described detector elements will require several power and control lines starting from the supply of the HV for the gas gain, and the supply for the front-end electronics, the trigger PAD system and the infrastructure which is all to be operated in the detector area with radiation and high magnetic field

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Summary

The Atlas Resistive Place Chambers

Resistive Plate Chambers (RPC)[1] provide the barrel region of the ATLAS detector[2] with an independent muon trigger as well as a two-coordinate measurement. The HV working point is chosen to be at 9.6 kV at a temperature of 22◦C and a pressure of 970 mbar In these conditions the RPC work in saturated avalanche mode inducing, for a minimum ionizing particle, a prompt charge of about 1 pC on the pick-up strips and delivering in the gas an average total charge of 30 pC[5]. Custom read-out electronics amplifies, discriminates and converts the detector signals to ECL standard. These signals are passed to the on-detector trigger electronics (PAD)[6] which, by requiring appropriate coincidences in η and φ detector layers, provide ATLAS with a Level 1 trigger decision as well as with the detector data

The Power and Control System
DCS Architecture and Software Framework
Local Control Stations CAEN Power System Sectors
Device Representation and FSM Design
Environmental Sensors and HV Working Point Correction
Currents and Peak Measurements in Gap Currents
Online Data Quality through the RPC DCS
Conclusions
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