Drift velocity and pressure monitoring of the CMS muon drift chambers

TL;DR

This paper discusses the importance of monitoring drift velocity and pressure in CMS muon drift chambers to ensure accurate muon tracking, highlighting the effects of environmental factors and presenting initial data from a dedicated velocity measurement device.

Contribution

It introduces a new Velocity Drift Chamber (VDC) for precise drift velocity monitoring and discusses initial results and pressure monitoring strategies for CMS muon chambers.

Findings

Drift velocity is affected by pressure, gas composition, temperature, and magnetic field.

The VDC provides a means for real-time drift velocity measurement.

Pressure monitoring is crucial to prevent air ingress and maintain chamber performance.

Abstract

The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers. The differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest drift velocity monitoring results are discussed.