The CMS Magnet Test and Cosmic Challenge

The CMS detector is under construction for imminent operation at the Large Hadron Collider at CERN near Geneva, Switzerland. The installation and commissioning is performed in a surface hall. Thereafter, all the main heavy elements of the detector, the disks and wheels, are lowered in the experimental cavern starting at the end of 2006. The superconducting magnet of CMS requires testing before lowering, providing a unique opportunity to operate all the sub-detectors and sub-systems together and to take data with cosmic muons as an important commissioning test. This is called the MTCC - Magnet Test and Cosmic Challenge. The participating systems include a 60deg sector of the muon system comprising gas detectors like the drift tubes (DTs), cathode strip chambers (CSCs) and resistive plate chambers (RPCs), both in the Barrel and Endcaps. The tracking system comprises elements of the silicon-strip tracker, and parts of the electromagnetic and hadronic calorimeter detected energy depositions of the traversing muons. In this article, a description of the operational experience and the lessons learnt are presented.