Gamma-ray sensitivity of a thin gap chamber

The Large Hadron Collider (LHC) at the European Laboratory for Particle Physics (CERN) is expected to operate at a luminosity of 1034 cm−2 s−1 resulting in a rather large background radiation in the experimental hall. A Thin Gap Chamber (TGC) will be used for forward muon triggering in the ATLAS experiment. According to a simulation, the main source of background around the TGC in the experimental hall will be neutrons and photons. In this report, we describe measurement of the sensitivity of the TGC to γ-rays. The measurements were made with γ-rays from radioactive sources with energies between 20 keV and 1.8 MeV. The sensitivity was found to be less than 1%, which is in good agreement with the EGS4-based simulator.