Resolution and Efficiency Studies with a BOS Monitored Drift-Tube Chamber and a Silicon Telescope at the Gamma Irradiation Facility

The resolution and efficiency performance of a monitored drift-tube chamber of type BOS was investigated under different levels of photon irradiation. The chamber was irradiated with a photon count rate up to 183~s$^{-1}$cm$^{-2}$. A silicon detector was used as external reference. As a result, the spatial resolution of a drift tube is degraded by 20~$\mu$m at the highest background rate. While the tube efficiency is unchanged under irradiation, the probability of a wrong measurement of an impact radius is increased by 11\%. The consequences of the operation of the chamber at a reduced gas pressure are also discussed in the article.