Induced radioactivity in the forward shielding and semiconductor tracker of the ATLAS detector

The radioactivity induced in the forward shielding, copper collimator and semiconductor tracker modules of the ATLAS detector has been studied. The ATLAS detector is a long-term experiment which, during operation, will require to have service and access to all of its parts and components. The radioactivity induced in the forward shielding was calculated by Monte Carlo methods based on GEANT3 software tool. The results show that the equivalent dose rates on the outer surface of the forward shielding are very low (at most 0.038 μSv h - 1 ). On the other hand, the equivalent dose rates are significantly higher on the inner surface of the forward shielding (up to 661 μSv h - 1 ) and, especially, at the copper collimator close to the beampipe (up to 60 mSv h - 1 ). The radioactivity induced in the semiconductor tracker modules was studied experimentally. The module was activated by neutrons in a training nuclear reactor and the delayed gamma ray spectra were measured. From these measurements, the equivalent dose rate on the surface of the semiconductor tracker module was estimated to be <100 pSv h - 1 after 100 d of Large Hadron Collider (LHC) operation and 10 d of cooling.