This thesis contains two major topics related to the ATLAS experiment: the calibration of electronic noise in the tile calorimeter and the development of a detailed map of the material in the inner tracker used in searches for long-lived particles.

The noise in TileCal is shown to be consistent with the expectations based on heat and radiation. Some channels are masked until they can be repaired during the shutdowns of the LHC, when maintenance work can be done. Monitoring scripts where written, producing an overview of the status of the cells easily.

The material map is produced mainly using secondary vertices reconstructed in data, which are complemented by a simulation model of the detector. The material map is used to veto regions of the detector when searching for decays of long-lived particles and spans out to 300 mm in radius and ± 300 mm in z. The material map was used in a search for long-lived particles at ATLAS where no excess was observed, and is being used in ongoing studies as well.