Radiation in the FoCal detector and the photon response and resolution of the FoCal detector with a background

Abstract

In this thesis two questions related to the development of the to be built FoCal detector are investigated. FoCal is a silicon-tungsten Forward Electromagnetic Calorimeter. Firstly we investigate the radiation load in the detector by means of event simulations and subsequent transportation through the detector by GEANT. The radiation load plays an important role in calculating the lifetime of the detector (especially the silicon chips are sensitive to radiation). We first calculate the incident radiation on the detector due to p+p and Pb+Pb collisions per event, taking into account as well particles scattering off elements of the ALICE detector. After multiplying with the number of events to be expected in a 10 year running scenario used by previous research we cross check our findings with this literature. Next we calculate at which location in the detector the radiation is most intense and calculate a.o. the maximal dose the silicon chips have to endure at this location (integrated over the p+p and Pb+Pb collisions of the running scenario). Radial distributions of the incident radiation and radial distributions and spectra of the radiation inside the detector are given as well. Secondly we investigate the response and resolution to photons with and without a Pb+Pb background and try to specify an optimal granularity for the silicon pads or pixels. The resolution given this background is important since for this collision type the detector can complement both the ALICE and CERN physics program. We investigate the response and resolution as function of three variables: the energy of the photon, the cut radius around the photon axis and the amount of background. We investigate this using both analog and digitized readout. For the digitized readout two pixel sizes are investigated with and without a cutoff.