Irradiation of silicon detectors for HEP experiments in the Triga Mark II reactor of ATI

Abstract

Due to its semiconducting properties silicon is a very attractive material for particle detectors in High Energy Physics (HEP). A small band gap allows relatively large signals and low noise without the need for cryogenic cooling. High charge carrier mobility implies high detector speed. Impinging particles not only cause the creation of electron-hole pairs, which are responsible for the signal by drift in an electric field, but also deteriorate the detector performance because of radiation damage.Therefore, microscopic radiation effects like point and cluster defects of the single crystal and nuclear reaction of silicon atoms need to be studied by measuring macroscopic parameters like dark current increase, change of full depletion voltage and charge collection efficiency.The irradiation facilities used for such investigations are very different with respect to spectral distribution and particle type. Therefore the NIEL (Non-Ionizing Energy Loss) hypothesis is used to scale the radiation damage to those of neutrons of 1 MeV energy.The aim of this Master’s thesis, performed at the Institute of High Energy Physics (HEPHY) of the Austrian Academy of Sciences, is to characterize the spectrum of the Triga Mark II nuclear reactor of the Atominstitut (ATI) and to find the correct correlation coefficients of the different irradiation channels to 1MeV neutrons used for the NIEL scaling. Moreover, the temperature profile of the samples during irradiation need to be studied. This information is essential to understand the time-dependent annealing of radiation damage because of diffusion effects.