Studies on the radiation hardness of silcon sensors

The main part of this thesis covers the Irradiation Qualification of CMS silicon strip sensors with protons. The infrastructure for the irradiation tests was developed at the compact cyclotron at the Forschungszentrum Karlsruhe. The 320 μm(500 μm) thick sensors are expected to receive equivalent fluences of 1.6 x 1014n1/MeV/cm2 (0.35 x 1014n1MeV/cm2). The measured full depletion voltages on mini-sensors were used to adjust the parameters of the 'Hamburg'-model. Several scenarios of the annealing during 10 years of operation could be calculated with the resulting parametrisation. Two weeks of annealing at 20 C each year results in maximum full depletion voltages for the thin sensors of about 400 V after an exposure to 1.6 x 1014n1MeV/cm2. The leakage current of large sensors was measured to reach about 1.7 mA. This causes a power dissipation of 850 mW at 500 V and -10 C. A big difference was observed in the inter-strip capacitance of thin and thick mini-sensors. Some of these test-structures were further investigated according to the depletion behaviour. The CV-curves of mini-sensors and diodes were compared. A minimum ionising particle was simulated using an infra-red laser. This enables a measurement of the charge collection of the sensors. After irradiation the charge collection is reduced due to trapping effects, but increases with applied bias voltage. Thus one has to operate the irradiated sensors at voltages as high as possible. (orig.)