Energy Dependence of Proton Radiation Damage in Si-Sensors

Irradiation experiments on silicon sensors are used to mimic the radiation environment at collider experiments with the aim to forecast the change of the electrical properties of a detector with irradiation. Measurements on irradiated sensors are invaluable in choosing a material well suited for a silicon tracking detector. This is especially true for the upgraded detectors to be used in the high-luminosity phase of the LHC (HL-LHC), where silicon sensors as currently used would suffer severe loss in signal from irradiation with charged and neutral hadrons.\\ The CMS Tracker Collaboration has initiated irradiation studies with protons with energies ranging from 23 MeV to 23 GeV. They are often used instead of charged hadrons, their radiation induced damage to the silicon being rather similar. However, in oxygen rich silicon, NIEL violation concerning the full depletion voltage has been observed.\\ In this paper results from investigations on bulk defects compared to the change of the electrical properties of silicon pad-sensors will be summarized after irradiations with 23 MeV and 23 GeV protons. Differences in the generation of specific defects in the bulk were observed depending on the proton energy. A possible impact of such defects on the electrical properties will be evaluated.