Challenges for silicon pixel sensors at the European XFEL

A systematic experimental study of the main challenges for silicon-pixel sensors at the European XFEL is presented. The high instantaneous density of X-rays and the high repetition rate of the XFEL pulses result in signal distortions due to the plasma effect and in severe radiation damage. The main parameters of X-ray-radiation damage have been determined and their impact on p+n sensors is investigated. These studies form the basis of the optimized design of a pixel-sensor for experimentation at the European XFEL.