The invention relates to a detector (6) for detecting radiation, especially x-ray radiation used in a computed tomography system. The detector comprises a direct conversion material (9) for converting radiation into electrons and holes, which are used for generating an electrical detection signal. The direct conversion material is illuminated with illumination light being broadband visible and/or broadband infrared light for reducing, in particular, eliminating, a polarization of the direct conversion material, which may occur when being traversed by the radiation to be detected and which may reduce the detection performance. By reducing the polarization of the direct conversion material the detection performance can be improved.