Abstract: A detector for ionizing radiation, comprising a semiconductor plate having electrode strips, which extend along the upper surface of the plate, which is passed through by the rays, from an edge portion of the semiconductor plate in the direction of its opposite edge portion, and which communicate with a signal utilizing arrangement, the latter of which forms signals from the signals tapped from the electrode strips in correspondence with or indicative of the locations of the focal points of the radiation spots produced on the detector. All electrode strips are positioned on one side of the semiconductor plate, and vary in cross-section along the direction of their longitudinal extension pursuant to a predetermined function, and wherein on the other side of the semiconductor plate there is mounted a common electrode covering substantially the entire surface of the plate.