An of the invention relates to a direct-conversion x-ray detector for detection of x-ray radiation, including a direct converter used for detection of the x-ray radiation, at least one collimator disposed at least partly in the direction of radiation of the x-ray radiation in front of the direct converter and a least one radiation source which is disposed to the side of the direct converter and irradiates the direct converter indirectly with an additional radiation. In at least one embodiment, the a least one collimator, on a side facing towards the direct converter, includes at least one reflection layer, on which the additional radiation is reflected onto the direct converter, and includes a cooling facility through which the at least one radiation source is able to be cooled.
