A radiation detector with: - a detector housing in which a detector chamber is formed; - a radiation window, which is integrated into the detector housing and is permeable for radiation to be detected, in such a way that the radiation to be detected can pass through the radiation window into the detector chamber; - a radiation sensor, which is accommodated in an evacuated environment of the detector chamber, in such a way that the radiation passing through the radiation window can be detected by the radiation sensor; - a mounting device, with which the radiation sensor is mounted on the detector housing; - a temperature-regulating device, which is in the detector chamber and is thermally coupled with the radiation sensor in order to temperature-regulate the latter, wherein a dissipation of heat, which arises during the operation of the temperature-regulating device, takes place via the detector housing, wherein, for the heat dissipation of heat arising during operation, the temperature-regulating device is thermally coupled with the detector housing via a thermal energy conductor, which is configured to permit a displacement of the temperature-regulating device by means of the displacement device; - a connection device, in which one or more lines are led out of the detector chamber, in a fluid-tight sealed manner, through the detector housing to the exterior; and - the displacement device, which is disposed on the mounting device and is configured to displace the radiation sensor in the detector chamber into different measurement positions in which, respectively, radiation incident at the time can be detected with the radiation sensor. - a detector housing in which a detector chamber is formed; - a radiation window, which is integrated into the detector housing and is permeable for radiation to be detected, in such a way that the radiation to be detected can pass through the radiation window into the detector chamber; - a radiation sensor, which is accommodated in an evacuated environment of the detector chamber, in such a way that the radiation passing through the radiation window can be detected by the radiation sensor; - a mounting device, with which the radiation sensor is mounted on the detector housing; - a temperature-regulating device, which is in the detector chamber and is thermally coupled with the radiation sensor in order to temperature-regulate the latter, wherein a dissipation of heat, which arises during the operation of the temperature-regulating device, takes place via the detector housing, wherein, for the heat dissipation of heat arising during operation, the temperature-regulating device is thermally coupled with the detector housing via a thermal energy conductor, which is configured to permit a displacement of the temperature-regulating device by means of the displacement device; - a connection device, in which one or more lines are led out of the detector chamber, in a fluid-tight sealed manner, through the detector housing to the exterior; and - the displacement device, which is disposed on the mounting device and is configured to displace the radiation sensor in the detector chamber into different measurement positions in which, respectively, radiation incident at the time can be detected with the radiation sensor.