Described herein are a pressure-sealed detector housing for securing a detector, such as a gamma ray detector in a tool for use in a wellbore. A detector housing is described which includes a body portion with an internal cavity to receive the detector, and having flanges extending therefrom. The flanges can extend, in some cases, generally alongside at least a portion of the internal cavity. Flanges may have one or more mounting holes for mounting the housing to a tool. An opening will be provided in the detector housing to provide access to the internal cavity to facilitate placement of the detector therein. A closure device is coupled into the opening to substantially seal the opening and provide electrical connections to the detector.