Abstract: An infrared radiation (IR) detector device that comprises a casing, having an optical window for admitting radiation; a cold shield having a detector mounted therein and having a filter mounted between the optical window and the detector; a cooler tube in coiled configuration, having an inlet in communication with a pressurized gas source and an expansion nozzle located in the vicinity of the detector and a pre-cooling jacket, enclosing the cooler tube and having a gas inlet in the vicinity of the detector and a gas discharge vent to the outside. The cooler tube comprises a first section, beginning at the gas inlet, a second section, terminating at the expansion nozzle, and a communication between the first and second sections. The pre-cooling jacket comprises a first section, housing the first section of the cooler tube, a second section, housing the second section of the cooler tube, and a communication between the first and second sections.