Abstract: In a cryostatic device for cooling an infrared detector, based on the Joule-Thomson effect, a countercurrent heat exchanger is located with a forward flow conduit in a Dewar vessel. The forward flow conduit ends in an expansion nozzle. The infrared detector is located on the front side of the inner wall of the Dewar vessel. To reduce the heat load, a heat insulating layer is arranged between the Dewar vessel and a base. To improve the cooling power of the Joule-Thomson process achievable with a predetermined pressurized gas mass flow, an inlet end of the forward flow conduit is cooled by Peltier elements. Thus the required pressurized gas flow is reduced.