An apparatus for detecting radiation has a substrate, a protective housing fitting on the substrate, which has an electrically conductive material and a top facing away from the substrate, and that has an aperture therein. A stack is fitted on the substrate inside the protective housing and includes at least one detector substrate having at least one thermal detector element thereon that converts incoming thermal radiation into an electrical signal, at least one circuit carrier having at least one read circuit for reading out the electrical signal, and at least one cover that covers the detector element. The detector substrate is located between the circuit substrate and the cover. The detector substrate and the cover are arranged on each other such that the detector element of the detector substrate and the cover have at least one first stack cavity of the stack therebetween, the stack cavity being defined by the detector support and the cover. The circuit substrate and the detector substrate are arranged on each other such that the detector substrate and the circuit substrate have at least one second stack cavity therebetween, the second stack cavity being defined by the circuit substrate and the detector substrate. At least one of the first stack cavity and the second stack cavity is evacuated. The stack top that faces the substrate is accessible from outside of the protective housing.