A high strength window for a radiation detection system has a plurality of ribs comprising beryllium material. There are openings between the plurality of ribs. The tops of the ribs terminate generally in a common plane. The high strength window also has a support frame around a perimeter of the ribs. A layer of thin polymer film material is disposed over and spans the plurality of ribs and openings to pass radiation therethrough. A radiation detection system comprises a high strength window as described above and a sensor behind the window. The sensor is configured to detect radiation that passes through the window.