Entrance window design parameters for high-pressure gas x-ray imaging detectors

Gas ionization x-ray detectors operating at pressures up to 100 atm offer inherently high spatial and contrast resolution. However, incorporating the detector x-ray entrance window in a conventional pressure vessel designed for such pressures can result in high primary beam loss in the window and a much reduced overall detective quantum efficiency. The design of a gas chamber cover plate for a strip beam detector which mechanically isolates the x-ray entrance window from the lateral tensile stresses in the chamber body is described. A number of test windows of this design, varying in three geometric parameters-thickness, window curvature, and fillet radius-were fabricated from wrought aluminum [6061-T651 ] and subjected to pressures of up to 400 atm for the purpose of selecting an optimum window for a prototype digital x-ray imaging detector. The experimental data indicate that windows can be designed for a detector admitting a 1.0 cm wide x-ray beam that have rupture pressures exceeding 500 atm while maintaining x-ray transmittances of as much as 93.4% for a 120 kVp tungsten anode spectrum.