Neutral attenuating pinhole for x-ray imaging of high-intensity sources

Pinhole imagers are common x-ray diagnostics in high energy density physics experiments, where temperatures exceeding 10⁷K are reached in the laboratory. In such extreme conditions, self-emitted black-body x-ray radiation is the main drive for physical phenomena (energy transport, shock waves). In order to avoid damages to the detector, high-pass filters are commonly used. The passed photons are ∼10 times more energetic than the common photon (maximum of the Planckian) and may fail to show the main drive in the experiment. Here we propose a neutral attenuation pinhole (NAP)-a novel, to the best of our knowledge, pinhole design that provides uniform x-ray attenuation over wavelength while keeping the optimal pinhole diameter. Semi-random distribution of thousands of sub-holes, all located within optimal diameter, results in essential large attenuation while keeping image resolution. Simulations and experimental results of the NAP spatial resolution are similar to a regular pinhole. By using a thick enough substrate, the attenuation is uniform over a wide spectrum. A NAP consisting of a 1 µm thick Au substrate allows constant 1:100 attenuation up to 1.5 keV, while a 3 µm thick substrate can be used up to 5 keV.