URA coded-aperture camera for ICF plasma diagnostics

In the inertial confinement fusion (ICF) research, imaging for x-rays and high energy particles is regarded to be one of the most important techniques to solve the implosion dynamics. A single pinhole camera and a Fresnel zone plate (FZP) camera have been used as the imaging instrument so far. The single pinhole camera, however, has low SN ratio especially for a weak radiation source because of its small opening area. The FZP camera inevitably produces an artifact in the reconstructed image. The uniformly redundant arrays (URA) were predicted to be artifact-free and expected to superior to FZP. From the above consideration, the URA camera has been introduced to ICF research at Los Alamos National Laboratory. The authors have successfully applied the URA camera to x-ray imaging of a compressed core with a cannon ball target. The URA aperture consists of 2,046 square pinholes and was fabricated by a photo-etching method in a 10 μm thick nickel foil. Each pinhole size was 30 μm square that was made small compared to the center-to-center spacings of 50 μm for self-supporting. The pattern of pinhole arrays was based on a 31 x 33 element m-sequence URA