Application of a New Type of Coded Aperture for Reconstruction of Laser Plasma Images in the Soft X-ray Range

To study the spatial distribution of the soft X-ray radiation intensity of a laser-produced plasma, a new type of coded aperture was used. This aperture is a structure with a mutually perpendicular arrangement of opaque strips, the distances between which and their widths were calculated with the use of a random number generator. The radiation transmitted through such aperture gives an intricate pattern of the encoded image, which was recorded on a Fuji TR imaging plate without a protective coating. To reconstruct the spatial distribution of the plasma radiation intensity from this pattern, a mathematical algorithm was developed that is an iterative method for solving an ill-posed problem—the Fredholm integral equation of the first kind. It has been shown that the use of the coded aperture not only enhances the efficiency of the registration system by many times but also allows one to get a spatial resolution no worse than in the case of the use of a pinhole camera. It is established that the developed iterative method can be used both for sources which differ little from point sources and for spatially extended objects.