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

Abstract

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 1-st kind. It has been shown that the use of the coded aperture not only enhances the efficiency of the registration system 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.