Variational design of zone plates for the VUV and soft X-ray ranges

Many materials become appreciably translucent in the soft X-ray range, making them suitable for use as optical elements. However, since none is Perfectly transparent, it is crucial that optimum design procedures be followed in order to minimize unnecessary optical losses. In this paper we demonstrate such a solution for the ordinary metallic zone plate and compare its performance to some recently proposed configurations which were advanced on the basis of more restricted considerations.