Design and fabrication of low-cost x-ray mirrors

Traditional x-ray mirrors are quite expensive because of the fabrication cost involved in achieving a very high surface finish of the order of 15 angstrom or better. Currently, zerodur, and silicon carbide are commonly used as the substrate materials of choice for x-ray mirrors, and the required surface finish is achieved thorugh traditional through traditional polishing methods, which are very expensive and time consuming. The cost of instruments for many new applications in the areas of biomedicine, nondestructive testing and space can be greatly reduced by using the replication methods for producing x-ray quality grazing-incidence type mirrors. This paper presents the optical and optomechanical design for a Wolter type I mirror and its mount, and the fabrication methods used to produce a low cost replicated nickel mirror. The finite element analysis (FEA) results for this mirror are also presented. The fabrication steps including the design and nickel and gold plating of the aluminum master mandrel used for the replication are also discussed. A surface finish of 10-15 angstrom was achieved for a mirror with a wall thickness of only 1 mm for such an electroformed mirror. These kind of replicated x-ray mirrors can result in a major saving in the weight as well as cost, while also making the resulting instruments much more compact and rugged.