Development of spider micro-structured optical arrays for X-ray optics

The Smart X-Ray Optics (SXO) project comprises a U.K.-based consortium developing active/adaptive micro-structured optical arrays (MOAs). These devices are designed to focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels etched in silicon. Adaptability is achieved using a combination of piezoelectric actuators, which bend the edges of the silicon chip, and a spider structure, which forms a series of levers connecting the edges of the chip with the active area at the centre, effectively amplifying the bend radius. Test spider structures, have been bent to a radius of curvature smaller than 5 cm, indicating that in complete devices a suitable focal length using a tandem pair configuration could be achieved. Finite Element Analysis (FEA) modelling has been carried out for the optimization of the spider MOA device design. Prototype devices have been manufactured using a Viscous Plastic Processing technique for the PZT piezoelectric actuators, and a single wet etch step using {111} planes in a (110) silicon wafer for both the silicon channels and the spider structure. A surface roughness of 1.2 nm was achieved on the silicon channel walls. Characterisation techniques have been developed in order to evaluate the device performance in terms of the bending of the MOA channels produced by the actuators. This paper evaluates the progress to date on the development of spider MOA's comparing FEA modelling with the results obtained for prototype structures.