Multilayer Period Uniformity and Performance of Soft X-ray Imaging Systems

Because multilayer x-ray structures are bandpass reflectors, the variation in multilayer period across the surfaces of near normal-incidence soft x-ray focussing optics has implications for performance of imaging systems. We have investigated these issues as they relate to Schwarzschild objectives coated with Mo/Si multilayers for use at wavelengths ranging from roughly 12.4 to 21.0 nm. The results can be generalized to other types of compound reflective imaging or projection systems and wavelength ranges.