Numerical simulations of achromatic X-ray lenses

Over the last decade refractive lenses for monochromatic X-ray radiation have been realized for man, v different materials by microfabrication technology. All these lens systems axe successfully working only for one discrete energy, i.e., the lenses are chromatic. Thus each discrete energy within a certain energy range has a different focal length. While the focal spot size is smaller than a micron for a particular energy at the corresponding focal distance, it increases up to several tens of microns for a larger energy range. We present results of numerical simulations for a new type of lens system which addresses this problem. We are developing achromats by combining. different, refractive elements of different materials. Via ray-tracing we determine the parameters of the lenses by minimizing the focal spot size for an energy range of about E +/- triangle E with triangle E = 15%. Thus the spot size of an energy range can be noticeably reduced compared with conventional refractive (chromatic) lens systems.