抄録
The X-ray focusing efficiency of the Fresnel zone plate (FZP) used for X-ray microscopes is only 10%; this low efficiency necessiates a strong X-ray source and/or a long exposure time. This problem is at last partially overcome by usingthe phase zone plate (PZP). The PZP replaces the opaque zones of the FZP with transparentones which shift the phase of X-rays by π radians. The focusing efficiency of the ideal PZP is 40%. For such a PZP it is essential to find materials which have high transparency at a given thickness to induce a π-radian phase shift. The search of such materials and the investigation of the X-ray focusing properties of the PZP are performed by computer simulation and experiments using a nickel PZP, leading us to an idea of a new type of zone plate, a gradient refractive index phase zone plate (GRIPZP), whose focusing efficiency is higher than that of PZP's.
