Design of a beam size monitor using Fresnel zone plates

Measuring electron-beam sizes is very important to estimate horizontal and vertical emittances in low-emittance rings. The beam size monitor using Fresnel zone plates (FZPs) has been designed for the Super-SOR ring (a new name of the VSX ring), which is a third-generation synchrotron light source being planned by the University of Tokyo. The monitor system has a structure of a long-distance X-ray microscope using two FZPs and has an advantage of direct and real-time monitoring of the electron beam profile. The synchrotron radiation from the electron beam at a bending magnet is monochromatized by a double-crystal monochromator and the electron beam profile is magnified and imaged on an X-ray CCD camera by two FZPs. The spatial resolution is estimated to be about 1 /spl mu/m for the photon energy of 5 keV and it is sufficiently high to measure the horizontal and vertical beam sizes, 14 /spl mu/m and 3.6 /spl mu/m at minimum, respectively. The design of the new beam profile monitor using Fresnel zone plates is presented in this paper.