An Electron-Beam Profile Monitor Using Fresnel Zone Plates

Abstract

We have developed a beam profile monitor using two Fresnel zone plates (FZPs) at the KEK‐ATF (Accelerator Test Facility) damping ring to measure small electron‐beam sizes for low‐emittance synchrotron radiation sources. The monitor has a structure of an X‐ray microscope, where two FZPs constitute an X‐ray imaging optics. In the monitor system, the synchrotron radiation from the electron beam at the bending magnet is monochromatized to 3.235‐keV X‐rays by a crystal monochromator and the transverse electron‐beam image is twenty‐times magnified by the two FZPs and detected on an X‐ray CCD camera. This monitor has the following advantages: (1) high spatial resolution, (2) non‐destructive measurement, (3) real‐time monitoring and (4) direct electron‐beam imaging. With the beam profile monitor, we have succeeded in obtaining a clear electron‐beam image and measuring the extremely small beam size less than 10 μm. The measured magnification of the imaging optics was in good agreement with the design value.