Diamond-based semi-transparent beam-position monitor for synchrotron radiation applications

A soft X-ray beam-position monitor based on a thin CVD diamond photodetector has been developed for use on third-generation synchrotron radiation facilities, and has been tested on beamlines ID26 and ID12 at the European Synchrotron Radiation Facility. Since diamond exhibits a low absorption to low-energy X-ray photons, this device allows beam-position monitoring with very little beam attenuation at photon energies as low as 2 keV. The devices presented here find their use essentially on low-energy monochromatic beamlines with narrow beam sizes (typically below 1 mm²). Measurements performed on a 20 µm-thick device show that a position sensitivity of 2 µm can readily be achieved with a photon flux attenuation of 22% at 4 keV. This allows permanent in-situ monitoring of beam instabilities during experiments.