Beryllium and aluminium refractive collimators for synchrotron radiation

Be and Al refractive lenses with long focal lengths provide a simple and ef ficient method of collimating synchrotron radiation. The divergence of an u ndulator beam at SPring-8 is reduced from >11 mu rad full width at half max imum without the collimators to <3 mu rad downstream of the collimators. Th e Be collimators have almost no losses (similar to 90% transmission) while the Al collimators reduce the flux by a factor of two (similar to 45% trans mission). Data are shown at 14.4 and 18.5 keV.