Beryllium and aluminium refractive collimators for synchrotron radiation

Be and Al refractive lenses with long focal lengths provide a simple and efficient method of collimating synchrotron radiation. The divergence of an undulator beam at SPring-8 is reduced from >11 µrad full width at half maximum without the collimators to <3 µrad downstream of the collimators. The Be collimators have almost no losses (∼90% transmission) while the Al collimators reduce the flux by a factor of two (∼45% transmission). Data are shown at 14.4 and 18.5 keV.