Parabolic refractive X-ray lenses: a breakthrough in X-ray optics

Refractive X-ray lenses, considered for a long time as unfeasible. have bee n realized with a rotational parabolic profile at our institute: The main f eatures of the new lenses are: they focus in two directions and are free of spherical aberration. By varying the number of individual lenses in the st ack the focal length can be chosen in a typical range from 0.5 to 2 in for photon energies between about 6 and 60 keV, The aperture of the lens is abo ut 1 mm matching the angular divergence Of Undulator beams at 3d generation synchrotron radiation sources. They cope without problems with the heat lo ad from the white beam of an undulator. Finally, they are easy to align and to operate. Refractive X-ray lenses can be used with hard X-rays in the sa me way as glass lenses can be used for visible light, if it is taken into a ccount that the numerical aperture is small (of the order 10(-4)). Being hi gh-quality optical elements, the refractive X-ray lenses can be used for ge nerating a focal spot in the mum range with a gain of a factor 1000 and mor e, or for imaging purposes as in a hard X-ray microscope. Recent examples f rom microanalysis. microtomography, fluorescence tomography, X-ray microsco py will be shown to demonstrate the state of the art. Possible new developm ents will be discussed. (C) 2001 Elsevier Science B.V. All rights reserved.