X-ray focusing by planar parabolic refractive lenses made of silicon

First refractive planar parabolic lenses are realized in Si. They comprise a set of parabolic profiles (planar parabolic lenses) or parabolic segments (planar parabolic lenses with minimized absorption) with symmetry axis lying in Si wafer surface plane. The relief depth achieved by dry etching processes is 100 mu m. Experimental testing of lenses has been carried out on an RU-200 rotating anode generator with Cu K alpha radiation (8.05 keV). The focal length, estimated and confirmed by experiment, is F = 18 cm for planar parabolic lenses. The lenses with minimized absorption have shorter focal length F = 16.8 cm, showing a 5 mu m recorded source image. The calculated transmission for these lenses reaches T = 37%, approaching values of transmission for compound refractive lenses made of low Z materials. (C) 2000 Elsevier Science B.V. All rights reserved.