Sagittal focusing of synchrotron radiation diffracted on the walls of a longitudinal hole drilled into a single-crystal monochromator

Abstract

A very simple method of sagittal focusing of X-ray synchrotron radiation is presented. A special ray-tracing program which utilizes the diffraction-refraction effect is developed. It is demonstrated both by ray-tracing simulations and by an experiment whereby a reasonably good sagittal concentration of 8 keV synchrotron radiation may be achieved by diffraction on the walls of a cylindrical hole drilled into an Si crystal. The holes were drilled parallel to the (111) planes and their diameter, 1 mm, was chosen so that the focusing distance fits the geometrical arrangement of beamline BM5 at the ESRF. Two such crystals have been used in a dispersive and non-dispersive arrangement. The better result was achieved using the dispersive arrangement. The intensity at the centre of the focus is increased by five times with respect to unfocused radiation. Excellent agreement exists between the ray-tracing simulations and experimental results.

First observation of meridional focusing of an X-ray beam using diffraction by a crystal with a transverse groove

“…The focusing effect was demonstrated experimentally. When using a cylindrical hole instead of a parabolic groove (Artemiev et al, 2001;Hrdy  et al, 2001), a signi®cant focusing effect has also been observed. This type of focusing is based on a diffractive±refractive phenomenon or, in other words, on the refraction effect occurring during Bragg diffraction.…”

Diffractive–refractive optics in the Laue case: first experiment

“…It was shown that this effect may be utilized to sagittally focus the diffracted radiation if the diffraction surface is profiled into a longitudinal parabolic shape. This has been proved experimentally at ESRF, APS and NSLS (Hrdý & Siddons, 1999;Artemiev et al, 2001Artemiev et al, , 2003Hrdý et al, 2001). This kind of optics is called Bragg diffractive-refractive optics, because the effect of the sagittal deviation of the diffracted beam is due to refraction occurring during Bragg diffraction.…”

Theoretical consideration of an X-ray Bragg-reflection lens using the eikonal approximation

“…The focusing of a diffracted X-ray beam may be achieved using a perfect crystal with parabolic-shaped surface. Theoretical and experimental investigations of sagittal focusing in the Bragg case by such a crystal has been carried out by Hrdý (1998), Hrdý et al (2001a), Hrdý & Siddons (1999) and Artemiev et al (2001). Meridional focusing in the Bragg case has been investigated by Hrdý & Hrdá (2000) and Hrdý et al (2001b), and Laue-case focusing was considered by Hrdý et al (2003).…”