X-ray diffraction on Si single crystal with a W-shaped longitudinal groove

Artemiev

et al. 2001

Self Cite

A new approach to focusing X‐ray optics based on asymmetric inclined (or rotated inclined) diffraction has been experimentally studied. Using a linear longitudinal W‐groove cut into the surface of an asymmetric silicon (111) diffractor perpendicularly to the line of intersection of its surface and crystallographic (111) planes, the out‐of‐diffraction‐plane (or sagittal) deviation of the X‐ray diffracted beam has been measured for three angles of asymmetry and constant angle of inclination on BM5 at the ESRF for a wavelength of 0.1 nm. It has been demonstrated that in the grazing‐emergence case the sagittal deviation increases with increasing asymmetry angle. A discrepancy with the theoretical value for the largest asymmetry angle and inhomogeneities in the contrast of the diffraction spot have been discussed.

Section: Introductionsupporting

confidence: 53%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

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Sagittal X-ray beam deviation at asymmetric inclined diffractors

Korytár

Artemiev

et al. 2001

Self Cite

“…First of all, this is related to the shape of the working surfaces of the crystals and the corresponding optical paths of the geometrical rays through the optical system. Also, for the parallel arrangement the smearing effect accompanying inclined Bragg diffraction (Artemiev et al, 2000) is increased by a factor which is equal to the number of re¯ections, while in the case of an antiparallel (dispersive) arrangement this effect is practically cancelled out, or is at least less noticeable. Despite the fact that the intensity distribution in the case of the parallel arrangement of the crystals is broader, the peak intensity is 17% higher than in the case of the antiparallel arrangement.…”

Section: Resultsmentioning

confidence: 99%

“…According to this simpli®ed solution, the sagittal deviation of a ray diffracted on an inclined surface is proportional to the tangent of the inclination angle , nm] for Si (Hrdy Â, 1998). The validity of this simple formula has been experimentally checked and its limitation has been determined from exact calculations (Artemiev et al, 2000).…”

Section: Resultsmentioning

confidence: 99%

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

Artemiev

Peredkov

et al. 2001

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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.

Refraction in general asymmetric X-ray Bragg diffraction

2001

When the surface of a single-crystal monochromator is not parallel to the diffracting crystallographic planes, the diffracted beam is generally deviated from the plane of diffraction and the angle between the diffracted beam and the diffracting planes is different from the angle between the incident beam and the diffracting planes. The angular diffraction regions for the incident and diffracted beams are also different. This is the manifestation of the refraction occurring during Bragg diffraction. Very simple formulae are presented which describe this situation in a general case (e.g. for a rotated-inclined X-ray monochromator). These formulae allow sagittally focusing monochromators for synchrotron radiation to be easily designed, based on X-ray diffraction-refraction phenomena. Some important properties of such types of monochromators are deduced.