Diffractive–refractive optics: X-ray splitter

Abstract

The possibility of splitting a thin (e.g. undulator) X-ray beam based on diffraction-refraction effects is discussed. The beam is diffracted from a crystal whose diffracting surface has the shape of a roof with the ridge lying in the plane of diffraction. The crystal is cut asymmetrically. One half of the beam impinges on the left-hand part of the roof and the other half impinges on the right-hand side of the roof. Owing to refraction the left part of the beam is deviated to the left whereas the right part is deviated to the right. The device proposed consists of two channel-cut crystals with roof-like diffraction surfaces; the crystals are set in a dispersive position. The separation of the beams after splitting is calculated at a distance of 10 m from the crystals for various asymmetry and inclination angles. It is shown that such a splitting may be utilized for long beamlines. Advantages and disadvantages of this method are discussed.

Diffractive–refractive optics: (+,−,−,+) X-ray crystal monochromator with harmonics separation

“…A new monochromator acting as an X-ray splitter was proposed by Hrdý (2010) and it was shown that this device also separates the first harmonic from the higher harmonics. However, its roof-shape is somewhat complicated and more demanding for fabrication.…”

“…the harmonics can be easily separated by slits. As follows from Hrdý (2010), the deviation may be substantially enhanced if asymmetric crystals are used. However, the asymmetry may delimit the usable wavelength range of the monochromator.…”

“…This, in our case, reduces the peak intensity of harmonics (as compared with non-inclined channel-cut crystals) by about five times. This is a drawback of this arrangement and it also concerns the X-ray splitter (Hrdý, 2010). The system behaves as a source with finite horizontal dimension (here 1 mm) and with divergent radiation (the sagittal spread).…”