The invention relates to the field of x-ray diffraction analysis using synchrotron radiation. The use of synchrotron radiation (SR) to study the atomic structure of single crystals and polycrystalline materials can reduce the time of obtaining the diffraction pattern by several orders of magnitude, to increase the angular resolution, to reduce the spectral interval, to reduce the background, tuned to the desired wavelength, to apply the methods of decryption patterns based on anomalous scattering.
In the study of the atomic structure of the SR beam is focused on the sample size of 0.3-0.6 mm, collecting divergent in the horizontal plane of the beam in the greatest possible range of angles for maximum intensity.
For the realization of focus can be used double-crystal monochromator with a fixed location monochromatic beam and sagittal bending of the second crystal /1/. The design of the holder in the monochromator /1/ allows you to change the sagittal bending plate monochromator when changing the wavelength of the SI.
The bend radius decreases with decreasing wavelength (Bragg angle θ) and the reduction of distance monochromator - sample in accordance with the relationship:
where R1- the distance light source is to the radiation - the monochromator,
P2- length monochromator - sample.
If you want to use short wavelengths (small θ) and by the limited length of the focusing channel (R2requirements regarding the bending of the crystal to increase the radius of the order of 0.3 m When the value of the radius occurs simultaneously bending in the meridional plane, perpendicular to the plane of the primary curve, which is unacceptable due to the narrow width of the reflection curve of the single crystal silicon (a few arc seconds).
To eliminate the bend in the meridional plane are used crystals with ribs.
Known for focusing monochromator with variable radius of curvature, made in the form of a rectangular plate of dislocation of the silicon single crystal orientation (111) with ribs arranged in parallel across the width of the plate /2/.
The disadvantage of this monochromator is the inability to obtain a focal distance corresponding to a radius of about 1.2 m, and the high cost and complexity of manufacture plates with ribs made of single crystal silicon.
The claimed invention is directed to the creation of the focusing monochromator with variable radius of curvature, allowing you to get a shorter focal length and, thus, has more diapason the focal lengths, and also reduce the cost of the monochromator and the improvement of the efficiency of production.
The solution of the problem with achievement of a specified result is that in focusing monochromator with variable radius of curvature, made in the form of a rectangular plate with ribs arranged in parallel across the width of the plate, the plate with ribs made of metal, and the ends of the ribs are reflecting plate of a single crystal.
The invention is illustrated in the drawing, which shows a focusing monochromator.
The monochromator consists of a metal plate 1 of rectangular shape with ribs 2. At the ends of stiffeners are reflective plate 3 from the single crystal. Plate with ribs can be made for example of titanium. Ribs can be formed by the method of electric discharge machining. The reflective plate may be made for example of silicon with the same orientation of the crystallographic planes and glued to the ends of the ribs, for example, epoxy resin.
The monochromator works as follows.
The metal plate 1 is applied bending force, so that the reflective plate 3 were located on a sector of a cylindrical surface, the axis of which RA is placed in the same plane with the direction of the incident synchrotron radiation. Diverging beam of synchrotron radiation falls on the surface of the reflecting plate 3 from a single crystal at an angle Bragg and reflected from the cylindrical surface formed by the plates 3, is focused at the point defined by the radius of curvature of the curved plate 1. Changing the bending force applied to the plate 1, change the radius of curvature of the cylindrical surface and, thereby, the position of the focal point.
Since the plate 1 is made of metal, allowing for a stronger curve than silicon, without loss of elastic properties, it is possible to get a shorter focal length.
Sources of information:
1. AG Harutyunyan and other protein crystallography Station at the synchrotron radiation source Siberia-2”, Surface, 1999, No. 12, p.88-94.
2. D.W. Batterman et al. Sagittal Focusing of Sinchrotron radiation, Nuclear Instruments and Methods, 208 1983, p.327-331.
Focusing monochromator with variable radius of curvature, made in the form of a rectangular plate with ribs arranged in parallel across the width of the plate, wherein the plate with ribs made of metal, and the ends of the ribs are reflecting plate of a single crystal.