RU1790758C - Three-crystal r-ray diffractometer - Google Patents

Abstract

SUMMARY OF THE INVENTION: X-ray radiation, after passing through a collimator, is successively reflected from two perfect crystals combined into a monochromator assembly, and enters the crystal under study located on the axis of the GS-2 goniometer and, after reflection from it, into the detector. All parts of the device are fortified based on the GS-2 goniometer. The diffractometer allows precise measurements of the absolute Bragg angles in the range of 0 ... + 85 ° C, studies of the degree of perfection of the crystals and determination of the angles of their crystal section. 1 ill.

Description

The invention relates to x-ray spectroscopy and can be used to study single and polycrystals, films, X-ray mirrors.

Known schemes of three-crystal X-ray diffractometer spectrometers do not allow rapid precision measurements of the lattice parameters of single crystals in a wide range of diffraction angles without changing and reconfiguring monochromator crystals.

Known x-ray diffractometers (spectrometers) containing three crystals (ed. St. USSR No. 441488, 1974, ed. St., USSR No. 487338, 1975; ed. St. USSR No. 779866.1980).

On a three-crystal vacuum spectrometer (Aut. St. No. 441488), there is a restriction on the possible Bragg angles of the investigated crystal at 60 ° due to the selected kinematic scheme of motion of the crystals, X-ray tube and detector and their relative position.

The disadvantage of a three-crystal spectrometer according to ed. No. 487338, in which the axes of rotation of the 2nd and 3rd crystals are aligned, is that the crystal under investigation must have a lattice parameter close to the monochromator crystal and be so thin that the x-ray radiation intensity remains sufficient for detection after double passing - not a beam through this crystal. In addition, absolute Bragg angles cannot be measured, but only their small measurements with respect to the monochromator crystal.

As a prototype, a three-crystal diffractometer was used (autoswitch No. 779866), including an X-ray source, rotary holders of a first monochromator crystal, a second test crystal and a third analyzer crystal, radiation detectors and angle measuring instruments.

(L

WITH

1 o

10

U

00

 Oj

In order to increase the accuracy of measurements, a second analog three-crystal spectrometer with rotatable crystal holders was introduced into it; moreover, the x-ray sources and crystal analyzer crystal holders of the spectrometers are mounted with the possibility of independent rotations around common axes, the holders of the first crystals are mounted on common platforms configured to their independent rotation of the relative common axis passing through the middle of the segment connecting the axis of rotation of the X-ray sources and passing through their foci and the axis of rotation of the third crystal analyzer.

The disadvantages of the device on avt.sv. N 779866 are as follows.

The design of the device does not allow the first two crystals to be placed in antiparallel position and to provide monochromatic x-ray radiation for the study of the third crystal. This is due to the fact that the axis of rotation of the plate with the first two crystals is located in the middle of the segment connecting the focus of the x-ray source and the axis of the third crystal.

Absolute Bragg angles cannot be measured, only small changes in them can be measured with respect to the standard.

The device is not stable in operation. To ensure the operability of the device, it is doubled, made two-story. The upper diffractometer contains, in addition to the monochromator crystals, the crystal under study, and the lower one contains the reference crystal. Such a doubling of the device makes it even more susceptible to mechanical and thermal influences, and makes it difficult to align it.

The aim of the invention is to provide the possibility of measuring the absolute Bragg diffraction angles in the range of O - 85 ° C with an absolute error of not more than 2 and the stability of the instrument when the temperature fluctuates within 18-25 ° C.

This goal is achieved by the fact that in the three-crystal X-ray diffractometer, consisting of an X-ray source, two monochromator crystals, the third investigated crystal and at least one detector, mounted to rotate them around the axis of rotation of the goniometer, a movable plate with mono-crystals chromatators installed with the ability to rotate around an axis passing through the focus of the x-ray tube and parallel to the axis of the goniometer, monochromator crystals have the ability to rotate wok the axis of the axes lying in their reflecting planes and parallel to the axis of the goniometer, the crystal holder of the second crystal is mounted on a movable plate with the ability to move along a guide groove made along an arc of a circle centered on the axis

the first crystal, and the monochromator crystals are installed in antiparallel position so that they receive almost a beam of monochromatic x-ray radiation directed to the axis of rotation

goniometer with the investigated crystal.

In the proposed diffractometer, the aforementioned disadvantages of the prototype were eliminated due to the fact that two monochromator crystals are in the antiparallel position, and their crystal holders, together with the x-ray collimator, are mounted on a plate that can rotate around an axis passing through the x-ray focus tube.

For a given radiation wavelength, an x-ray tube, a collimator and monochromator crystals are permanently installed with precision sensitive devices using two-way screws, ensuring a stable, almost monochromatic

 4 o

Y 10-10 A beam of x-rays with angular divergence, depending on

the quality of the monochromator crystals used, 0.01 - 3. In contrast to the prototype, the diffractometer allows the absolute values of Bragg angles to be measured from 0 to 85 ° C. To ensure stability, everything

its parts are tightly connected to the base of the GS-2 goniometer, which allows Bragg angles to be measured with an error not exceeding 2.

The drawing shows a diagram of the proposed x-ray diffractometer.

The diffractometer consists of an x-ray source 1, a plate 2, on which a collimator 3 and crystal monochromators 4 and 5 are mounted, and mounted with the possibility of rotation around axis 0 passing through the focus of the x-ray tube, the crystal under investigation 6 and detectors 7 and 8, which can be rotated around

axis 0 of rotation of the goniometer 9, with the base 10 of which all parts of the device are rigidly connected. On the plate 2 there is a guide groove 11, made along an arc of a circle centered on the axis of rotation 0 of the first crystal-monochromator 4.

The diffractometer works as follows. The x-ray beam from the source 1, passing through the collimator 3, is successively reflected from the monochromator crystals 4 and 5 installed in reflecting antiparallel position at an angle of 180 ° - Sv1 - dj to each other, where dv1 and Bragg for the first and second crystals accordingly, it lands on the third test crystal 6, which is installed in the reflective position so that the axis of rotation of the goniometer 9 lies in the reflective plane of this crystal b. The beam reflected from the crystal 6 at the Bragg angle enters the detector 7, and the beam transmitted through the crystal 6 enters the detector 8.

It is possible to measure the absolute value of the Bragg angle YB on the diffractometer either from the angular reflective position of the studied crystal 6 with respect to its zero position (Sv), or from the readings of two symmetrical relative to the beam of the reflecting positions of the studied crystal, incident on the crystal 6 at point O (2 ЗБ ); to investigate the degree of perfection of the crystal in the shape and width of its diffraction maximum; explore the full external

X-ray reflection and scattering from crystals and films; to investigate the phenomenon of anomalous transmission of X-rays (the Bormann effect) during Bragg and Laue diffraction; to study small-angle scattering of x-rays in crystalline, polycrystalline and amorphous substances; determine with an accuracy of 2 cut angles of crystals,

those. angles between the surface of the crystal and reflecting crystallographic planes.

Due to the fact that when the x-ray tube 1 and the monochromatic device 2 remain at the same wavelength at a different diffraction angle of the crystal under study, it is possible to determine the Bragg angle and the angles between the surface of the crystal and

crystallographic planes for several (1 - 2) minutes. This expressiveness of measurements with their high accuracy (1 - 2) determines the high economic efficiency of the device when using

it in those laboratories, including factory ones, where a large number of such measurements are necessary to control the quality of crystals in their mass production.

Claims (1)

The claims Three-crystal X-ray diffractometer, consisting of an X-ray tube placed on a single base, a movable plate with two monochromator crystals, a crystal holder of the crystal under study and at least one detector rotatable around the axis of the goniometer, characterized in that, with in order to provide the possibility of measuring the absolute Bragg angles of the sample in the range of angles 0 - 85 ° with an absolute error of not more than 2 and stability of operation, examples at temperature fluctuations of 18-25 ° C, movable monochromatic crystal litha configured to rotate around an axis passing through the focus of the x-ray tube and parallel to the axis of the goniometer, monochromator crystals have the ability to rotate around the axes, lying in their reflecting crystallographic planes and parallel to the axis of the goniometer, the crystal holder of the second monochromator crystal is mounted on a guide made in a movable plate and having the shape of a circular arc centered on the axis of rotation of the first monochromator crystal, the monochromator crystals being installed antiparallel to each other.