SU1245968A1 - Method of determining radius of curvature of monocrystal plate - Google Patents

Abstract

This invention relates to X-ray structural analysis. The aim of the invention is to increase the sensitivity, accuracy and expressiness. The method is based on the fact that when using asymmetric reflection, due to the difference in X-ray refraction, the diffraction maximum on the sample is shifted relative to the maximum obtained from the edge of the sample. At the same time, the swing curve of a sample “bathed in a stray beam formed by a monochromator consists of two diffraction maxima. Allocating two regions on a sample using slits and obtaining diffraction peaks from them, it is possible to determine the distance between them with a high degree of accuracy, using the diffraction maximum in both cases, § obtained from the edge of the sample. 1 il. (L y 4 sd; about O5 00

Description

The invention relates to X-ray diffraction analysis and can be used for non-destructive testing of stresses in single-crystal plates.

The purpose of the invention is to increase the sensitivity, accuracy and rapidity of determining the radius of curvature of single-crystal plates.

The drawing shows the scheme of the proposed method.

The scheme contains a system of slits C: fixed slit I and movable slit II (III and Ib - the position of the movable slit, respectively, during the first and second recording of the swing curve), X-ray quantum counter P, crystal plate K, X-ray source And and crystal monochromator M.

The essence of the method is that due to the difference in X-ray refraction on a sample and on its edge, using a recording system, it is possible to obtain a swing curve consisting of two diffraction peaks, one of which (obtained from the edge) is a frame, and the offset another (obtained from a selected sample area) can be used to determine the radius of curvature of the sample. The separation of the oscillation curve into two peaks is due to the fact that when a scaled beam falls onto a sample at a small sliding angle, the sample is in an asymmetric diffraction geometry (Bragg and Laue), and its edge is close to the symmetrical Laue diffraction. Therefore, the diffraction peak reflected from the sample will be shifted due to the X-ray refraction from the cycle corresponding to its edge. The magnitude of this displacement p will be the greater. 1, the smaller the slip angle

, 1, () c. ft

F -JUy. and - - :,

  2sshg;

In order for the diffraction peaks obtained from the sample and its edge to be reliably resolved, it is necessary that the angular interval between them be much larger than the half-width of the swing curve of an ideal sample:

sini | 3 "sin2e.

In order to determine the radius of curvature of the sample, in the case of diffraction for passage in front of the counter, two slits are installed. The first (stationary) passes the diffracted beam going from the edge of the sample, the second (movable) - from the selected area of the sample. In the case of diffraction by reflection on a beam diffracted at the edge of the sample, a beam diffracted from the area adjacent to the edge of the sample is superimposed. Therefore, to shield this area, a slit is placed in front of the sample. Two consecutive recordings of sample rocking curves are made, which

characterized by the position of the second slit. The movable slot can be replaced by two fixed ones, which overlap alternately when recording the swing curves. If the specimen is bent, then the displacement of the second slit

leads to a change in the angular position of the diffraction peak, while the position of the first slit remains unchanged, which corresponds to the unchanged angular position of the reference peak. Curvature radius

determined by the ratio

{J-

1P1-P2 |

The sensitivity of the method is given by

 - d where D is the sample size;

Dr is the measurement accuracy of Pi - 9. If D is 5 cm, D r 0.2, then 500 km, which is more than an order of magnitude greater than the sensitivity of the known method. Another advantage of the proposed method is its high accuracy: to ensure that it requires a smooth rotation of the sample in a limited range of angles, and in the known method it is necessary to precisely fix the angular position of the sample during surveys, which places very high demands on the quality of the mechanics of the sample turning system. In addition, the method is rapid (it is not

0 is associated with a photographic process), especially in the case of measuring a radius of curvature not exceeding a few kilometers, since in this case it is possible to limit one recording of the swing curve.

The method can be used for

express control of the curvature of single crystal plates in laboratories of scientific research institutes and industrial enterprises.

Claims (1)

Invention Formula 0 The method for determining the radius of curvature of single crystal plates, in which a wide beam of x-rays formed by the monochromator is directed onto the sample, takes the sample to the reflecting position for the selected system of crystallographic planes, determines the position of the diffraction peaks recorded from two regions of the sample, characterized in that in order to increase sensitivity, accuracy and expressiness, Q the beam is guided to the sample under a slip-1ZTM angle φ, which meets the condition sinaj) "- sin2e, HP where ho and Xn are the zero and the lth 5th Fourier members respectively - decomposed -, dielectric constant of the sample; 9 - Bragg angle, five ." remove the swing curve from one region of the sample and its edge, then from the second region and the same edge of the sample, and determine the radius of curvature / sample by the formula P - P2l L is the distance between the selected areas on the sample; p2 is the angular interval between the diffraction peaks obtained from the sample and its edge during the first and second recording of the swing curves. Jd  : IT