SU68370A1 - Cassette for radiographic camera - Google Patents

Description

The widespread use of X-ray diffraction analysis in production practice is hampered by the extremely long exposure time required for obtaining high-quality X-ray photographs covering the entire spectrum of the crystalline substance under study (for example, steel) or a substantial part of it.

In the well-known works, it was shown that in the case of a normal cylindrical camera when shooting with Debye-Scherrer or in the case of a flat cassette when shooting with Zachs, exposure can be easily reduced by increasing the X-ray beam section using focusing methods on a well-defined line.

However, using the well-known methods of high-speed shooting, it is not possible to obtain sufficiently clear lines of the entire spectrum. When focusing on one line, the other lines of the spectrum are blurred.

Meanwhile, it is not difficult to focus on all the lines of the radiograph, taking the tape with the x-ray film not in the form of a cylinder with a constant given radius, but arranging the film along a known curvilinear contour.

The subject of the present invention is such a cassette for

an X-ray camera designed for shooting flat sections according to Debye-Scherrer, which, in order to obtain sharpness for all lines of the X-ray pattern, is curved in cross-section and with such a calculation that the distance from the sample to the film is:

 - cosatgp) 20 V tga

where / is the distance from the sample to

films;

a is the angle between the mg direction of the x-ray beam and the sample;

p is the angle of divergence of the beam; 6 is the angle between the directions of the incident and reflected rays;

L is the distance from the sample to the focus of the tube or the first diaphragm. Indeed, when focusing on a known line, the angle between the direction of the x-ray beam and the sample in the form of a slip is determined by an approximate formula;

sin 26

(1) tg -; -fcos 26

where R is the camera radius or the distance from the center of the thin section to the film.

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The approximate expression obtained by considering the geometrical conditions of the reflection allows focusing on all the lines, taking the cylindrical camera, in which the film is located around the circumference, and the camera, in which the distance from the sample to the film depends on the angle of reflection.

The distance from sample d, o of the film, provided that all lines are focused, according to expression (1), will approximately be:

g P 1 1 so82o l. . . (2) L tgaJ

or, more precisely, taking into account the yioi divergence of the beam directed to the sample:

Z L l-cosatgpjГ -26 1. (3) L tgaJ

Cases (2) and (3) determine the configuration of the location of the film around the sample depending on the angle of reflection for given values of tga, Ig and A. Because the configuration of the cartridge in which the x-ray film is placed is determined by the values of A, tga, tg , a cassette must be manufactured for operation under well-defined specified conditions.

FIG. 1 shows a general view of the cassette in plan and side view; in fig. 2 - cassette frame; in fig. 3 - the mechanism of its movement.

The metal disk 1, mounted on the base of the camera, is mounted on three screws. There is a table 2 on it, on which the test specimen is fixed. The table can be rotated around its own axis, and the angle of rotation can be counted on the limb 3. Sample 4. Using the help of the clamping screw 6 is pressed against the frame 5 mounted on the table. A collimator 7 with a diaphragm is installed in the lead inlet 8 or directly on the tube body (on the protective cylinder of the electron tube). With the aid of the creamer, the entire chamber can be moved radially towards the tube. 414

The film, wrapped in black paper, is fixed on the frame 9 of the cassette and pressed against it by the back cover 10, which is a plate of brass or steel, curved around the contour of the film.

The frame of the cassette consists of templates, cut along a given contour. The distance between them is determined by the width of one frame of the radiograph and is equal to 8-10 mm. A frame with a film pressed against the back cover is inserted into the grooves of the protective shield and in which at the level of the location of the test sample there is a cut in; X-rays reflected from the sample are passed into it.

Moving the frame with the film and the back cover of the cassette can be easily mechanized. A rack-shaped rack 12 is fastened on the back cover. The cassette in the slots of the security screen should walk freely enough and fall under its own weight (or the weight of the weight attached to it when the cassette is mounted).

A pawl 3 prevents the cassette from falling free, consisting of two tabs a and b placed between the teeth of the rail 12 at half the distance equal to the width of one frame of the roentgenogram. The dog is mounted on a rack 14 attached to the base of the camera.

The cassette is moved when the current is turned on into the magnetizing winding of the electromagnet 15. When the current is turned on, the measles 16 connected to the ratchet are drawn into the winding of the electromagnet 15. The cassette is then moved by half the width of one frame. When the current is turned off, the cassette moves another half the width of one frame, i.e. the next film is installed.

Control alarms can be made extremely simply. Thus, the film can be moved by pressing a button directly from the control panel; The angle of divergence of the beam can be quite large and only limited by the possible size of the irradiated surface of the sample.

Due to the possibility of using wide powerful X-ray beams, sharp focusing and the possibility of relatively close positioning of the sample from the tube, the proposed cameras can significantly reduce the exposure, bringing them to minutes and even seconds, and on the resulting radiographs cover the whole spectrum or, in all cases, wide range of angles.

The camera, with small changes, allows to obtain double-sided radiographs. In some cases, if it allows to dry up the tube configuration, it is convenient to arrange the cassette horizontally.

Subject of the invention. A cassette for an X-ray camera intended for shooting flat sections according to Debye Scherrer, ex. that in order to obtain sharpness for all lines of the radiograph, it is curvilinear in cross section so that the distance from the sample to the film is:

g.L (I-cos atg P) (- cos 20 tga}

where / is the distance from the sample to

films; a-angle between direction

x-ray beam and

sample;

S is the beam divergence angle; B - angle between directions

falling and reflected

rays; L is the distance from the sample to

focus of the tube or first diaphragm.

/ ff