X-ray tube

 

Usage: to generate x-ray radiation. Essence: is that the x-ray tube includes a vacuum envelope with the outlet box placed in the recess in the form of glass made in the side wall of the shell, inside which is placed the source of electrons is the cathode, a focusing system and a reflective target, the metal which is deposited on a substrate is the anode. The latter has a radial groove not reaching the continuation of the centerline of the electron beam (coincident with the longitudinal axis of the tube), and the edge surface of the reflective target is adjacent to the edge of the recess in the anode. The proposed implementation allows to obtain a small distance between the focal spot and the surface of the exit window and use the tube together with short-focus x-ray lens. This ensures the preservation of power, characteristic of the tube with a reflective anode. Effect: provision of small distances between the focal spot of the reflective target and the surface of the exit window without reducing the capacity of the tube. 1 C.p. f-crystals, 2 Il.

The invention relates to x-ray techniques, and more particularly to means for generating a roentgen(Rechentechnik. The Handbook. Book 1. - M.: Mashinostroenie, 1992, S. 90-121 [1]), containing the vacuum envelope, a source of electrons, a focusing electron optical system, a target for receiving x-ray radiation and outlet box. The target is a layer of metal (cu, Ag, Mo, W, etc.) deposited on a solid substrate, having forced liquid or gas cooling. The target is oriented so that the plane of the surface of the target was some angle with the axis of the electron beam from the side of the exit window. Outlet box is made of metal with a small atomic number and fixed in the sheath tube in the area of the anode.

The disadvantage of this design is a significant distance from the focal spot to the surface of the exit window. This leads, in particular, to the inability to use, the tube together with short-focus x-ray lens.

Closest to the present invention is the design of the x-ray tube described in U.S. patent No. 6 282 263 (publ. 28.08.01) [2]. X-ray tube according to the patent [2] contains the vacuum shell with the outlet box. Inside the vacuum shell is placed a source of electrons, a focusing system and a reflective target located at the end of the heat sink p is prevalent in the form of a radiolucent tubular element, part of the side wall of the vacuum casing and surrounding the reflective target.

This x-ray tube is specifically designed to lead to the window outside was close to summarize the input device for focusing x-rays. In one best described in the patent [2] examples when using a reflective target, the distance from the focal spot to the outer surface of the exit window is 7 mm

This distance is not always acceptable when using the x-ray tube together with short-focus x-ray lens. However, the possibility of reducing it to a known structure according to the patent [2] is limited due to the fact that the outlet box is located in the side wall of the vacuum casing tube, which is located inside the target, which is placed on the heat sink substrate. Therefore, the outlet box may not be from the focal spot at a distance less than the radius of the heat sink substrate placed on her target. Reduction of the radius of the substrate with a target closer to the center of the part of the vacuum envelope, which is the output window in the form of a tubular element, would entail a decrease in mechanical strength E from the target and reducing power tubes.

The present invention aims to obtain a technical result, which is to offer small distance between the focal spot of the reflective target and the surface of the exit window without reducing the capacity of the tube.

To achieve this, the technical result of the proposed x-ray tube as mentioned above is known, is closest to it, contains the vacuum shell with the outlet box, made in its side surface, and placed inside the vacuum shell electron source, a focusing system and cooling the substrate with the target located at the end of the heat sink substrate facing the electron source.

In contrast to the known x-ray tube, the proposed x-ray tube facing the electron source end heat sink substrate has a radial recess, not reaching the continuation of the centerline of the electron beam. Outlet box placed in the cavity, which is made in the side wall of the vacuum casing and includes its more remote from the electron source part specified in the hollow heat sink substrate. To the edge of this recess is adjacent the edge surface of the target.

Describes how to perform pozemky to heat the substrate, is close to the axial line of the electron beam, the distance from the center of the focal spot to the output window commensurate with the radius of the electron beam and does not depend on the size of the heat sink substrate and the target.

It is preferable for this embodiment of the recess in the heat sink substrate, when she has a flat section that is tangent to the continuation of the electron beam, and thus the output window parallel to the specified plane area of the recess in the heat sink substrate and the target surface is inclined in the direction of the exit window.

This can be achieved the greatest approximation of the output window to the center of the focal spot.

The invention in one possible specific variants of its execution illustrated by drawings:

in Fig.1 shows the x-ray tube in section;

in Fig.2 on a larger scale showing part of the recess in the side surface of the vacuum shell, the recess in the heat sink substrate and the target with the incident electron beam.

X-ray tube (Fig.1) contains the vacuum shell 1, the source of electrons is the cathode 2, the focusing electrode 3, the diaphragm 4 and the heat sink substrate - massive anode 5 coated with a metal target 6. In the sides of the Noi to the longitudinal axis 8 of the tube, posted by outlet box 9. The output window does not reach the continuation of the centerline of the electron beam, matching shown in Fig.1 with the longitudinal axis 8 of the tube, about the size of the radius r of the electron beam. The anode 5 is made with a radial recess 10 (Fig.1 shows a dashed line) in its end portion facing the cathode 2. The side surface of the recess 10 are similar to the half. In this radial recess is more remote from the cathode 2 half Cup 7 (right in Fig.1). The anode 5 may be forced liquid or air cooled (cooling means not shown).

The recess in the vacuum casing 1 in the form of glass 7 is designed to accommodate short-focus x-ray lens (or part of such lenses adjacent to its input end) or small objects to be irradiated.

In the form shown in Fig.1 (and in larger scale in Fig.2) embodiment, the tube radial recess 10 in the anode 5 has a flat portion 11. This section of the tangent to the continuation of the beam 13 of the electrons, i.e. the continuation of the generatrix 12 of the electron beam, closest to the pin box 9, lies in the plane of the section 11. The edge 14 of the reflective surface of the target adjacent to the edge Wielkie from the axis of the electron beam (the same shown on the drawings with the longitudinal axis 8 of the tube at some distance, approximately equal to the radius r of the beam, or that the same is the radius of the focal spot. Due to this, the beam 13 electrons completely hits the target 6 and are not inhibited by lead in box 9. The reflective surface of the target 6 and the end surface of the anode 5 (left in Fig.1), which is applied to the target, which is inclined towards the outlet box 9, i.e., the form with the plane of the exit window is an acute angle. This orientation of the reflective surface of the target improves the conditions of withdrawal of the stimulated emission from the focal spot through the window 9.

From what was said above about the mutual position of the exit window 9, the notches 10 and the target 6 shows that further reduction of the distance between the outlet box and the focal spot on the target is impossible. In fact, this distance becomes close to the distance, characteristic x-ray tube with target "through" type and does not depend on the sizes of the anode and the target.

The electron beam in the described x-ray tube may have a cross-section not only a circular shape, but the shape of an elongated rectangle and shape on the target so-called linear focus. In this case, the minimum distance from the geometric center of the focal spot to the output window 9 occurs when the PR is pendicular to the plane of the drawing.

The proposed x-ray tube operates as follows. When the supply voltage in the area of the cathode 2 through the focusing electrode 3 is formed by converging the electron beam, which is accelerated in the direction of the diaphragm 4, is an equipotential space and inhibited in the target 6 inducyruya x-rays. Part of this radiation exits through the exit window 9 and may be collected by the x-ray lens located in the cavity of the Cup 7 or influence the irradiated object is placed in this cavity.

In the case of the proposed technical solutions in the design of x-ray tubes, high power (1 kW or more) outlet box can be moved away from the plane of the recess at a distance of about 0.2-1 mm in order to provide thermal isolation from the anode.

In really tested the tubes with a capacity of 50 watts and above the plane 11 of the recess 10 has not reached the axis of the electron beam 13 at a distance of less than 0.3 mm, the minimum distance from this plane to the inner surface of the exit window was 0.2 mm, and the angle of its inclination relative to the longitudinal axis of the tube 2.

Thus, the technical solution according to the invention allows the POPs who inim spot and the inner surface of the exit window.

Sources of information

1. Rechentechnik. The Handbook. Book 1. M: mechanical engineering, 1992, S. 90-121.

2. U.S. patent No. 6282263, publ. 28.08.01.

Claims

1. X-ray tube containing a vacuum envelope with the outlet box, made in its side wall, and placed inside the vacuum shell electron source, a focusing system and a reflective target from the heat sink substrate, characterized in that facing the electron source end heat sink substrate has a radial recess, not reaching the continuation of the centerline of the electron beam, the exit window is placed in the cavity, which is made in the side wall of the vacuum casing and includes its more remote from the electron source part specified in the hollow heat sink substrate, and the edge surface of the reflective target is adjacent to the edge of this recess.

2. X-ray tube under item 1, characterized in that the radial recess in the heat sink substrate has a flat section that is tangent to the continuation of the electron beam, the exit window parallel to the specified plane area of the radial grooves in the heat sink substrate and the surface of the reflective target is tilted in the direction of the exit window.

 

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