JP2001135265A - X-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray tube having small distortions for the focal point of a plurality of electron beams with different sizes formed on the anode. SOLUTION: On a focusing electrode 21 disposed to face the target surface of the anode where X-ray is generated, a valley bottom wall face M0 located farthest from the anode and two slanting wall faces M1, M2 sandwiching this valley bottom wall face M0 are formed, and nearly rectangular focusing grooves 22a through 22c are formed on these three wall faces M0, M1, M2, respectively. And filaments 23a to 23c are disposed in the nearly rectangular focusing grooves 22a to 22c, where the largest focusing groove 22a and filament 23a are disposed on the central valley bottom wall face M0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray tube in which a plurality of electron beam focal points having different sizes formed on an anode are reduced in distortion.

[0002]

2. Description of the Related Art An X-ray tube is an electron tube that emits thermoelectrons generated by a filament cathode of an electron gun to an anode to generate X-rays from the anode.
It is used for radiography. When a subject is photographed with X-rays, for example, the amount of X-rays is adjusted depending on the use.

[0003] Perspective imaging for observing a subject image while irradiating X-rays is performed with a small amount of X-ray, and normal imaging for printing the subject image on a film or the like is performed with a larger amount of X-ray. When adjusting the X-ray dose, the conventional X-ray tube has a structure in which, for example, electron beam focal points having different sizes are formed on the anode. In the case of fluoroscopy with a small amount of X-rays, a small focus is used, and in the case of normal imaging requiring a large amount of X-rays, a large focus is used. However, when reducing geometric blur in normal shooting, or
For example, when performing fluoroscopic imaging with a large current, a medium focus larger than the small focus and smaller than the large focus is used.

As described above, a conventional X-ray tube has three focal points of different sizes, large, medium, and small, as described above, or has two focuses so as to be applicable to various imaging applications. One having one large focal point and one small focal point, one having one large focal point and two small focal points, and the like have been put to practical use.

[0005] By the way, an X-ray tube having a plurality of focal points is an X-ray tube.
When transitioning from fluoroscopy with different doses to normal imaging,
Conversely, focus switching is performed, for example, when shifting from normal imaging to fluoroscopy imaging. At this time, it is necessary to reduce the deviation of the photographing position of the subject, so that the focal points formed on the target surface of the anode are at the same position. Therefore, for example, in the case of an X-ray tube forming three electron beam focal points, the valley bottom portion of the focusing electrode farthest from the anode is made a flat surface, and inclined surfaces are formed on both sides thereof so as to face each other. A substantially rectangular converging groove for converging thermoelectrons is provided on each of the flat surface and the two inclined surfaces, and a filament is arranged in each converging groove.

Here, a conventional X-ray tube for forming a plurality of focal points having different sizes will be described with reference to FIG. FIG. 5A is a cross-sectional view showing an anode portion and a focusing electrode portion of the X-ray tube, in which an anode 41 and a focusing electrode 42 are provided to face each other. The converging electrode 42 has a flat valley bottom wall surface M0 formed at a valley bottom portion farthest from the anode 41, and first and second inclined wall surfaces M1 and M2 formed on both sides thereof so as to face each other. A convergence groove 43a for small focus is formed on the valley bottom flat wall surface M0, and a filament 44a for small focus that emits thermoelectrons is arranged in the convergence groove 43a. The first inclined wall surface M1 has a converging groove 43 for large focus.
b is formed, and a filament 44b for large focus is arranged in the converging groove 43b. A convergence groove 43c for the middle focus is formed on the second inclined wall surface M2, and a filament 44c for the middle focus is arranged in the convergence groove 43c.

In the above configuration, the filament 44
The thermoelectrons emitted from a, 44b, and 44c are converged by electric fields near the converging grooves 43a, 43b, and 43c, respectively.
A focal point 46 is formed on the anode 41 by drawing the orbits 45a, 45b, 45c. First and second inclined wall surfaces M1, M2
Are inclined at predetermined angles α and β with respect to the valley bottom flat wall surface M0 so that the electron beam focal points 46 emitted from the filaments 44a, 44b and 44c are located at the same position on the anode 41.

[0008]

SUMMARY OF THE INVENTION Focusing electrode 42 of an X-ray tube
Is generally formed in a substantially round shape when viewed from the direction of the focal point collection position on the anode target. On the other hand, convergent groove 4
3a, 43b and 43c have a substantially rectangular cross section. Further, the length differs depending on the size of the focal point. For this reason, the electric field near the converging groove becomes non-uniform, and the electron beam focus on the anode 41 becomes, for example, as shown in FIG. Reference numeral 46a is a small focus, reference numeral 4
Reference numeral 6b denotes a large focus, and reference numeral 46c denotes a middle focus. Among them, the large focal point 46b and the middle focal point 46c have a shape with a bow-like bulge inward in the longitudinal direction of the filament, that is, in the vertical direction in the figure. As a result, as shown by A1 and A2, the effective dimensions of the large focal point 46b and the middle focal point 46c are increased by the amount of the distortion, and the image quality is deteriorated.

The cause of the distortion of the focal point is that the converging groove 43 for the large focal point is used.
b and the surface of the convergence electrode 42 where the convergence groove 43c for the middle focus is formed, and the convergence groove 4 formed therein is formed while the outer shape of the convergence electrode 42 is cylindrical.
3a, 43b, 43c are rectangular and the converging grooves 43a,
For example, the lengths of the converging grooves 43a, 43b, and 43c at the longitudinal ends of the filaments 44a, 44b, and 44c, for example, because the lengths of the filaments 43b and 43c vary.
Of the filaments 44a, 44b,
This is probably because the uniformity of the traveling trajectory of the electron beam emitted from 44c is lost.

In order to solve this problem, the present inventors have proposed a method of providing an auxiliary groove in the longitudinal direction of a converging groove for a small focal point, although it is not a known technique. Here, a structure in which an auxiliary groove is provided adjacent to the converging groove will be described with reference to FIG.

FIG. 6A is a front view of the focusing electrode viewed from the anode side. A flat valley bottom flat wall surface M0 is formed at the valley bottom portion of the focusing electrode 51 farthest from the anode, and opposing sides are opposed to each other. The first and second inclined wall surfaces M1 and M2 are formed in such a manner. Convergent groove 52 for small focus on valley bottom flat wall surface M0
a, a small-focus filament 53a that emits thermoelectrons is disposed in the converging groove 52a. An auxiliary groove 55 is provided adjacent to the convergent groove 52a with a narrow wall 54 interposed therebetween in the extension direction of the valley bottom flat wall surface M0, that is, in the vertical direction in the drawing. A convergent groove 52b for large focus is formed on the first inclined wall surface M1, and a filament 53b for large focus is disposed in the convergent groove 52b. A convergent groove 52c for the middle focus is formed on the second inclined wall surface M2, and a filament 53c for the middle focus is disposed in the convergent groove 52c.

FIG. 6B is a view in which the focusing electrode 51 is sectioned in the tube axis direction. At the same time, an anode 56 disposed opposite to the focusing electrode 51 and a large electrode formed on the anode 56 are formed.
Medium and small focal positions 57 are shown. FIG.
In FIG. 6B, parts corresponding to those in FIG. 6A are denoted by the same reference numerals, and overlapping description is partially omitted.

In the above-described configuration, the auxiliary groove 55 is provided adjacent to the short focus convergence groove 52a having a short length.
In this case, the valley bottom flat wall surface M0 and the first groove
The length of each groove portion formed on each of the inclined wall surface M1 and the second inclined wall surface M2 is made uniform, and distortion is reduced.

However, in this case, the wall 54 located on the boundary between the small focus convergence groove 52a and the auxiliary groove 55 formed on the valley bottom flat wall surface M0 affects the shape of the other large focus or middle focus. , The large focal point X and the middle focal point Y are indicated by the symbol X in FIG.
As shown by 1, Y1, the valley bottom flat wall surface M0 has a concave shape. As a result, the effective size of the focal point becomes large and the image quality of the image is reduced, so that there is room for further improvement.

An object of the present invention is to solve the above-mentioned drawbacks and to provide an X-ray tube capable of further reducing distortion of a plurality of electron beam focal points having different sizes formed on an anode.

[0016]

According to the present invention, there is provided an anode having a target surface for generating X-rays from an X-ray focal position by collision of an electron beam, an anode disposed opposite the target surface of the anode, and A valley bottom flat wall surface located farthest from the X-ray focal point position, first and second inclined wall surfaces which rise obliquely in the direction of the anode with the valley bottom flat wall surface interposed therebetween, and a substantially rectangular shape formed on the valley bottom flat wall surface A converging electrode comprising a valley bottom converging groove, a substantially rectangular first converging groove formed on the first inclined wall surface, and a substantially rectangular second converging groove formed on the second inclined wall surface; An X-ray tube comprising: an electron beam emitting filament disposed in a groove in parallel with each other along an extension direction of the flat wall surface of the valley bottom. The length of the is characterized by longer than a length of the first focusing groove and the second convergent groove.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the schematic structural diagram of FIG. Reference numeral 11 denotes a housing constituting the X-ray tube device, and an X-ray tube 12 is disposed in the housing 11. The X-ray tube 12 includes a vacuum envelope 13 and a cathode assembly 14 and a cathode assembly 1 provided in the vacuum envelope 13.
4 and a rotating anode 15 opposed thereto. On the rotary anode 15, a conical target surface 15a made of a heat-resistant metal such as tungsten is provided. A stator 16 for rotating the rotary anode 15 is provided outside the vacuum envelope 13. The inside of the housing 11 is filled with an insulating oil 17. A line segment m indicates a tube axis of the X-ray tube 12, for example, a center axis around which the rotating anode 15 rotates.

Here, the cathode assembly 1 constituting the X-ray tube 12
4 will be described with reference to FIG. FIG. 2A is a cross-sectional view of the cathode structure 14 taken substantially in the tube axis direction. The cathode structure 14 includes a focusing electrode 21 and the like.

On the surface of the converging electrode 21 facing the target surface 15a of the rotating anode 15 (FIG. 1), a flat valley bottom wall M0 is formed at a valley bottom furthest from the rotating anode 15, and rotating valleys are formed on both sides thereof. Flat inclined wall surfaces M1 and M2 are formed so as to rise obliquely in the direction of the anode 15 and face each other. The valley bottom flat wall surface M0 has a valley bottom flat wall surface M0.
A substantially rectangular converging groove 22 for a large focal point elongated in the longitudinal direction
a is formed, and a filament 23a for large focus which emits thermoelectrons is arranged in the converging groove 22a. First
On the inclined wall surface M1, a substantially rectangular convergent groove 22b for the middle focus is formed which is elongated along the longitudinal direction of the flat bottom wall M0, and the filament 23 for the middle focus is formed in the convergent groove 22b.
b is arranged. The second inclined wall surface M2 is formed with a convergent groove 22c for small focus, which is elongated in a substantially rectangular shape along the longitudinal direction of the flat bottom wall M0, and the filament 23c for small focus is disposed in the convergent groove 22c. I have.

The first and second inclined wall surfaces M1, M2 are:
The predetermined angles α and β different from each other with respect to the valley bottom flat wall surface M0
And each filament 23a, 23b, 23
Each electron beam emitted from the target surface of the anode 1
Focusing is made at the same position on 5a (FIG. 1).

Next, the converging groove 22a for the large focal point, the converging groove 22b for the middle focal point, and the converging groove 22c for the small focal point will be described with respect to the flat bottom wall M0, the first inclined wall M1, and the second inclined wall M2. Each case viewed from the vertical direction will be described with reference to FIG. In FIG. 2B, parts corresponding to those in FIG. 2A are denoted by the same reference numerals, and a duplicate description will be partially omitted.

As shown in the figure, a converging groove 22a for large focus
, The four corners Q1 to Q4 of the convergence groove 22b for the middle focus, and the four corners R1 to R4 of the convergence groove 22c for the small focus.
Are each formed of a curved surface having a predetermined radius of curvature. The convergence grooves 22b for the middle focus and the convergence grooves 22c for the small focus have radii of curvature at two corners located farther from the other convergence groove, for example, the convergence groove 22b for the middle focus.
In the case of, the radii of curvature of the corners Q1 and Q2, and in the case of the convergent groove 22c for a small focus, the radii of curvature of the corners R1 and R2 are two corners located closer to the other convergent groove, for example, for the middle focus. In the case of the convergent groove 22b, the corners are larger than the corners Q3 and Q4, and in the case of the convergent groove 22c for small focus, the corners are larger than the corners R3 and R4.

Also, corners Q1,
The radius of curvature of Q2 is set to the width Qw of the convergent groove 22b at the center in the direction orthogonal to the extension direction of the valley bottom flat wall surface M0.
1/3 or more. Similarly, the focusing groove 2 for the small focus
The radii of curvature of the corners R1 and R2 of 2c are set to be at least 1/3 of the width Rw of the convergent groove 22c at the center in the direction orthogonal to the extending direction of the flat bottom wall M0.

FIG. 2 shows a structure in which the focusing electrode 21 is viewed from or near the focal position on the rotating anode target surface.
It is shown in (c). In this figure, the position of the rotating anode is indicated by a dotted line 30. As shown in the figure, the length of the converging groove 22a for large focus in the extension direction of the flat bottom wall M0 and the length of the filament 23a for large focus in the extension direction of the flat bottom wall M0 are respectively the middle focus. And the focusing grooves 22b and 22c and the filaments 23b and 23c.

According to the above-described configuration, the convergence groove 22 for the large focal point having the longest length is formed on the flat bottom wall M0 of the convergence electrode 21.
a on the inclined wall surfaces M1 and M2 located on both sides of the flat bottom wall M0, the convergence grooves 22b and 22c for the middle focus and the small focus shorter in length than the convergence groove 22a for the large focus.
Is arranged.

As a result, the electric field in the converging groove 22a for large focus becomes uniform. Also, the central valley bottom flat wall surface M0
Is the longest, and an auxiliary groove for making the length of the groove uniform is not required. Therefore, there is no wall that separates the converging groove and the auxiliary groove, and the influence of the electric field on the converging grooves 22b and 22c for the middle focus and the small focus is reduced, and the distortion of the focus is reduced.

The radii of curvature of the two corners Q1, Q2, R1, R2 of the convergence grooves 22b, 22c located on the inclined wall surfaces M1, M2, respectively, are located on the side farther from the other convergence groove.
Two corners Q3, Q located on the side closer to the other convergent groove, respectively
4, R3 and R4 are larger than the radius of curvature. This configuration also reduces distortion of the focus formed on the target surface of the anode. This is considered to be because the electric field in the vicinity of the converging groove, in particular, the electric field in the longitudinal direction of the rectangular converging groove is made uniform by increasing the radius of curvature of the corner farther from the other converging groove.

In the above embodiment, the radii of curvature of the two corner portions located farther from the other convergence groove with respect to the convergence grooves for the middle focus and the small focus arranged on the inclined wall surface are given by:
The radius of curvature of the two corners located closer to the other converging groove is larger than the radius of curvature. However, although the degree of distortion of the focal point is reduced, it is also possible to adopt a configuration in which only the radius of curvature at one corner is increased.

In a configuration in which the radii of curvature of the two corners located on the side farther from the other converging groove are larger than the radii of curvature of the two corners located on the side closer to the other converging groove, the valley bottom is flat. If there is a large or small deviation between both ends in the extension direction of the wall surface M0 and the end of the converging groove 22a for the large focal point, the radius of curvature of the corner on the side where the deviation is large should be made larger. Thereby, the distortion of the focal point can be further reduced.

In the configuration in which only the radius of curvature of one corner is increased, the size of the deviation between the two ends in the extending direction of the flat bottom wall M0 and the end of the converging groove 22a for the large focal point is small. In some cases, it is desirable to increase the radius of curvature of the corner on the side where the deviation is large.

Further, with respect to the convergent grooves for the middle focus and the small focus arranged on the inclined wall surface, the radii of curvature of the two corners located on the side farther from the other convergent groove are set to one of the widths of the respective convergent grooves. / 3 or more. In this case as well, although the degree of distortion of the focal point is reduced, of the two corners located on the side farther from the other converging groove, only one of the radii of curvature is configured to be １ ／ or more of the width of the converging groove. Can also.

Further, a structure in which the radius of curvature of the corner located farther from the other converging groove is increased, or the radius of curvature of the corner located farther from the other converging groove is set to 1/1 / the width of the converging groove. The structure of three or more is not necessarily required to be adopted simultaneously for both the focusing focus for the middle focus and the focusing focus for the small focus, and can be adopted for only one of them.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 3 is a view of the direction of the converging groove from or near the focal position on the rotating anode target surface.
Parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and duplicate description will be partially omitted.

FIG. 3 shows that the upper end Ec of the small focus convergence groove 22c in the drawing and the upper end Ea of the large focus valley bottom convergent groove 22a in the drawing extend in the extension direction of the valley bottom flat wall surface M0. In the case where they are substantially at the same position, an auxiliary groove 32 is provided on one side of the converging groove 22c for small focus with a thin wall 31 interposed therebetween. The auxiliary groove 32 is an empty groove having a depth of at least 0.3 times the depth of the converging groove 22c for the small focal point and having no filament or the like inside. In this case, the auxiliary groove 3
The two four corners T1 to T4 are formed on a curved surface having a predetermined radius of curvature, for example, the four corners T1 to T4 have the same radius of curvature.
However, the corners T1, T3, T near the convergence grooves 22a, 22c
4 may be smaller than the radius of curvature of the corner T2. At this time, the partition wall between the converging grooves 22a and 22c and the auxiliary groove 32 becomes thin, and the effect of correcting the focus distortion is increased. In addition, the sum of the length lc of the converging groove 22c for small focus, the thickness t of the wall 31, and the length lp of the auxiliary groove 32 in the extension direction of the flat bottom wall M0 is the flat bottom wall M0.
Is approximately the same as the length la of the valley bottom converging groove 22a for the large focal point in the extension direction of. According to this configuration, the lengths of the groove portions formed in the valley bottom flat wall surface M0 and the inclined wall surfaces M1 and M2 are made uniform, and the valley bottom flat wall surface M0 and the inclined wall surface M0 are made uniform.
1, the positions of both ends of the groove formed in M2 are almost the same, and the distortion of the focal point is reduced.

FIG. 4 shows that the groove center in the longitudinal direction of the valley bottom converging groove 22a for large focus, that is, the direction along the extension direction of the valley bottom flat surface M0, and the corresponding center of the converging groove 22c for small focus are substantially the same. They are arranged in a position. Then, on both sides of the converging groove 22c for small focus, the auxiliary grooves 32a, 3a having empty inside are sandwiched by the thin partition walls 31a, 31b, respectively.
2b is provided. Note that the upper and lower ends Ec1 and Ec2 of the small focus convergence groove 22c in the figure are slightly shifted from the upper and lower ends Ea1 and Ea2 of the large focus valley bottom convergence groove 22a in the figure. Also in this case, four corners T1 to T1 of each of the auxiliary grooves 32a and 32b are provided.
T4 is formed on a curved surface having a predetermined radius of curvature.
The curvature radii of 1 to T4 are the same. However, as in the case of FIG. 3, the corner near the converging grooves 22a and 22c, the auxiliary groove 3
In the case of 2a, the radius of curvature of the corners T2, T3, T4 is made smaller than the radius of curvature of the corner T1, and in the case of the auxiliary groove 32b, the corner T
The radius of curvature of 1, T3, and T4 may be smaller than the radius of curvature of corner T2. At this time, the partition wall between the convergence grooves 22a and 22c and the auxiliary grooves 32a and 32b becomes thin, and the effect of correcting the focus distortion is increased.

The length lc of the converging groove 22c for small focus in the extension direction of the flat wall M0 of the valley bottom and the wall 31
The sum of the thickness ta of the a, the thickness tb of the wall 31b, the length lpa of the auxiliary groove 32a, and the length lpb of the auxiliary groove 32b is a valley bottom converging groove 2 for large focus in the extension direction of the valley bottom flat wall surface M0.
The length 2a is almost the same as or slightly longer than the length la. Note that the length lc may be slightly shorter than the length la. According to this configuration, the lengths of the groove portions formed on the valley bottom flat wall surface M0 and the inclined wall surfaces M1 and M2 are made uniform,
In addition, the positions of both ends of the groove portion formed on the flat bottom wall M0 and the inclined wall surfaces M1 and M2 substantially match, and the distortion of the focal point is reduced.

In the embodiments shown in FIGS. 3 and 4, an auxiliary groove is provided in the converging groove for small focus. However, when the length of the convergence groove for the middle focus is different from the length of the valley bottom convergence groove for the large focus, similarly to the case of the convergence groove for the small focus, the same applies to the convergence groove for the middle focus. An auxiliary groove having an empty interior can be provided on one side or both sides in the extension direction of the flat bottom wall surface.

According to the above configuration, the electrons emitted from the plurality of filaments converge in the substantially rectangular focusing groove,
When electron beam focal points having different sizes are formed on the anode surface, the electric field near the converging groove becomes uniform. As a result, the distortion of the focal shape is suppressed, the effective dimension of the focal point is reduced,
An X-ray tube with improved focus resolution is obtained.

In particular, since a focusing groove for a large focus and its filament, whose focus distortion has the greatest influence on the image quality of X-ray imaging, are formed on the flat bottom wall surface at the center of the focusing electrode, the large focusing focus groove is formed. The electron beam is least susceptible to the distortion of the surrounding electric field and can produce a large focus with little or very little distortion on the anode target surface. The distortion of the focal point due to the converging groove for the middle focal point or the small focal point and the filament on the inclined walls on both sides can also be reduced by the above configuration.

Further, in the above-described embodiment, an example has been described in which the cathode is a direct heat type coiled filament.
However, the invention is not limited to this, and the same applies to the case of an indirectly heated cathode.

The present invention can be applied to a fixed anode X-ray tube in which the anode target surface is oblique or perpendicular to the tube axis.

[0042]

According to the present invention, when at least two or more kinds of electron beam focal points having different sizes are formed on the anode target surface, an X-ray tube with a small distortion of the focal point shape can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic structural diagram for explaining an embodiment of the present invention.

FIG. 2 is a schematic structural diagram for explaining a cathode structure used in the embodiment of the present invention.

FIG. 3 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 4 is a schematic structural diagram for explaining another embodiment of the present invention.

FIG. 5 is a diagram for explaining a conventional example, and is a diagram in which respective portions of a cathode assembly and a rotating anode are extracted and shown.

FIG. 6 is a diagram for explaining another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... X-ray tube apparatus 12 ... X-ray tube 13 ... Vacuum envelope 14 ... Cathode assembly 15 ... Rotating anode 15a ... Rotating anode target surface 16 ... Stator 17 ... Insulating oil 21 ... Focusing electrode 22a ... Focusing for large focus Groove 22b: Focusing groove for middle focus 22c ... Focusing groove for small focus 23a ... Filament for large focus 23b ... Filament for middle focus 23c ... Filament for small focus M0 ...

Claims (6)

[Claims] 1. An anode having a target surface for generating X-rays from an X-ray focal position by collision of an electron beam, and an anode disposed to face the target surface of the anode and furthest from the X-ray focal position. A first and a second inclined wall which rises obliquely in the direction of the anode with the valley bottom flat wall interposed therebetween, a substantially rectangular valley bottom converging groove formed in the valley bottom flat wall, A substantially rectangular first converging groove formed on one inclined wall surface, a converging electrode composed of a substantially rectangular second converging groove formed on the second inclined wall surface, and a valley bottom flat wall surface in each of the converging grooves. An X-ray tube comprising: an electron beam emitting cathode disposed in parallel with each other along an extension direction, wherein the length of the valley bottom converging groove in the extension direction of the valley bottom flat wall surface is the first converging groove and An X-ray tube having a length longer than the length of the second focusing groove. 2. A focus formed on a target surface by an electron beam emitted from a cathode in a valley bottom focusing groove,
The X-ray tube according to claim 1, wherein the X-ray tube is larger than a focal point formed on a target surface by an electron beam emitted from the cathode in the first focusing groove and the second focusing groove. 3. At least one of the first converging groove and the second converging groove has four corners formed by curved surfaces having a predetermined radius of curvature,
2. The X-ray tube according to claim 1, wherein at least one radius of curvature of the two corner portions located farther from the other converging groove is larger than the two corner portions located closer to the other converging groove. 4. A curvature radius of at least one corner portion having a larger radius of curvature than two corner portions located closer to the other convergence groove among two corner portions located farther from the other convergence groove is: 4. The X according to claim 3, wherein the width of the converging groove in the direction perpendicular to the direction in which the flat bottom wall surface extends is at least 1/3 of the width of the converging groove.
Wire tube. 5. An auxiliary groove is provided adjacent to at least one of the first converging groove and the second converging groove via a thin partition at at least one end extending along the direction in which the flat bottom wall surface extends. The X-ray tube device according to claim 1, wherein 6. A length in a direction along an extension direction of the flat bottom wall surface of at least one of the first converging groove and the second converging groove provided adjacent to the auxiliary groove, and the same direction of the auxiliary groove. And the sum of the thickness of the partition wall between at least one of the first converging groove and the second converging groove provided with the auxiliary groove is equal to or equal to the length of the valley bottom converging groove in the extension direction of the valley bottom portion. The X-ray tube according to claim 5, which is substantially equivalent.