JP2002083560A - Rotary-anode type x-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary-anode type X-ray tube with reduced variations in positional relation, due to thermal expansion, between a focal point of thermions formed on a target layer and a cathode electron gun for generating thermions. SOLUTION: This rotary-anode type X-ray tube is equipped with a rotary anode 12 disposed in a vacuum enclosure 11 and provided with the target layer 14 for emitting X rays, the cathode electron gun 19 for generating thermions to be applied to the target layer 14, and a cathode carrier 13 fixed on the vacuum enclosure 11 on one side thereof and carrying the electron gun 19 on the other side mechanically connected to the one side. The other side of the cathode carrier 13 for carrying the electron gun 19 extends in the opposite direction to the rotary anode 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary anode type X-ray tube in which the positional relationship between a focal point of thermoelectrons formed on a target layer and a cathode electron gun that generates thermoelectrons due to thermal expansion is reduced. .

[0002]

2. Description of the Related Art A conventional rotary anode X-ray tube will be described with reference to FIG. Rotating anode type X
The vacuum envelope 51 constituting the wire tube is formed of an insulating material or an insulating material provided with a metal part on a part thereof. A disk-shaped rotating anode 52 for emitting X-rays in a vacuum envelope 51;
In addition, a cathode assembly 53 that generates thermoelectrons is arranged to face each other.

[0003] A target layer 54 for emitting X-rays is provided in a ring shape on the surface of a disk-shaped rotating anode 52. The disk-shaped rotating anode 52 is rotated by a rotating mechanism 56 via a rotating shaft 55.
And rotatably supported by a rotation mechanism 56. The rotating mechanism 56 includes a rotating body 57 connected to the rotating shaft 55, a fixed body 58 fitted to the rotating body 57, and the like. A part of the fixed body 58 is fixed to one end of the vacuum envelope 51, for example, a lower end portion in the drawing, and a front end portion extends outside the vacuum envelope 51.

The cathode assembly 53 includes a cathode electron gun 59 for generating thermoelectrons, a cathode support 60 for supporting the cathode electron gun 59, and the like. The cathode support 60 is
One side is fixed to the other end of the vacuum envelope 51, for example, the upper end in the figure, and the other side supports the cathode electron gun 59.

The cathode electron gun 59 comprises a filament 61 for generating thermoelectrons, a focusing electrode 62 for focusing thermoelectrons, and the like. The cathode support 60 has a cathode flange 63 extending from a fixed portion fixed to the vacuum envelope 51 in the direction of the disk-shaped rotating anode 52, and is mechanically connected to the cathode flange 63, and is perpendicular to the tube axis. A cathode electron gun 59 is supported on the disk-shaped rotating anode 52 side of the supporting desk 64. The cathode electron gun 59 is provided with a filament 61 at a position facing the target layer 54.

Here, the structure of the cathode electron gun 59 will be described with reference to an enlarged view of FIG. FIG. 6 is a view of the cathode electron gun 59 as viewed from the right side of FIG. The cathode electron gun 59 includes a substantially cylindrical focusing electrode 62, and filaments 61a and 61b forming two large and small focal points having different dimensions. On one surface of the focusing electrode 62,
Two focusing grooves 65a and 65b for focusing the thermoelectrons generated from the filaments 61a and 61b, respectively, are formed at positions displaced by a predetermined distance from the center line m of the cathode electron gun 59. The openings of the focusing grooves 65a and 65b are formed by thermionic electrons Ea and Eb generated from the filaments 61a and 61b.
Intersect at a predetermined angle so as to form mutually overlapping focal planes Sa and Sb on the target layer 54 located on the center line m of the cathode electron gun 59.

The focusing electrode 62 has focusing grooves 65a and 65b.
Holes 66a and 66b extending to the other surface are formed continuously, and the filaments 61a and 61b are
a, 65b are arranged at positions near the bottom. Both ends of the two filaments 61a and 61b are connected to a lead wire L, and the lead wire L is a column 67a extending in a vertical direction.
67b, and the columns 67a, 67b are connected to the through holes 66 of the focusing electrode 62 via insulators 68a, 68b.
a, 66b.

When the rotating anode type X-ray tube enters an operating state, the rotating anode 52 is rotated, and at the same time, a high voltage is applied between the cathode electron gun 59 and the rotating anode 52. In addition, an electric current is supplied to the filament 61a (or 61b). At this time, the filament 61a (or 61
b) heats and emits thermionic electrons Ea (or Eb).
Thermionic electrons Ea (or Eb) are accelerated by the high voltage applied to the disk-shaped rotating anode 52 and collide with the target layer 54, and from the focal plane Sa (or Sb) on the target layer 54, as shown in FIG. Line 69 is emitted. X-ray 69
Is extracted to the outside through an X-ray output window 70, passes through a non-irradiated object 71 such as a human body, and an X-ray image of the non-irradiated object 71 is detected by a detector 72.

By the way, when the target layer 54 generates X
The dose and quality of the line 69 differ depending on the voltage and current, and the shape of the focal plane. Therefore, the conventional rotating anode X-ray tube can be provided with, for example, two filaments 61a and 61b having different sizes as described above, and can form a plurality of focal planes Sa and Sb having different shapes on the target layer 54. Like that. Then, it is switched to the filaments 61a and 61b corresponding to the dose and the radiation quality required for each application.

[0010]

In the conventional rotary anode X-ray tube, the temperature of the target layer increases due to the collision of thermions. This temperature varies depending on the magnitude of the applied voltage and current, the input time and the pause time, and is repeated. The heat of the target layer is transmitted to the disk-shaped rotating anode and the rotating mechanism, and causes them to thermally expand. At this time, the disk-shaped rotating anode and the rotating mechanism thermally expand toward the cathode assembly structure starting from a portion fixed to the vacuum envelope. Further, the temperature of the cathode assembly increases due to the heat generated by the filament and the radiant heat of the target layer, and the cathode assembly expands. At this time, the cathode assembly structure thermally expands toward the disk-shaped rotating anode starting from the portion fixed to the vacuum envelope.

Here, a description will be given of a pattern in which the disk-shaped rotating anode and cathode assembly are thermally expanded with reference to FIG. In FIG. 7, portions corresponding to FIGS. 5 and 6 are denoted by the same reference numerals, and duplicate description will be partially omitted. For example, the disk-shaped rotating anode 52 is displaced from the position A1 to a position A2 indicated by a dotted line due to expansion of the rotating mechanism 56 and the like. The cathode electron gun 59 is displaced from the position B1 to a position B2 indicated by a dotted line due to expansion of the cathode support 60 and the like. In the following drawings including FIG. 7, the degree of expansion is exaggerated, and the actual displacement is smaller than this.

Next, the disk-shaped rotating anode 52 and the cathode electron gun 5
The effect of displacement of 9 will be described with reference to the enlarged views of FIGS. 8 and 9, parts corresponding to those in FIGS. 5 to 7 are denoted by the same reference numerals, and overlapping description is partially omitted.

FIG. 8 is a view when the direction of the cathode electron gun 59 is viewed from the front side of FIG. 7, and shows the influence of the displacement in the tube axis direction. The disk-shaped rotating anode 52 is displaced in the direction of the cathode electron gun 59, and the cathode electron gun 59 is displaced in the direction of the disk-shaped rotating anode 52. As a result, the focal plane S0 on the target layer 54 and the X-rays 69 emitted from the focal plane S0 are respectively dotted lines S1
And 691.

FIG. 9 is a view of the direction of the cathode electron gun 59 from the right side of FIG. 7, and shows the influence of the displacement in the tangential direction of the anode rotation. In this case, the focal plane S0, the X-ray 69, and the trajectory 91 of the thermoelectrons change as indicated by dotted lines S1, 691, and 911, respectively.

The conventional rotary anode type X-ray tube is provided, for example, on the side of a detector (reference numeral 72 in FIG. 5) in order to reduce the influence of the focal plane, X-ray, and orbital displacement of thermoelectrons due to thermal expansion. There is a method of providing a correction mechanism. In the case of this method, since the amount of displacement is not constant or the amount of correction is limited, it is desired that displacement due to thermal expansion be as small as possible. In addition, since it is difficult to perform correction on the detector side, it is particularly required to reduce displacement in the tangential direction of the anode rotating shaft.

As another method of reducing displacement due to thermal expansion, there is a method of providing a folded structure in a target portion and a rotating body portion to offset thermal expansion and reduce thermal expansion on the anode side. This method requires a large space due to the provision of the folded structure, and the structure becomes complicated and the cost increases. For this reason, it is difficult to apply it to anything other than a large X-ray tube.

The present invention solves the above-mentioned drawbacks, and reduces the fluctuation of the positional relationship due to thermal expansion between the focal point of the thermoelectrons formed on the target layer and the cathode electron gun that generates the thermoelectrons. It is intended to provide a wire tube.

[0018]

SUMMARY OF THE INVENTION The present invention provides a rotating anode provided in a vacuum envelope and provided with a target layer for emitting X-rays, and a cathode electron gun for generating thermal electrons for irradiating the target layer. And a cathode support supporting the cathode electron gun on the other side, one side of which is fixed to the vacuum envelope and mechanically connected to the one side. The other side of the cathode support extends from a portion mechanically connected to the one side in a direction opposite to the rotating anode.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.

A vacuum envelope 1 constituting a rotary anode type X-ray tube
1 is made of an insulator or an insulator having a metal part in part. A disk-shaped rotating anode 12 that emits X-rays is arranged on one side of the vacuum envelope 11, and a cathode assembly 13 that generates thermoelectrons is arranged on the other side.

A target layer 14 for emitting X-rays is provided in a ring shape on a part of the disk-shaped rotary anode 12. The disk-shaped rotating anode 12 is rotated by the rotating mechanism 1 via a rotating shaft 15.
6 and is rotatably supported by a rotation mechanism 16. The rotating mechanism 16 includes a rotating body 17 connected to the rotating shaft 15 and a fixed body 18 fitted to the rotating body 17.
It is composed of A part of the fixed body 18 is fixed to one end of the vacuum envelope 11, for example, a lower end portion in the drawing, and further extends beyond the vacuum envelope 11.

The cathode assembly structure 13 is composed of a cathode electron gun 19 for generating thermoelectrons, a cathode support 20 for supporting the cathode electron gun 19, and the like. The cathode 11 is fixed to the other end of the vessel 11, for example, the upper end in the figure, and supports the cathode electron gun 19 on the other side.

The cathode electron gun 19 is composed of a filament 21 for generating thermoelectrons, a substantially cylindrical focusing electrode 22 for focusing thermoelectrons, and the like.

The cathode support 20 has a cylindrical cathode flange 23 extending from the portion fixed to the vacuum envelope 11 in the direction of the disk-shaped rotary anode 12, and is mechanically connected to the cathode flange 23 and is connected to the tube shaft. It comprises a plate-like support desk 24 extending in a substantially perpendicular direction, and a cylindrical electron gun support 25 mechanically connected to the support desk 24 and turned back in the opposite direction to the disk-shaped rotary anode 12. The cathode electron gun 19, for example, a part of the outer surface of the focusing electrode 22 is fixed to the inner surface of the electron gun support 25. The cathode 2 has a filament 2 at a position facing the target layer 14.
1 is provided.

Here, the structure of the cathode support 20 viewed from above in FIG. 1 will be described with reference to FIG. The cathode flange 23 and the electron gun support 25 are both cylindrical, and the cathode flange 23 is formed to have a larger outer diameter than the electron gun support 25. The support desk 24 for connecting the cathode flange 23 and the electron gun support 25 has one end on the cathode flange 23 side slightly larger than the outer diameter of the cathode flange 23, and the end face of the cathode flange 23 is formed on one end thereof. Are joined. The other end on the electron gun support 25 side is also formed on a surface slightly larger than the outer diameter of the electron gun support 25, and at the same time, a through hole 24a is formed, and the cathode electron gun support 25 is formed in the through hole 24a. Are fitted and joined.

Next, the cathode support 20 and the cathode electron gun 1
9 will be described with reference to FIG. In FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 2A is a view of the cathode electron gun 19 viewed from the right side of FIG. 1 and shows a cross section of the cathode electron gun 19 portion. The cathode electron gun 19 includes a focusing electrode 22 having a substantially cylindrical shape as a whole, and filaments 21a and 21b forming two large and small focal points having different dimensions. On one surface of the focusing electrode 22, the filament 21
a, two focusing grooves 2 for focusing the thermoelectrons generated by 21b
6a and 26b are formed at positions displaced from the center line m of the cathode electron gun 19 by a predetermined distance. Focusing groove 26
The focal planes Sa, S where the thermoelectrons generated from the filaments 21a, 21b overlap with each other on the target layer 14 located on the center line m of the cathode electron gun 19 are formed in the openings of the a, 26b.
It is formed on a plane intersecting at a predetermined angle so as to form b. Behind the cathode electron gun 19, a part of the cathode flange 23 is shown, and further, a support desk 24 connecting the cathode flange 23 and the electron gun support 25 is shown.

FIG. 2B shows the structure of the cathode support 20 and the cathode electron gun 19 as viewed from the target layer 14 side.
Shown in In FIG. 2B, portions corresponding to those in FIG. 2A are denoted by the same reference numerals, and redundant description will be omitted.

In the case of the above embodiment, the electron gun support 25
Is, for example, a portion P mechanically connected to the support desk 24.
, And has a cylindrical portion surrounding a space between the cathode electron gun 19 and the target layer 14 in a part thereof. In this case, the cylindrical portion of the electron gun support 25 functions as a focusing electrode, and can effectively focus thermoelectrons.

When the rotating anode type X-ray tube having the above-described structure enters the operating state, the rotating anode 12 is rotated, and at the same time, a high voltage is applied between the cathode electron gun 19 and the rotating anode 12. And the filament 21a (or 21
Apply current to b). At this time, the filament 21a (or 21b) is heated and emits thermoelectrons E. Thermoelectron E
Is accelerated by the high voltage applied to the disk-shaped rotating anode 12, collides with the target layer 14, and the X-ray 30 is emitted from the focal plane Sa (or Sb) on the target layer 14 as shown in FIG. The X-ray 30 is extracted to the outside through the X-ray output window 31, passes through a non-irradiated object such as a human body, and an X-ray image of the non-irradiated object is detected by a detector or the like.

When the rotating anode type X-ray tube enters an operating state, the temperature of the cathode support 25 and the like rises due to the heat generated by the filaments 21a and 21b and the radiant heat of the target layer 14, and gradually expands. At this time, the cathode flange 23, the electron gun support 25, and the cathode electron gun 19 are indicated by arrows Y1, Y2, and Y, respectively.
It extends in the direction of 3.

Accordingly, the average temperature rise (ΔT) of each component of the cathode flange 23, the electron gun support 25, and the cathode electron gun 19, the average linear expansion coefficient (α) of the material constituting each component, Assuming that the effective length (L) of the component in the tube axis direction is a value as shown in FIG. 3, the target layer direction is-(minus), and the cathode electron gun 19 direction is + (plus), the tube axis direction due to thermal expansion is obtained. The overall elongation (ΔLc) is shown by equation (1). ΔLc = −ΔT1 × α1 × L1 + ΔT2 × α2 × L2−ΔT3 × α3 × L3 (1) In the actual case, the temperature distribution in each part is not uniform, and the coefficient of thermal expansion with respect to temperature is not necessarily linear. Therefore, the value differs from the expression (1). Here, for convenience of explanation, it is assumed that the temperature distribution in each part is uniform, the coefficient of thermal expansion with respect to temperature is linear, and the elongation of the vacuum envelope is also omitted.

When ΔLc in the equation (1) is negative, the cathode electron gun 19 is displaced in the direction of the target layer 14, and when ΔLc is positive, it is displaced in the direction opposite to the target layer 14. The disk-shaped rotary anode 12 also thermally expands, and the disk-shaped rotary anode 1
2 is always displaced in the plus direction, that is, in the direction of the cathode electron gun 19.

Here, assuming that the extension of the disk-shaped rotating anode 12 in the tube axis direction is ΔLa, if ΔLa−ΔLc = 0 (2), the distance between the target layer 14 and the cathode electron gun 19 does not change. .

However, the temperature of the anode side such as the disk-shaped rotary anode 12 is higher than that of the cathode side, and the length in the axial direction is longer. Therefore, ΔLa becomes larger than ΔLc, and in most cases, ΔLa−ΔLc> 0 (3).

Therefore, in order to reduce the variation in the distance between the target layer 14 and the cathode electron gun 19, ΔL
c will be increased.

For example, ΔT2 × α2 × L2> ΔT1 × α1 × L1 + ΔT3 × α3 × L3 (4)

In a conventional rotating anode type X-ray tube, a cathode electron gun is arranged on a target layer side of an electron gun support. Therefore, the cathode electron gun is always displaced in the direction of the target layer. The target layer is always displaced in the direction of the cathode electron gun. Therefore, the cathode electron gun and the target layer are displaced in a direction approaching each other, the interval between them is largely fluctuated, and the shape and position of the focal point are largely changed.

In the case of the present invention, the side of the cathode support which supports, for example, an electron gun has a structure extending in the direction opposite to the target layer. Therefore, each part constituting the cathode support, for example, the cathode flange 23 and the electron gun support 2
By selecting the combination of materials and lengths of No. 5, the cathode electron gun 19 can be moved in the opposite direction to the target layer 14 during thermal expansion.
For example, it can be displaced in the same direction as the target layer 14. As a result, the cathode electron gun 19 and the target layer 14
Variations in the spacing between them due to thermal expansion are reduced.

For example, in the structure shown in FIG. 1, the cathode flange 23 is made of an Fe—Ni—Co alloy having a small coefficient of thermal expansion (linear expansion coefficient: about 4.8 × 10 ⁻⁶ ), and the electron gun support 25 is formed.
Is made of Cu having a large coefficient of thermal expansion (linear expansion coefficient of about 17 × 10 ⁻⁶ ), and the focusing electrode of the cathode electron gun 19 is made of the same material as the cathode flange 23.
The fluctuation of the distance between the target layer 9 and the target layer 14 is reduced.

The cathode flange 23 and the electron gun support 2
5. The effective length L1, L2, L3 of the cathode electron gun 19 is X
It is limited by the electrical insulation distance of the tube, the emission power of the cathode electron gun, and the space inside the tube. Within that limit, each effective length L1, L2, L3 is, for example, 7
0, 20, and 5 mm, and the average temperature ΔT1, ΔT2, and ΔT3 of each part is maximized in the use range of the tube.
ΔLc = + 0.07 at 0, 400, and 500 ° C.
mm, and the cathode electron gun 19 is displaced in the same direction as the target layer 14.

In the above case, the target layer 14, the cathode electron gun 19, and the filament are, for example, A1 in FIG.
→ Displaced as A2, B1 → B2, C1 → C2. Therefore, the variation in the distance between the cathode electron gun 19 and the target layer 14 is reduced, and, for example, the electron trajectory converging from an oblique direction to the focal plane on the target layer 14, that is, the focus movement in the anode rotation tangential direction is reduced.

In the above embodiment, the support desk 24 is provided between the cathode flange 23 and the electron gun support 25 so as to extend in a direction perpendicular to the tube axis. In this case, the whole or a part of the support desk 24 is made of a material having a larger coefficient of thermal expansion than the material of the cathode flange 23.
At this time, when the support desk 24 thermally expands, the cathode electron gun 19 is displaced away from the tube axis, and the cathode electron gun 19 moves to the lower side along the inclined target layer 14. On the other hand, the target layer 14 is displaced in the direction of the cathode electron gun 19 due to thermal expansion. As a result, the focal point shift in the tangential direction of the anode rotation is reduced.

Next, another embodiment of the present invention will be described with reference to FIG. 4 in which a cathode electron gun and a target portion are extracted. 4, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and redundant description is partially omitted.

The focusing electrode 22 has focusing grooves 26a, 26b
Holes 40a, 40b extending to the other surface are formed continuously to the filaments 21a, 21b.
a, 26b are disposed at positions near the bottom. Both ends of the two filaments 21a and 21b are connected to a lead wire L, and the lead wire L is a column 41a extending in the vertical direction.
41b, and the supporting columns 41a and 41b have through holes 40a of the focusing electrode 22 through insulators 42a and 42b.
It is fixed to the portion 40b.

In this embodiment, one of the filaments 21a and 21b forming two large and small focal points having different dimensions, for example, the filament 21a, and the focusing groove 26a for focusing the thermoelectrons generated by the filament are formed. ,
It is positioned on the center line m of the cathode electron gun 19 and, at the same time, on a vertical line of an imaginary plane that is in contact with the focal planes Sa and Sb where the thermoelectrons E collide. In this case, during thermal expansion, the focal plane Sa of the filament 21a on the center line m hardly moves in the tangential direction of the anode rotation.

It is desirable that the filament 21a disposed on the center line m be a smaller focal point for which higher accuracy is required or a focal point for more frequent use.

According to the configuration of the present invention described above, the thermal expansion of the target layer and the thermal expansion of the cathode electron gun are in the same direction, and the focal shift in the tangential direction of the anode rotation is greatly reduced.
Further, since the structure is simple, it can be configured at low cost.

In the above embodiment, the case where the number of filaments is two has been described. However, the invention
Applicable to any number of filaments. Further, the cathode flange fixed to the vacuum envelope of the cathode support is formed in parallel with the tube axis, but the cathode flange may have a structure extending in the tube axis direction. It is also possible to adopt a structure in which the structure extends, or a structure in which only a part of the structure extends obliquely to the tube axis. Further, the support desk is not limited to the direction perpendicular to the tube axis, but may be a structure extending entirely inclining with respect to the direction perpendicular to the tube axis, or a structure in which a part thereof extends inclining.

[0050]

According to the present invention, there is provided a rotating anode type X-ray tube in which a change in a positional relationship due to thermal expansion between a focal point of thermoelectrons formed on a target layer and a cathode electron gun for generating thermoelectrons is reduced. realizable.

[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 electron gun unit in the embodiment of the present invention.

FIG. 3 is an explanatory diagram for explaining the operation of the present invention, showing numerical examples of components constituting the present invention.

FIG. 4 is a schematic structural view for explaining an embodiment of the present invention, in which a cathode electron gun portion is extracted.

FIG. 5 is a schematic structural diagram for explaining a conventional example.

FIG. 6 is a schematic structural view for explaining a cathode electron gun section in a conventional example.

FIG. 7 is a schematic structural diagram for explaining a thermally expanded state in a conventional example.

FIG. 8 is a schematic structural diagram for explaining an operation in a thermal expansion state of a conventional example.

FIG. 9 is a schematic structural diagram for explaining an operation in a thermal expansion state of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Vacuum envelope 12 ... Disk-shaped rotating anode 13 ... Cathode assembly structure 14 ... Target layer 15 ... Rotating shaft 16 ... Rotating mechanism 17 ... Rotating body 18 ... Fixed body 19 ... Cathode electron gun 20 ... Cathode support 21 ... Filament 22 ... Focusing electrode 23 ... Cathode flange 24 ... Support desk 25 ... Electron gun support

Claims (8)

[Claims] A rotating anode provided in a vacuum envelope and provided with a target layer for emitting X-rays; a cathode electron gun for generating thermoelectrons for irradiating the target layer; A cathode support supporting the cathode electron gun on the other side fixed to the enclosure and mechanically connected to the one side, wherein the other side of the cathode support A rotating anode type X-ray tube, wherein a side extends in a direction opposite to the rotating anode from a portion mechanically connected to the one side. 2. The other side of the cathode support is made of a material having a higher coefficient of thermal expansion than a portion of the cathode support fixed to the vacuum envelope and extending in the direction of the rotating anode. Item 7. A rotary anode type X-ray tube according to Item 1. 3. The rotating anode type X-ray tube according to claim 1, wherein the other side of the cathode support is made of copper or a copper alloy. 4. The rotating anode X-ray tube according to claim 1, wherein the other side of the cathode support has a cylindrical portion surrounding a space between the cathode electron gun and the target layer. 5. The rotary anode X-ray tube according to claim 4, wherein the cylindrical portion functions as a part of the focusing electrode. 6. The respective materials constituting the cathode support and the cathode electron gun, and the dimensions of the cathode support and the cathode electron gun are determined by the direction in which the cathode electron gun is displaced by a rise in temperature during operation. 2. The rotating anode type X-ray tube according to claim 1, wherein the direction in which the target layer is displaced is set to be the same. 7. An orthogonal extension extending in a direction orthogonal to the tube axis between one side of the cathode support fixed to the vacuum envelope and the other side of the cathode support supporting the cathode electron gun. A portion is provided, and at least a portion of the orthogonal extension portion is made of a material having a larger coefficient of thermal expansion than a portion extending in the direction of the rotating anode from a portion of the cathode support fixed to the vacuum envelope. The rotating anode type X-ray tube according to claim 1, wherein 8. A cathode electron gun having a plurality of filaments,
The rotating anode X-ray tube according to claim 1, wherein one of the plurality of filaments is located on a vertical line of an imaginary plane that is in contact with a focal plane where the thermoelectrons collide.