JP2010262784A - X-ray tube, and x-ray tube device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray tube and an X-ray tube device capable of restraining direct hit of recoil electron on an X-ray radiation window. <P>SOLUTION: The X-ray tube 30 is provided with a vacuum envelope 31 equipped with an anode target 35 having a target face 35b emitting X rays by getting electron beams incident, a cathode 36 forming a focal point F on the target face by having the electron beams incident on the target face from a direction at a first angle α, an X-ray radiation window 33 housing an anode target and the cathode, with its inside in a vacuum state, and positioned in a direction at a second angle β with the target face, and a metal surface portion 34 fitted inside including a surface side of the X-ray radiation window at a vacuum side and set at the same potential as the cathode. The first angle α is within a range of 8° to 30°, and the second angle β is within a range of 5-25°. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an X-ray tube and an X-ray tube device including the X-ray tube.

  The X-ray tube apparatus includes an X-ray tube. The X-ray tube is configured to generate an X-ray by colliding an electron beam with an anode target. Such an X-ray tube apparatus is used in many applications such as a medical diagnostic apparatus, an industrial nondestructive inspection apparatus, and a material analysis apparatus.

  In an X-ray tube apparatus, an electron beam emitted from a cathode is accelerated and focused by a potential gradient between the cathode and the anode target, and typically has an energy of 20 to 150 keV and is substantially perpendicular to the target surface of the anode target. A focal point that forms an X-ray generation source by colliding with (90 ° ± 20 °) is formed. When an electron beam with high energy collides with the focal point, the electron beam is rapidly decelerated by the target material, so that X-rays are emitted. The rate of conversion to X-rays is as small as 1% or less of the kinetic energy of electrons that collide with the anode target. The remaining energy is converted to heat.

  On the other hand, it is known that about 50% of the electron beam colliding with the target surface is scattered backward (electron beam incident side). Electrons scattered backward (hereinafter referred to as recoil electrons) once move away from the target surface, but are accelerated again to the anode target side by the potential gradient between the cathode and the anode target, and most of them are again near the focus of the target surface. collide. As a result of the re-impact of the recoil electrons on the target surface, the target surface is heated and the focal temperature is increased.

  As a result, discharge easily occurs between the cathode and the anode target, or the target surface on which the focal point is formed is roughened, resulting in a decrease in X-ray output. Furthermore, since X-rays are emitted from other than the focal point, the clarity of the X-ray image is impaired. That is, recoil electrons do not contribute to the generation of available X-rays and only heat the target surface. For this reason, the recoil electrons increase the electron beam output to increase the X-ray output, emit X-rays more frequently, or emit X-rays continuously for a longer time. This is an obstacle for improving the performance of the X-ray tube device.

  Therefore, a technique (system 1) is disclosed in which a shield structure that captures recoil electrons is disposed between a cathode and an anode target for the purpose of increasing the X-ray output of the X-ray tube (for example, Patent Documents 1 to 3). 4).

  In the X-ray tube of the method 1, a shield structure that is supplied with the same potential as the anode target or a substantially intermediate potential between the cathode potential and the anode potential is disposed between the cathode and the anode target. The shield structure has an opening through which an electron beam passes. Thereby, since most of recoil electrons collide with the shield structure and are captured, it is possible to reduce the recoil electrons that collide with the target surface again.

  In addition, a technique (method 2) for increasing the X-ray output of the X-ray tube is disclosed (see, for example, Patent Documents 5 to 9).

  The positional relationship between the focal point and the X-ray emission window of the method 2 X-ray tube is substantially the same as that of the conventional X-ray tube including the method 1 X-ray tube. The X-ray tube of method 2 is different from other conventional X-ray tubes in that an X-ray emitted from the X-ray emission window is formed by making an electron beam incident on the target surface at a relatively shallow angle to form a focal point. The line output is increased. Under the condition that the electron beam intensity is the same, the X-ray tube of the method 2 can increase the X-ray output by up to 1.5 times compared to the conventional X-ray tube including the X-ray tube of the method 1. .

US Pat. No. 4,309,637 US Pat. No. 5,689,542 US Pat. No. 6,215,852 US Pat. No. 6,714,626 US Pat. No. 3719846 US Pat. No. 4,607,380 US Pat. No. 5,128,977 US Pat. No. 5,828,727 US Pat. No. 7068749

The X-ray tube of method 1 has the following problems.
Recoil electrons generated at the focal point jump out of the target surface in a direction opposite to the incident direction of the electron beam over a wide angular range with substantially the same energy as the incident electrons. Therefore, recoil electrons that have jumped toward the X-ray emission window still strike the X-ray emission window directly, and it is difficult to reduce heating of the X-ray emission window.

When the X-ray emission window is heated, the X-ray emission window may be damaged. For example, cracks and deformations occur in the X-ray emission window. For this reason, there exists a possibility that the airtightness of a vacuum envelope may deteriorate. In addition, when the coolant is boiled near the X-ray emission window due to the heat of the X-ray emission window and gas is generated, the transmittance of X-rays varies depending on the location, and the clarity of the X-ray image may be impaired. .
Due to the above, there is a problem that there is a limit in increasing the X-ray output. This problem is particularly serious when the X-ray emission window is at the same potential as the anode.

The method 2 X-ray tube has the following problems.
In the X-ray tube of method 2, the potential of the X-ray emission window is the same potential as that of the anode target, or approximately the middle potential between the cathode potential and the anode potential. The recoil electrons that jump out in the direction of the X-ray emission window directly hit the X-ray emission window, so it is difficult to reduce the heating of the X-ray emission window.

Recoil electrons jump out with an angular distribution that increases in the direction from the focal point toward the X-ray emission window. Therefore, the heating of the X-ray emission window by the recoil electrons hitting the X-ray emission window directly is expected to be more serious than the conventional X-ray tube including the X-ray tube of the method 1.
Due to the above, there is a problem that there is a limit in increasing the X-ray output. This problem is particularly serious when the X-ray emission window is at the same potential as the anode.
The present invention has been made in view of the above points, and an object of the present invention is to provide an X-ray tube and an X-ray tube apparatus capable of suppressing the direct hit of recoil electrons to the X-ray emission window.

In order to solve the above-described problem, an X-ray tube according to an aspect of the present invention includes:
An anode target having a target surface that emits X-rays upon incidence of an electron beam;
A cathode that makes an electron beam incident on the target surface from a direction at a first angle from the target surface, and forms a focal point on the target surface;
An inside containing the anode target and the cathode, the inside being in a vacuum state, including an X-ray emission window positioned in a direction at a second angle from the target surface, and a surface side of the X-ray emission window on the vacuum side A vacuum envelope having a metal surface portion set to the same potential as the cathode, and
The first angle is in the range of 8 ° to 30 °, and the second angle is in the range of 5 ° to 25 °.

In addition, an X-ray tube apparatus according to another aspect of the present invention includes:
An anode target having a target surface that emits X-rays upon incidence of an electron beam, and an electron beam incident on the target surface from a direction that forms a first angle from the target surface, and the target surface is focused. A cathode to be formed; an X-ray emission window that accommodates the anode target and the cathode, the inside of which is in a vacuum state; and is positioned at a second angle from the target surface; and the X-ray emission window on the vacuum side A vacuum envelope provided on the inner side including the surface side and having a metal surface portion set to the same potential as the cathode, and an X-ray tube,
The first angle is in the range of 8 ° to 30 °, and the second angle is in the range of 5 ° to 25 °.

  According to the present invention, it is possible to provide an X-ray tube and an X-ray tube device that can suppress direct hit of recoil electrons to the X-ray emission window.

It is a schematic diagram which shows the X-ray tube which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the X-ray tube which concerns on the 2nd Embodiment of this invention. The cathode voltage, the voltage of the vacuum envelope including the X-ray emission window, the anode target voltage, the counter voltage of the first and second embodiments, the comparative examples 1 to 3 of the system 1 and the comparative examples 1 to 3 of the system 2 It is the figure which showed the recoil electron capture structure body voltage and the equipotential surface formation electrode by the table | surface. It is sectional drawing which shows the X-ray tube apparatus containing the X-ray tube which concerns on the 3rd Embodiment of this invention. In the X-ray tube which concerns on the said 3rd Embodiment, it is a perspective view which shows the shape of the focus formed in the target surface. It is sectional drawing which shows the modification of the bearing of the X-ray tube which concerns on the said 3rd Embodiment. It is sectional drawing which shows the X-ray tube apparatus containing the X-ray tube which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the X-ray tube apparatus containing the X-ray tube which concerns on the 5th Embodiment of this invention. It is another sectional drawing which shows the X-ray tube apparatus shown in FIG. It is sectional drawing which expanded and showed a part of X-ray tube shown in FIG. It is sectional drawing which shows the modification of the X-ray tube apparatus of the said 5th Embodiment. FIG. 12 is another sectional view showing the X-ray tube apparatus shown in FIG.

Hereinafter, an X-ray tube according to a first embodiment of the present invention will be described in detail with reference to the drawings. In the first embodiment, a basic concept of an X-ray tube will be described.
As shown in FIG. 1, the X-ray tube 30 includes an anode target 35, a cathode 36, and a vacuum envelope 31.

  The anode target 35 has a target surface 35b provided on a part of the outer surface of the anode target. The target surface 35b emits X-rays when an electron beam emitted from the cathode 36 is incident thereon. The anode target 35 is made of a metal such as a tungsten alloy. A relatively positive voltage is applied to the anode target 35.

  The cathode 36 causes an electron beam to enter the target surface 35b from a direction that forms the first angle α from the target surface 35b, and forms a focal point F on the target surface 35b. A relatively negative voltage is applied to the cathode 36, and a voltage and current applied to the cathode 36 are supplied to a filament (electron emission source) (not shown) of the cathode 36.

  The vacuum envelope 31 contains an anode target 35 and a cathode 36. The vacuum envelope 31 has a vacuum vessel 32, an X-ray emission window 33, and a metal surface portion 34. The inside of the vacuum envelope 31 is in a vacuum state. The vacuum container 32 is made of a metal such as copper, stainless steel, or aluminum. The X-ray radiation window 33 is located in a direction that forms the second angle β from the target surface 35b. The X-ray radiation window 33 is provided in the vacuum container 32 in an airtight manner. Here, the X-ray emission window 33 is made of beryllium. The metal surface portion 34 is provided inside the vacuum envelope 31 including the surface side of the vacuum side X-ray emission window 33 and is set to the same potential as the cathode 36.

  In this embodiment, since the vacuum vessel 32 and the X-ray radiation window 33 are made of metal, the vacuum envelope 31 is entirely made of metal, not just the metal surface portion 34 on the vacuum side.

  The first angle α is in the range of 8 ° to 30 °, and the second angle β is in the range of 5 ° to 25 °. In this embodiment, α = 20 ° and β = 15 °.

  A perpendicular extending from the center point of the surface of the X-ray radiation window 33 on the vacuum side is LP1, and an extended plane located on the same plane as the target surface 35b and deviating from the target surface 35b is S. Let PA be the intersection where the perpendicular line LP1 and the target surface 35b or the extension plane S intersect. The intersection PA is located farther from the focal point F when viewed from the cathode 36. In this embodiment, the intersection PA is a point where the perpendicular line LP1 and the extension plane S intersect.

  As shown in FIGS. 1 and 3, a tube voltage V is applied between the cathode 36 and the anode target 35 of the X-ray tube 30. When the potential of the anode target 35 is VA and the potential of the cathode 36 is VC, the tube voltage V is VA-VC. In this embodiment, the tube voltage V is 20 kV to 40 kV. The vacuum envelope 31 including the cathode 36 and the X-ray emission window 33 is grounded (0 V). A voltage + V of +20 kV to 40 kV is applied to the anode target 35.

  In the X-ray tube 30 configured as described above, a high voltage of +20 kV to 40 kV is applied to the anode target 35. The cathode 36 and the vacuum envelope 31 are grounded. A low voltage of ± 100 V or less and a filament current are applied to the filament of the cathode 36.

  As a result, an electron beam is emitted from the cathode 36 to the target surface 35b of the anode target 35, X-rays are emitted from the focal point F formed on the target surface 35b, and the X-rays are transmitted through the X-ray emission window 33 to the outside. To be emitted.

  According to the X-ray tube 30 configured as described above, the X-ray tube 30 includes the anode target 35, the cathode 36, and the vacuum envelope 31. The first angle α is in the range of 8 ° to 30 °, and the second angle β is in the range of 5 ° to 25 °. The metal surface portion 34 including the surface side of the X-ray emission window 33 on the vacuum side is set to substantially the same potential as the cathode 36.

  Recoil electrons are emitted with an angular distribution that increases in the direction from the focal point F toward the X-ray emission window 33. However, since the surface side of the vacuum side X-ray emission window 33 is set to the same potential as the cathode 36, recoil electrons can be pushed back by the influence of the electric field in the vicinity of the X-ray emission window 33. Since direct hitting of recoil electrons on the X-ray emission window 33 can be suppressed, heating of the X-ray emission window 33 can be suppressed. And damage to the X-ray radiation window 33 can be prevented.

  In addition, since scattering of recoil electrons upward from the target surface 35b can be reduced, recollision of recoil electrons to the target surface 35b including the vicinity of the focal point F can be suppressed. Thereby, the temperature rise of the target surface 35b (focal point F) and the roughness caused by the target surface 35b can be suppressed, and the occurrence of discharge and the decrease in the output of X-rays can be suppressed. Furthermore, since the emission of X-rays from other than the focal point F can be suppressed, it is possible to suppress a decrease in the clarity of the X-ray image.

  Furthermore, since the focal point F is formed by making the electron beam incident on the target surface 35b at a relatively shallow angle, the X-ray output emitted from the X-ray emission window 33 can be increased.

The intersection PA is located farther from the focal point F when viewed from the cathode 36. For this reason, the X-ray radiation window 33 can be pushed back so that recoil electrons do not collide with the target surface 35b again. In the above-described embodiment, the intersection PA is a point where the perpendicular line LP1 and the extension plane S intersect, so that re-collision of recoil electrons to the target surface 35b can be further suppressed. In this case, most of the recoil electrons impact the side surface and the back surface of the anode target 35.
As described above, it is possible to obtain the X-ray tube 30 that can increase the X-ray output without excessively increasing the temperature of the X-ray emission window 33.

Next explained is an X-ray tube according to the second embodiment of the invention. In the second embodiment, another basic concept of the configuration of the X-ray tube will be described. The concept of the second embodiment is similar to the concept of the first embodiment. In this embodiment, the same reference numerals are given to the same functional portions as those in the first embodiment, and detailed description thereof will be omitted.
As shown in FIG. 2, the X-ray tube 30 includes an anode target 35, a cathode 36, a vacuum envelope 31, and an equipotential surface forming electrode 60.

  The equipotential surface forming electrode 60 is located between the focal point F and the X-ray radiation window 33. The equipotential surface forming electrode 60 is attached to the vacuum envelope 31. The equipotential surface forming electrode 60 has an equipotential surface 61 and an X-ray passage hole 62. The equipotential surface 61 faces the focal point F. The equipotential surface 61 is set to the same potential as the cathode 36 and the vacuum envelope 31. The X-ray passage hole 62 is formed through a part of the equipotential surface 61. The X-ray passage hole 62 allows X-rays from the focal point F toward the X-ray radiation window 33 to pass therethrough.

  In this embodiment, the equipotential surface forming electrode 60 is formed of a metal such as copper, stainless steel, or aluminum. For this reason, the equipotential surface forming electrode 60 is formed not only of the equipotential surface 61 but entirely of metal.

  The first angle α is in the range of 8 ° to 30 °, and the second angle β is in the range of 5 ° to 25 °. In this embodiment, α = 20 ° and β = 10 °.

  A line connecting the focal point F and the center point of the X-ray emission window 33 is defined as LC. A point where the line LC and the X-ray passage hole 62 intersect is defined as a first intersection point P1. A perpendicular extending from the first intersection P1 in the direction perpendicular to the equipotential surface 61 is defined as LP2. A point where the perpendicular line LP2 and the target surface or the extended plane S intersect is defined as a second intersection point P2.

  The second intersection point P2 is located farther from the focal point F when viewed from the cathode 36. In this embodiment, the second intersection point P2 is a point where the perpendicular line LP2 and the extension plane S intersect. The line LC overlaps the perpendicular line LP1 extending from the center point of the surface of the vacuum side X-ray radiation window 33.

  As shown in FIGS. 2 and 3, a tube voltage V is applied between the cathode 36 and the anode target 35 of the X-ray tube 30. In this embodiment, the tube voltage V is 20 kV to 40 kV. The cathode 36, the vacuum envelope 31 including the X-ray emission window 33, and the equipotential surface forming electrode 60 are grounded (0V). A voltage + V of +20 kV to 40 kV is applied to the anode target 35.

  In the X-ray tube 30 configured as described above, a high voltage of +20 kV to 40 kV is applied to the anode target 35. The cathode 36, the vacuum envelope 31, and the equipotential surface forming electrode 60 are grounded. A low voltage of ± 100 V or less and a filament current are applied to the filament of the cathode 36.

  As a result, an electron beam is emitted from the cathode 36 to the target surface 35b of the anode target 35, X-rays are emitted from the focal point F formed on the target surface 35b, and the X-rays pass through the X-ray passage hole 62, The light is emitted through the line radiation window 33 to the outside.

  According to the X-ray tube 30 configured as described above, the X-ray tube 30 includes the anode target 35, the cathode 36, the vacuum envelope 31, and the equipotential surface forming electrode 60. The first angle α is in the range of 8 ° to 30 °, and the second angle β is in the range of 5 ° to 25 °. The equipotential surface 61 and the metal surface portion 34 are set to substantially the same potential as the cathode 36.

  Recoil electrons are emitted with an angular distribution that increases in the direction from the focal point F toward the X-ray emission window 33. However, since the equipotential surface 61 of the equipotential surface forming electrode 60 located between the focal point F and the X-ray emission window 33 is set to the same potential as the cathode 36, the influence of the electric field near the equipotential surface forming electrode 60 is affected. Thus, recoil electrons can be pushed back. Since direct hitting of recoil electrons on the X-ray emission window 33 can be suppressed, heating of the X-ray emission window 33 can be suppressed. And damage to the X-ray radiation window 33 can be prevented.

  In addition, since scattering of recoil electrons upward from the target surface 35b can be reduced, recollision of recoil electrons to the target surface 35b including the vicinity of the focal point F can be suppressed. Thereby, the temperature rise of the target surface 35b (focal point F) and the roughness caused by the target surface 35b can be suppressed, and the occurrence of discharge and the decrease in the output of X-rays can be suppressed. Furthermore, since the emission of X-rays from other than the focal point F can be suppressed, it is possible to suppress a decrease in the clarity of the X-ray image.

  Furthermore, since the focal point F is formed by making the electron beam incident on the target surface 35b at a relatively shallow angle, the X-ray output emitted from the X-ray emission window 33 can be increased.

  The second intersection point P2 is located farther from the focal point F when viewed from the cathode 36. For this reason, the X-ray radiation window 33 can be pushed back so that recoil electrons do not collide with the target surface 35b again. In the above embodiment, since the second intersection point P2 is a point where the perpendicular line LP2 and the extension plane S intersect, re-collision of recoil electrons to the target surface 35b can be further suppressed. In this case, most of the recoil electrons impact the side surface and the back surface of the anode target 35.

Line LC overlaps perpendicular line LP1. For this reason, the X-ray absorption amount by the X-ray radiation window 33 can be minimized. This is particularly effective for an X-ray tube having a relatively small X-ray energy, such as the X-ray tube 30 (tube voltage V = 20 kV to 40 kV) of this embodiment.
From the above, it is possible to obtain the X-ray tube 30 capable of suppressing the direct hit of recoil electrons to the X-ray emission window 33.

Here, in order to investigate the state of the X-ray radiation window 33 when the voltage applied to the X-ray tube is changed, the inventor of the present application, the X-ray tube 30 of the first and second embodiments, and The X-ray tubes of Comparative Examples 1 to 3 of Method 1 and Comparative Examples 1 to 3 of Method 2 were compared.
As shown in FIG. 3, the X-ray tubes of Comparative Examples 1 to 3 of the method 1 are arranged between the cathode and the anode target and have a recoil electron capturing structure that captures recoil electrons. The X-ray tubes of Comparative Examples 1 to 3 of the method 2 form a focal point by making an electron beam incident at a relatively shallow angle with respect to the target surface.

(Comparative example 1 of method 1)
A voltage −V / 2 is applied to the cathode. The vacuum envelope including the X-ray emission window is grounded (0V). A voltage + V / 2 is applied to the anode target and the recoil electron capturing structure.

(Comparative example 2 of method 1)
A voltage −V / 2 is applied to the cathode. The vacuum envelope including the X-ray emission window and the recoil electron capture structure are grounded (0V). A voltage + V / 2 is applied to the anode target.

(Comparative example 3 of method 1)
A voltage −V is applied to the cathode. The vacuum envelope including the X-ray emission window, the anode target, and the recoil electron capture structure are grounded (0V).

(Comparative example 1 of method 2)
A voltage −V / 2 is applied to the cathode. The vacuum envelope including the X-ray emission window is grounded (0V). A voltage + V / 2 is applied to the anode target.

(Comparative example 2 of method 2)
A voltage −V / 2 is applied to the cathode. A voltage + V / 2 is applied to the vacuum envelope including the X-ray emission window and the anode target.

(Comparative example 3 of method 2)
A voltage −V is applied to the cathode. The vacuum envelope including the X-ray emission window and the anode target are grounded (0V).

  When the X-ray tubes of Comparative Examples 1 to 3 of Method 1 and Comparative Examples 1 to 3 of Method 2 were examined, each X-ray tube was formed so as to reduce recoil electrons re-collised with the target surface. I understand that. However, in each X-ray tube, the cathode voltage and the voltage of the vacuum envelope including the X-ray emission window are different. In these X-ray tubes, direct hit of recoil electrons to the X-ray emission window cannot be suppressed, and the X-ray emission window 33 is heated. For this reason, in these X-ray tubes, the X-ray radiation window 33 may be damaged.

  From the above, in the X-ray tubes of the comparative examples 1 to 3 of the method 1 and the comparative examples 1 to 3 of the method 2, the direct hit of recoil electrons to the X-ray radiation window cannot be suppressed. As a result, the X-ray emission window is damaged.

  Next explained is an X-ray tube according to the third embodiment of the invention. In this embodiment, the X-ray tube is a rotary anode type X-ray tube. Hereinafter, a rotary anode type X-ray tube device including a rotary anode type X-ray tube will be described. In this embodiment, the same reference numerals are given to the same functional portions as those in the first embodiment, and detailed description thereof will be omitted.

  As shown in FIG. 4, the X-ray tube apparatus 10 includes a cylindrical housing 20 whose one end is closed, an X-ray tube 30 housed in the housing 20, and the inside of the housing 20 is filled with an X-ray tube. 30 and a coolant 7 filling between the housing 20 and a stator coil 910 as a rotational drive device. The housing 20 is provided with a rubber bellows 21 to adjust the pressure of the coolant 7. The housing 20 has a radiation window 24 that emits X-rays to the outside of the housing 20.

  The X-ray tube 30 includes a vacuum envelope 31. The vacuum envelope 31 includes a vacuum vessel 32 made of metal, a high voltage insulating member 40, and an insulating member 38. An anode target 35 is indirectly attached to the high voltage insulating member 40, and a cathode 36 is indirectly attached to the insulating member 38. The cathode 36 emits an electron beam to the anode target 35. The anode target 35 and the cathode 36 are housed in a vacuum envelope 31.

  The inside of the vacuum envelope 31 is in a vacuum state. The X-ray radiation window 33 is provided in the vacuum container 32 in an airtight manner. Here, the X-ray emission window 33 is made of beryllium. The metal surface portion 34 is provided inside the vacuum vessel 32 including the surface side of the vacuum side X-ray emission window 33 and is set to substantially the same potential as the cathode 36.

  The anode target 35 is formed in an annular shape. The anode target 35 has a target layer 35a provided on a part of the outer surface of the anode target. The target layer 35a emits X-rays when an electron beam emitted from the cathode 36 collides with it. The target layer 35a is formed of a metal such as molybdenum, a molybdenum alloy, or a tungsten alloy. The anode target 35 can rotate around the tube axis. A relatively positive voltage is applied to the anode target 35.

  A voltage supply terminal 54 is connected to the cathode 36. The voltage supply terminal 54 applies a relatively negative voltage to the cathode 36 and supplies voltage and current to an electron emission source (not shown) of the cathode 36.

  The X-ray tube 30 includes a rotor 920, a bearing 930, a fixed body 1, and a rotating body 2. The fixed body 1 is formed in a cylindrical shape and is fixed to the high voltage insulating member 40. The fixed body 1 supports the rotating body 2 in a rotatable manner. The rotating body 2 is formed in a cylindrical shape and is provided coaxially with the fixed body 1. A rotor 920 is attached to the outer surface of the rotating body 2. The rotating body 2 and the anode target 35 are joined via a joint portion 35c. The rotating body 2 is provided so as to be rotatable together with the anode target 35.

  The high voltage insulating member 40 forms a part of the vacuum envelope 31. The high voltage insulating member 40 is formed by a cylindrical portion 46 and a bottom portion 47 that closes one end side of the cylindrical portion 46. The high voltage insulating member 40 has an external end face 41 exposed to the outside of the housing 20. In this embodiment, the outer end surface 41 is a flat surface.

A voltage supply terminal 44 is provided on the external end face 41. The voltage supply terminal 44 is connected to the fixed body 1. In this embodiment, the voltage supply terminal 44 is a high voltage supply terminal. The voltage supply terminal 44 supplies a high voltage to the anode target 35 via the fixed body 1 or the like.
The support member 25 is formed in an annular shape. The support member 25 supports the high voltage insulating member 40 in a liquid-tight manner with respect to the housing 20.

  The insulating member 38 forms a part of the vacuum envelope 31. The voltage supply terminal 54 is provided through the insulating member 38. The voltage supply terminal 54 exposed to the outside of the vacuum envelope 31 is covered with a mold insulating part 39. The mold insulating part 39 is formed of a mold insulating material such as a rubber material. For this reason, the voltage supply terminal 54 is waterproofed and electrically insulated. The voltage supply terminal 54 is supported by a KOV member 55 that is a low expansion alloy. Between the KOV member 55 and the cathode 36, and between the KOV member 55 and the insulating member 38 are brazed.

  The high-voltage connector 100 includes a bottomed cylindrical housing 101, a cable 102 having a tip inserted into the housing 101, and the housing 101 filled with the terminal 102a of the cable 102 facing the opening side of the housing 101. And a fixed portion 103 made of an epoxy resin material and a silicone plate 104 made of a silicone resin material inserted between the fixed portion 103 and the outer end face 41 of the bottom portion 47. In this embodiment, the cable 102 is a high voltage cable. The fixing part 103 is an electrical insulating material.

  In this embodiment, the fixing portion 103 as an electrical insulating material of the high voltage connector 100 is in intimate contact with the external end surface 41 of the bottom portion 47. Note that the fixing portion 103 may be in direct contact with the outer end surface 41. The high voltage connector 100 provides a high voltage to the voltage supply terminal 44.

  The X-ray tube apparatus configured as described above is used as follows. When the high voltage connector 100 is attached to the housing 20, the silicone plate 104 is pressed so as to be in close contact with the fixing portion 103 and the external end surface 41 of the high voltage insulating member 40.

  An X-ray shielding cap 300 as an X-ray shielding part is detachably attached to the housing 20 so as to cover the high voltage connector 100. The X-ray shielding cap 300 is made of a material containing an X-ray opaque material.

When the anode target 35 is formed of molybdenum or a molybdenum alloy, the anode target 35 can shield X-rays. In this case, the X-ray tube apparatus 10 may not be provided with the X-ray shielding cap 300.
The cable 202 is connected to the voltage supply terminal 54. The cable 202 is drawn out of the housing 20.

  A focusing electrode 9 is located between the focal point F and the cathode 36. The focusing electrode 9 focuses the electron beam. The focusing electrode 9 is provided so as to surround the trajectory of the electron beam from the cathode 36 toward the focal point F. The focusing electrode 9 is attached to the fixed body 1.

  The coolant 7 is filled in the housing 20 and fills the space between the X-ray tube 30 and the housing 20. As the coolant 7, insulating oil or an aqueous coolant can be used. In this embodiment, an aqueous coolant is used as the coolant 7.

  In the X-ray tube apparatus 10 configured as described above, by applying a predetermined current to the stator coil 910, the rotor 920 rotates and the anode target 35 rotates. Next, a predetermined high voltage is applied to the high voltage connector 100. The high voltage applied to the high voltage connector 100 is applied to the anode target 35 and the focusing electrode 9 through the voltage supply terminal 44, the fixed body 1, the bearing 930, the rotating body 2, and the joint portion 35c. The vacuum envelope 31 including the cathode 36 and the X-ray emission window 33 is grounded.

  As a result, an electron beam is emitted from the cathode 36 to the target surface 35b of the anode target 35, X-rays are emitted from the focal point F formed on the target surface 35b, and the X-rays pass through the X-ray emission window 33 and the emission window 24. It is transmitted through and radiated to the outside.

Next, the X-ray tube apparatus 10 of FIG. 4 will be described with reference to FIG.
The cathode 36 causes an electron beam to enter the target surface 35b from a direction that forms the first angle α from the target surface 35b, and forms a focal point F on the target surface 35b. The X-ray radiation window 33 is located in a direction that forms the second angle β from the target surface 35b. The first angle α is in the range of 8 ° to 30 °, and the second angle β is in the range of 5 ° to 25 °.

  A perpendicular extending from the center point of the surface of the X-ray radiation window 33 on the vacuum side is LP1, and an extended plane located on the same plane as the target surface 35b and deviating from the target surface 35b is S. Let PA be the intersection where the perpendicular line LP1 and the target surface 35b or the extension plane S intersect. The intersection PA is located farther from the focal point F when viewed from the cathode 36. In this embodiment, the intersection PA is a point where the perpendicular line LP1 and the target surface 35b intersect.

Next, the electron emission source, electron beam, and focus F of the cathode 36 will be described.
As shown in FIG. 5, the electron emission source of the cathode 36 emits an electron beam having a circular cross section in a direction perpendicular to the trajectory of the electron beam from the cathode 36 toward the focal point F. For this reason, the electron emission source is not a filament but is formed of a disk-shaped electrode. Since the focal point F is formed by making the electron beam incident at the first angle α, the focal point F is formed in an elliptical shape having the major axis A. The first angle α and the second angle β are angles formed from the major axis A.

  According to the X-ray tube 30 and the X-ray tube apparatus 10 configured as described above, the X-ray tube 30 includes the anode target 35, the cathode 36, and the vacuum envelope 31. The first angle α is in the range of 8 ° to 30 °, and the second angle β is in the range of 5 ° to 25 °. The metal surface portion 34 including the surface side of the vacuum side X-ray emission window 33 is set to the same potential as the cathode 36.

  Recoil electrons are emitted with an angular distribution that increases in the direction from the focal point F toward the X-ray emission window 33. However, since the surface side of the vacuum side X-ray emission window 33 is set to the same potential as the cathode 36, recoil electrons can be pushed back by the influence of the electric field in the vicinity of the X-ray emission window 33. Since direct hitting of recoil electrons on the X-ray emission window 33 can be suppressed, heating of the X-ray emission window 33 can be suppressed. And damage to the X-ray radiation window 33 can be prevented.

  Furthermore, since heating of the X-ray radiation window 33 is suppressed, boiling of the coolant 7 near the X-ray radiation window 33 can be suppressed. The generation of gas accompanying the boiling of the coolant 7 can be suppressed, and the X-ray transmittance is not adversely affected, so that a reduction in the clarity of the X-ray image can be suppressed.

  In addition, since scattering of recoil electrons upward from the target surface 35b can be reduced, recollision of recoil electrons to the target surface 35b including the vicinity of the focal point F can be suppressed. Thereby, the temperature rise of the target surface 35b (focal point F) and the roughness caused by the target surface 35b can be suppressed, and the occurrence of discharge and the decrease in the output of X-rays can be suppressed. Furthermore, since the emission of X-rays from other than the focal point F can be suppressed, it is possible to suppress a decrease in the clarity of the X-ray image.

Furthermore, since the focal point F is formed by making the electron beam incident on the target surface 35b at a relatively shallow angle, the X-ray output emitted from the X-ray emission window 33 can be increased.
The intersection PA is located farther from the focal point F when viewed from the cathode 36. For this reason, the X-ray radiation window 33 can be pushed back so that recoil electrons do not collide with the target surface 35b again.

  As the coolant 7, an aqueous coolant having the highest heat transfer coefficient and containing water as a main component can be used. For this reason, the coolant 7 can most effectively remove the heat transmitted to the high voltage insulating member 40. Further, since the water-based coolant has a larger specific heat than the insulating oil (about twice that of the insulating oil), the temperature rise of the coolant due to the heat radiation of the X-ray tube 30 is suppressed to a low level.

  Further, since the high voltage insulating member 40 is in contact with the coolant 7, heat from the anode target 35 can be effectively dissipated into the coolant 7, and the temperature of the high voltage connector 100 connected to the high voltage insulating member 40 can be lowered. Insulation of the high voltage connector 100 can be ensured over a long period of time.

  As described above, it is possible to obtain the X-ray tube 30 and the X-ray tube apparatus 10 that can increase the X-ray output without excessively increasing the temperature of the X-ray emission window 33. Moreover, the heat release characteristics can be improved, and the X-ray tube 30 and the X-ray tube apparatus 10 can be obtained with high reliability over a long period of time. It is particularly suitable as an X-ray tube device for mammography.

  Next, a modification of the X-ray tube 30 according to the third embodiment will be described. The X-ray tube 30 according to the third embodiment uses a rolling bearing such as a ball bearing as a bearing. However, as shown in FIG. 6, the X-ray tube 30 may use a dynamic pressure sliding bearing as a bearing. FIG. 6 is a cross-sectional view showing a part of the X-ray tube 30, but the fixed body 1 is a side view.

  The rotating body 2 has a bearing surface 2S on the inner surface of the rotating body. The fixed body 1 has another bearing surface 1S opposed to the bearing surface 2S on the outer surface of the fixed body. The rotating body 2 and the fixed body 1 are provided in a region where the bearing surface 2S and the other bearing surface 1S face each other with a gap of about 10 to 30 μm.

  A gap between the rotating body 2 and the fixed body 1 is filled with a liquid metal lubricant 3. In this embodiment, the liquid metal lubricant 3 is gallium (Ga) or gallium-indium-tin alloy (GaInSn). The bearing surface 2S, the other bearing surface 1S, and the liquid metal lubricant 3 form a dynamic pressure sliding bearing.

  At least one of the bearing surface 2S and the other bearing surface 1S has a scraping portion. In this embodiment, only the other bearing surface 1S has a scraping portion. The fixed body 1 has a plurality of scraping portions 11, 12, 13, and 14 arranged in a direction along the rotation axis (tube axis).

  The scraping portions 11, 12, 13, and 14 are formed on the other bearing surface 1 </ b> S and are arranged along the rotation direction of the rotating body 2. The scraping portions 11, 12, 13, and 14 each have a plurality of pattern portions 1a that are spirally formed in the rotational direction. In this embodiment, the pattern portion 1a is formed by a groove having a depth of several tens of μm.

  A pair of adjacent scrapers 11, 12 form a herringbone pattern. A pair of adjacent scrapers 13 and 14 form a herringbone pattern. For this reason, two sets of herringbone patterns are formed on the stationary body 1.

  Inside the rotating body 2, seal portions 2a and 2b protruding from the bearing surface 2S are provided. The seal portions 2 a and 2 b are formed in an annular shape, and are provided with a gap around the entire side surface of the fixed body 1. The seal portions 2a and 2b also function as thrust bearings due to the action of the liquid metal lubricant filled in the gap in the direction along the rotation axis (tube axis) of the rotating body 2 and the fixed body 1.

  The radial gap (clearance) between the seal portions 2a and 2b and the fixed body 1 is set to a value that can maintain the rotation of the rotating body 2 and suppress the leakage of the liquid metal lubricant 3. From the above, the gap is slight. For this reason, seal part 2a, 2b functions as a labyrinth seal ring (labyrinth seal ring).

  Since the dynamic pressure sliding bearing as described above has less rotational noise than a ball bearing, it is optimal as an anode rotation mechanism for an X-ray tube device arranged close to the human body like an X-ray tube device for mammography. .

  Next explained is an X-ray tube according to the fourth embodiment of the invention. In this embodiment, the X-ray tube is a fixed anode type X-ray tube. Hereinafter, a fixed anode type X-ray tube device including a fixed anode type X-ray tube will be described. In this embodiment, the same reference numerals are given to the same functional portions as those in the first embodiment, and detailed description thereof will be omitted.

  As shown in FIG. 7, the X-ray tube device 10 includes a housing 20 having a bottomed cylindrical shape, an X-ray tube 30 accommodated in the housing 20, and the inside of the housing 20 filled with the X-ray tube 30 and The coolant 7 filling the space between the housings 20 is provided. The housing 20 is provided with a rubber bellows 21 and a radiation window 24.

  The X-ray tube 30 includes a vacuum envelope 31. The vacuum envelope 31 includes a vacuum vessel 32 made of a metal material, a high voltage insulating member 40, and an insulating member 38. An anode target 35 is attached to the high voltage insulating member 40, and a cathode 36 is indirectly attached to the vacuum vessel 32.

The high voltage insulating member 40 forms a part of the vacuum envelope 31. The high voltage insulating member 40 is formed by a cylindrical portion 46 and a bottom portion 47 that closes one end side of the cylindrical portion 46. The high voltage insulating member 40 has an external end face 41 exposed to the outside of the housing 20. In this embodiment, the outer end surface 41 is a flat surface.
The support member 25 is formed in an annular shape. The support member 25 supports the high-voltage insulating member 40 in a liquid-tight manner with respect to the housing 20.

  Inside the high voltage insulating member 40, a voltage supply terminal 44 connected to the anode target 35 and led out to the external end face 41 side is provided. In this embodiment, the voltage supply terminal 44 is a high voltage supply terminal. The voltage supply terminal 44 is provided through the outer end face 41 and supplies a high voltage to the anode target 35 attached to the high voltage insulating member 40.

  The anode target 35 is located at a distance from the bottom 47. The anode target 35 is joined to the inner surface of the cylindrical portion 46. The anode target 35 is supported by the cylindrical portion 46. The anode target 35 is made of metal. The anode target 35 and the cathode 36 are housed in a vacuum envelope 31.

  The anode target 35 has a target layer 35a. The target layer 35a emits X-rays when an electron beam emitted from the cathode 36 collides with it. A relatively positive voltage is applied to the anode target 35. The anode target 35 is stationary with respect to the vacuum envelope 31.

  The insulating member 38 forms a part of the vacuum envelope 31. The voltage supply terminal 54 is provided through the insulating member 38. The voltage supply terminal 54 exposed to the outside of the vacuum envelope 31 is covered with a mold insulating part 39. The mold insulating part 39 is formed of a mold insulating material such as a rubber material. For this reason, the voltage supply terminal 54 is waterproofed and electrically insulated. The voltage supply terminal 54 is supported by a KOV member 55 that is a low expansion alloy. Between the KOV member 55 and the cathode 36, and between the KOV member 55 and the insulating member 38 are brazed.

  The inside of the vacuum envelope 31 is in a vacuum state. The X-ray radiation window 33 is provided in the vacuum container 32 in an airtight manner. Here, the X-ray emission window 33 is made of beryllium. The metal surface portion 34 is provided inside the vacuum vessel 32 including the surface side of the X-ray emission window 33 on the vacuum side, and is set to the same potential as the cathode 36.

  A shield electrode 8 is attached to the anode target 35. The shield electrode 8 is formed in an annular shape so as to surround the outer periphery of the anode target 35. The shield electrode 8 receives impact of recoil electrons. The shield electrode 8 suppresses direct hit of recoil electrons to the high voltage insulating member 40. Thereby, the fall of the insulation of the high voltage insulating member 40 can be suppressed.

  A focusing electrode 9 is located between the focal point F and the cathode 36. The focusing electrode 9 is attached to the shield electrode 8. Here, the shield electrode 8 and the focusing electrode 9 are integrally formed. The focusing electrode 9 is provided so as to surround the trajectory of the electron beam from the cathode 36 toward the focal point F. The focusing electrode 9 is indirectly attached to the anode target 35. The shield electrode 8 and the focusing electrode 9 are at the same potential as the anode target 35.

  The high-voltage connector 100 includes a bottomed cylindrical housing 101, a cable 102 having a tip inserted into the housing 101, and the housing 101 filled with the terminal 102a of the cable 102 facing the opening side of the housing 101. And a fixed portion 103 made of an epoxy resin material and a silicone plate 104 made of a silicone resin material inserted between the fixed portion 103 and the outer end face 41 of the bottom portion 47. In this embodiment, the cable 102 is a high voltage cable. The fixing part 103 is an electrical insulating material.

  In this embodiment, the fixing portion 103 as an electrical insulating material of the high voltage connector 100 is in intimate contact with the external end surface 41 of the bottom portion 47. Note that the fixing portion 103 may be in direct contact with the outer end surface 41. The high voltage connector 100 provides a high voltage to the voltage supply terminal 44.

  The X-ray tube apparatus configured as described above is used as follows. When the high voltage connector 100 is attached to the housing 20, the silicone plate 104 is pressed so as to be in close contact with the fixing portion 103 and the external end surface 41 of the high voltage insulating member 40.

An X-ray shielding cap 300 as an X-ray shielding part is detachably attached to the housing 20 so as to cover the high voltage connector 100. The X-ray shielding cap 300 is made of a material containing an X-ray opaque material.
The cable 202 is connected to the voltage supply terminal 54. The cable 202 is drawn out of the housing 20.

  The coolant 7 is filled in the housing 20 and fills the space between the X-ray tube 30 and the housing 20. As the coolant 7, insulating oil or an aqueous coolant can be used. In this embodiment, an aqueous coolant is used as the coolant 7.

  In the X-ray tube apparatus 10 configured as described above, a predetermined high voltage is applied to the high voltage connector 100. A high voltage applied to the high voltage connector 100 is applied to the anode target 35, the shield electrode 8, and the focusing electrode 9 via the voltage supply terminal 44. The vacuum envelope 31 including the cathode 36 and the X-ray emission window 33 is grounded.

  As a result, an electron beam is emitted from the cathode 36 to the target surface 35b of the anode target 35, X-rays are emitted from the focal point F formed on the target surface 35b, and the X-rays pass through the X-ray emission window 33 and the emission window 24. It is transmitted through and radiated to the outside.

Next, the X-ray tube apparatus 10 of FIG. 7 will be described with reference to FIG.
The cathode 36 causes an electron beam to enter the target surface 35b from a direction that forms the first angle α from the target surface 35b, and forms a focal point F on the target surface 35b. The X-ray radiation window 33 is located in a direction that forms the second angle β from the target surface 35b. The first angle α is in the range of 8 ° to 30 °, and the second angle β is in the range of 5 ° to 25 °.

  A perpendicular extending from the center point of the surface of the X-ray radiation window 33 on the vacuum side is LP1, and an extended plane located on the same plane as the target surface 35b and deviating from the target surface 35b is S. Let PA be the intersection where the perpendicular line LP1 and the target surface 35b or the extension plane S intersect. The intersection PA is located farther from the focal point F when viewed from the cathode 36. In this embodiment, the intersection PA is a point where the perpendicular line LP1 and the extension plane S intersect.

  According to the X-ray tube 30 and the X-ray tube apparatus 10 configured as described above, the X-ray tube 30 includes the anode target 35, the cathode 36, and the vacuum envelope 31. The first angle α is in the range of 8 ° to 30 °, and the second angle β is in the range of 5 ° to 25 °. The metal surface portion 34 including the surface side of the vacuum side X-ray emission window 33 is set to the same potential as the cathode 36.

  Recoil electrons are emitted with an angular distribution that increases in the direction from the focal point F toward the X-ray emission window 33. However, since the surface side of the vacuum side X-ray emission window 33 is set to the same potential as the cathode 36, recoil electrons can be pushed back by the influence of the electric field in the vicinity of the X-ray emission window 33. Since direct hitting of recoil electrons on the X-ray emission window 33 can be suppressed, heating of the X-ray emission window 33 can be suppressed. And damage to the X-ray radiation window 33 can be prevented.

  Furthermore, since heating of the X-ray radiation window 33 is suppressed, boiling of the coolant 7 near the X-ray radiation window 33 can be suppressed. The generation of gas accompanying the boiling of the coolant 7 can be suppressed, and the X-ray transmittance is not adversely affected, so that a reduction in the clarity of the X-ray image can be suppressed.

  In addition, since scattering of recoil electrons upward from the target surface 35b can be reduced, recollision of recoil electrons to the target surface 35b including the vicinity of the focal point F can be suppressed. Thereby, the temperature rise of the target surface 35b (focal point F) and the roughness caused by the target surface 35b can be suppressed, and the occurrence of discharge and the decrease in the output of X-rays can be suppressed. Furthermore, since the emission of X-rays from other than the focal point F can be suppressed, it is possible to suppress a decrease in the clarity of the X-ray image.

  Furthermore, since the focal point F is formed by making the electron beam incident on the target surface 35b at a relatively shallow angle, the X-ray output emitted from the X-ray emission window 33 can be increased.

  The intersection PA is located farther from the focal point F when viewed from the cathode 36. For this reason, the X-ray radiation window 33 can be pushed back so that recoil electrons do not collide with the target surface 35b again.

In this embodiment, the intersection point PA is a point where the perpendicular line LP1 and the extension plane S intersect, so that re-collision of recoil electrons to the target surface 35b can be further suppressed. In this case, most of the recoil electrons impact the side surface of the anode target 35.
As the coolant 7, an aqueous coolant having the highest heat transfer coefficient and containing water as a main component can be used. For this reason, the coolant 7 can most effectively remove the heat transmitted to the high voltage insulating member 40. Further, since the water-based coolant has a larger specific heat than the insulating oil (about twice that of the insulating oil), the temperature rise of the coolant due to the heat radiation of the X-ray tube 30 is suppressed to a low level.

  Further, since the high voltage insulating member 40 is in contact with the coolant 7, heat from the anode target 35 can be effectively dissipated into the coolant 7, and the temperature of the high voltage connector 100 connected to the high voltage insulating member 40 can be lowered. Insulation of the high voltage connector 100 can be ensured over a long period of time.

  As described above, it is possible to obtain the X-ray tube 30 and the X-ray tube apparatus 10 that can increase the X-ray output without excessively increasing the temperature of the X-ray emission window 33. Moreover, the heat release characteristics can be improved, and the X-ray tube 30 and the X-ray tube apparatus 10 can be obtained with high reliability over a long period of time.

  Next explained is an X-ray tube according to the fifth embodiment of the invention. In this embodiment, the X-ray tube is a fixed anode type X-ray tube. Hereinafter, a fixed anode type X-ray tube device including a fixed anode type X-ray tube will be described. In this embodiment, the same reference numerals are given to the same functional parts as those in the fourth embodiment, and detailed description thereof will be omitted.

  As shown in FIGS. 8 to 10, the X-ray tube apparatus 10 includes an X-ray tube 30, a magnetic field deflection electrode 70 as a deflection control unit, and a pump unit 90.

  The X-ray tube 30 includes a vacuum envelope 31. The vacuum envelope 31 includes a vacuum vessel 32 and a high voltage insulating member 40. An anode target 35 is attached to the high voltage insulating member 40, and the high voltage insulating member 40 forms a part of the vacuum envelope 31. The high voltage insulating member 40 is formed integrally with a cylindrical portion and a ring portion connected to one end of the cylindrical portion.

  The anode target 35 is bonded to the high voltage insulating member 40. The anode target 35 has a recess 35d. The recess 35d is formed in a disc shape. The anode target 35 and the cathode 36 are housed in a vacuum envelope 31. A relatively positive voltage is applied to the anode target 35 and the focusing electrode 9.

  The inside of the vacuum envelope 31 is in a vacuum state. The X-ray transmission window 31a for detecting the focal position is provided in the vacuum vessel 32 in an airtight manner. The metal surface portion 34 is provided inside the vacuum vessel 32 including the surface side of the vacuum side X-ray emission window 33 and is set to substantially the same potential as the cathode 36.

  The X-ray tube 30 includes a tube portion 51, a ring portion 52, and a coolant 53. In this embodiment, the coolant 53 is an insulating oil. The tube portion 51 is formed of a high voltage insulating material. The tube portion 51 is provided inside the high voltage insulating member 40. One end portion of the tube portion 51 extends to the outside of the vacuum envelope 31. The pipe part 51 forms an introduction path C1 into which the coolant 53 is introduced. The high voltage insulating member 40 and the pipe portion 51 form a discharge path C2 for discharging the coolant 53 therebetween.

  The ring portion 52 is provided in a region surrounded by the recess 35 d and the high voltage insulating member 40. The ring portion 52 is formed integrally with the tube portion 51 so as to surround the side surface of the end portion of the tube portion 51. The ring portion 52 is provided with a gap in the recess 35 d and the high voltage insulating member 40.

The anode target 35 has a passage C3 provided therein. The passage C3 is connected to the introduction passage C1 and the discharge passage C2. The pump unit 90 sends out the cooling liquid 53 to the introduction path C1, takes in the cooling liquid 53 from the discharge path C2, and circulates the cooling liquid 53. For this reason, the coolant 53 introduced from the introduction path C1 circulates through the passage C3 and is discharged from the discharge path C2.

  The magnetic field deflection electrode 70 is provided outside the vacuum vessel 32 so as to surround the trajectory of the electron beam. The magnetic field deflection electrode 70 deflects the electron beam emitted from the cathode 36 so that the focal point F moves continuously or intermittently on the target surface 35b.

Next, the X-ray tube apparatus 10 shown in FIGS. 8 to 10 will be described with reference to FIG.
The cathode 36 causes an electron beam to enter the target surface 35b from a direction that forms the first angle α from the target surface 35b, and forms a focal point F on the target surface 35b. The X-ray radiation window 33 is located in a direction that forms the second angle β from the target surface 35b. The first angle α is in the range of 8 ° to 30 °, and the second angle β is in the range of 5 ° to 25 °.

  A perpendicular extending from the center point of the surface of the X-ray radiation window 33 on the vacuum side is LP1, and an extended plane located on the same plane as the target surface 35b and deviating from the target surface 35b is S. Let PA be the intersection where the perpendicular line LP1 and the target surface 35b or the extension plane S intersect. The intersection PA is located farther from the focal point F when viewed from the cathode 36. In this embodiment, the intersection PA is a point where the perpendicular line LP1 and the target surface 35b intersect.

  According to the X-ray tube 30 and the X-ray tube apparatus 10 configured as described above, the X-ray tube 30 includes the anode target 35, the cathode 36, and the vacuum envelope 31. The first angle α is in the range of 8 ° to 30 °, and the second angle β is in the range of 5 ° to 25 °. The metal surface portion 34 including the surface side of the X-ray emission window 33 on the vacuum side is set to substantially the same potential as the cathode 36.

  Recoil electrons are emitted with an angular distribution that increases in the direction from the focal point F toward the X-ray emission window 33. However, since the surface side of the vacuum side X-ray emission window 33 is set to the same potential as the cathode 36, recoil electrons can be pushed back by the influence of the electric field in the vicinity of the X-ray emission window 33. Since direct hitting of recoil electrons on the X-ray emission window 33 can be suppressed, heating of the X-ray emission window 33 can be suppressed. And damage to the X-ray radiation window 33 can be prevented.

  Furthermore, since the heating of the X-ray radiation window 33 is suppressed, it is not necessary to cool the X-ray radiation window 33 with the coolant. Further, in the X-ray tube 30, the heat generated by the anode target 35 is cooled by the coolant 53 flowing through the passage C <b> 3 provided inside the anode target 35. Since the X-ray tube 30 does not have to be installed in the housing together with the cooling liquid, the housing and the cooling liquid filling the housing can be made unnecessary. In that case, the X-ray tube apparatus can be made more compact and lighter.

  In addition, since scattering of recoil electrons upward from the target surface 35b can be reduced, recollision of recoil electrons to the target surface 35b including the vicinity of the focal point F can be suppressed. Thereby, the temperature rise of the target surface 35b (focal point F) and the roughness caused by the target surface 35b can be suppressed, and the occurrence of discharge and the decrease in the output of X-rays can be suppressed. Furthermore, since the emission of X-rays from other than the focal point F can be suppressed, it is possible to suppress a decrease in the clarity of the X-ray image.

  Furthermore, since the focal point F is formed by making the electron beam incident on the target surface 35b at a relatively shallow angle, the X-ray output emitted from the X-ray emission window 33 can be increased.

  The intersection PA is located farther from the focal point F when viewed from the cathode 36. For this reason, the X-ray radiation window 33 can be pushed back so that recoil electrons do not collide with the target surface 35b again.

  The magnetic field deflection electrode 70 scans the target surface 35b with an electron beam.

For this reason, the X-ray tube 30 of this embodiment can reduce a weight and a size compared with a rotary anode type X-ray tube. When the X-ray tube apparatus 10 of this embodiment is mounted on a CT apparatus, the CT gantry can be rotated at a higher speed than before, and the imaging time can be further shortened. Moreover, the X-ray tube apparatus 10 of this embodiment can also be mounted on a plurality of CT mounts. In this case, it is possible to shorten the shooting time without increasing the rotation speed of the gantry.

  Furthermore, since the electron beam is scanned on the target surface 35b at a sufficiently high speed by the magnetic field deflection electrode 70, an increase in the focus F temperature can be reduced.

Most of the recoil electrons impact the side surface and back surface of the anode target 35, not the target surface 35b, and heat the anode target 35. This heat is applied to the coolant 53 flowing through the passage C3 provided inside the anode target 35. Because it is transmitted, heat is dissipated well. Moreover, since the heat generated at the focal point F of the target surface 35b is similarly transmitted to the coolant 53, it is radiated well.
From the above, it is possible to obtain the X-ray tube 30 and the X-ray tube device 10 that can suppress direct hit of recoil electrons to the X-ray emission window 33.

Next, a modification of the X-ray tube apparatus 10 according to the fifth embodiment will be described.
As shown in FIGS. 11 and 12, the X-ray tube apparatus 10 may include an electrostatic deflection electrode 80 as a deflection control unit.

  The electrostatic deflection electrode 80 is provided inside the vacuum vessel 32 so as to surround the trajectory of the electron beam. The electrostatic deflection electrode 80 deflects the electron beam emitted from the cathode 36 so that the focal point F moves continuously or intermittently on the target surface 35b.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  For example, the vacuum envelope 31 including the cathode 36 and the X-ray emission window 33 is not limited to the ground potential (0 V), and can be variously modified as long as they have the same potential. As a specific example, a voltage −V is applied to the vacuum envelope 31 including the cathode 36 and the X-ray emission window 33, and the anode target 35 is grounded (0 V). In addition, there is an example in which the voltage −V / 2 is applied to the vacuum envelope 31 including the cathode 36 and the X-ray emission window 33 and the voltage + V / 2 is applied to the anode target 35.

The X-ray tube according to the first embodiment, the X-ray tube according to the third embodiment, the X-ray tube according to the fourth embodiment, and the X-ray according to the fifth embodiment. In the modification of the X-ray tube according to the fifth embodiment, when the X-ray emission window is changed to the same arrangement as that of the conventional X-ray tube, that is, the focal point and the center point of the X-ray emission window are set. X-ray output without excessive temperature rise of the X-ray emission window even when the connecting line is changed to an arrangement that substantially overlaps the perpendicular extending from the center point of the surface of the X-ray emission window on the vacuum side As described above, can be increased.
The present invention is not limited to the above X-ray tube and X-ray tube device, but can be applied to various X-ray tubes and X-ray tube devices.

  DESCRIPTION OF SYMBOLS 1 ... Fixed body, 1S ... Other bearing surface, 1a ... Pattern part, 2 ... Rotating body, 2S ... Bearing surface, 3 ... Liquid metal lubricant, 7 ... Coolant, 9 ... Focusing electrode, 10 ... X-ray tube apparatus , 20 ... Housing, 30 ... X-ray tube, 31 ... Vacuum envelope, 32 ... Vacuum container, 33 ... X-ray emission window, 34 ... Metal surface portion, 35 ... Anode target, 35b ... Target surface, 36 ... Cathode, 40 ... high voltage insulating member, 51 ... tube portion, 52 ... ring portion, 53 ... coolant, 60 ... equipotential surface forming electrode, 61 ... equipotential surface, 62 ... X-ray passage hole, 70 ... magnetic field deflection electrode, 80 ... Electrostatic deflection electrode, 90 ... Pump unit, A ... Long axis, C1 ... Introduction path, C2 ... Discharge path, C3 ... Passage, F ... Focus, LP1, LP2 ... Vertical, LC ... Line, PA ... Intersection, P1 ... First intersection point, P2 ... second intersection point, S ... extension plane, α ... first angle, β ... second angle.

Claims (15)

An anode target having a target surface that emits X-rays upon incidence of an electron beam;
A cathode that makes an electron beam incident on the target surface from a direction at a first angle from the target surface, and forms a focal point on the target surface;
An inside containing the anode target and the cathode, the inside being in a vacuum state, including an X-ray emission window positioned in a direction at a second angle from the target surface, and a surface side of the X-ray emission window on the vacuum side A vacuum envelope having a metal surface portion set to the same potential as the cathode, and
The X-ray tube, wherein the first angle is in a range of 8 ° to 30 °, and the second angle is in a range of 5 ° to 25 °. The cathode emits an electron beam having a circular cross section in a direction perpendicular to the trajectory of the electron beam from the cathode toward the focal point,
The focal point is formed in an elliptical shape having a long axis,
The X-ray tube according to claim 1, wherein the first angle and the second angle are angles formed from the major axis.   The X-ray tube according to claim 1, further comprising a focusing electrode positioned between the focal point and the cathode, surrounding a trajectory of an electron beam from the cathode toward the focal point, and attached to the anode target.   The perpendicular extending from the center point of the surface of the X-ray emission window on the vacuum side and the intersection where the target plane or the extension plane located on the same plane as the target plane and deviating from the target plane intersects is seen from the cathode The X-ray tube according to claim 1, which is located farther from the focal point.   The X-ray tube according to claim 4, wherein the intersection is a point where the perpendicular and the extension plane intersect. An equipotential surface located between the focal point and the X-ray emission window, attached to the vacuum envelope, facing the focal point and set to the same potential as the cathode, and penetrating a part of the equipotential surface. And an equipotential surface forming electrode having an X-ray passage hole formed through the X-ray passage from the focal point toward the X-ray radiation window.
A line connecting the focal point and the center point of the X-ray radiation window, a point where the X-ray passage hole intersects, a first intersection, a perpendicular extending from the first intersection in a direction perpendicular to the equipotential surface, and the target When the second intersection point is a point where the extended plane that is located on the same plane as the surface or the target surface and deviates from the target surface intersects,
The X-ray tube according to claim 1, wherein the second intersection point is located farther from the focal point as viewed from the cathode.   The X-ray tube according to claim 6, wherein the second intersection is a point where the perpendicular and the extension plane intersect.   The X-ray tube according to claim 6, wherein a line connecting the focal point and the center point of the X-ray emission window overlaps a perpendicular extending from the center point of the surface of the X-ray emission window on the vacuum side. The anode target is fixed, is formed in a cylindrical shape extending along a rotation axis, and is rotatable around the rotation axis;
A fixed body that extends along the rotation axis and penetrates the inside of the rotating body, and rotatably supports the rotating body;
A bearing provided between the fixed body and the rotating body;
The X-ray tube according to claim 1, further comprising: a focusing electrode positioned between the focal point and the cathode, surrounding a trajectory of an electron beam from the cathode toward the focal point, and attached to the fixed body. The anode target is fixed, is formed in a cylindrical shape extending along the rotation axis, includes a bearing surface on the inner surface, and a rotating body that is rotatable about the rotation axis;
A fixed body that extends along the rotating shaft and penetrates the inside of the rotating body, includes another bearing surface facing the bearing surface on an outer surface, and rotatably supports the rotating body;
A liquid metal lubricant that fills a gap between the bearing surface and the other bearing surface, and forms a dynamic pressure sliding bearing together with the bearing surface and the other bearing surface;
The X-ray tube according to claim 1, further comprising: a focusing electrode positioned between the focal point and the cathode, surrounding a trajectory of an electron beam from the cathode toward the focal point, and attached to the fixed body.   The X-ray tube according to claim 10, wherein at least one of the bearing surface and the other bearing surface has a groove formed in a spiral shape.   The X-ray tube according to claim 1, wherein the anode target is stationary with respect to the vacuum envelope. An anode target having a target surface that emits X-rays upon incidence of an electron beam, and an electron beam incident on the target surface from a direction that forms a first angle from the target surface, and the target surface is focused. A cathode to be formed; an X-ray emission window that accommodates the anode target and the cathode, the inside of which is in a vacuum state; and is positioned at a second angle from the target surface; and the X-ray emission window on the vacuum side A vacuum envelope provided on the inner side including the surface side and having a metal surface portion set to the same potential as the cathode, and an X-ray tube,
The X-ray tube apparatus, wherein the first angle is in a range of 8 ° to 30 °, and the second angle is in a range of 5 ° to 25 °. An introduction path formed of a high voltage insulating material;
A discharge channel formed of high voltage insulation material;
A pump unit for sending the cooling liquid to the introduction path, taking the cooling liquid from the discharge path, and circulating the cooling liquid;
The X-ray tube apparatus according to claim 13, wherein the anode target is provided inside and connected to the introduction path and the discharge path, and has a passage through which a coolant circulates.   The X-ray tube apparatus according to claim 13, further comprising a deflection control unit that deflects an electron beam emitted from the cathode so that the focal point moves continuously or intermittently on the target surface.

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