JP2011086462A - 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 in which X-ray output can be increased and direct strokes of recoil electrons to an X-ray irradiation window can be suppressed. <P>SOLUTION: The X-ray tube 30 is provided with an anode target 35, which has a target surface 35b that emits X-rays by making electron beams be incident; a cathode 36 which makes electron beams incident on the target face 35b from a first direction d1 and forms a focus F on the target face 35b; and a vacuum envelope 31, which houses the anode target 35 and the cathode 36 with the interior vacuum, and has the X-ray irradiation window 33, located from the focus F along the second direction d2. The angle which a second plane S2 and a third plane S3 forming inward is set in the range of 45° to 135°. The angle which the first direction d1 makes with the first plane S1 is in the range of 8° to 30°. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an X-ray tube and an X-ray tube apparatus.

  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.

  Therefore, a technique for increasing the X-ray output of the X-ray tube has been disclosed (see, for example, Patent Documents 1 to 5).

  In this type of X-ray tube, the positional relationship between the focal point and the X-ray emission window is substantially the same as that of a conventional X-ray tube. Further, unlike the other conventional X-ray tubes, the X-ray tube emits an X-ray emitted from the X-ray emission window by forming an focal point by making an electron beam incident at a relatively shallow angle with respect to the target surface. The line output is increased. Under the condition that the electron beam intensity is the same, the X-ray tube can increase the X-ray output by up to 1.5 times compared to the conventional X-ray tube.

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 above X-ray tube has the following problems.
The potential of the X-ray emission window is the same as the potential of the anode target, or a potential approximately halfway 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 due to the recoil electrons directly hitting the X-ray emission window is expected to be more serious than the conventional X-ray tube.
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 increase the X-ray output and suppress the recoil electron direct hit to the X-ray emission window and the X-ray tube. To provide a tube device.

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 first direction and forms a focal point on the target surface;
A vacuum envelope containing the anode target and the cathode, the inside of which is in a vacuum state, and having an X-ray emission window located along the second direction from the focal point,
A plane in contact with the target surface at a position where the focal point is formed is a first plane, a direction passing through the focal point and above the target surface and perpendicular to the first plane is a third direction, the first direction, and the third direction. When the plane along the direction is the second plane, the plane along the second direction and the third direction is the third plane,
The angle formed by the second plane and the third plane on the inside is any one of the range of 45 ° to 135 °,
The angle formed by the first direction from the first plane is any of 8 ° to 30 °.

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; a cathode that causes an electron beam to enter the target surface from a first direction to form a focal point; and the anode target And a vacuum envelope having an X-ray emission window that contains a cathode and has an X-ray emission window located in a second direction from the focal point,
A plane in contact with the target surface at a position where the focal point is formed is a first plane, a direction passing through the focal point and above the target surface and perpendicular to the first plane is a third direction, the first direction, and the third direction. When the plane along the direction is the second plane, the plane along the second direction and the third direction is the third plane,
The angle formed by the second plane and the third plane on the inside is any one of the range of 45 ° to 135 °,
The angle formed by the first direction from the first plane is any of 8 ° to 30 °.

  According to the present invention, it is possible to provide an X-ray tube and an X-ray tube apparatus that can increase the X-ray output and suppress the 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 perspective view which shows the anode target shown in FIG. 1, and is a figure which shows a mode that an electron beam injects into an anode target, an X-ray is emitted from an anode target, and a recoil electron jumps out from an anode target. It is sectional drawing which shows the said anode target, and is a figure which shows a mode that an electron beam penetrate | invades inside an anode target and an X-ray is emitted from the inside of an anode target. It is sectional drawing which shows the anode target of the comparative example of the said X-ray tube, and is a figure which shows a mode that an electron beam penetrate | invades inside an anode target and an X-ray is emitted from the inside of an anode target. It is a figure which shows the said cathode, an anode target, and an X-ray radiation window, and is a figure which shows a mode that the position of the said cathode is changed and the direction of a 1st direction is changed. It is a perspective view which shows the said anode target, and is a figure which shows the shape of the track | orbit of an electron beam, and the focus formed in an anode target. It is a top view which expands and shows the focus shown in FIG. It is a figure which shows the said cathode, an anode target, and an X-ray radiation window, and is a figure which shows the state which changed the direction of the 1st direction by changing the position of the said cathode. It is a schematic block diagram which shows the electron emission source and focus of a cathode shown in FIG. FIG. 10 is a schematic configuration diagram illustrating an electron emission source and a focal point of the cathode illustrated in FIG. 8, and is a diagram viewed from an angle different from FIG. 9. It is the schematic block diagram which shows the electron emission source and focus of a cathode shown in FIG. 8, and is the figure seen from the angle different from FIG.9 and FIG.10. It is sectional drawing which shows the X-ray tube apparatus containing the X-ray tube which concerns on the 2nd Embodiment of this invention. It is the schematic which took out and shows the anode target, cathode, vacuum envelope, and housing which were shown in FIG. 12, and was the figure which looked at these from the cathode side. 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. It is the schematic which took out and shows the anode target, cathode, vacuum envelope, and housing which were shown in FIG. 14, and was the figure which looked at these from the cathode side.

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 FIGS. 1 and 2, 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 makes an electron beam incident on the target surface 35b from the first direction d1, and forms a focal point F on the target surface 35b. A relatively negative voltage is applied to the cathode 36. A voltage and current applied to the cathode 36 are supplied to the electron emission source 36 a of the cathode 36. The electron emission source 36a is formed of an electrode, a coiled filament, or the like. Here, the electron emission source 36a is formed of a rectangular electrode.

  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 along the second direction d2 from the focal point F. 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 part 34 is provided inside the vacuum envelope 31 including the surface side of the X-ray radiation window 33 on the vacuum side, and is set to the ground potential (0 V).

  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.

  Here, a plane in contact with the target surface 35b at the position where the focal point F is formed is defined as a first plane S1. A direction that passes through the focal point F and faces the target surface 35b and is perpendicular to the first plane S1 is defined as a third direction d3. A plane along the first direction d1 and the third direction d3 is defined as a second plane S2. A plane along the second direction d2 and the third direction d3 is defined as a third plane S3.

  Further, an angle formed by the second plane S2 and the third plane S3 on the inside is δ. An angle formed by the first direction d1 from the first plane S1 is α. An angle formed by the second direction d2 from the first plane S1 is β.

  The angle δ is in the range of 45 ° to 135 °. In this embodiment, the angle δ is 90 °. The angle α is in the range of 8 ° to 30 °. In this embodiment, the angle α is 15 °. The range of the angle β is not particularly limited, but the angle β is preferably in the range of 5 ° to 25 °.

  A high voltage power supply 15 is connected to the X-ray tube 30. The high voltage power supply 15 is for supplying a high voltage to the cathode 36 and the anode target 35. In this embodiment, the high voltage power supply 15 supplies a high voltage only to the cathode 36.

  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. The tube voltage V is 20 kV to 100 kV.

  In this embodiment, the high voltage power supply 15 supplies a voltage of −V to the cathode 36. The vacuum envelope 31 including the anode target 35 and the X-ray radiation window 33 is grounded (0 V).

  The potential of the cathode 36 is not limited to −V, and may be set to any value within the range of −V to −V / 2 (−V ≦ VC ≦ −V / 2). The potential of the anode target 35 is not limited to the ground potential, and may be set to any value within the range of the ground potential to + V / 2 (0 ≦ VA ≦ + V / 2).

  In the X-ray tube 30 configured as described above, for example, a negative high voltage of −100 kV or more is applied to the cathode 36. The anode target 35 and the vacuum envelope 31 are grounded. The electron emission source 36a of the cathode 36 is further given a low voltage and current of ± 100 V or less.

  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.

  FIG. 3 is a diagram illustrating a state in which an electron beam is incident on the anode target 35 and X-rays are emitted from the anode target 35 in the above embodiment, and the second plane S2 and the third plane S3 are set as one plane. FIG.

  FIG. 4 is a diagram illustrating a comparative example of FIG. FIG. 4 is a diagram illustrating a state in which an electron beam is incident on the anode target 35 of the comparative example and X-rays are emitted from the anode target 35, and is a diagram illustrating the third plane S3.

  As shown in FIG. 3, the angle α is in the range of 8 ° to 30 °. The angle α is 15 °. Let the penetration depth of the electron beam into the anode target 35 be d. The depth d is a specific length. Then, the distance through which the X-rays pass through the anode target 35 is d × sin α / sin β. As the value of d × sin α / sin β is smaller, that is, as the angle α is closer to 0 °, X-ray absorption by the anode target 35 can be suppressed, and the X-ray dose emitted from the anode target 35 is increased. Can be made.

  As in the example of FIG. 3, when the angle α is 15 °, the value of d × sin α / sin β can be reduced, so that the X-ray dose emitted from the anode target 35 can be increased.

  On the other hand, the larger the value of d × sin α / sin β, that is, the closer the angle α is to 90 °, the greater the amount of X-ray absorption by the anode target 35 and the lower the X-ray dose emitted from the anode target 35. Will do.

  As shown in FIG. 4, for this reason, when an electron beam is incident on the anode target 35 from a direction perpendicular to the first plane S1, the distance that X-rays pass through the anode target 35 is d × sin 90 ° / sin β = d / sin β. In this case, since the value of d × sin α / sin β cannot be reduced, the X-ray dose emitted from the anode target 35 decreases.

  According to the X-ray tube 30 according to the first embodiment configured as described above, the X-ray tube 30 includes the anode target 35, the cathode 36, and the vacuum envelope 31. The cathode 36 is set to a negative high potential, the anode target 35 is set to a range from the ground potential to a positive high potential, and the vacuum envelope 31 including the X-ray emission window 33 is grounded.

The angle δ is 90 °. The X-ray radiation window 33 is located far from the second plane S2. Recoil electrons jump out from the focal point F with an angular distribution that increases in the direction along the second plane S2. However, since the X-ray emission window 33 is not located on the second plane S2, it is possible to suppress recoil electrons from directly hitting the X-ray emission window 33 and to suppress heating of the X-ray emission window 33. Can do. And damage to the X-ray radiation window 33 can be prevented. Note that most of the recoil electrons that jump out of the focal point F impact the inner surface of the vacuum vessel 32 that is out of the X-ray emission window 33.
The above effect can be obtained when the angle δ is in the range of 45 ° to 135 °.

  The angle α is 15 °. 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.

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.
The above-described effect can be obtained when the angle α is any of 8 ° to 30 °.

  As described above, an X-ray tube that can suppress recoil electrons directly hitting the X-ray emission window 33 and increase the X-ray output without excessive temperature rise of the X-ray emission window 33. 30 can be obtained.

  Next, a method for setting the angle δ to any one within the range of 45 ° to 135 ° will be described. In order to obtain the angle δ, for example, the position of the cathode 36 may be changed as shown in FIG. This can be dealt with by changing the direction of the first direction d1.

  In addition, although not shown, the position of the X-ray emission window 33 may be changed without changing the position of the cathode 36 in order to obtain the angle δ. This can be dealt with by changing the direction of the second direction d2.

  Next, a case where the electron emission source 36a is formed of an electrode having a long axis or a coiled filament will be described. Here, the case where the electron emission source 36a is formed of a coiled filament will be described as an example.

  As shown in FIGS. 1, 6 and 7, the cathode 36 emits an electron beam having a rectangular cross section perpendicular to the trajectory of the electron beam from the cathode 36 (electron emission source 36a) toward the focal point F. This cross section has a major axis.

  The focal point F is formed in a rectangular shape. The focal point F has a major axis a along the third plane S3 and a minor axis orthogonal to the major axis a. In this example, since the angle δ is 90 °, the shape of the focal point F is a rectangle.

Next, the case where the electron emission source 36a is formed of a coiled filament and the angle δ is not 90 ° will be described. In this case, the shape of the focal point F is a parallelogram.
As shown in FIGS. 8, 9, 10 and 11, the position of one end of the electron emission source 36a is a point A1, the position of the other end is a point B1, and the center position of the points A1 and B1 is a point C1. To do. The shape of the focal point F is a parallelogram having a long axis a along the third plane S3. The position of one end of the focal point F is point A2, the position of the other end is point B2, and the center position of the points A2 and B2 is point C2. Point A2 is a point at which electrons emitted from point A1 of electron emission source 36a collide. Point B2 is a point where electrons emitted from point B1 of electron emission source 36a collide.

  An angle of the second direction d2 formed from a plane orthogonal to the second plane S2 is ε. In the direction along the straight line where the first plane S1 and the second plane S2 intersect, the length between the point A2 and the point C2 and the length between the point B2 and the point C2 are set to x. In the direction along the third direction d3, the length between the point A1 and the point C1 and the length between the point B1 and the point C1 are y. In the direction along the first plane S1, L is the length between the point A1 and the point C1 and the length between the point B1 and the point C1. Let ζ be the angle of the electron emission source 36a formed from a plane parallel to the first plane S1.

  From the above length x, length y, length L, angle α, angle ε, and angle ζ, the following relational expression holds.

x / L = tan ε
y / x = tan α
Furthermore, the following relational expression holds from the above relational expression.

y / L = tan ζ = tan α · tan ε
From the above relational expression, when the angle δ is not 90 °, the electron emission source 36a may be tilted, whereby the focal point F having the long axis a along the third plane S3 can be formed.

  Next explained is an X-ray tube according to the second 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 FIGS. 12 and 13, the X-ray tube device 10 includes a cylindrical housing 20, 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 A coolant 7 filling the space between the housings 20 and a stator coil 910 as a rotational drive device are provided. 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 container 32 made of metal, an insulating member 40, and an insulating member 50. In this embodiment, the insulating member 50 is formed of a high voltage insulating member. An anode target 35 is indirectly attached to the insulating member 40, and a cathode 36 is indirectly attached to the insulating member 50. 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 X-ray radiation window 33 on the vacuum side, and is set to the ground potential.

  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. In this embodiment, the anode target 35 is set to the ground potential.

  A cathode support member 37 is connected to the cathode 36. The voltage supply terminal 54 is connected to the cathode 36 through the inside of the cathode support member 37. The voltage supply terminal 54 applies a negative high voltage to the cathode 36 and supplies voltage and current to the electron emission source 36 a 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 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 insulating member 40 forms a part of the vacuum envelope 31. The 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 insulating member 40 is liquid-tightly provided on the housing 20.

  The insulating member 50 forms a part of the vacuum envelope 31. The insulating member 50 has an external end surface 50 </ b> S exposed to the outside of the housing 20. In this embodiment, the outer end surface 50S is a flat surface.

  Inside the insulating member 50, a voltage supply terminal 54 connected to the cathode 36 and led out to the external end face 50S side is provided. In this embodiment, the voltage supply terminal 54 is a high voltage supply terminal. The voltage supply terminal 54 is provided so as to penetrate the external end face 50 </ b> S and supplies a high voltage to the cathode 36. 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 support member 37 and between the KOV member 55 and the insulating member 50 are brazed.

  The cable 102 is connected to the end of the fixed body 1 exposed to the outside of the housing 20. The cable 102 sets the anode target 35 to the ground potential via the fixed body 1 or the like.

  The high-voltage connector 200 includes a bottomed cylindrical housing 201, a cable 202 having a tip inserted into the housing 201, and the housing 201 filled with the terminal of the cable 202 facing the opening of the housing 201. A fixing portion 203 made of an epoxy resin material to be fixed and a silicone plate 204 made of a silicone resin material inserted between the fixing portion 203 and the outer end surface 50S of the insulating member 50 are provided. In this embodiment, cable 202 is a high voltage cable. The fixing part 203 is an electrical insulating material.

  In this embodiment, the fixing portion 203 as an electrical insulating material of the high voltage connector 200 is in intimate contact with the outer end surface 50 </ b> S of the insulating member 50. Note that the fixing portion 203 may be in direct contact with the outer end surface 50S. The high voltage connector 200 applies a high voltage to the voltage supply terminal 54.

  The X-ray tube apparatus configured as described above is used as follows. When attaching the high voltage connector 200 to the housing 20, the silicone plates 204 are pressed so as to be in close contact with the fixing portion 203 and the outer end surface 50 </ b> S of the insulating member 50.

  An X-ray shielding cap 400 as an X-ray shielding part is detachably attached to the housing 20 so as to cover the high voltage connector 200. The X-ray shielding cap 400 is made of a material containing an X-ray opaque material.

  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 cathode support member 37, for example. The focusing electrode 9 is set to a negative high voltage.

  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 each of the high voltage connectors 200.

  The fixed body 1, the bearing 930, the rotating body 2, the joint portion 35c, and the anode target 35 are set to the ground potential via the cable 102. The high voltage applied to the high voltage connector 200 is applied to the cathode 36 via the voltage supply terminal 54. The vacuum envelope 31 including the X-ray radiation window 33 is grounded. The potential of the cathode 36 is set to -V. The potential of the anode target 35 is set to the ground potential.

  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 shown in FIGS. 12 and 13 will be described with reference to FIG.
The cathode 36 makes an electron beam incident on the target surface 35b from the first direction d1, and forms a focal point F on the target surface 35b. The cathode 36 emits an electron beam having a rectangular cross section perpendicular to the trajectory of the electron beam from the cathode 36 toward the focal point F. The focal point F has a long axis a along the third plane S3 and is formed in a rectangular shape. The long axis a of the focal point F is orthogonal to the rotation direction of the anode target 35.

  The X-ray radiation window 33 is located along the second direction d2 from the focal point F. The angle δ formed by the second plane S2 and the third plane S3 on the inner side is any of the range of 45 ° to 135 °. In this embodiment, the angle δ is 90 °. The angle α formed by the first direction d1 from the first plane S1 is any of 8 ° to 30 °.

  According to the X-ray tube 30 and the X-ray tube device 10 according to the second embodiment configured as described above, the X-ray tube 30 causes the electron beam to be incident from the anode target 35 and the first direction d1. The cathode 36 that forms the focal point F on the target surface 35b, and the vacuum envelope 31 that includes the X-ray emission window 33 that is located along the second direction d2 from the focal point F. The cathode 36 is set to a negative high potential, the anode target 35 is set to the ground potential, and the vacuum envelope 31 including the X-ray emission window 33 is grounded.

The angle δ is 90 °. The X-ray radiation window 33 is located far from the second plane S2. Recoil electrons jump out from the focal point F with an angular distribution that increases in the direction along the second plane S2. However, since the X-ray emission window 33 is not located on the second plane S2, it is possible to suppress recoil electrons from directly hitting the X-ray emission window 33 and to suppress heating of the X-ray emission window 33. Can do. And damage to the X-ray radiation window 33 can be prevented. Note that most of the recoil electrons that jump out of the focal point F impact the inner surface of the vacuum vessel 32 that is out of the X-ray emission window 33.
The above effect can be obtained when the angle δ is in the range of 45 ° to 135 °.

  The angle α is in the range of 8 ° to 30 °. 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.

  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.

  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 transferred to the vacuum vessel 32 and the insulating members 40 and 50. 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.

  Since the insulating member 40 is in contact with the coolant 7, the heat from the anode target 35 can be effectively dissipated into the coolant 7. Since the insulating member 50 is in contact with the coolant 7, heat from the cathode 36 can be effectively dissipated into the coolant 7, the temperature of the high voltage connector 200 connected to the insulating member 50 can be lowered, and the high voltage connector 200 can be maintained over a long period of time. Insulating properties can be ensured. The inner surface of the vacuum vessel 32 is heated by receiving most of the recoil electrons jumping out from the focal point F or receiving heat radiation from the anode target 35 which has become high temperature. Therefore, these heats can be effectively dissipated into the coolant 7.

  As described above, an X-ray tube that can suppress recoil electrons directly hitting the X-ray emission window 33 and increase the X-ray output without excessive temperature rise of the X-ray emission window 33. 30 and the X-ray tube apparatus 10 can be obtained. 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 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 above embodiment, and detailed description thereof will be omitted.

  As shown in FIGS. 14 and 15, the X-ray tube apparatus 10 includes a cylindrical housing 20, an X-ray tube 30 housed in the housing 20, and the inside of the housing 20 filled with the X-ray tube 30 and A coolant 7 filling the space between the housings 20 and a stator coil 910 as a rotational drive device are provided.

  The X-ray tube 30 includes a vacuum envelope 31. The vacuum envelope 31 includes a vacuum container 32 and insulating members 40 and 50. An anode target 35 is indirectly attached to the insulating member 40, and a cathode 36 is indirectly attached to the insulating member 50. 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 X-ray radiation window 33 is provided in the vacuum container 32 in an airtight manner. The metal surface portion 34 is provided inside the vacuum vessel 32 including the surface side of the X-ray radiation window 33 on the vacuum side, and is set to the ground potential.

  A voltage supply terminal 54 is connected to the cathode 36. The voltage supply terminal 54 applies a negative voltage to the cathode 36 and supplies a voltage and a current to the electron emission source 36 a of the cathode 36.

  In this embodiment, the insulating member 40 is a high voltage insulating member. The insulating member 40 has an external end face 40 </ b> S exposed to the outside of the housing 20. In this embodiment, the outer end surface 40S is a flat surface.

  A voltage supply terminal 44 is provided on the external end face 40S. 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 insulating member 40 in a liquid-tight manner with respect to the housing 20.
In this embodiment, the insulating member 50 is a high voltage insulating member.

  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 surface 40S 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 outer end surface 40S of the bottom portion 47. Note that the fixing portion 103 may be in direct contact with the outer end surface 40S. 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 outer end surface 40 </ b> S of the insulating member 40.

  The high voltage connector 200 includes a housing 201, a cable 202, a fixing portion 203, and a silicone plate 204. In this embodiment, cable 202 is a high voltage cable. The fixing part 203 is an electrical insulating material.

  In this embodiment, the fixing portion 203 as an electrical insulating material of the high voltage connector 200 is in intimate contact with the outer end surface 50 </ b> S of the insulating member 50. Note that the fixing portion 203 may be in direct contact with the outer end surface 50S. The high voltage connector 200 applies a high voltage to the voltage supply terminal 54.

  The X-ray tube apparatus configured as described above is used as follows. When attaching the high voltage connector 200 to the housing 20, the silicone plates 204 are pressed so as to be in close contact with the fixing portion 203 and the outer end surface 50 </ b> S of the insulating member 50.

  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. An X-ray shielding cap 400 as an X-ray shielding part is detachably attached to the housing 20 so as to cover the high voltage connector 200. The X-ray shielding cap 300 and the X-ray shielding cap 400 are 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.

  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 each of the high voltage connectors 100 and 200.

  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 high voltage applied to the high voltage connector 200 is applied to the cathode 36 via the voltage supply terminal 54. The vacuum envelope 31 including the X-ray radiation window 33 is grounded. The potential of the cathode 36 is set to -V / 2. The potential of the anode target 35 is set to + V / 2.

  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 shown in FIGS. 14 and 15 will be described with reference to FIG.
The cathode 36 makes an electron beam incident on the target surface 35b from the first direction d1, and forms a focal point F on the target surface 35b. The cathode 36 emits an electron beam having a rectangular cross section perpendicular to the trajectory of the electron beam from the cathode 36 toward the focal point F. The focal point F has a long axis a along the third plane S3 and is formed in a rectangular shape. The X-ray radiation window 33 is located along the second direction d2 from the focal point F. The angle δ formed by the second plane S2 and the third plane S3 on the inner side is any of the range of 45 ° to 135 °. In this embodiment, the angle δ is 90 °. The angle α formed by the first direction d1 from the first plane S1 is any of 8 ° to 30 °.

  According to the X-ray tube 30 and the X-ray tube apparatus 10 according to the third embodiment configured as described above, the X-ray tube 30 causes the electron beam to enter from the anode target 35 and the first direction d1. The cathode 36 that forms the focal point F on the target surface 35b, and the vacuum envelope 31 that includes the X-ray emission window 33 that is located along the second direction d2 from the focal point F. The cathode 36 is set to a negative high potential, the anode target 35 is set to a positive high potential, and the vacuum envelope 31 including the X-ray emission window 33 is grounded.

The angle δ is 90 °. The X-ray radiation window 33 is located far from the second plane S2. Recoil electrons jump out from the focal point F with an angular distribution that increases in the direction along the second plane S2. However, since the X-ray emission window 33 is not located on the second plane S2, it is possible to suppress recoil electrons from directly hitting the X-ray emission window 33 and to suppress heating of the X-ray emission window 33. Can do. And damage to the X-ray radiation window 33 can be prevented. Note that most of the recoil electrons that jump out of the focal point F impact the inner surface of the vacuum vessel 32 that is out of the X-ray emission window 33.
The above effect can be obtained when the angle δ is in the range of 45 ° to 135 °.

  The angle α is in the range of 8 ° to 30 °. 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.

  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.

  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 transferred to the vacuum vessel 32 and the insulating members 40 and 50. 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.

  Since the insulating members 40 and 50 are in contact with the cooling liquid 7, heat from the anode target 35 and the cathode 36 can be effectively dissipated into the cooling liquid 7, and the temperature of the high voltage connectors 100 and 200 connected to the insulating members 40 and 50. The insulation of the high voltage connectors 100 and 200 can be secured over a long period of time. The inner surface of the vacuum vessel 32 is heated by receiving most of the recoil electrons jumping out from the focal point F or receiving heat radiation from the anode target 35 which has become high temperature. Therefore, these heats can be effectively dissipated into the coolant 7.

  As described above, an X-ray tube that can suppress recoil electrons directly hitting the X-ray emission window 33 and increase the X-ray output without excessive temperature rise of the X-ray emission window 33. 30 and the X-ray tube apparatus 10 can be obtained. 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.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components 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, in the above embodiment, most recoil electrons impact the inner surface of the vacuum envelope 32. However, a structure that receives the most impact of recoil electrons may be disposed inside the vacuum envelope 32. Is possible.

  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, 2 ... Rotating body, 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, 36a ... electron emission source, 40, 50 ... insulating member, a ... long axis, F ... focal point, d1 ... 1st direction, d2 ... 2nd direction, d3 ... 3rd direction, S1 ... 1st plane, S2 ... 2nd plane, S3 ... 3rd plane, (alpha), (beta), (delta), (epsilon), (zeta) ... angle.

Claims (9)

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 first direction and forms a focal point on the target surface;
A vacuum envelope containing the anode target and the cathode, the inside of which is in a vacuum state, and having an X-ray emission window located along the second direction from the focal point,
A plane in contact with the target surface at a position where the focal point is formed is a first plane, a direction passing through the focal point and above the target surface and perpendicular to the first plane is a third direction, the first direction, and the third direction. When the plane along the direction is the second plane, the plane along the second direction and the third direction is the third plane,
The angle formed by the second plane and the third plane on the inside is any one of the range of 45 ° to 135 °,
An X-ray tube in which the angle formed by the first direction from the first plane is in the range of 8 ° to 30 °.   The X-ray tube according to claim 1, wherein the anode target is set to a ground potential.   2. The X-ray tube according to claim 1, wherein the vacuum envelope further includes a metal surface portion that is provided on an inner side including a surface side of the X-ray emission window on a vacuum side and is set to a ground potential.   2. The X-ray tube according to claim 1, wherein an angle formed by the second direction from the first plane is in a range of 5 ° to 25 °. The cathode emits an electron beam having a rectangular cross section perpendicular to the trajectory of the electron beam from the cathode toward the focal point,
The X-ray tube according to claim 1, wherein the focal point has a long axis along the third plane and is formed in a rectangular shape. 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 is provided inside 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 5, wherein a long axis of the focal point is orthogonal to a rotation direction of the anode target around the rotation axis. 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 is provided inside 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 5, wherein a long axis of the focal point is parallel to a rotation direction of the anode target around the rotation axis. 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 5, 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. An anode target having a target surface that emits X-rays upon incidence of an electron beam; a cathode that causes an electron beam to enter the target surface from a first direction to form a focal point; and the anode target And a vacuum envelope having an X-ray emission window that contains a cathode and has an X-ray emission window located in a second direction from the focal point,
A plane in contact with the target surface at a position where the focal point is formed is a first plane, a direction passing through the focal point and above the target surface and perpendicular to the first plane is a third direction, the first direction, and the third direction. When the plane along the direction is the second plane, the plane along the second direction and the third direction is the third plane,
The angle formed by the second plane and the third plane on the inside is any one of the range of 45 ° to 135 °,
The X-ray tube apparatus, wherein an angle formed by the first direction from the first plane is in a range of 8 ° to 30 °.

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