JP4210645B2 - Rotating anti-cathode X-ray tube and X-ray generator - Google Patents

Description

The present invention relates to a rotating anode X-ray tube characterized by the separator disposed in the refrigerant passage of the internal rotating anode, also relates to the X-ray generating equipment comprising such a rotating anode X-ray tube.

  A cooling water passage is formed in the rotating counter cathode of the rotating cathode X-ray tube, and the rotating counter cathode is cooled by flowing cooling water into the cooling water passage. FIG. 13 is a longitudinal sectional view of a conventional rotating anti-cathode (a sectional view cut along a plane including the rotation center line). A cooling water passage 12 is formed inside the rotating counter cathode 10, and a separator 14 is disposed in the cooling water passage 12. When the rotating counter cathode 10 rotates, the separator 14 is stationary. The outer peripheral surface of the rotating counter cathode 10 is composed of a target member made of an X-ray generating material. When the electron beam 16 is irradiated on the outer peripheral surface of the target member, X-rays are generated from the electron beam irradiation region 18. Of the inner surface of the rotating counter cathode 10 (the surface of the cooling water passage), the portion on the back side of the electron beam irradiation region 18 is the portion that requires the most cooling, and this will be referred to as the cooled surface 20. Of the surface of the separator 14, a portion facing the surface to be cooled 20 is referred to as an approach surface 22. The distance between the inner surface of the rotating anti-cathode 10 and the surface of the separator 14 is the smallest between the cooled surface 20 and the approaching surface 22 (hereinafter referred to as the approaching passage). If the distance between the inner surface of the rotating cathode 10 and the surface of the separator 14 in this approach path is the approach distance G, this approach distance G is set to about 1.5 mm. By narrowing the approach distance G in this way, the ability to cool the cooled surface 20 is enhanced.

In the focus size called normal focus, the axial length (length in the direction of the rotation axis of the rotating cathode) L1 of the electron beam 16 is, for example, about 10 mm. The circumferential length of the electron beam 16 (the length in the circumferential direction of the outer peripheral surface of the rotating cathode is the length in the direction perpendicular to the paper surface of FIG. 13) is, for example, about 1 mm. Therefore, the cross-sectional size of the electron beam 16 at this time is about 10 mm × 1 mm, which is equal to the size of the electron beam irradiation region 18. In order to sufficiently cool the surface 20 to be cooled on the back side of the electron beam irradiation region 18, the axial length L2 of the approaching surface 22 is preferably longer than the above-described L1. For example, L2 is about 15 mm. The rotating counter cathode is used after being rotated at a rotation speed of about 6000 rpm. A rotating counter cathode having such a separator is disclosed in, for example, the following Patent Document 1.
JP 2000-251810 A

  In the conventional rotating anti-cathode shown in FIG. 13, a fine focus size called fine focus may be used. FIG. 14 is a longitudinal sectional view similar to FIG. 13 in the case of fine focus. The electron beam 16 becomes thinner, and its cross-sectional size is, for example, about 1 mm × 0.1 mm. That is, the axial length L1 of the electron beam 16 is about 1 mm, and the circumferential length is about 0.1 mm. At this time, the axial length of the electron beam irradiation region 18 is also equal to L1 and is about 1 mm. Conventionally, in this fine focus, the same separator 14 as in the normal focus is used as it is.

  In FIG. 14, in order to obtain an X-ray beam with fine focus and high intensity, the energy of the electron beam 16 needs to be increased. Specifically, it is necessary to increase the X-ray generation power (which depends on the product of the tube voltage and the tube current) to be input to the X-ray tube. When the X-ray generation power is increased, the electron beam irradiation region 18 needs to be cooled more powerfully. One way to increase the cooling capacity is to increase the rotating speed of the rotating cathode. When the rotation speed is increased, the time during which the same region on the outer peripheral surface of the rotating cathode is continuously irradiated with the electron beam is shortened, and before the electron beam irradiation region melts with high heat, the high heat part is removed from the electron beam. Become. The present invention relates to increasing the intensity of a fine focus X-ray beam by increasing the rotational speed.

  In the conventional rotating anti-cathode shown in FIG. 14, if the rotating speed of the rotating anti-cathode is increased from 6000 rpm to, for example, 9000 rpm, the following problem occurs. Since cooling water exists between the rotating rotating cathode 10 and the stationary separator 14, the viscous resistance of the cooling water acts as a load for the electric motor that rotates the rotating cathode 10. The place where the rotating counter cathode 10 and the separator 14 are closest to each other is the approaching surface 22 of the separator 14, and the viscous resistance of the cooling water in this portion greatly affects the rotating load. The approach distance G is narrowed to about 1.5 mm, and the axial length L2 of the approach surface 22 is as long as about 15 mm. Therefore, when the rotational speed is increased, an increase in rotational load at this portion is a problem. become. When the rotational load increases, it is necessary to increase the input power of the electric motor as the rotational drive source. Also, it is necessary to replace the motor driver with a larger one.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a rotating anti-cathode X-ray tube in which the load of the rotating drive source does not increase so much even when rotating at high speed. is there. Another object of the present invention, Ru near to provide an X-ray generator comprising such a rotating anode X-ray tube.

The rotating counter-cathode X-ray tube of the present invention includes a rotating counter-cathode, a refrigerant passage, and a separator. The rotating counter cathode includes a cylindrical target member made of an X-ray generating material and has a rotation speed of 9000 rpm when in use. The refrigerant passage is formed inside the rotating counter cathode, and the refrigerant in the refrigerant passage flows along the surface to be cooled that exists on the back side of the electron beam irradiation region on the outer peripheral surface of the target member. The coolant is typically cooling water, but other cooling liquids may be used. The separator is disposed in the refrigerant passage and is stationary. This separator has an approach surface facing the surface to be cooled. The separator divides the refrigerant passage into an inflow passage and an outflow passage, and the refrigerant in the inflow passage flows toward the approach passage between the cooled surface and the approach surface. The refrigerant in the outflow passage flows away from the approach passage. The distance from the approaching surface to the surface to be cooled is 1.5 mm. The axial length of the outer peripheral surface of the cylindrical target member is 43 mm. That is, it is possible to use a rotating counter cathode having a relatively long axial length and capable of normal focusing, instead of a rotating cathode having a particularly short axial length for fine focusing. In contrast, the axial length of the proximal surface of the separator Ru 2mm der. Assuming a fine focus electron beam irradiation region, the cooling capacity is sufficient even if the axial length of the approaching surface is 2 mm . Thus, by shortening the axial length of the approaching surface, it is not necessary to increase the load of the rotary drive source so much even if the rotating anti-cathode is rotated at a high speed. When an electric motor is used as a rotational drive source, it is not necessary to change the capacity of the motor driver to a large one.

  The rotating anti-cathode X-ray tube of the present invention is suitable for generating a powerful X-ray beam with fine focus. The upper limit of the size of the fine focus electron beam irradiation region is about 3 mm × 0.3 mm, and its axial length is 3 mm or less. More preferably, the size of the fine focus electron beam irradiation region is 1 mm × 0.1 mm or less (for example, 0.7 mm × 0.07 mm), and its axial length is 1 mm or less.

  The separator can include, for example, a disk part and an inclined part connected to the outer periphery of the disk part. The inclined portion has a truncated cone shape, and the outer peripheral surface at the radially outer end of the inclined portion can be the approaching surface.

An X-ray generator according to the present invention includes a rotating anti-cathode X-ray tube as described above, a refrigerant supply device that supplies refrigerant to the refrigerant passage of the rotating anti-cathode X-ray tube, and a tube voltage applied to the rotating anti-cathode X-ray tube. and that have a high-voltage power supply for supplying the tube current.

  In the rotating anti-cathode X-ray tube of the present invention, since the axial length of the approaching surface of the separator is shortened, the effect of not having to increase the load of the rotating drive source so much when the rotating speed is increased. There is.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view (a cross-sectional view taken along a plane including a rotation center line of a rotating anti-cathode) of an embodiment of the rotating anti-cathode X-ray tube of the present invention. The rotating counter-cathode X-ray tube includes a vacuum vessel 24 and a rotating counter-cathode 10 and an electron gun 26 housed therein. By applying a high voltage from a high voltage power source between the electron gun 26 and the rotating counter cathode 10, the electron beam 16 can be generated from the electron gun 26. X-rays are generated by irradiating the outer peripheral surface of the cylindrical rotating counter cathode 10 (target member) with the electron beam 16. The rotating anti-cathode 10 belongs to the counter-cathode assembly 28, and the counter-cathode assembly 28 is attached to the vacuum vessel 24 so that the rotating anti-cathode 10 can be arranged at a predetermined position in the internal space of the vacuum vessel 24. it can.

  The counter cathode assembly 28 includes a casing 30. The flange 32 of the casing 30 can be attached to the vacuum vessel 24 in an airtight manner. A rotating shaft 34 is fixed to the rotating counter cathode 10. Between the outer peripheral surface of the rotating shaft 34 and the inner wall of the casing 30, a magnetic fluid sealing device 36 for rotating vacuum sealing, rolling bearings 38 and 40 that rotatably support the rotating shaft 34, and the casing from the rotating shaft 34 to the casing. An electric brush 42 for releasing electric current and a mechanical seal 44 for rotating and sealing the cooling water are arranged. A stator 46 of a direct motor is fixed to the inner wall of the casing 30. On the other hand, a rotor 48 of a direct motor is fixed to the outer peripheral surface of the rotary shaft 34. Due to the action of the direct motor, the rotating shaft 34 rotates, and as a result, the rotating counter cathode 10 rotates.

  FIG. 2 is an enlarged cross-sectional view of a part of the rotating counter cathode 10. A first cooling water passage 50 is formed in the rotating counter cathode 10. The first cooling water passage 50 is divided into a first inflow passage 56 and a first outflow passage 54 by a separator 52. On the other hand, a second cooling water passage 58 is formed inside the rotary shaft 34. The second cooling water passage 58 is also divided into an outer second inflow passage 64 and an inner second outflow passage 62 by a partition pipe 60. The separator 52 is fixed to the partition pipe 60, and as shown in FIG. 1, the root (right end in FIG. 1) of the partition pipe 60 is fixed to the casing 30. The rotating counter cathode 10 and the rotating shaft 34 rotate, but the separator 14 and the partition pipe 60 inside thereof are stationary. In FIG. 2, the first inflow passage 56 communicates with the second inflow passage 64, and the first outflow passage 54 communicates with the second outflow passage 62. As shown in FIG. 1, a cooling water inlet 68 and a cooling water outlet 66 are formed in the casing 30. An inlet piping nipple 72 is attached to the cooling water inlet 68, and an outlet piping nipple 70 is attached to the cooling water outlet 66. The cooling water that has entered the cooling water inlet 68 passes through the second inflow passage 64 (see FIG. 2) and enters the first inflow passage 56 to cool the rotating counter cathode 10 from the inner surface. The return side cooling water exits from the cooling water outlet 66 through the first outflow passage 54 and the second outflow passage 62 (see FIG. 2).

  In FIG. 2, the separator 52 includes a disc portion 74, an inclined portion 76, and a blade 78. FIG. 3 is a front view of the separator 52, and FIG. 4 is a perspective view in which a part of the separator 52 is cut away. Referring to FIGS. 2 to 4, a through hole 80 through which cooling water passes is formed at the center of the disc portion 74, and the disc portion 74 is joined to the partition pipe 60 at the through hole 80. ing. The outer periphery of the disc part 74 is connected to the inclined part 76. The inclined portion 76 has a truncated cone shape as clearly shown in FIG. In the cross section taken along the rotation center line of the rotating anti-cathode, the inclined portion 76 is inclined by an angle θ with respect to the axial direction of the rotating anti-cathode as shown in FIG. In this embodiment, θ is 30 degrees. The outer peripheral surface at the outer end in the radial direction of the inclined portion 76 becomes the approach surface 82. The approach surface 82 is a cylindrical surface, and its axial length L2 is 2 mm. As shown in FIG. 3, four blades 78 are attached to the disk portion 74 in a radial manner.

  In FIG. 2, the rotating anti-cathode 10 includes a cup-shaped first member 84 and a second member 86 formed integrally with the rotating shaft 34. The entire first member 84 is made of a target member (for example, copper). The first member 84 is coupled to the second member 86 by a screw portion 88. Cooling water is sealed by an O-ring 90 at the joint between the first member 84 and the second member 86. The first cooling water passage 50 is formed by combining the first member 84 and the second member 86. The outer peripheral surface of the first member 84 is irradiated with the fine focus electron beam 16. The sectional size of the electron beam 16 is about 1 mm × 0.1 mm in this embodiment. That is, the axial length of the electron beam 16 is about 1 mm, and the circumferential length is about 0.1 mm. At this time, the axial length L1 of the electron beam irradiation region 18 is about 1 mm. When the X-ray beam is extracted at an extraction angle of 6 degrees in the left direction in FIG. 2 at such a focal size, a point focus X-ray source of about 0.1 mm × 0.1 mm is obtained.

  The outer diameter of the rotating cathode 10 is 100 mm, and the axial length L3 is about 43 mm. Since this rotating anti-cathode 10 can be used as a rotating anti-cathode for normal focus only by changing the separator, the length L3 is smaller than that of a rotating anti-cathode made exclusively for fine focus. , It is as long as a normal rotating anti-cathode.

  Of the cylindrical portion of the first member 84, the inner surface on the back side of the electron beam irradiation region 18 is a cooled surface 92 (a surface to be cooled with cooling water). The approach distance G between the cooled surface 92 and the approach surface 82 of the separator is about 1.5 mm. When the passage between the cooled surface 92 and the approach surface 82 is referred to as an approach passage 93, the first cooling water passage 50 is divided into the first inflow passage 56 and the first outflow passage 54 with the approach passage 93 as a boundary. It is divided into FIG. 5 is a cross-sectional view showing the vicinity of the approaching surface 82 of the separator. In the first inflow passage 56, the cooling water 94 flows toward the approach passage 93, and in the first outflow passage 54, the cooling water 94 flows away from the approach passage 93. Since the passage of the cooling water is narrow in the approach passage 93, the flow velocity is increased in this portion, and the cooled surface 92 is cooled with a sufficient cooling capacity. Since the axial length of the approaching surface 82 is as short as 2 mm, the rotational load due to the viscous resistance of the cooling water in the approaching passage 93 is smaller than when using a conventional separator, and the rotational speed is reduced. For example, even if the power is increased to 9000 rpm, the electric power supplied to the motor does not increase as much as in the prior art. With regard to the fact that the separator having a short axial length of the approach surface 82 has sufficient cooling capacity, a powerful electron beam with a fine focus is used at a rotation speed of 9000 rpm, a tube voltage of 40 kV, and a tube current of 30 mA. This was confirmed by the fact that the surface of the target member was not roughened when X-rays were generated by irradiation.

  FIG. 6 shows a first modification of the separator and is a cross-sectional view similar to FIG. FIG. 7 is a perspective view similar to FIG. 4 of the separator shown in FIG. In FIG. 6, the separator 52 a has a cylindrical portion 96 connected to the outer periphery of the disc portion 74, and a protruding portion 98 protruding outward in the radial direction is formed at the axial end of the cylindrical portion 96. . An outer peripheral surface of the projecting portion 98 is an approach surface 82a. The axial length L2 of the approach surface 82a is 2 mm. The approach distance G in the approach passage 93a is about 1.5 mm. The protruding amount of the approach surface 82a with respect to the cylindrical portion 96 is about 2 mm.

  FIG. 8 shows a second modification of the separator, and is a perspective view similar to FIG. The separator 52b is similar to FIG. 6 when viewed in a cross-sectional view, but the approach surface 82b is shaped to repeat triangular irregularities in the circumferential direction. The distance between the top of the mountain of the approaching surface 82b and the surface to be cooled is about 1.5 mm. The height measured in the radial direction from the top of the mountain to the bottom of the valley is about 2 mm.

  FIG. 9 shows a third modification of the separator and is a cross-sectional view similar to FIG. FIG. 10 is a perspective view of the separator shown in FIG. 9 similar to FIG. The separator 52c has a cylindrical portion 96 connected to the outer periphery of the disc portion 74, and a protruding portion 100 having a triangular cross section is formed at the axial end of the cylindrical portion 96 and protrudes outward in the radial direction. Yes. The distance between the apex of the triangular protrusion 100 and the cooled surface 92 is about 1.5 mm. The radial height of the triangular protrusion 100 is about 2 mm. Of the slope of the protrusion 100, a region whose distance from the cooled surface 92 is within a predetermined value D (for example, 3 mm) functions as an approaching surface. When the distance from the surface to be cooled 92 is more than D, the role for sufficiently cooling the surface to be cooled 92 is diminished. The axial length L2 of the protrusion 100, measured at a distance D from the surface to be cooled 92, is 2 mm.

  Next, experimental results on the motor load of the rotating cathode X-ray tube of the present invention will be described. FIG. 11 shows the experimental results of the motor load for the rotating anti-cathode X-ray tube (invention) having the separator 52 shown in FIG. 2 and the rotating anti-cathode X-ray tube (conventional example) having the separator 14 shown in FIG. It is a graph. However, each separator used what removed the blade | wing 78 (refer FIG. 4). The horizontal axis of the graph represents the rotational speed of the rotating cathode. The vertical axis represents the current flowing in the winding of the direct motor directly connected to the rotary shaft 34. This is an experiment assuming that the rotational speed is increased to 9000 rpm, with the main aim of increasing the X-ray intensity of the fine focus X-ray beam. In order to obtain a rotational speed of 9000 rpm, in the conventional example, the motor current required 13.1A. On the other hand, in the present invention, the motor current is only 9.3 A. In the case of the motor used this time, when the motor current is about 9A, the power is about 800W. Since the conventional example and the present invention differ only in the shape of the separator, in the present invention, the axial length L2 of the approaching surface 82 (FIG. 2) of the separator 52 is shortened, so that the load on the motor is considerably reduced. I understand that.

  FIG. 12 is a graph of the water pressure of the cooling water when the experimental data of the present invention in FIG. 11 is obtained. Even an actual rotating anti-cathode X-ray tube is used at such a supply pressure.

  The rotating anti-cathode X-ray tube of the present invention is assumed to irradiate a fine focus electron beam. However, if it is replaced with the separator shown in FIG. 13, normal focus (for example, focus size of about 10 mm × 1 mm) is obtained. It can also be used to irradiate an electron beam. Furthermore, depending on the input power for generating X-rays, the separator can be used as in the normal focus with the one shown in FIG. This is because, in normal focus, the electron beam energy per unit area is not so large, and therefore the cooling capacity is often sufficient even for an approach surface that is shorter than the axial length of the electron beam irradiation region.

  FIG. 15 is a block diagram of an X-ray generator provided with a rotating anti-cathode X-ray tube of the present invention. The X-ray generator includes a rotating anti-cathode X-ray tube 102, a high voltage power source 104, and a refrigerant supply device 106. The high-voltage power source 104 applies a tube voltage E between the cathode filament 108 of the electron gun of the rotating anti-cathode X-ray tube 102 and the rotating anti-cathode 10 (which is at the ground potential) and causes the tube current I to flow. . A negative high voltage (for example, minus 60 kV) is applied to the cathode filament 108 relative to the rotating cathode 10. The cathode filament 108 irradiates the outer peripheral surface of the rotating cathode 10 with the electron beam 16, and X-rays 110 are generated from the irradiated region.

  Cooling water 112 is supplied from the refrigerant supply device 106 to the inlet pipe nipple 72 of the rotating anti-cathode X-ray tube 102. Cooling water 114 (temperature rising) that has returned after cooling the rotating counter-cathode 10 comes out from the outlet pipe nipple 74, but this return cooling water 114 may be drained as it is, The refrigerant may be cooled and recirculated by the refrigerant supply device 106.

It is sectional drawing of the principal part of one Example of the rotation anti-cathode X-ray tube of this invention. It is sectional drawing which expanded and showed a part of rotation counter cathode. It is a front view of a separator. It is the perspective view which notched and showed a part of separator. It is sectional drawing which shows the vicinity of the approach surface of a separator. FIG. 6 shows a first modification of the separator, and is a cross-sectional view similar to FIG. It is a perspective view similar to FIG. 4 of the separator shown in FIG. FIG. 5 is a perspective view similar to FIG. 4, showing a second modification of the separator. FIG. 10 shows a third modification of the separator, and is a cross-sectional view similar to FIG. FIG. 10 is a perspective view of the separator shown in FIG. 9 similar to FIG. It is a graph of the experimental result of the motor load about the rotation anti-cathode X-ray tube (this invention) which has a separator shown in FIG. 2, and the rotation anti-cathode X-ray tube (conventional example) which has a separator shown in FIG. It is a graph of the water pressure of the cooling water when obtaining the experimental data of the direction of the present invention in FIG. It is a longitudinal cross-sectional view of the conventional rotating counter cathode. It is the same longitudinal cross-sectional view as FIG. 13 at the time of setting it as a fine focus. It is a block diagram of the X-ray generator provided with the rotation anti-cathode X-ray tube of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rotating anti-cathode 16 Electron beam 18 Electron beam irradiation area | region 20 Cooled surface 22 Approaching surface 50 1st cooling water path 52 Separator 54 1st outflow path 56 1st inflow path 58 2nd cooling water path 60 Partition pipe 62 second outflow passage 64 second inflow passage 74 disc portion 76 inclined portion 82 approach surface 84 first member 86 second member 92 surface to be cooled 93 approach passage 94 cooling water 102 rotating cathode X-ray tube 104 high voltage power source 106 Refrigerant supply device 108 Cathode filament 110 X-ray 112 Cooling water L1 Axial length of electron beam L2 Axial length of approaching surface L3 Axial length of rotating counter-cathode G Approach between cooled surface and approaching surface distance

Claims (4)

A rotating anti-cathode X-ray tube having the following configuration.
(A) A rotating anti-cathode comprising a cylindrical target member made of an X-ray generating material, the axial length of the outer peripheral surface of the cylindrical target member is 43 mm, and the rotational speed during use is A rotating counter cathode that is 9000 rpm.
(B) A refrigerant passage formed inside the rotating counter cathode, wherein the refrigerant flows along a surface to be cooled that exists on the back side of the electron beam irradiation region on the outer peripheral surface of the target member. Refrigerant passage.
(C) a separator which is disposed in the refrigerant passage and is stationary, and is provided with an approaching surface facing the cooled surface and having a distance to the cooled surface of 1.5 mm , The refrigerant passage is divided into an inflow passage through which the refrigerant flows toward the approach passage between the surface to be cooled and the approach surface and an outflow passage through which the coolant flows away from the access passage, and the axial length of the access surface is divided. Separator whose length is 2 mm .   The rotating anti-cathode X-ray tube according to claim 1, wherein the outer peripheral surface of the target member is irradiated with a fine focus electron beam.   3. The rotating anti-cathode X-ray tube according to claim 1, wherein the separator includes a disc portion and an inclined portion connected to an outer periphery of the disc portion, and the inclined portion is a truncated cone. A rotating anti-cathode X-ray tube characterized in that the outer peripheral surface at the radially outer end of the inclined portion is the approaching surface. An X-ray generator having the following configuration.
(A) The rotating counter-cathode X-ray tube according to any one of claims 1 to 3.
(A) A refrigerant supply device that supplies a refrigerant to the refrigerant passage of the rotating cathode X-ray tube.
(C) A high voltage power source for supplying a tube voltage and a tube current to the rotating cathode X-ray tube.

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