JPS59221950A - Rotary anode x-ray tube - Google Patents

Abstract

PURPOSE:To improve cooling efficiency while unifying distribution of X-ray intensity and the size of an apparent focal point by making the heat radiation part formed on one part of an envelope to face the base of a disc target in the vicinity thereof. CONSTITUTION:A metal 16 is arranged to face the upper base side of a target 11 in the vicinity thereof, while the metal 15 also is arranged near the lower base side of the target 11. A cathode part 20 having a filament 19 is mounted on the part of a ceramic 17 so as to face a V groove 12, while thermoelectrons emitted from the filament 19 collide with the V groove 12 so as to form a focal point 21 on both sides of said V groove 12 for emitting X-rays from said focal point 21. Thereby, the heat radiated from the target 11 is emitted outside through the parts of metalls 15 and 16 of the envelope 18, while the parts of said metals 15 and 16 are arranged close and in opposition to the wide range of the base of the target 11 so as to raise efficiency of emitting radiant heat.

Description

[Detailed description of the invention] (b) Industrial application fields This invention relates to a rotating anode X-ray tube.

(B) Prior Art A conventional rotating anode X-ray tube is normally constructed as shown in FIG. In FIG. 1, a target 4 and a cathode part 5 are housed in an envelope 3 made of glass 1 and metal 2. A focal point 6 is formed on the target 4, and the target 4 is attached to a rotor 7, and the target 4 is rotated by the rotor 7 driven by an external induced magnetic field.
is set to rotate. A filament 8 is housed in the cathode section 5 and held by a holding section 9. Thermionic electrons emitted from the filament 8 of the cathode section 5 collide with the target 4 to form a focal point 6, and X-rays are emitted from this focal point 6 and are irradiated to the outside through the X-ray irradiation window IO.

By the way, only a small amount of the thermoelectrons that collide with the target 4 are converted into X-rays, and most of them become heat. Some of this heat is released to the outside by conduction, while the rest is released by radiation. However, due to the distance between the target 4, which is a heat source, and the metal 2 of the envelope 3, and the small area of the portion facing the target 4, the emission efficiency is poor, in other words, the cooling efficiency is low. In addition, a part of the radiant heat is absorbed by the cathode part 5 and the holding part 9, which causes temperature rise and deformation of the cathode part 5 and the holding part 9, and the focal point 6
There were problems in that dimensional changes in the filament 8 and short-circuit failures of the filament 8 occurred.

Furthermore, as shown in FIG. 2, the angle of the target 4 is 12
When the angle is 0°, the irradiation field range is ±lO°, but at -10°, the X-ray intensity is 30% of that at O' (center). Also, as shown in Figure 3, the apparent focal spot size force (changes) at each position within the irradiation field.For example, if the focal spot size is 1.OX 1.Omm at 0°, then at +10° it is 1.
．． OX 1.802 am.

-10' = 1. OXo, 188 mm. As a result, shading occurs on the film, and the resolution at each position becomes non-uniform, resulting in a decline in image quality.

(c) Purpose The purpose of the present invention is to provide a rotating anode X-ray tube that improves image quality by improving cooling efficiency and uniformity of X-ray intensity distribution and apparent focal spot size. do.

(D) Structure The rotary anode X-ray tube according to the present invention is provided with a groove that goes around the side circumferential surface of a disk-shaped target, and a cathode section that is disposed opposite to this side circumferential surface. In addition to forming focal points on both side surfaces, the disk-shaped target is held by a rotor on one side of both bottom surfaces of the disk-shaped target, and the heat dissipation part formed in a part of the envelope is attached to at least one of the bottom surfaces of the disk-shaped target. It is characterized by being close to and facing the bottom of the other.

(E) Example In FIGS. 4 and 5, "disc-shaped target ll
A V-groove 12 is formed all around the side circumferential surface of the
This target 11 is held by a rotor 13 on the lower bottom surface side. 11 and rotor 13
is enclosed within an envelope 18 made of glass 14, metal 15, 16 and ceramic 17. The metal 16 is arranged close to the upper bottom surface of the target 11 and facing the target 11, and the metal 15 is also arranged close to the lower bottom surface of the target 11. A cathode part 20 having a filament 19 is attached to the ceramic 17 so as to face the V-groove 12, and the thermoelectrons emitted from the filament 19 are
The collision with the groove 12 forms a focal point 21 on both sides of the V-groove 12, and X-rays are emitted from this focal point 21, and these X-rays are irradiated to the outside through an X-ray irradiation window 22 provided in the ceramic 17. be done.

In this configuration, the heat radiated from the target 11 is radiated to the outside through the metal 15.16 portion of the envelope 18, and the metal 15.16 portion spreads over a wide range of the bottom surface of the target 11. Since they are arranged close to each other and facing each other, the efficiency of releasing radiant heat is high. In other words, the metal portions 15 and 16 function as a heat dissipation section, thereby improving cooling efficiency.

Furthermore, since the focal point 21 is formed on both side surfaces of the V-groove 12, the following effects can be obtained. First, as shown in Figure 6,
If one side of the focal point 21 is A and the other side is B, the X-ray intensity distribution will be a dotted line a for A and a dotted line for H, so the overall X-ray intensity distribution will be a + b, which is a solid line. It becomes like this. Therefore, the X-ray intensity distribution is made uniform within the irradiation field of ±lO0, and the occurrence of shading on the film can be improved. Next, as shown in FIG. 7, it is possible to suppress the apparent focal size change at each position within the irradiation field of ±10°. For example, when the focal point size is 0°, 1. OX
1. If it is Omm, then +lO0 or -10' is 1. OXo, 985 m, m. Therefore, the resolving power at each position can be made uniform.

These ultimately have a great effect on improving image quality.

(f) Effects According to the present invention, cooling efficiency can be improved, and the X-ray intensity distribution and apparent focal size can be made uniform, thereby greatly contributing to improvement in image quality.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view of the conventional example, and Figure 2 is the
FIG. 3 is a schematic diagram for explaining the line intensity distribution, FIG. 3 is a schematic diagram for explaining the apparent focus size at each position with respect to FIG. 1, and FIG. 4 is a longitudinal cross-sectional view of an embodiment of the present invention. , 5th
The figure is a cross-sectional view of the same embodiment, and FIG.
FIG. 7 is a schematic diagram for explaining the line intensity distribution, and FIG. 7 is a schematic diagram for explaining the apparent focus size at each position regarding the same embodiment. ■, 14...Glass 2.15.16...Metal 3.18...Envelope 4.11...Target 5.20...Cathode part 6.21...Focus 7.1
3...Rotor 8.19...Filament 10
．． 22...X-ray irradiation window 12...V groove 17...
Ceramic patent applicant Shimadzu Corporation

Claims (1)

[Claims] (1) A groove is provided on the side circumferential surface of a disc-shaped target, and a cathode portion is arranged opposite to this side circumferential surface,
A focal point is formed on both sides of the groove, and the disk-shaped target is held by a rotor on one side of both bottom surfaces of the disk-shaped target, and the heat dissipation part formed in a part of the envelope is A rotating anode X-ray tube, characterized in that the rotating anode X-ray tube is arranged so as to approach and face at least the other bottom surface of a disc-shaped target.