JP5449118B2 - Transmission type radiation tube, radiation generator, and radiation imaging apparatus - Google Patents

Description

The present invention is a transmission type radiation tube that can be applied to non-destructive X-ray imaging or the like in the medical equipment and industrial equipment fields, a radiation imaging apparatus including a radiation generating equipment Contact and the radiation generating apparatus using the same.

  In general, a radiation tube (radiation generating tube) accelerates electrons emitted from an electron emission source to high energy and irradiates a target made of a metal such as tungsten to generate radiation such as X-rays. The radiation generated at this time is emitted in all directions. Therefore, in order to shield radiation that is not necessary, the container containing the radiation tube or the surroundings of the radiation tube is covered with a shield (radiation shielding member) such as lead so that unnecessary radiation is not leaked to the outside. Yes. For this reason, it has been difficult to reduce the size and weight of such a radiation tube and a radiation generator that houses the radiation tube.

  As means for solving this problem, in the transmission type radiation tube, by arranging shields on the radiation emission side and the electron incidence side of the target, unnecessary radiation is shielded with a simple structure, and the apparatus is reduced in size and weight. Has been proposed (see Patent Document 1).

  However, in general, such a target (anode) -fixed transmission type radiation tube is relatively inferior in heat dissipation, and it is difficult to generate high-energy radiation. Regarding the heat radiation of the target, the transmission radiation tube of Patent Document 1 has a structure in which the target and the shield are joined, so that heat generated in the target is transmitted to the shield and dissipated, and the temperature rise of the target can be suppressed. It is described.

JP 2007-265981 A

  However, in the transmission type radiation tube of Patent Document 1, the shield is disposed in the vacuum vessel, and the heat transfer area from the shield to the outside of the vacuum vessel is limited. For this reason, the heat dissipation of the target is not always sufficient, and there is a problem in achieving both the cooling capability of the target and the reduction in size and weight of the apparatus.

The present invention provides radiation having possible and then, and transmission type radiation tube which allows reduction in size and weight, the radiation generating equipment Contact and it using the same cooling unnecessary radiation shielding and targets with a simple structure An object is to provide a photographing apparatus.

In order to solve the above problems, the present invention includes an envelope having an opening,
An electron emission source disposed inside the envelope;
A transmission radiation tube comprising a target unit that generates radiation by irradiation of electrons emitted from the electron emission source;
The target portion is composed of a diamond transmissive substrate and a target disposed on the surface of the transmissive substrate,
Furthermore, the shield surrounds the target , is disposed in the opening, and has a shield partly protruding to the outside of the envelope ,
The shield is intended to provide a transmission type radiation tube, wherein the benzalkonium shielding a portion of the target is collected by either et emission radiation.
Further, the present invention includes a storage container in which the transmission radiation tube of the present invention is stored, and a cooling medium filled between the storage container and the transmission radiation tube. A portion of the envelope projecting to the outside is in contact with the cooling medium, the radiation generator of the present invention, and the subject emitted from the radiation generator and subject The present invention also provides a radiation imaging apparatus comprising: a radiation detector that detects radiation transmitted through the light source; and a control unit that controls the radiation generation apparatus and the radiation detector.

  According to the present invention, the shield is bonded to the transmission substrate that supports the target, and at least a part of the shield is in contact with the cooling medium. Therefore, the heat generated in the target is transmitted to the shielding body, is transmitted to the cooling medium through the shielding body, and is quickly radiated. Thereby, it is possible to realize a radiation generating apparatus that can shield unnecessary radiation and cool a target with a simple structure. In addition, since the number of members that shield unnecessary radiation can be reduced, the radiation generator can be reduced in size and weight.

It is a schematic diagram of the radiation generator of 1st Embodiment and a target peripheral part. It is a block diagram of the radiography apparatus using the radiation generator of this invention.

  Hereinafter, although embodiment of this invention is described using drawing, this invention is not limited to these embodiment. In addition, the well-known or well-known technique of the said technical field is applied regarding the part which is not illustrated or described in particular in this specification.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to FIG. Fig.1 (a) is a schematic diagram of the radiation generator of this embodiment, FIG.1 (b) is the schematic diagram which expanded and represented the target periphery part in Fig.1 (a). The radiation generating apparatus according to the present embodiment includes a transmissive radiation tube 10, and the transmissive radiation tube 10 is accommodated in the storage container 1. The extra space in which the transmissive radiation tube 10 is accommodated inside the storage container 1 is filled with a cooling medium 8. The storage container 1 may be provided with a voltage control unit 3 (voltage control means) including a circuit board (not shown) and an insulating transformer as in the present embodiment. When the voltage control unit 3 is provided, for example, a voltage signal is applied from the voltage control unit 3 to the transmission radiation tube 10 via the terminals 4, 5, 6, and 7, so that the generation of radiation can be controlled.

  The storage container 1 only needs to have sufficient strength as a container, and is made of metal, plastics material, or the like. The storage container 1 may be provided with a radiation transmission window 2 made of glass, aluminum, beryllium or the like as in the present embodiment. When the radiation transmissive window 2 is provided, the radiation emitted from the transmissive radiation tube 10 is emitted to the outside through the radiation transmissive window 2.

  The cooling medium 8 only needs to have electrical insulation, and it is preferable to use, for example, an insulating medium and an electrical insulating oil having a role as a cooling medium for the transmission type radiation tube 10. As the electrical insulating oil, mineral oil, silicone oil or the like is preferably used. Another usable cooling medium 8 is a fluorine-based electrically insulating liquid.

  The transmission radiation tube 10 includes an envelope 19, an electron emission source 11, a target 14, a transmission substrate 15, and a shield 16. The transmission radiation tube 10 may be provided with an extraction electrode 12 and a lens electrode 13 as in the present embodiment. When these are provided, electrons are emitted from the electron emission source 11 by the electric field formed by the extraction electrode 12, and the emitted electrons are converged by the lens electrode 13 and incident on the target 14 to generate radiation. Moreover, you may provide the exhaust pipe 20 like this embodiment. When the exhaust pipe 20 is provided, for example, after the inside of the envelope 19 is evacuated through the exhaust pipe 20, the inside of the envelope 19 can be evacuated by sealing a part of the exhaust pipe 20. .

The envelope 19 is for keeping the inside of the transmissive radiation tube 10 in a vacuum, and glass, ceramic material, or the like is used. The degree of vacuum in the envelope 19 may be about 10 ⁻⁴ to 10 ⁻⁸ Pa. A getter (not shown) may be disposed inside the envelope 19 in order to maintain the degree of vacuum. The envelope 19 has an opening, and the shield 16 is joined to the opening. The shield 16 has a passage communicating with the opening of the envelope 19, and the envelope 19 is sealed by joining the transmission substrate 15 to the passage.

  The electron emission source 11 is disposed inside the envelope 19 so as to face the opening of the envelope 19. The electron emission source 11 may be a tungsten filament, a hot cathode such as an impregnated cathode, or a cold cathode such as a carbon nanotube. An extraction electrode 12 is disposed in the vicinity of the electron emission source 11, and electrons emitted by the electric field formed by the extraction electrode 12 are converged by the lens electrode 13 and incident on the target 14 to generate radiation. At this time, the voltage Va applied between the electron emission source 11 and the target 14 is approximately 40 to 120 kV, although it varies depending on the intended use of radiation.

  The transmissive substrate 15 supports the target 14 and transmits at least part of the radiation generated by the target 14, and is provided in a passage of the shield 16 that communicates with the opening of the envelope 19. The material constituting the transmissive substrate 15 is preferably strong enough to support the target 14, has little absorption of radiation generated by the target 14, and has high thermal conductivity so that heat generated by the target 14 can be quickly dissipated. . For example, diamond, silicon nitride, aluminum nitride, or the like can be used. In order to satisfy the above requirements for the transmissive substrate 15, the thickness of the transmissive substrate 15 is suitably about 0.1 mm to several mm.

  The target 14 is installed on the surface of the transmission substrate 15 on the electron emission source side. The material constituting the target 14 is preferably a material having a high melting point and high radiation generation efficiency. For example, tungsten, tantalum, molybdenum, or the like can be used. In order to reduce the absorption that occurs when the generated radiation passes through the target 14, the thickness of the target 14 is suitably about several μm to several tens of μm.

  The shield 16 shields radiation emitted from the target 14. The shield 16 is joined to the opening of the envelope 19 and has a passage communicating with the opening. The transmission substrate 15 is joined to the passage. Has been. The target 14 may not be joined to the passage. Further, the shield 16 may be composed of two shields (first shield 17 and second shield 18) having a cylindrical shape such as a cylinder as in the present embodiment (FIG. 1 ( b)).

  The first shield 17 has a function of shielding radiation scattered toward the electron emission source side of the target 14 when electrons enter the target 14 and radiation is generated. There is a communicating passage. The electrons emitted from the electron emission source 11 pass through the passage of the first shield 17 communicating with the opening of the envelope 19, and the radiation scattered to the electron emission source side of the target 14 is the first shield 17. It is shielded with.

  The second shield 18 has a function of shielding unnecessary radiation out of the radiation transmitted through the transmissive substrate 15 and has a passage communicating with the opening of the envelope 19. The radiation that has passed through the transmissive substrate 15 passes through the passage of the second shield 18 that communicates with the opening of the envelope 19, and unnecessary radiation is shielded by the second shield 18.

  In the present embodiment, as shown in FIG. 1B, the opening area of the passage of the second shield 18 is gradually increased (away from the transmissive substrate 15) on the side opposite to the electron emission source from the transmissive substrate 15. Is preferable). This is because the radiation transmitted through the transmission substrate 15 has a radial spread.

  Further, in the present embodiment, the center of gravity of the opening of the passage on each side (the passage of the first shield 17) on the electron emission source side with respect to the transmission substrate 15 and on the opposite side of the transmission substrate 15 with respect to the electron emission source. The center of gravity of the opening of the second shield 18 preferably coincides with the center of gravity of the opening of the passage of the second shield 18. That is, as shown in FIG. 1B, the opening of the passage of the first shield 17 and the opening of the passage of the second shield 18 are in the same vertical direction perpendicular to the target installation surface of the transmission substrate 15 with the transmission substrate 15 in between. It is preferable to arrange on a line. This is because in the present embodiment, the target 14 is irradiated with electrons to generate radiation, and the radiation transmitted through the transmission substrate 15 is emitted.

  The material constituting the shield 16 (the first shield 17 and the second shield 18) is preferably a material having a high radiation absorption rate and a high thermal conductivity. For example, a metal material such as tungsten or tantalum can be used. In order to shield unnecessary radiation, the thickness of the first shield 17 and the second shield 18 is suitably 3 mm or more.

  In the radiation generator of this embodiment, the target 14, the first shield 17, and the second shield 18 are in mechanical and thermal contact with each other directly or through the transmission substrate 15. Further, the surface of the transmission substrate 15 opposite to the electron emission source and the second shield 18 constitute a part of the outer wall of the envelope 19, and contact the cooling medium 8 in the storage container 1. ing. For this reason, the heat generated when electrons enter the target 14 is radiated to the cooling medium 8 from the surface of the transmission substrate 15 opposite to the electron emission source, and is also cooled via the second shield 18. Heat is quickly radiated to the medium 8. Therefore, the temperature rise of the target 14 is suppressed.

  As described above, according to the radiation generator of the present embodiment, unnecessary radiation can be shielded and the target can be cooled with a simple structure, and the radiation generator can be reduced in size and weight.

  Further, in the radiation generating apparatus according to the present embodiment, the shield 16 may be configured by only the second shield 18. Also in this case, the heat generated when electrons are incident on the target 14 is radiated to the cooling medium 8 from the surface of the transmission substrate 15 opposite to the electron emission source, and also through the second shield 18. Heat is quickly radiated to the cooling medium 8. Therefore, the temperature rise of the target 14 is suppressed. In order to shield the radiation scattered toward the electron emission source side of the target 14, another shielding member (for example, a shielding member made of a lead plate covering a part of the outer wall of the envelope 19) is required. Since it is not necessary to cover the entire surface of the radiation tube, the radiation generator can be reduced in size and weight.

  Further, as the voltage control means in the radiation generating apparatus of the present embodiment, either an anode grounding method or a midpoint grounding method can be adopted, but it is preferable to adopt a midpoint grounding method. In the anode grounding method, when the voltage applied between the target 14 and the electron emission source 11 is Va [V], the voltage of the anode target 14 is set to the ground (0 [V]), and the electron emission is performed. In this method, the voltage of the source 11 is set to -Va [V]. On the other hand, in the midpoint grounding method, the voltage of the target 14 is set to + (Va−α) [V], and the voltage of the electron emission source 11 is set to −α [V] (where Va> α> 0). It is a method to do. The value of α is an arbitrary value within the range of Va> α> 0, but is generally a value close to Va / 2. By adopting the midpoint grounding method, the absolute value of the voltage with respect to the ground can be reduced, and the creepage distance can be shortened. Here, the creepage distance is a distance between the voltage control unit 3 and the storage container 1 and a distance between the transmission radiation tube 10 and the storage container 1. If the creepage distance can be shortened, the size of the storage container 1 can be reduced, and the weight of the cooling medium 8 can be reduced accordingly, so that the radiation generator can be further reduced in size and weight. Become.

[Second Embodiment]
Next, a radiation imaging apparatus using the radiation generator of the present invention will be described with reference to FIG. FIG. 2 is a configuration diagram of the radiation imaging apparatus of the present embodiment. The radiation imaging apparatus according to the present embodiment includes a radiation generation apparatus 30, a radiation detector 31, a signal processing unit 32, an apparatus control unit 33, and a display unit 34. As the radiation generator 30, for example, the radiation generator of the first embodiment is preferably used. The radiation detector 31 is connected to the device control unit 33 via the signal processing unit 32, and the device control unit 33 is connected to the display unit 34 and the voltage control unit 3.

  The processing in the radiation generating apparatus 30 is comprehensively controlled by the apparatus control unit 33. For example, the device control unit 33 controls radiation imaging by the radiation generator 30 and the radiation detector 31. The radiation emitted from the radiation generator 30 is detected by the radiation detector 31 through the subject 35 and a radiation transmission image of the subject 35 is taken. The captured radiation transmission image is displayed on the display unit 34. Further, for example, the device control unit 33 controls driving of the radiation generating device 30 and controls a voltage signal applied to the transmission radiation tube 10 via the voltage control unit 3.

  1: storage container, 8: cooling medium, 10: transmission radiation tube, 11: electron emission source, 14: target, 15: transmission substrate, 16: shield, 19: envelope

Claims (10)

An envelope having an opening;
An electron emission source disposed inside the envelope;
A transmission radiation tube comprising a target unit that generates radiation by irradiation of electrons emitted from the electron emission source;
The target portion is composed of a diamond transmissive substrate and a target disposed on the surface of the transmissive substrate,
Furthermore, the shield surrounds the target , is disposed in the opening, and has a shield partly protruding to the outside of the envelope ,
The shield, transmission radiation tube, wherein the benzalkonium shielding a portion of the target is collected by either et emission radiation. The transmission radiation tube according to claim 1 , wherein the shield shields radiation scattered from the target toward the electron emission source . The shield includes a first shield disposed on the electron emission source side with respect to the target portion, and a second shield disposed on a side facing the first shield with respect to the target portion. The body,
The first shield has a first passage formed by the first shield inside the envelope;
The second shield has a second passage formed by the second shield outside the envelope;
The electrons emitted from the electron emission source are irradiated to the target unit through the first passage,
The transmission radiation tube according to claim 1, wherein the radiation emitted from the target unit is radiated to the outside of the envelope through the second passage. The transmission radiation tube according to claim 3 , wherein the opening diameter of the second passage gradually increases toward the outside. The first shielding body and the second shielding body are arranged so that the center of the opening of the first passage and the center of the opening of the second passage are arranged on the same straight line. The transmission radiation tube according to claim 3 or 4 , characterized by the above. The transmission radiation tube according to any one of claims 1 to 5 , wherein the target is made of tungsten. A storage container storing therein the transmission radiation tube according to claim 1;
A cooling medium filled between the storage container and the transmission radiation tube;
A radiation generating apparatus, wherein a portion of the shield projecting outside the envelope is in contact with the cooling medium. The radiation generating apparatus according to claim 7 , wherein the cooling medium is an electrical insulating oil. It further has voltage control means for setting the voltage of the target unit to + (Va−α) [V], the voltage of the electron emission source to −α [V] (where Va>α> 0), respectively. The radiation generator according to claim 7 . A radiation generator according to any one of claims 7 to 9 , a radiation detector that detects radiation emitted from the radiation generator and transmitted through a subject, the radiation generator, and the radiation detector A radiation imaging apparatus comprising: a control unit that controls

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