JP2015060731A - Radiation generating tube and radiation generator using the same, radiographic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable radiation generator which can be used for a long time, by preventing dose reduction and quality pollution of radiation due to a bonding material used for bonding a lid to a shield in order to provide the sealed space, in a radiation generating tube provided with a sealed space on the radiation emission side of a target, in order to prevent impairment of a target and a cooling medium due to contact.SOLUTION: On the opening end of a shield 8, at least one of the shield 8 and a lid 9 is provided with a protrusion, and brought into contact with the other. On the outer periphery of the protrusion, the shield 8 and the lid 9 are bonded by disposing a bonding material 10 in a housing part held by the shield 8 and the lid 9.

Description

  The present invention relates to a radiation generating tube applicable to, for example, a medical device, a nondestructive inspection apparatus, and the like, and a radiation generating apparatus and a radiation imaging system including the same.

  A radiation generator is an apparatus that generates radiation from a target by accelerating electrons emitted from an electron emission source to high energy and irradiating the target. At this time, since the target becomes high temperature, a heat dissipation structure for releasing the heat generated in the target is required. Patent Document 1 discloses a transmissive radiation generating tube in which a radiation shield having an opening for emitting radiation from a target to the outside is bonded to a transmissive substrate that supports a target layer. In such a radiation generating tube, at least a part of the shielding body is in contact with the cooling medium, so that heat generated by the target is transmitted to the shielding body and is quickly dissipated by being transmitted to the cooling medium through the shielding body. It has a structure. Furthermore, in order to suppress deterioration of the cooling medium due to heat conduction from the transmission substrate to the cooling medium, a lid substrate is joined to the tip of the opening of the cylindrical shield, and the shield, target, and lid substrate are formed. A technique is disclosed in which the space to be formed is evacuated or filled with gas to form a heat insulating structure.

  Further, in Patent Document 2, in the X-ray apparatus, a lid that transmits X-rays is attached to the concave portion of the structure in which the target material is installed, and the inside of the concave portion is set as a non-oxidizing atmosphere such as vacuum or inert gas, A technique that prevents oxidation of the target is disclosed.

JP 2012-1204099 A US Pat. No. 7,831,021

  As disclosed in Patent Documents 1 and 2, by providing a sealed space on the radiation emission side of the target that is at a high temperature, it is possible to prevent deterioration and alteration of the cooling medium by the target and at the same time prevent oxidation of the target. Can do. However, as in Patent Documents 1 and 2, when a lid is joined to the opening of the shield or the recess, the joining material used for joining may adhere to the radiation transmitting region of the lid. Normally, a material with negative temperature dependence is used as the bonding material, and bonding is performed when the temperature rises to near the melting point due to heat generated during the operation of the radiation generator tube or when the temperature is higher than the melting point. This is because it flows out of the place. As described above, when the bonding material adheres to the radiation transmitting region of the lid, there is a fear that the dose is reduced or the radiation quality is deteriorated due to the absorption of the radiation by the bonding material or the emission of the radiation derived from the bonding material.

  In view of the above problems, an object of the present invention is to provide a radiation generating tube in which a sealed space is provided on the radiation emission side of a target using a shield, and for joining a lid to the shield to form the space. The purpose is to prevent dose reduction and radiation contamination due to the bonding material. Another object of the present invention is to provide a radiation generation apparatus and a radiography system in which dose reduction and radiation quality contamination are prevented by using a radiation generation tube that solves such problems.

A first aspect of the present invention is a transmission target having a radiation-transmissive support substrate and a target layer,
A shield that surrounds the outer periphery of the support substrate and protrudes toward the radiation emitting side;
A lid for closing the open end of the shield,
In the radiation generating tube in which the shield and the lid are bonded by a bonding material having a negative temperature dependency of viscosity,
A contact portion where the shield and the lid contact each other;
The bonding material is disposed in an outer periphery of the abutting portion and in a storage portion sandwiched between the shield and the lid.

  A second aspect of the present invention includes the first radiation generating tube of the present invention, and a storage container that houses the radiation generating tube and has a discharge window for taking out radiation generated from the radiation generating tube, The radiation generator is characterized in that an excess space inside the storage container is filled with an insulating fluid.

According to a third aspect of the present invention, the second radiation generator of the present invention,
A radiation detector that detects radiation emitted from the radiation generator and transmitted through the subject;
A radiation imaging system comprising: a control device that controls the radiation generation device and the radiation detection device in a coordinated manner.

  According to the present invention, by providing a sealed space on the radiation emission side of the target that becomes high in temperature, it is possible to prevent deterioration of the cooling medium and alteration by the target and at the same time prevent oxidation of the target. In addition, by providing a joint portion between the lid and the shield for sealing the space on the outer periphery of the contact portion between the lid and the shield, the lid is prevented from being contaminated by the joining material. Reduced dose and contamination due to materials are prevented. Therefore, according to the present invention, it is possible to provide a highly reliable radiation generating tube that can be used for a long time, and further, using such a radiation generating tube, a highly reliable radiation generating apparatus and radiography. A system is provided.

It is sectional drawing which shows typically the structure of one Embodiment of the radiation generating tube of this invention. FIG. 2 is an enlarged view and a schematic plan view of the anode in FIG. 1. It is a schematic diagram which shows typically the other example of the joining form of the shielding body and cover body in the radiation generating tube of this invention. It is sectional drawing which shows typically the structure of one Embodiment of the radiation generator of this invention. It is a block diagram which shows typically the structure of the radiography apparatus of this invention.

  The configuration of the radiation generating tube of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view schematically showing the configuration of an embodiment of the radiation generating tube of the present invention. 2A is an enlarged view of the anode 4 in FIG. 1, and FIG. 2B is a plan view seen from the opening side with the lid 9 of the anode 4 removed.

  The radiation generating tube 1 of the present invention includes an electron emission source 2 inside an envelope 3 having an opening, and an anode 4 disposed in the opening of the envelope 3. The electrons emitted from the electron emission source 2 are accelerated by a voltage of 30 kV to 150 kV applied to the anode 4 disposed opposite to the electron emission source 2 and transmitted as an electron beam 5 installed on the anode 4. Radiation is generated by colliding with the mold target 7. That is, the radiation generating tube 1 of the present invention is a transmission type radiation generating tube.

  As an electron emission mechanism of the electron emission source 2, any electron emission source capable of controlling the amount of electron emission from the outside of the vacuum vessel may be used, and a hot cathode type electron emission source, a cold cathode type electron emission source, and the like are appropriately applied. Is possible. The electron emission source 2 has a current introduction terminal 6 disposed so as to penetrate the envelope 3, and is electrically connected to an external drive circuit for controlling the amount of electron emission and the on / off state of electron emission. Can be connected to.

  Hereinafter, the configuration of the anode 4 will be described in detail with reference to FIGS. The anode 4 includes a transmission target 7, a shield 8, and a lid 9.

  The target 7 is composed of a radiation-transmissive support substrate 7a and a target layer 7b, and radiation is generated when the target 7 is irradiated with the electron beam 5 emitted from the electron emission source 2.

  The support substrate 7a must have high radiation transparency, good heat conduction, and withstand vacuum sealing. For example, diamond, silicon nitride, silicon carbide, aluminum nitride, graphite, beryllium, or the like can be used. More preferably, diamond, aluminum nitride, or silicon nitride having a radiation transmittance smaller than that of aluminum and a thermal conductivity larger than that of tungsten is desirable. The thickness of the support substrate 7a only needs to satisfy the above-described function, and varies depending on the material, but is preferably 0.3 mm or more and 2 mm or less. In particular, diamond is superior in that it has extremely high thermal conductivity compared to other materials, has high radiation transparency, and can easily maintain a vacuum.

  In general, a metal material having an atomic number of 26 or more can be used for the target layer 7b. More preferably, the higher the thermal conductivity, the higher the melting point. Specifically, a metal material such as tungsten, molybdenum, chromium, copper, cobalt, iron, rhodium, rhenium, or an alloy material thereof can be preferably used. The thickness of the target layer 7b is 1 μm to 15 μm, although the optimum value differs because the penetration depth of the electron beam 5 into the target layer 7b, that is, the radiation generation region differs depending on the acceleration voltage. Integration of the target layer 7b with the support substrate 7a can be performed by means such as sputtering, vapor deposition, screen printing, jet printing, and the like, and can be used as a target. As another method, a target layer 7b having a predetermined thickness can be separately produced by rolling or polishing, and diffusion-bonded to the support substrate 7a under high temperature and high pressure to obtain a target.

  The shield 8 is a member that surrounds the outer periphery of the support substrate 7a of the target 7 and protrudes toward the radiation emission side (outside the radiation generating tube 1). In other words, the shield 8 has a passage opened at both ends, and the target 7 is installed at the end of the passage on the electron emission source 2 side or in the middle. The passage of the shield 8 is a passage for guiding the electron beam 5 to the electron beam irradiation region of the target layer 7b on the electron emission source 2 side with respect to the target 7, and the opposite side transmits radiation to the outside of the radiation generating tube 1. It becomes a passage for guiding.

  The shield 8 is a member that shields radiation, and unnecessary radiation out of the radiation emitted from the target layer 7b is shielded by the shield 8, and only the necessary radiation passes through the above-described passage and passes through the lid 9. The light passes through and is emitted to the outside of the radiation generating tube 1. The shield 8 also has a function as a heat radiator. Heat generated by irradiating the target 7 with the electron beam 5 is radiated to the outside through the shield 8. The material constituting the shield 8 preferably has a high radiation absorption rate from the viewpoint of a radiation shielding member, and preferably has a high thermal conductivity from the viewpoint of a radiator. For example, a metal material such as tantalum or molybdenum can be used. Moreover, it is also possible to comprise by combining these materials having a high radiation absorption rate and materials having a higher thermal conductivity (for example, copper or aluminum).

  The target 7 is placed on the shield 8 by bonding by brazing or the like. In joining, it is important to set the joining state so that the inside of the envelope 3 can be maintained in a vacuum state. The target 7 and the shield 8 are bonded together in a state where airtightness is maintained over the entire circumference at one or both of the side surface portion and the peripheral portion of the support substrate 7a of the target 7.

  In the present invention, by joining the lid 9 to the opening end of the shield 8, damage to the target 7 due to the cause outside the radiation generating tube 1 is suppressed, and at the same time, the cooling medium filled outside the radiation generating tube 1 It is possible to prevent deterioration and alteration due to the target 7 becoming high temperature.

The lid 9 is joined to the opening end of the shield 8, and the shield 8 and the support substrate 7 a of the target 7 form a sealed space. The atmosphere of the sealed space can be appropriately selected from an air atmosphere, a vacuum atmosphere, a non-oxidizing atmosphere such as Ar or N _{2, and the} like as necessary. By providing the lid 9, the target 7 that generates radiation and becomes high temperature can be separated from the external environment of the radiation generating tube 1. Therefore, contamination due to the adhesion of particles to the target 7 can be prevented, and damage to both the cooling medium and the target 7 can be prevented because the target 7 and the cooling medium that are at high temperatures are not in direct contact. As the material of the lid 9, a material having a low radiation absorption rate such as diamond, glass, beryllium, aluminum, silicon nitride, aluminum nitride is preferable. Further, in order to have strength as a substrate and reduce radiation absorption, it is appropriate that the thickness of the lid is about several tens of μm to several mm.

  The shield 8 and the lid 9 are in contact with each other at the abutting portion 11, and the bonding material 10 that joins the shield 8 and the lid 9 is the outer periphery of the corresponding portion 11, and the shield 8 And a storage part sandwiched between the lid body 9. In the present invention, since the bonding material 10 is disposed on the outer periphery of the contact portion 11, the bonding material 10 is formed by the target 7, the shield 8, and the lid 9 even when the bonding material 10 is softened during bonding or operation. It is possible to prevent the bonding material 10 from entering the space.

  In the present invention, as the form of the contact portion 11, at least one of the shielding body 8 and the lid body 9 has a projecting portion projecting toward the other, and the shielding body 8 and the lid body 9 are in contact with each other at the projecting portion. The form which touches is mentioned. For example, in the configuration shown in FIGS. 2A and 3A, the shield 8 is provided with a protrusion 12 that protrudes toward the lid 9, and the tip of the protrusion 12 abuts the lid 9. ing. FIG. 3D shows a form in which a protrusion 13 protruding toward the shield 8 is provided on the lid 9, and the tip of the protrusion 13 is in contact with the shield 8. In these forms, a storage portion for the bonding material 10 sandwiched between the shield 8 and the lid 9 is formed in contact with the side surface of the protruding portion 13.

  In FIG. 3B, the opening end of the shield 8 forms an inclined surface that recedes from the contact portion 11 toward the outside from the outer periphery of the flat contact portion 11. Accordingly, the storage portion of the bonding material 10 has a tapered shape in which the distance from the lid body 9 gradually increases between the outer periphery of the contact portion 11 and the lid body 9 due to the inclined surface. In FIG. 3C, contrary to FIG. 3B, the lid 9 forms an inclined surface that recedes from the contact portion 11 toward the outside from the outer periphery of the flat contact portion 11. Accordingly, the storage portion of the bonding material 10 has a tapered shape in which the distance from the lid body 9 gradually increases between the outer periphery of the contact portion 11 and the lid body 9 due to the inclined surface. In any case, the bonding material 10 is sandwiched between the lid body 9 and the shielding body 8 in the tapered storage portion, and these are favorably bonded. In the present invention, the storage portion sandwiched between the lid body 9 and the shield body 8 means that the wall surfaces of the shield body 8 and the lid body 9 are parallel or inclined in the longitudinal direction of the shield body 8. Say opposite areas.

  2A, 3A, 3C, and 3D, the shield 8 protrudes only from the support substrate 7a of the target 7 toward the radiation emission side, that is, the target 7 is shielded. In this configuration, the opening end on the electron emission source 2 side of the passage of the body 8 is closed. On the other hand, FIG. 3B shows a form in which the shield 8 also protrudes toward the electron emission source 2 and has a path for guiding the electron beam 5 emitted from the electron emission source 2 to the target layer 7b.

  In the present invention, at the opening end of the shield 8, the contact portion 11 is provided on the side close to the opening portion, and the bonding material 10 is disposed outside the contact portion 11. That is, even if the bonding material 10 softens and flows, the bonding material 10 is prevented by the contact portion 11 and cannot enter the opening of the shield 8. Therefore, when the bonding material 10 is applied or operated, the softened bonding material 10 is prevented from adhering to the radiation transmitting region of the lid 9 and causing a decrease in dose and radiation quality contamination.

  As the bonding material 10 used in the present invention, a material having a negative temperature dependency of viscosity such as solder or silver solder is melted by heating and used. When selecting a specific method, the heat resistance such as the material of the lid 9 and the shield 8 and the use environment of the radiation generating tube 1 should be selected in consideration of the heat resistance, adhesive strength, airtightness, etc. Good.

In the present invention, the envelope 3 can be made of glass, ceramics, or the like, and the inside of the radiation generating tube 1 is a space that is evacuated (depressurized). The inside of the radiation generating tube 1 may have a distance between the electron emission source 2 and the target layer 7b that emits radiation as a mean free path so long as the degree of vacuum is such that at least electrons can fly. A vacuum degree of ^-4 Pa or less is applicable. It is possible to appropriately select the electron emission source to be used and the operating temperature, and in the case of a cold cathode type electron emission source, it is more preferable to set the degree of vacuum to 1 × 10 ⁻⁶ Pa or less. preferable. In order to maintain the degree of vacuum in the radiation generating tube 1, a getter (not shown) can be arranged inside the envelope 3 or installed in an auxiliary space (not shown) communicating with the internal space. It is.

  Next, the radiation generator of the present invention will be described. FIG. 4 is a schematic cross-sectional view showing an example of the configuration of the radiation generating apparatus 20 including the radiation generating tube 1 of FIG. As shown in FIG. 4, the radiation generating apparatus of the present invention includes the radiation generating tube 1 of the present invention and a storage container 22 for storing the tube, and an insulating fluid 23 is provided as a cooling medium in a surplus space of the storage container 22. Is satisfied. Further, the storage container 22 is provided with a radiation emission window 21 for taking out the radiation generated from the radiation generating tube 1.

  A drive circuit 24 including a circuit board (not shown) and an insulating transformer may be provided inside the storage container 22. In the case where the drive circuit 24 is provided, for example, a predetermined voltage signal is applied from the drive circuit 24 to the radiation generating tube 1 so that the generation of radiation can be controlled.

  The storage container 22 only needs to have sufficient strength as a container, and is made of metal, plastics material, or the like. The storage container 22 is provided with a discharge window 21 for transmitting radiation and extracting the radiation outside the storage container 22. The radiation emitted from the radiation generating tube 1 is emitted to the outside through the emission window 21. Glass, aluminum, beryllium or the like is used for the discharge window 21.

  The insulating fluid 23 is preferably an insulating liquid having high electrical insulation, high cooling capacity, and little deterioration due to heat. For example, an electrical insulating oil such as silicone oil, transformer oil, and fluorine oil, hydrofluoroether, etc. A fluorine-based insulating liquid or the like can be used.

  Next, an embodiment of a radiation imaging system according to the present invention will be described with reference to FIG.

  As shown in FIG. 5, the radiation generator 20 of the present invention includes a movable aperture unit 25 provided in the radiation emission window 21 as necessary. The movable aperture unit 25 has a function of adjusting the width of the irradiation field of the radiation 26 irradiated from the radiation generator 20. Further, as the movable diaphragm unit 25, a unit to which a function capable of simulating and displaying a radiation irradiation field with visible light can be used.

  The system control device 32 controls the radiation generation device 20 and the radiation detection device 31 in a coordinated manner. The drive circuit 24 outputs various control signals to the radiation generating tube 1 under the control of the system control device 32. The emission state of the radiation 26 emitted from the radiation generator 20 is controlled by this control signal. The radiation 26 emitted from the radiation generator 20 passes through the subject 34 and is detected by the detector 36. The detector 36 converts the detected radiation into an image signal and outputs the image signal to the signal processing unit 35. The signal processing unit 35 performs predetermined signal processing on the image signal under the control of the system control device 32, and outputs the processed image signal to the system control device 32. The system control device 32 outputs a display signal for displaying an image on the display device 33 to the display device 33 based on the processed image signal. The display device 33 displays an image based on the display signal on the screen as a captured image of the subject 34.

  A representative example of radiation is X-rays, and the radiation generator and radiography system of the present invention can be used as an X-ray generator and X-ray imaging system. The X-ray imaging system can be used for nondestructive inspection of industrial products and pathological diagnosis of human bodies and animals.

Example 1
In this example, a radiation generating tube 1 having the configuration shown in FIGS. 1 and 2 was produced. A manufacturing method is shown below.

  In order to fabricate the target 7, a disk-shaped (cylindrical) high-pressure synthetic diamond substrate having a diameter of 5 mm and a thickness of 1 mm was prepared as a support substrate 7a, and organic substances on the surface were previously removed by a UV-ozone asher. A tungsten film having a diameter of 3 mm and a thickness of 6 μm was formed as a target layer 7b on one surface of the diamond substrate by a sputtering method using a metal mask. In this embodiment, the tungsten film pattern is formed by using a metal mask. However, photolithography may be used, or a printing method or the like may be used.

  Subsequently, the shield 8 and the target 7 were integrated by brazing. The shield 8 was made of tungsten as a material and processed into a shape as shown in FIGS. 1B and 1C by machining. Further, a metallized layer containing titanium as an active metal component was formed around the side surface of the target 7 for brazing. The target 7 and a brazing material made of silver, copper, and titanium were set on the holding portion 9 of the shield 8 and were integrated by firing at 850 ° C.

  Next, as shown in FIG. 1A, the target 7 can be irradiated with the electron beam 5 with the shield 8 integrated with the target 7 facing the electron emission source 2 having an impregnated type hot cathode. Were positioned and vacuum sealed. At this time, a getter (not shown) was also arranged in the envelope 3.

  Finally, the lid body 9 was joined to the opening end of the shielding body 8 on the radiation emission side using a solder mainly composed of Sn as the joining material 10. As the lid 9, an aluminum one having a thickness of 1 mm and a diameter of 16 mm was used. The lid 9 and the shield 8 were joined by soldering in a state where the annular protrusion 12 provided at the opening end of the shield 8 was abutted against the lid 9. The protrusion 12 provided on the shield 8 has an outer diameter of 14 mm, an inner diameter of 12 mm, and a height of 2 mm. The inner diameter of the shield 8 on the lid 9 side is also 12 mm. Thereby, the lid 9 and the shield 8 could be joined without the bonding material 10 entering the sealed space surrounded by the lid 9, the shield 8 and the target 7. Further, the distance between the target 7 and the lid body 9 could be determined with high accuracy because the position of the lid body 9 was determined by the position of the protruding portion 12.

  When the spectrum of the radiation of the radiation generating tube 1 produced in this way was measured, the spectrum of Sn or the like contained in the solder of the bonding material 10 was a desired one that was not observed. Moreover, even when it was used continuously for a long time, it had good performance capable of stably generating radiation.

(Example 2)
The radiation generating tube of this example was produced in the same manner as in Example 1 except that the anode part had the shape shown in FIG. The lid 9 has a shape in which the thickness gradually decreases from the position of 14 mm in diameter toward the outside on the shield 8 side, and the cross section in the thickness direction becomes a trapezoid as shown in FIG. The shield 8 has a flat shape at the open end without providing the protrusion 12. Also in this example, like Example 1, the spectrum of Sn or the like contained in the solder was a desired one that was not observed. Moreover, even when it was used continuously for a long time, it had good performance capable of stably generating radiation.

1: radiation generating tube, 7: target, 7a: support substrate, 7b: target layer, 8: shield, 9: lid, 10: bonding material, 11: contact portion, 12, 13: protrusion, 20: Radiation generator, 21: emission window, 22: storage container, 23: insulating fluid, 24: drive circuit, 31: radiation detector, 32: controller, 34: subject,

Claims (6)

A transmissive target having a radiation transmissive support substrate and a target layer;
A shield that surrounds the outer periphery of the support substrate and protrudes toward the radiation emitting side;
A lid for closing the open end of the shield,
In the radiation generating tube in which the shield and the lid are bonded by a bonding material having a negative temperature dependency of viscosity,
A contact portion where the shield and the lid contact each other;
The radiation generating tube according to claim 1, wherein the bonding material is disposed in an outer periphery of the abutting portion and sandwiched between the shielding body and the lid.   The at least one of the said shielding body and the said cover body has a protrusion part which protrudes toward the other, The said shield body and the said cover body are contact | abutting in the said protrusion part. The radiation generating tube as described.   2. The radiation generating tube according to claim 1, wherein the storage portion has a tapered shape in which a distance between the shield and the lid gradually increases from the outer periphery of the contact portion toward the outside. .   The radiation generating tube according to claim 1, wherein the bonding material is solder or silver solder.   A storage container comprising: the radiation generating tube according to any one of claims 1 to 4; and a storage container that stores the radiation generating tube and has a discharge window for taking out radiation generated from the radiation generating tube. A radiation generator characterized in that an extra space inside a container is filled with an insulating fluid. A radiation generator according to claim 5;
A radiation detector that detects radiation emitted from the radiation generator and transmitted through the subject;
A radiation imaging system comprising: a control device that controls the radiation generation device and the radiation detection device in a coordinated manner.

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