JP6537679B2 - Radiation tube, radiation source and radiation inspection apparatus - Google Patents

Description

  The present invention relates to a nondestructive X-ray inspection apparatus in the field of industrial equipment, a radiation tube applicable to diagnostic applications in the field of medical equipment, and a radiation inspection apparatus using the same.

  The radiation tube generates a radiation such as X-ray by applying a high voltage between the cathode and the anode and irradiating the target with electrons emitted from the electron source. The radiation tube is applied, for example, as an X-ray source to an inspection apparatus that inspects foreign matter on an article.

  Patent Document 1 discloses an X-ray inspection apparatus including an X-ray source that irradiates an article with X-rays, a slit forming member that adjusts an irradiation range of the X-rays, and a transport unit that transports the article.

JP, 2013-88199, A

  The configuration of a conventional X-ray inspection apparatus 301 is shown in FIG. The X-ray tube 306 irradiates the article 307 with X-rays while the article 307 is transported by the transport device 304, and the X-ray transmitted through the article 307 is detected by the X-ray line sensor 305. The irradiation range of the cone beam X-ray 308 emitted from the X-ray tube 302 is adjusted by the slit forming member 306 having a slit extending in the direction orthogonal to the conveyance direction of the article 307. The dashed arrows indicate X-rays scattered from the slit forming member 306. An X-ray shielding wall 309 is provided to shield X-rays from the inspection space.

  However, since the X-ray focal position (target) and the position of the slit are apart, scattering of X-rays between the target and the slit occurs in a wide range. Therefore, there is a problem that the entire apparatus becomes large by wide-ranging the area where the X-ray shielding wall is provided.

The radiation tube of the present invention comprises: a cathode having an electron source emitting electrons; an anode having a target portion generating radiation by irradiation of electrons; and a tubular front shield for holding the target portion; an insulating tube which is connected to said anode and Oite the cathode at both ends, a radiation tube having,
The target unit has a target layer and a substrate supporting the target layer, and the front shield is a part of the radiation emitted from the side of the target unit opposite to the electron source. slit-like opening for forming the radiation fan beam is passed is provided, wherein the short side direction of the opening width of the side of the target portion of the front shield Ri der less in diameter before Symbol target layer, the front shielding The longitudinal opening width at the side of the target portion of the body is characterized in that it is larger than the diameter of the target layer.

  According to the present invention, radiation is emitted as a fan beam suitable for application to an inspection apparatus in a simplified configuration by using a radiation tube in which a front shield having a slit-like opening is formed. . Further, since unnecessary radiation in the vicinity of the target portion can be effectively shielded, scattering of radiation between the target portion and the slit portion can be suppressed. As a result, scattering of radiation out of the examination space is also suppressed, and a safe and miniaturized radiation examination apparatus is provided.

It is a schematic diagram which shows the radiation source which concerns on 1st Embodiment. It is a schematic diagram which shows the front shield and target part which concern on 1st Embodiment. It is a schematic diagram which shows the front shield which concerns on 2nd Embodiment. It is a schematic diagram for demonstrating the opening of the back shield which concerns on 1st Embodiment. It is a schematic diagram which shows the radiation source which concerns on 3rd Embodiment. It is a schematic diagram which shows the back shield which concerns on 3rd Embodiment. It is a block diagram of a radiation inspection device concerning a 4th embodiment. FIG. 7 is a schematic view showing a radiation inspection apparatus according to a second embodiment. FIG. 8 is a schematic view showing a radiation inspection apparatus according to a third embodiment. It is a schematic diagram which shows the conventional radiation inspection apparatus.

  Hereinafter, embodiments of the present invention will be described using the drawings. As radiation used in the present invention, X-rays are suitable, but radiation such as neutrons and protons may also be applied.

First Embodiment
FIG. 1 is a schematic view of a radiation source according to the present embodiment. The radiation source 81 comprises a radiation pipe 88 disposed in the storage container and a high pressure generating unit 82, and the remaining space in the storage container is filled with the insulating oil 87. The radiation tube 88 has an envelope in which one end of the cylindrical insulating tube 83 and the cathode 84 are joined and the other end and the anode 85 are joined. The high voltage generator 82 applies a desired voltage to the cathode 84 and the anode 85. Electrons emitted from the electron source 86 constituting the cathode 84 are accelerated by the acceleration voltage (a cathode / anode voltage) and collide with the target portion 12. Among the radiation generated by the collision of the electrons, the radiation emitted from the side opposite to the surface on which the electrons of the target unit 12 collide is emitted to the outside of the envelope. That is, the radiation tube 88 used in the present embodiment is a transmission type.

  The front shield 21 is connected to the opening of the envelope (portion of the anode flange) and shields part of the radiation emitted from the target unit 12. That is, the radiation generated from the radiation tube 88 is emitted as a fan beam whose radiation region is fan-shaped by the front shield 21 having the slit-like (rectangular) opening 25 connected to the target unit 12.

  For the insulating pipe 83, a ceramic material such as alumina or an electrically insulating material such as glass is used. Monel (US registered trademark: MONEL, Ni-Cu based alloy), Inconel (US registered trademark: INCONEL, superalloy of Ni based), Kovar (US registered trademark: KOVAR, Fe) It consists of metals, such as low linear expansion coefficient alloys, such as-alloy of Ni-Co type | system | group, and stainless steel.

  The electron source 86 is disposed inside the envelope so as to face the target portion 12 constituting the anode 85. The electron source 86 includes a tungsten filament, a hot cathode such as an impregnated cathode, or a cold cathode such as a carbon nanotube. The electron source 86 is provided with an extraction electrode and a lens electrode for controlling the electrons to reach a desired position and range of the target unit 12.

  Fig.2 (a) is a schematic diagram of the front shield 21, a front view, A-A 'sectional drawing, B-B' sectional drawing. The front shield 21 has a slit-like opening (radiation passage hole) 25 and the ratio of the longitudinal width (L1) of the opening 25 to the short width (L2) is about 2: 1 to 50: 1, Desirably, it is about 4: 1 to 20: 1.

  The target portion 12 shown in FIG. 2B is formed in a circular shape on the surface of the disk-shaped base 18 and the electron source side of the base 18 (opposite to the connecting surface with the front shield 21). And a target film 19. The base 18 preferably supports the target film 19 and has a strength capable of holding a vacuum in the envelope. Further, it is preferable that the thermal conductivity is high so that absorption of radiation generated in the target film 19 is small and heat generated in the target film 19 can be dissipated quickly. For example, diamond, silicon carbide, aluminum nitride or the like can be used.

  The material constituting the target film 19 preferably has a high melting point and a high radiation generation efficiency. For example, tungsten, tantalum, molybdenum or the like can be used. In order to reduce absorption generated when the generated radiation passes through the target film 19, the thickness of the target film 19 is preferably about 1 μm to 100 μm. Similarly, the thickness of the substrate 18 is preferably 500 μm to 5 mm.

  The front shield 21 preferably has a high radiation shielding ability and a high thermal conductivity so that the heat generated in the target unit 12 can be dissipated to the outside, preferably a metal such as copper, iron, nickel, tungsten, lead or the like or And alloys containing them as their main components, and composite materials thereof. Further, since a part of the front shield 21 is disposed so as to protrude outside the envelope, the heat generated in the target unit 12 is rapidly dissipated to the outside through the front shield 21.

  FIG. 4A is a schematic view showing the positional relationship between the slit-like opening 25 of the front shield 21 and the diameter of the electron beam irradiated to the target film 19, that is, the focal point 23. In FIG. The focal diameter d1, the diameter D1 of the target film 19, and the short width L2 of the opening 25 satisfy d1 <L2 ≦ D1 (the short width is larger than the focal diameter and smaller than or equal to the diameter of the target film). With such a relationship, radiation emitted in the form of a cone beam at the focal point 23 can be effectively shaped into fan beam radiation, and radiation in unnecessary directions can be shielded effectively.

Second Embodiment
FIG. 3: is a schematic diagram of the front shield 21 of this embodiment, and is a front view, an AA 'sectional view, and a BB' sectional view. The slit-like opening 25 is tapered such that the longitudinal width widens from the target portion side to the outer side. By increasing the thickness in the vicinity of the target portion where the amount of radiation to be shielded is large, the size of the front shield 21 necessary for shielding unnecessary radiation can be reduced. Further, the taper need not be a straight taper as long as the target side in the longitudinal direction of the opening 25 is narrower than the radiation side, or may be a stepped structure or the like. The longitudinal width of the end on the target portion side is larger than the focal diameter, preferably the same as the opening diameter of the rear shield 64 described later, and the longitudinal width and the short width are equal (L3 = L2) Become.

  FIG. 4 (b) is a schematic view showing the arrangement relationship between the opening 25 of the front shield 21 and the focal point 23. The focal diameter d1, the diameter D1 of the target film 19, and the short width L2 of the opening 25 satisfy d1 <L2 ≦ D1. With this relationship, radiation emitted in the form of a cone beam at the focal point 23 can be more effectively shaped into fan beam radiation, and radiation in unnecessary directions can be shielded effectively.

Third Embodiment
FIG. 5 is a schematic view of a radiation source according to the present embodiment. The configuration except that the rear shield 64 is disposed is the same as that of the first embodiment or the second embodiment.

  Radiation and reflected electrons generated on the cathode side from the target unit 12 are shielded by the rear shield 64. The rear shield 64 is made of the same material as the front shield 21. Also, the front shield 21 and the rear shield 64 have a two-layer configuration in which a material (for example, tungsten) having a high shielding effect is disposed inside and a material (for example, copper) having a high thermal conductivity is disposed outside. Good.

  FIG. 6 is a schematic view of the rear shield 64, and is a front view, an A-A 'sectional view, and a B-B' sectional view. As shown in FIG. 6A, the rear shield 64 has a cylindrical opening (electron passing hole) 66, and is connected to the target unit 12. The target portion 12 is housed and joined in a notch formed at the end of the rear shield 64. The front shield 21, the target unit 12, and the rear shield 64 are integrally joined to the opening of the anode flange.

  Also, as shown in FIG. 6 (b), the opening 66 may be tapered. With this structure, shielding is efficiently performed in the vicinity of the target portion having a large amount of unnecessary radiation, and electrons are prevented from colliding with the side surface of the cathode of the rear shield to prevent generation of unnecessary radiation. Further, if the target portion side of the opening 66 of the rear shield is narrower than the cathode side, the taper does not have to be a straight taper or may be a step-like structure or the like.

Fourth Embodiment
Next, a radiation inspection apparatus of the present embodiment will be described using FIG. The system control unit 502 cooperatively controls the radiation tube 88, the radiation detection unit 501, and the transport drive unit 505. As the radiation tube 88, those described in the first to third embodiments are used. The radiation tube control unit 504 outputs various control signals to the radiation source 81 under the control of the system control unit 502. The control signal controls the emission of radiation emitted from the radiation tube 88. The conveyance drive unit 505 drives the article placement unit 506 to pass the inspection object 509 across the space between the radiation tube 88 and the detector 507. Radiation emitted from the radiation tube 88 is transmitted through the article 509 and detected by the detector 507. The detector 507 converts the detected radiation into an electrical signal and outputs the electrical signal to the signal processing circuit 508. The signal processing circuit 508 performs predetermined signal processing on the electrical signal under the control of the system control unit 502, and outputs the processed electrical signal to the system control unit 502. The system control unit 502 generates an image signal based on the processed signal and causes the display unit 503 to display an image of the inside of the article based on the image signal. Furthermore, the system control unit 502 determines the presence or absence of a foreign substance included in the inside of the article based on the video information. The determination result is displayed on the display device 503. The articles 509 for which the inspection has been completed are conveyed by the article placement unit 506 driven by the conveyance drive device 505 to different predetermined places according to the determination result. The article 509 is continuously transported at a predetermined interval, and radiation is emitted from the radiation tube 88 in synchronization with the timing when the article 509 enters the irradiation range of the radiation tube 88 and the timing when it leaves the irradiation range.

Example 1
One embodiment of the radiation tube of the present invention will be described with reference to FIGS. 4, 5 and 6. FIG. The radiation tube 88 has a cathode 84 bonded to one end of an alumina insulating tube 83 and an anode 85 connected to the other end to form an envelope. The material of the cathode and the flange of the anode is Kovar. The anode 85 includes a target portion 12, a front shield 21, and a rear shield 64. The target portion 12 is formed of tungsten of 3 mm × t 5 μm on the cathode side of the diamond substrate of φ 5 mm × t 2 mm. The front shield 21 is copper and has a substantially cylindrical shape of φ20 mm × t10 mm. The slit-like opening 25 is tapered such that the radial length L1 is 10 mm, the target length L3 is 2.5 mm, and the short width L2 is 2.5 mm. Further, the target diameter D1 is 3 mm, the focal diameter d1 is 2 mm, and the relationship of d1 <L2 ≦ D1 is satisfied. The rear shield 64 is copper, and is provided with a cylindrical opening 66 of φ2 mm in a substantially cylindrical shape of φ20 mm × t10 mm. A digging of approximately the same size as the target portion 12 is made in the rear shield 64, and the target portion 12 is inserted therein and brazed with silver solder. Furthermore, the side where the opening 25 of the front shield 21 is smaller is brazed to the connection surface of the rear shield 64 with silver solder.

  The high voltage generating unit 82 includes a Cockcroft circuit, and applies a voltage of about 40 kV to about 120 kV according to the application of the radiation. The electron source 86 is an impregnated cathode. The generated radiation is converted by the front shield 21 into a fan beam of a proper shape and emitted to the outside. Also, the radiation generated on the cathode side was effectively shielded by the rear shield 64.

(Example 2)
An embodiment of the radiation inspection apparatus of the present invention will be described. FIG. 8 is a front view and a side view of a schematic sectional view showing the configuration of the radiation inspection apparatus of the present embodiment. The radiation inspection apparatus 101 performs a foreign substance inspection using the radiation irradiated from the radiation tube 88 while transporting the article 107 by the transport unit 104. The transport unit 104 transports the article 107 in the left-right direction by drive motors at both ends with a belt conveyor. The opening 25 of the front shield 21 is formed in a direction in which the longitudinal direction intersects, preferably is orthogonal to, the conveyance direction of the conveyance device 104. As a result, the radiation emitted from the radiation tube 88 has a fan angle that is larger than the size of the article 107 in the direction orthogonal to the transport direction, and an irradiation range smaller than the size of the article in the transport direction. And a radiation angle of The radiation transmitted through the article 107 is detected by a line sensor 105 which is a detector.

  The radiation inspection apparatus 101 according to the present embodiment shields unnecessary radiation with the front shielding member 21. Therefore, there is no scattered radiation from the slit forming member 306 as shown in the conventional example of FIG. Therefore, even if the radiation shielding wall 109 is simplified, the scattered radiation can be sufficiently shielded.

(Example 3)
Another embodiment of the radiation inspection apparatus of the present invention will be described. FIG. 9: is the front view and side view of a cross-sectional schematic diagram which shows the structure of the radiation inspection apparatus of a present Example. The second embodiment is the same as the second embodiment except that the slit portion 206 is disposed between the front shield 21 and the article 107. The slit portion 206 is made of tungsten, and a slit-like opening (slit) is formed in the direction orthogonal to the conveyance direction of the conveyance portion 104. The longitudinal direction of the slit coincides with the longitudinal direction of the opening 25 of the front shield 21.

  The radiation range of the fan beam emitted from the radiation tube 88 is maintained in the direction orthogonal to the transport direction by passing through the slit portion 206, and the fan beam whose radiation range is further reduced in the transport direction It becomes.

  According to the present embodiment, since the resolution in the transport direction is increased, it is possible to perform inspection with higher accuracy. In addition, since the amount of radiation scattered by the slit portion 206 is small compared to the conventional radiation inspection apparatus, the radiation shielding wall 109 is simplified and the entire apparatus is miniaturized.

86 electron source 12 target portion 21 front shield 25 slit-like aperture 18 substrate 19 target film 23 focus

Claims (13)

A cathode having an electron source for emitting electrons, an anode and a front shield tubular holding the target portion and the target section for generating a radiation by the irradiation of the electron, Oite the cathode at both ends of the tube axis direction A radiation tube comprising: and an insulating tube connected to the anode;
The target unit has a target layer and a substrate supporting the target layer, and the front shield is a part of the radiation emitted from the side of the target unit opposite to the electron source. slit-like opening for forming the radiation fan beam is passed is provided, wherein the short side direction of the opening width of the side of the target portion of the front shield Ri der less in diameter before Symbol target layer, the front shielding A radiation tube, characterized in that the longitudinal opening width at the side of the target part of the body is larger than the diameter of the target layer. Opening width of the lateral direction on the side of the target section, the radiation according to claim 1, wherein the greater than the diameter of the electron beam point focused that is formed on the target layer by irradiation of from the electron source tube. The longitudinal direction of the opening width of the side of the target section, according to claim 1 or 2 being greater than the diameter of the electron beam point focused that is formed on the target layer by irradiation of from the electron source Radiation tube. The opening, said longitudinal opening width defining a fan angle of the fan-beam, the lateral direction of the aperture width which defines the radiation angle of the longitudinal direction of a width less than the opening width the fan beam and The radiation tube according to any one of claims 1 to 3, characterized in that   The anode has a flange-shaped anode member connected to the insulating tube and connected to the front shield, and at least a portion of the front shield protrudes outward from the anode member. The radiation tube according to any one of claims 1 to 4, characterized in that: The opening width in the lateral direction on the side opposite to the target portion of the front shield is equal to the opening width in the lateral direction on the side of the target portion of the front shield. The radiation tube of any one of 5. It further comprises a rear shield located opposite to the front shield with respect to the target portion,
The radiation pipe according to any one of claims 1 to 6, wherein the rear shield is provided with an electron passing hole through which electrons emitted from the electron source pass.   The radiation pipe according to any one of claims 1 to 7, wherein the opening has an aspect ratio of 2 or more and 50 or less.   The radiation tube according to claim 8, wherein the opening has an aspect ratio of 4 or more and 20 or less. Insulating oil, and the radiation tube according to any one of claims 1 to 9.
An acceleration voltage circuit for applying an acceleration voltage between the cathode and the anode;
The radiation source characterized in that the acceleration voltage is 40 kV or more and 120 kV or less. A storage container for storing the radiation tube and having an opening;
11. The radiation source according to claim 10, wherein the front shield projects out of the storage container from the opening. A radiation source according to claim 10 or 11;
A transport unit configured to transport an article in a direction intersecting the longitudinal direction of the opening, and a detection unit configured to detect radiation emitted from the radiation tube and transmitted through the article;
A radiation inspection apparatus comprising: It further comprises a slit disposed between the front shield and the article,
The radiation inspection apparatus according to claim 12, wherein a longitudinal direction of the slit formed in the slit portion coincides with a longitudinal direction of the opening.

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