JP4886760B2 - X-ray equipment - Google Patents

Description

  The present invention relates to an X-ray apparatus that generates X-rays by irradiating a target with an electron beam.

  Conventionally, as an X-ray apparatus that generates this type of X-ray, there is a transmission type microfocus X-ray generation tube used for the microfocus X-ray generation apparatus.

  In the case of the reflective microfocus X-ray generation tube, there is no problem of the lifetime in most cases. On the other hand, the transmission-type microfocus X-ray tube generating tube is small and can be disposed close to the inspection object and the X-ray source. Therefore, the magnification can be increased and an ultra-precise X-ray transmission inspection can be performed. However, in the case of a transmission type microfocus X-ray generation tube, an X-ray is generated by irradiating a target with an electron beam. Since most of the energy becomes heat, the target deteriorates, and the target has a problem of life. Therefore, in the transmission type microfocus X-ray generator, it is necessary to periodically replace the target as an open type, and the structure becomes complicated and large and expensive. In addition, since it is necessary to adopt such a structure, it is difficult to make the distance from the target as the X-ray source to the measurement object, and the performance of the magnification rate of the X-ray inspection is limited.

  In recent years, a transparent microfocus X-ray generation tube having a small size and a simple structure has been developed. However, the lifetime is shortened due to thermal degradation of the target, and the focus size is 5 μm and 2 W. The degree of input is the target limit.

Therefore, for example, as a structure for extending the life of the target, a cathode that irradiates an electron beam in a vacuum vessel and a target that generates an X-ray by irradiating the electron beam from the cathode are disposed, and this target is placed on the axis of the electron beam It is arranged to be movable in a direction perpendicular to the direction, this target is moved by a magnet outside the vacuum vessel, the position of the target irradiated with the electron beam is changed, and the target electron beam is irradiated. When the position reaches the end of its life, it is known to restore the initial performance by moving the target with a magnet (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 3-22331 (page 2 to page 3, FIG. 1)

  However, when the target in the vacuum vessel is moved as described above, there is a problem that the structure itself becomes complicated, such as making the target itself movable and arranging a magnet for moving the target.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an X-ray apparatus that has a simple configuration and has a long life.

The present invention provides a vacuum container, a cathode disposed in the vacuum container and irradiating an electron beam, and disposed in the vacuum container, a positive voltage is applied to the cathode, and the electron beam is irradiated. An electrostatic type electrode that is disposed between a target that generates X-rays and the target and the cathode in the vacuum vessel, and to which a negative voltage smaller than the voltage applied to the target is applied. A first focusing electrode, and is disposed between the first focusing electrode and the target, and has a value larger than a voltage value applied to the first focusing electrode and smaller than a voltage value applied to the target. An electrostatic type second focusing electrode to which a positive voltage is applied, a distance between the first focusing electrode and the cathode, and the first focusing electrode and the first between the second focusing electrode and the target. Wider than the distance between the two focusing electrodes Are arranged intervals by spaced apart from the second focusing electrode, wherein the positive voltage of a value smaller than the value of the voltage applied to increase the target than the value of the first focusing electrode to the applied voltage is applied An electrostatic type third focusing electrode and a permanent magnet attached to the outside of the vacuum vessel are provided, and the center position along the axial direction of the electron beam is located between the third focusing electrode and the cathode, And a magnet portion that moves the irradiation position of the irradiated electron beam by the permanent magnet, and even if the irradiation position where the X-rays are generated by irradiating the electron beam reaches the end of its life, Since the irradiation position of the electron beam can be moved by a permanent magnet attached to the position outside the vacuum envelope of the magnet part, the initial performance can be improved by changing the irradiation position to a position where the target life is not reached. Rukoto can, together attained the life of, the center position in the axial direction of the electron beam of the magnet unit is located on the most target side of the cathode and the first to third focusing electrodes of the electrostatic By being positioned between the three focusing electrodes, a spin due to a magnetic field is applied in the initial stage of electrons emitted from the cathode, thereby minimizing distortion and blurring of the focal shape.

According to the present invention, even when the irradiation position where the X-rays are generated by irradiating the electron beam reaches the end of its life, the irradiation position of the electron beam is changed by the permanent magnet of the magnet portion located outside the vacuum container. Since it can be moved to a position, the initial performance can be obtained by changing the irradiation position to a position where the life of the target is not reached, the life can be extended, and the axis of the electron beam of the magnet part The center position along the direction is located between the cathode and the third focusing electrode located closest to the target among the electrostatic first to third focusing electrodes, so that the electrons emitted from the cathode By applying a spin due to a magnetic field in the initial stage, distortion and blurring of the focal shape can be minimized.

  Hereinafter, a transmission type microfocus X-ray tube of a microfocus X-ray apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, reference numeral 1 denotes a transmission type microfocus X-ray generation tube of a microfocus X-ray generation device which is a vacuum tube as an X-ray device. The microfocus X-ray generation tube 1 is vacuum-tight. A vacuum envelope 2 is provided as a vacuum container to be maintained, and the vacuum envelope 2 has a cylindrical tube portion 3, and an exhaust pipe attachment for attaching an exhaust pipe for vacuum exhaust to the cylindrical portion 3 Part 4 is formed. The exhaust pipe is sealed after being evacuated.

  An annular flange-shaped tube mounting bracket 5 is attached to the proximal end side of the cylindrical portion 3. The tube mounting bracket 5 is formed with a plurality of screw insertion holes 6 through which screws and the like for fixing the tube mounting bracket 5 are inserted. Cooling oil is provided on the back side of the tube mounting bracket 5. A mounting groove 7 for mounting an O-ring (not shown) that prevents leakage along the ball mounting bracket 5 is formed over the entire circumference.

  Further, a double-cylindrical glass container 11 whose base end side is closed is located on the back side of the tube fitting 5 that is the base end side of the cylindrical portion 3, and the glass container 11 is open. A metallic annular outer cylinder connector 12 is integrally attached to the tip of the outer cylinder, for example, by being welded to the glass container 11, and the outer cylinder connector 12 is welded to the tube fitting 5. And hermetically sealed. Further, a closing portion 13 for closing the inner cylinder is formed on the inner peripheral side of the inner cylinder of the glass container 11. Further, a metallic annular inner cylinder connector 14 is integrally attached to the tip of the inner cylinder of the glass container 11 by being welded to the glass container 11, and is attached to the tip of the inner cylinder connector 14. Is connected to a support 15.

  An annular plate holder 16 is attached to the tip of the support 15, a cathode holder 17 is attached inside the holder 16, and a cathode 18 is attached to the cathode holder 17. The cathode 18 incorporates a filament (not shown) and heats the filament to become thermoelectrons to emit an electron beam. Further, the cathode 18 has a filament 21, and a filament terminal 22 that penetrates the closed portion 13 of the glass container 11 in an airtight state is connected to the filament 21, and from the filament terminal 22 through the filament 21 from the outside Power is supplied to the cathode 18.

  The holding body 16 is attached with an electrostatic focusing electrode body 23 serving as an integrally formed electron lens, and the focusing electrode body 23 and the cathode 18 form a microfocus electron gun. In this focusing electrode body 23, a rod-shaped electrode holding insulator 24 is attached to a holding body 16, and this electrode holding insulator 24 is a first focusing electrode 25 for applying a voltage of minus several hundreds V from the cathode side, and a plus number. A second focusing electrode 26 for applying a voltage of kV and a third focusing electrode 27 for applying a voltage of plus several kV through a slightly larger gap are sequentially arranged according to a predetermined dimension. Further, an electron beam insertion hole (not shown) is formed at the center of the first focusing electrode 25 and the second focusing electrode 26, and the first focusing electrode 25 and the second focusing electrode 26 are formed at the center of the third focusing electrode 27. An electron beam insertion hole 28 that linearly communicates with an extension axis of the electron beam insertion hole is linearly disposed along the irradiation direction of the electron beam.

  On the other hand, a lid body 31 whose diameter decreases toward the distal end is attached to the distal end side of the cylindrical portion 3, and an attachment portion 32 is formed at the distal end of the lid body 31. The target holding body 34 is held in the mounting portion 32, the target holding body 34 has an opening 35, and a transmission type target 36 serving as a window is formed in the target holding body 34 of the vacuum envelope 2. It is airtightly attached as part. The target 36 is disposed to face the cathode 18 through the electron beam insertion hole of the first focusing electrode 25, the electron beam insertion hole of the second focusing electrode 26, and the electron beam insertion hole 28 of the third focusing electrode 27. ing. The target 36 is made of a beryllium thin plate or an Al substrate, which is an X-ray transmission window with a thickness of several hundreds of μm and has a small X-ray transmission loss for the purpose of a vacuum-tight partition wall. For example, a thin film serving as an X-ray source such as tungsten having excellent X-ray generation performance of about 5 μm to 10 μm is formed. A beryllium thin plate or the like is selected as a material having a small X-ray transmission loss for the purpose of a vacuum-tight partition. The thickness of the tungsten thin film is designed based on the penetration depth of the electron beam and the amount of attenuation of the generated X-ray.

  Further, as shown in FIG. 2, a magnet portion 40 is attached to the outer periphery of the vacuum envelope 2, and the magnet portion 40 is connected to the vacuum envelope 2 via a gap, for example, an annular magnet holder 41. The poles of the permanent magnets 42 and 42, which are attached manually and freely rotate, form a magnetic flux having a strength of about 10 to 50 gauss in the path through which the electron beam passes and face along the radial direction of the magnet holder 41, are different. It is arranged with directivity in the opposed state. Further, around the vacuum envelope 2, a digging structure is adopted, and for example, conical locking holes 43 are formed at 20 locations every 18 °. On the other hand, as shown in FIG. 3, the magnet holder 41 is formed with four hole grooves 44 along the radial direction every 90 °, and a ball pushing spring 45 is inserted into the hole groove 44, and this ball A positioning ball 46 of a size that can be inserted into the hole groove 44 is located at the tip of the push spring 45. The ball 46 of the magnet holder 41 is urged toward the center of the vacuum envelope 2 by the ball pressing spring 45 and is locked in the locking hole 43 of the vacuum envelope 2, so that the ball 46 is brought into a predetermined position. Positioned. Note that the line connecting the circumferential center of the permanent magnet 42 facing the center passes through the center of the target 36, and the position of the permanent magnet 42 along the axial direction of the electron beam is centered at the tip of the cathode 18 or closest to the target 36. It is located at a position included in L between the third focusing electrodes 27 located.

  Next, the operation of the above embodiment will be described.

  First, when a voltage is applied to the cathode 18, the filament is heated to become thermoelectrons to emit an electron beam, and the target 36 is irradiated through the focusing electrode body 23. Specifically, the electron beam emitted from the cathode 18 is focused by an electron lens having a voltage of minus several hundreds V of the first focusing electrode 25, and a plus number kV of the second focusing electrode 26 and the third focusing electrode 27. It is further focused by the voltage, applied to the target 36 at a voltage of about 100 kV, and becomes an electron beam having a diameter of 2 μm to 5 μm, for example, about 5 μm, and forms an image on the vacuum side of the target 36.

  Further, due to the magnetic field formed by the permanent magnet 42 of the magnet unit 40, the electron beam forms an image at a position slightly displaced from the center of the target 36 according to the position of the permanent magnet 42.

  Then, the electron beam focused on the vacuum side surface of the target 36 collides with the tungsten thin film of the target 36 and becomes X-rays. The X-rays pass through the beryllium thin plate and are taken out to the outside. Used as a radiation source.

  However, since energy of several watts is input to a focal diameter of several micrometers, the film formation surface of an X-ray source such as a tungsten thin film becomes high temperature and deteriorates, and the amount of X-ray generation gradually decreases with time. Therefore, the lifetime of an X-ray source such as a tungsten thin film becomes a lifetime in the order of several hundred hours to 1000 hours.

  Therefore, the magnet holder 41 of the magnet unit 40 is manually operated at an angle of 18 ° or around the center of the vacuum envelope 2 for several hundred hours, for example, about 300 to 800 hours, which is the life of an X-ray source such as a tungsten thin film. The ball 46 is accommodated in the hole groove 44 against the urging force of the ball pressing spring 45, and the ball 46 of the magnet holder 41 is again moved by the ball pressing spring 45 at the position of the adjacent locking hole 43. Is urged toward the center of the vacuum envelope 2 and locked in the locking hole 43 of the vacuum envelope 2, thereby being positioned at a predetermined position moved by 18 °. Then, the rotation of the magnet holder 41 changes the angle in the radial direction of the magnetic field formed by the permanent magnet 42, so that the electron beam differs from the previously irradiated position of the target 36 according to the position of the permanent magnet 42. For example, the image is formed at a position shifted from 50 μm to about 100 μm. This change in the imaging position of the electron beam causes the electron beam to collide with the position of an X-ray source such as a new tungsten thin film on the target 36, and the X-ray has an X-ray dose equal to the initial performance at the new position of the target 36. appear. In this operation, a total of 20 irradiation positions of the target 36 can be set including the relationship with the direction of the magnetic field according to a predetermined stop position of the magnet holder 41.

  Although the X-ray irradiation position sequentially moves from the initial position by the rotation of the magnet holder 41, the movement is about 0.3 mm or less until the end of the life, and the X-ray irradiation position of the inspection apparatus after irradiation with X-rays No adjustment on the image receiving side is necessary.

  In this way, by rotating the magnet holder 41 sequentially for each specified usage time, the sealed cut-through transmission type microfocus X-ray generating tube 1 having a focal point size of several μm has a lifetime exceeding 10,000 hours. Realized.

  In addition, when the magnetic force of the permanent magnet 42 is increased, the movement distance by one rotation of the magnet holder 41 is increased, and the movement amount can be set and adjusted according to the purpose or the size of the apparatus. In the method in which the focus of electrons is shifted by the permanent magnet 42, it is necessary to form an image on the target 36 without deteriorating the performance of the first focusing electrode 25, the second focusing electrode 26, and the third focusing electrode 27 to be an electron lens. It is.

  Further, the optimum position of the permanent magnet 42 is set based on the relationship between the strength of the permanent magnet 42, the movement of the focal dimension, the dimension of the focal diameter, and the lifetime. If the position of the permanent magnet 42 along the axial direction of the electron beam is between the first focusing electrode 25 and the target 36, the focal position as the irradiation position can be moved. If it is between the focusing electrode 27 and the target 36, the focal point size becomes non-uniform or the surroundings are blurred as the magnet holder 41 rotates, and the performance may deteriorate. Therefore, the position of the permanent magnet 42 along the axial direction of the electron beam is between the cathode 18 and the third focusing electrode 27, so that a spin due to a magnetic field is applied at the initial stage of electrons emitted from the cathode 18. The distortion and blurring of the focus shape can be minimized.

  Next, another embodiment will be described with reference to FIG.

  In the embodiment shown in FIG. 4, an annular external fitting 51 having an L-shaped cross section is fitted to the vacuum envelope 2 in a conventional one having no locking hole 43 on the outer periphery of the vacuum envelope 2. Then, a locking hole 52 is formed in the external fitting 51 in the same manner as the locking hole 43 in the embodiment shown in FIGS. 1 to 3, and the magnet of the magnet portion 40 is formed around the external fitting 51. A holding body 41 is rotatably attached to the vacuum envelope 2, and the ball 46 of the magnet holding body 41 is locked in the locking hole 52.

  In this way, by attaching the external fitting 51 to the vacuum envelope 2 without modifying the microfocus X-ray generation tube 1 itself, and attaching the magnet holder 41 to the external fitting 51, the conventional magnet portion The microfocus X-ray generation tube 1 that does not have 40 can also move the electron beam, and the life can be extended.

It is II sectional drawing shown in FIG. 2 of the micro focus X-ray generation tube of one embodiment of this invention. It is a top view same as the above. It is sectional drawing which expands and shows the locking hole of a vacuum envelope same as the above. It is sectional drawing which expands and shows the external metal fitting of the microfocus X-ray generation tube of other embodiment same as the above.

Explanation of symbols

1 Microfocus X-ray generator tube as an X-ray device
2 Vacuum envelope as a vacuum vessel
18 Cathode
25 First focusing electrode
26 Second focusing electrode
27 Third focusing electrode
36 targets
40 Magnet part
42 Permanent magnet

Claims (3)

A vacuum vessel;
A cathode disposed in the vacuum vessel and irradiating an electron beam;
A target disposed in the vacuum vessel, applied with a positive voltage to the cathode, and irradiated with the electron beam to generate X-rays;
An electrostatic first focusing electrode disposed between the target and the cathode in the vacuum vessel, to which a negative voltage smaller than the voltage applied to the target is applied;
A positive voltage which is disposed between the first focusing electrode and the target and which is larger than the voltage applied to the first focusing electrode and smaller than the voltage applied to the target is applied. An electrostatic second focusing electrode;
Between the second focusing electrode and the target, the distance from the second focusing electrode is wider than the distance between the first focusing electrode and the cathode and the distance between the first focusing electrode and the second focusing electrode. An electrostatic third focusing electrode that is spaced apart and applied with a positive voltage that is larger than the voltage applied to the first focusing electrode and smaller than the voltage applied to the target. When,
A permanent magnet attached to the outside of the vacuum vessel, the center position along the axial direction of the electron beam is located between the third focusing electrode and the cathode, and the irradiation position of the electron beam irradiated to the target is An X-ray apparatus comprising: a magnet unit that is moved by a permanent magnet. The X-ray apparatus according to claim 1, wherein the magnet portion is rotatable around the axial direction of the electron beam, and the irradiation position of the electron beam is changed by the rotation. The X-ray apparatus according to claim 2, wherein the magnet portions are disposed to face each other with the electron beam interposed therebetween.

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