JP3950389B2 - X-ray tube - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray tube in which an electron beam is incident on one surface of a target and X-rays are emitted from the other surface of the target.
[0002]
[Prior art]
Conventionally, so-called transmission X-rays in which an electron beam is incident on one surface of a target in a vacuum envelope and X-rays radiated from the other surface of the target are emitted to the outside through an emission window. The tube is known.
[0003]
In such a transmission type X-ray tube, the target is heated by the incidence of the electron beam, and damage to the target is promoted when the target becomes high temperature. For this reason, it is necessary to cool the target in order to suppress damage to the target. For example, JP-A-4-262348 discloses an X-ray tube that cools a target with a cooling member having a water-cooled tube. .
[0004]
[Problems to be solved by the invention]
Such a transmissive X-ray tube may include a deflection coil such as an electromagnetic coil that surrounds the vacuum envelope from the outside in order to deflect an electron beam incident on the target. However, since such a deflection coil generates heat during driving, the deflection characteristics change as the temperature changes. For this reason, a means capable of cooling the target and the deflection coil has been demanded.
[0005]
This invention is made | formed in view of the said subject, and it aims at providing the X-ray tube which can cool a target and a deflection | deviation coil suitably.
[0006]
[Means for Solving the Problems]
In the X-ray tube according to the present invention, an electron beam is incident on one surface of a target in the envelope, and X-rays radiated from the other surface of the target are passed through an emission window provided in the envelope. In an X-ray tube that emits light outside an envelope, a deflection coil that is disposed outside the envelope and deflects an electron beam incident on a target, and is interposed between the deflection coil and the envelope and the deflection coil And a cooling member thermally connected to the target.
[0007]
According to the X-ray tube of the present invention, when the cooling member is cooled, the target and the deflection coil that are thermally connected to the cooling member are cooled. Therefore, even if an electron beam is incident on the target and generates heat, the target can be maintained at a predetermined low temperature, damage to the target can be reduced, and even if the deflection coil generates heat, the deflection coil can be maintained at a predetermined low temperature. The deflection coil characteristic is hardly changed, and the deflection amount of the electron beam can be controlled with high accuracy. Further, since the cooling member is interposed between the deflection coil and the envelope and the deflection coil and the envelope are thermally blocked, the heat generated in the deflection coil is hardly transmitted to the envelope. In addition, deterioration of the X-ray tube and fluctuation of characteristics are reduced.
[0008]
Here, the target is preferably formed on the inner surface of the exit window, and the cooling member is preferably thermally connected to the target through the exit window.
[0009]
As a result, the X-ray tube has a small and simple structure, and the heat of the target is suitably transmitted to the cooling member through the exit window.
[0010]
Further, it is preferable that a heat radiating thin plate having higher thermal conductivity than the light emitting window is provided on the outer surface of the light emitting window, and the heat radiating thin plate is thermally connected to the cooling member.
[0011]
The heat of the target and the emission window is suitably transmitted to the cooling member through the heat dissipation thin plate having higher thermal conductivity than the target, and the heat of the target can be removed more efficiently.
[0012]
The cooling member preferably includes a flow path through which the cooling medium can pass. As a result, the cooling member can be easily and suitably cooled by the passage of the cooling medium.
[0013]
Moreover, it is preferable that an X-ray monitoring means for monitoring the state of X-rays generated from the target is provided, and the cooling member is further thermally connected to the X-ray monitoring means.
[0014]
As a result, the state of the X-rays generated from the target can be monitored in real time. Based on the state of the X-rays, the voltage or current of the electron beam incident on the target can be controlled, or the electron beam can be controlled. The state of X-rays generated from the target can be made constant by, for example, deflecting and moving the incident position of the electron beam. Moreover, since the X-ray monitoring means is cooled by the cooling member, the X-ray monitoring means can be maintained at a predetermined low temperature, and the X-ray monitoring accuracy can be improved.
[0015]
Further, the X-ray monitoring means is preferably installed on the surface side where the electron beam is incident on the target rather than the surface where the X-ray is emitted from the exit window.
[0016]
Thereby, when irradiating X-rays from the exit window to the object to be inspected as compared with the case where the X-ray monitoring means is installed on the X-ray exit direction side with respect to the surface from which the X-ray is emitted at the exit window. X-ray monitoring means do not get in the way. For this reason, it is possible to bring the exit window and the object to be irradiated close to each other, and an X-ray image or the like having a large magnification can be obtained.
[0017]
Further, it is preferable that the X-ray monitoring means is further installed inside the cooling member, whereby the X-ray tube can be further downsized.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of an X-ray tube according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted.
[0019]
FIG. 1 is a schematic configuration diagram showing an X-ray generator 1 including an X-ray tube 10 according to the first embodiment, and FIG. 2 is a cross-sectional view of the X-ray tube 10 in FIG. As shown in FIG. 1, the X-ray generator 1 of the present embodiment mainly includes an X-ray tube 10 that generates an X-ray by irradiating an electron beam to a target member 30, and a predetermined current voltage in the X-ray tube 10. An X-ray power source 12 that generates an electron beam by applying an X-ray, a cooling medium supply device 16 that supplies a cooling medium such as water to the X-ray tube 10 to cool the X-ray tube 10, And a controller 14 connected to the cooling medium supply device 16 and the like for controlling generation of X-rays from the X-ray tube 10 and the like.
[0020]
The cooling medium supply device 16 includes a temperature sensor 16a that measures the temperature of the cooling medium, a cooler 16b that cools the cooling medium to a predetermined low temperature based on the temperature measured by the temperature sensor 16a, and a predetermined low temperature. And a circulation pump 16c that supplies and recovers the cooling medium to the X-ray tube 10.
[0021]
The X-ray tube 10 is a so-called transmission type X-ray tube, and as shown in FIG. 2, a vacuum envelope (outside) having a substantially cylindrical shape extending in a horizontal direction and sealed in a substantially vacuum state. The outer shell is constituted by the (enclosure) 20.
[0022]
One end side in the axial direction of the vacuum envelope 20 (left side in FIG. 2) is an envelope body 21 made of a metal material, and has a horizontal cylindrical shape with one end side closed. On the other hand, the other end side in the axial direction of the vacuum envelope 20 (the right side in FIG. 2) is a bulb 22 formed of an insulator such as glass or ceramics, and has a horizontal cylindrical shape with the other end side closed. It is connected to the envelope body 21.
[0023]
An electron gun 23 that emits an electron beam toward one end along the central axis of the vacuum envelope 20 is disposed in the vacuum envelope 20, and the electron gun 23 is disposed on the other end side of the bulb 22. It is supported by a plurality of pins 24 fixed through. The pin 24 is electrically connected to an electrode, a filament, and the like (not shown) in the electron gun 23, and is also electrically connected to the X-ray power source 12 as shown in FIG. The electron gun 23 is driven by supplying a predetermined current voltage. As shown in FIG. 2, a focus electrode 25 is provided in the vacuum envelope 20 so as to surround the electron gun 23 and converge the electron beam.
[0024]
A flat target member 30 is fitted into a portion where the electron beam from the electron gun 23 is incident at an end portion on one end side of the envelope body 21.
[0025]
This target member 30 forms a target thin film (target) 34 that generates X-rays when an electron beam is incident on a target substrate 32 that easily transmits X-rays and has a predetermined intensity and functions as an exit window. The target thin film 34 faces the electron gun 23 and is fitted into one end of the envelope body 21 so that the target substrate 32 faces the outside of the envelope body 21. Here, for example, beryllium or the like can be used as the target substrate 32, and tungsten or the like can be used as the target thin film 34, for example.
[0026]
Further, as shown in FIG. 1, the target member 30 is electrically connected to the X-ray power source 12 via the envelope body 21 and a predetermined positive voltage is applied.
[0027]
As shown in FIG. 2, a deflection coil 26 is disposed outside the peripheral wall of the envelope body 21 so as to surround the envelope body 21 around its axis. The deflection coil 26 has an electromagnetic coil (not shown) and is connected to the controller 14 as shown in FIG. As shown in FIG. 2, the deflection coil 26 forms an electric field or magnetic field between the electron gun 23 and the target member 30, deflects the electron beam incident on the target member 30 from the electron gun 23, and The incident position of the electron beam on the thin film 34, the focusing degree of the electron beam, and the like are changed.
[0028]
The X-ray tube 10 of the present embodiment includes a cooling member 40 that is formed of a highly conductive material such as copper and covers the envelope body 21 from one end side in the axial direction.
[0029]
The cooling member 40 includes a cylindrical portion 40a that is coaxial with the vacuum envelope 20, and an annular collar portion 40b that is formed with an opening 40c at the center and is connected to an end portion on one axial end side of the cylindrical portion 40a. And have.
[0030]
The cylindrical portion 40 a has an inner peripheral wall that is in contact with the outer peripheral wall of the envelope body 21, and an outer peripheral wall of the cylindrical portion 40 a that is in contact with the inner peripheral wall of the deflection coil 26. Is intervening.
[0031]
The collar portion 40 b is in contact with the end face on one end side of the envelope body 21. Further, the opening area of the opening 40c of the collar portion 40b is set to be slightly smaller than the area of the target substrate 32, and the vicinity of the opening portion 40c of the collar portion 40b is in contact with the peripheral portion of the surface of the target substrate 32. is doing. The central portion of the surface of the target member 30 is exposed to the outside.
[0032]
In the cylindrical portion 40a of the cooling member 40, a refrigerant flow path (flow path) 40e through which a cooling medium such as water can flow is formed in a spiral shape in the circumferential direction. As shown in FIG. 1, both ends of the refrigerant flow path 40 e are connected to the cooling medium supply device 16 via the communication pipes 17. The cooling medium having a predetermined low temperature from the cooling medium supply device 16 is The cooling member 40 is cooled by passing through the refrigerant flow path 40 e in the cooling member 40, and the cooling medium heated by this cooling returns to the cooling medium supply device 16.
[0033]
Furthermore, in the X-ray tube 10 of this embodiment, as shown in FIG. 2, it is installed on the peripheral wall of the envelope body 21, and the X-rays from the target thin film 34 enter through a monitor window 52 such as Be. An X-ray monitor (X-ray monitoring means) 50 for monitoring the X-ray dose is provided.
[0034]
The X-ray monitor 50 is fitted into the peripheral wall of the envelope body 21 so as to be in contact with the inner surface of the peripheral wall of the cylindrical portion 40 a of the cooling member 40 and to be located closer to the electron gun 23 than the surface of the target substrate 32. It is.
[0035]
Further, as shown in FIG. 1, the X-ray monitor 50 is connected to the controller 14, and transmits a state such as an X-ray dose detected through the monitor window 52 to the controller 14.
[0036]
Next, the operation of the X-ray generator 1 having such an X-ray tube 10 will be described.
[0037]
The controller 14 controls the X-ray power supply 12, applies a predetermined current voltage to the electron gun 23 and the target member 30 of the X-ray tube 10, emits an electron beam from the electron gun 23, and enters the target thin film 34. .
[0038]
As a result, X-rays are emitted from the target thin film 34, and the X-rays are transmitted through the target substrate 32 as a transmission window and emitted from the vacuum envelope 20 to the outside.
[0039]
Further, the controller 14 monitors the state of the X-ray dose detected by the X-ray monitor 50 in real time, and the X-ray power source 12 and the deflection coil so that the X-ray dose generated from the target thin film 34 becomes constant. 26 is controlled.
[0040]
Further, the controller 14 controls the cooling medium supply device 16 so that cooling water having a predetermined low temperature flows through the cooling member 40.
[0041]
At this time, the target thin film 34 is heated by the incidence of the electron beam, and this heat is transmitted in order through the target substrate 32, the collar portion 40b of the cooling member 40, and the cylindrical portion 40a of the cooling member 40, and the refrigerant flow path 40e. Since the heat is removed by the cooling medium having a predetermined low temperature passing through the inside, the temperature of the target thin film 34 is maintained at a predetermined low temperature. For this reason, the deterioration of the target thin film 34 is reduced, and the life of the target member 30 can be extended.
[0042]
Further, the deflection coil 26 is driven to generate heat, and this heat is transmitted to the cylindrical portion 40a of the cooling member 40 that contacts the deflection coil 26 and is removed by the cooling medium in the refrigerant flow path 40e. Therefore, the temperature of the deflection coil 26 is maintained at a predetermined low temperature. For this reason, since the change of the deflection characteristic is almost eliminated, the electron beam can be deflected with high accuracy.
[0043]
In addition, since the cooling member 40 is interposed between the deflection coil 26 and the envelope body 21, the heat generated by the deflection coil 26 is hardly transmitted to the envelope body 21, and the envelope body 21 is heated. This also prevents the vacuum envelope 20 and the like from being deteriorated. Furthermore, since the envelope body 21 is also in contact with the cooling member 40, the envelope body 21 is also maintained at a predetermined constant temperature, and the deterioration of the vacuum envelope 20 is further reduced.
[0044]
It should be noted that the cooling member 40 is not interposed between the deflection coil 26 and the envelope body 21, and is disposed so that the deflection coil 26 is in contact with the outer periphery of the envelope body 21. In this case, heat from the deflection coil 26 passes through the inner surface of the peripheral wall of the deflection coil 26 and the vacuum envelope. 20 is not preferable.
[0045]
In addition, the X-ray tube 10 of the present embodiment includes an X-ray monitor 50. The target member 30 may be damaged by damage of the target member 30 due to long-time electron beam irradiation, unexpected fluctuations in current and voltage, and the like. Even if the generated X-ray dose varies, it can be detected immediately. For this reason, the X-ray dose is adjusted by adjusting the current voltage of the X-ray power supply 12 by the controller 14 or adjusting the deflection amount of the deflection coil 26 so that an electron beam is incident on the undamaged target thin film 34. The X-ray dose emitted from the target member 30 is constant and is suitable as an X-ray source.
[0046]
Further, in such an X-ray monitor 50, for example, when the dose is detected using a semiconductor element or the like, when the temperature of the X-ray monitor 50 itself fluctuates, the detection value greatly fluctuates and the accuracy deteriorates. There is. However, in this embodiment, since the X-ray monitor 50 is in contact with the cooling member 40 and the X-ray monitor 50 itself is maintained at a predetermined low temperature, fluctuations in detection characteristics of the X-ray monitor 50 are also reduced. It is possible to accurately measure a state such as an X-ray dose.
[0047]
Further, since the X-ray monitor 50 is installed closer to the electron beam incident surface side of the target thin film 34 than the X-ray emission surface of the target substrate 32, the X-ray monitor 50 emits from the target substrate 32. It does not interfere with the irradiated object side that receives X-rays. For this reason, since an irradiated object etc. can be made to adjoin to the target board | substrate 32, a high-magnification X-ray image etc. can be acquired. In addition, since the X-ray monitor 50 is fitted into the envelope body 21 and is located inside the cooling member 40, the X-ray tube 10 can be made compact.
[0048]
Next, an X-ray tube 120 according to a second embodiment of the present invention will be described with reference to FIG. The X-ray tube 120 of this embodiment differs from the X-ray tube 10 according to the first embodiment in that a heat radiating sheet (heat radiating thin plate) 122 is further provided on the target substrate 32 of the target member 30 instead of the target member 30. The target member 130 is provided, and the peripheral portion of the heat radiation sheet 122 is in contact with the flange portion 40 b of the cooling member 40 correspondingly.
[0049]
The heat radiating sheet 122 is a sheet made of a light element material having higher thermal conductivity and higher X-ray transmittance than the target substrate 32. For example, a graphite sheet (PGS graphite sheet manufactured by Matsushita Electronic Components Co., Ltd.) is used. it can.
[0050]
According to the present embodiment, the heat of the in-plane center portion of the target thin film 34 and the target substrate 32 is efficiently transmitted toward the peripheral portion of the target member 130 by the heat dissipation sheet 122 having high thermal conductivity, and the cooling member 40. Since the collar 40b is reached, the target thin film 34 can be cooled more efficiently.
[0051]
In addition, the X-ray tube which concerns on this invention is not limited to the said embodiment, A various deformation | transformation aspect can be taken.
[0052]
For example, in the above-described embodiment, the cooling member 40 and the deflection coil 26, the X-ray monitor 50, and the target members 30 and 130 are in direct contact with each other. In short, it is only necessary that they are thermally connected to the cooling member 40 in order to remove heat generated in the deflection coil 26, the X-ray monitor 50, and the target members 30 and 130. .
[0053]
In the above embodiment, the cooling member 40 includes the refrigerant flow path 40e through which the cooling medium can pass and is cooled by the passage of the cooling medium. However, the cooling member 40 may be electronically cooled by a Peltier element or the like, or cooled by a fan or the like. May be.
[0054]
Moreover, in the said embodiment, although the envelope main body 21 and the cooling member 40 are made into a separate member, you may integrate the envelope main body 21 with a cooling member as members, such as copper with high heat conductivity.
[0055]
Further, in the above embodiment, the target substrate 32 of the target member 30 is used as the exit window of the vacuum envelope 20 so as to have a small and simple structure, but an exit window different from the target substrate 32 is provided. It doesn't matter. Further, the target thin film 34 may be used as the exit window.
[0056]
In the above-described embodiment, the X-ray monitor 50 is disposed closer to the electron gun 23 than the target substrate 32 serving as an emission window. You may arrange | position in the line | wire emission direction side.
[0057]
In the above embodiment, the X-ray tube 10 includes the vacuum envelope 20, but instead of this, an open envelope in which the inside is depressurized during use and the inside is normal pressure when not in use. May be provided.
[0058]
【The invention's effect】
As described above, the X-ray tube according to the present invention includes the cooling member interposed between the deflection coil and the envelope and thermally connected to the deflection coil and the target. By cooling the cooling member, the target and the deflection coil that are thermally connected to the cooling member are cooled, and even if an electron beam is incident on the target, the target can be maintained at a predetermined low temperature, and damage to the target is reduced. On the other hand, even if the deflection coil is used, the deflection coil can be maintained at a predetermined low temperature, and the characteristics of the deflection coil are hardly changed, so that the deflection amount of the electron beam can be controlled with high accuracy. Further, since the cooling member is interposed between the deflection coil and the envelope and the deflection coil and the envelope are thermally blocked, the heat generated in the deflection coil is hardly transmitted to the envelope. In addition, deterioration of the X-ray tube and fluctuation of characteristics are reduced.
[0059]
Thereby, an X-ray tube capable of suitably cooling the target and the deflection coil is provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an X-ray generation apparatus including an X-ray tube according to a first embodiment.
FIG. 2 is a cross-sectional view of the X-ray tube in FIG.
FIG. 3 is a cross-sectional view of an X-ray tube according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... X-ray generator, 10, 120 ... X-ray tube, 20 ... Vacuum envelope (envelope), 26 ... Deflection coil, 32 ... Target substrate (output window), 34 ... Target thin film (target), 40 ... Cooling member, 40e ... Refrigerant flow path (flow path), 50 ... X-ray monitor (X-ray monitoring means), 122 ... Heat radiation sheet (heat radiation thin plate).

Claims (7)

An electron beam is incident on one surface of the target in the envelope, and X-rays radiated from the other surface of the target are exposed to the outside of the envelope through an emission window provided in the envelope. In the X-ray tube to be emitted,
A deflection coil disposed outside the envelope and deflecting an electron beam incident on the target;
A cooling member interposed between the deflection coil and the envelope and thermally connected to the deflection coil and the target;
An X-ray tube comprising: The X-ray tube according to claim 1, wherein the target is formed on an inner surface of the exit window, and the cooling member is thermally connected to the target through the exit window. 3. The X of claim 2, further comprising a heat radiating thin plate having higher heat conductivity than the light emitting window on an outer surface of the light emitting window, wherein the heat radiating thin plate is thermally connected to the cooling member. Wire tube. The X-ray tube according to claim 1, wherein the cooling member includes a flow path through which a cooling medium can pass. The X-ray monitoring means for monitoring the state of the X-rays generated from the target is provided, and the cooling member is further thermally connected to the X-ray monitoring means. The X-ray tube according to one item. The X-ray monitoring unit according to claim 5, wherein the X-ray monitoring unit is disposed closer to a surface on which the electron beam is incident on the target than a surface on which the X-ray is emitted from the emission window. Wire tube. The X-ray tube according to claim 6, wherein the X-ray monitoring unit is further installed inside the cooling member.

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