JP2012109186A - Power supply unit and x-ray device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit which gives a power supply to an X-ray source so that the X-ray source can emit normal X-rays, and to provide an X-ray device equipped with the power supply unit.SOLUTION: A power supply unit 50 gives a power supply to the X-ray source which includes an electron source 16, a suppression electrode 17, an extraction electrode 21, an acceleration electrode 25, an electron optical system, a target 13 and a vacuum vessel 11. The power supply unit 50 includes a first power supply Ef1 which heats the electron source 16 and a second power supply Ef2 which heats the electron source 16 independently from the first power supply Ef1.

Description

  Embodiments described herein relate generally to a power supply unit and an X-ray apparatus including the power supply unit.

  A general X-ray source having a micro focus has already been commercialized as a micro focus X-ray source, and is widely used in a non-destructive inspection apparatus for inspecting a micro area of an object with high resolution. This X-ray source focuses an electron beam emitted from a cathode by an electron optical diameter such as an electric field or a magnetic lens, forms a focal point in a narrow region on the order of μm or less, and is emitted from the focal point. X-rays transmitted through the target are emitted.

  Here, in order to inspect a minute object, it is necessary to make the focal point of the electron beam formed on the target minute, so that the electron beam is focused on a minute aperture on a metal target that is an X-ray generation source. There is a need. For this reason, the X-ray source includes an electron source, an extraction electrode to which a high voltage for making electrons flow into a beam, an acceleration electrode to which a high voltage for applying energy to the electron beam is applied, and a vacuum vessel maintained at a high vacuum A lens electrode or the like to which a high voltage for converging the electron beam to a small aperture is applied.

JP 2008-140687 A

  In order for the X-ray source to generate predetermined X-rays, it is necessary to heat the electron source to a high temperature to generate thermoelectrons, and focus and irradiate the electron beam with a small aperture on the target. That is, a predetermined high DC voltage is applied to the heated electron source, the extraction electrode for extracting the thermionic electrons as an electron beam, the acceleration electrode for accelerating the extracted electron beam, and the lens electrode for focusing the accelerated electron beam. There is a need to. In addition, in order to form only the central part of the thermoelectrons as an electron beam, a suppression electrode is installed in the vicinity of the electron source, and an aperture electrode that prevents the target from being irradiated with an unnecessary electron beam is disposed on them. A predetermined high DC voltage is applied.

  As described above, the X-ray source includes a plurality of electrodes that need to be applied with a DC high voltage, the voltage value is complicated, and the stability of the voltage value greatly affects the intensity and focusing performance of the electron beam. This greatly affects the source diameter (focus size) and intensity of X-rays. For this reason, it is necessary to feedback-control the power supply of each electrode by a computer or a sequencer.

  However, since a high DC voltage is applied to each electrode, abnormal discharge may occur due to gas generated in the vacuum vessel. This abnormal discharge causes the control computer or sequencer to malfunction. ing. Since the application of voltage to each electrode is cut off, the voltage suddenly becomes zero.

  This stop of the voltage application suddenly stops the heating of the electron source (hot cathode), and the liquid zirconium installed on the surface of the electron source with a small diameter is rapidly cooled and contracts at the time of solidification to cause cracks and There is a risk of dropping off. Liquid zirconium is installed to increase the generation efficiency of thermoelectrons at 1000 ° C. or higher. In order to generate normal thermionic electrons, zirconium must be uniformly present on the surface of the electron source. When the electron source is rapidly cooled, the X-ray source may not normally emit X-rays. It becomes possible.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a power supply unit that supplies power to the X-ray source so that the X-ray source can emit normal X-rays, and an X including the power supply unit. It is to provide a wire device.

The power supply unit according to an embodiment is:
An electron source that emits electrons, a suppression electrode that suppresses the amount of electron emission from the electron source, an extraction electrode that extracts electrons suppressed by the suppression electrode as an electron beam, and an electron beam extracted by the extraction electrode An accelerating electrode that accelerates, an electron optical system that focuses an electron beam accelerated by the accelerating electrode, and a transmissive target that emits X-rays when the electron beam focused by the electron optical system is incident; A vacuum vessel provided with the target, having an X-ray transmission window that transmits X-rays emitted from the target, and containing the electron source, suppression electrode, extraction electrode, acceleration electrode, and electron optical system; In a power supply unit that supplies power to
A first power source for heating the electron source;
And a second power source that heats the electron source independently of the first power source.

An X-ray apparatus according to an embodiment
An electron source that emits electrons, a suppression electrode that suppresses the amount of electron emission from the electron source, an extraction electrode that extracts electrons suppressed by the suppression electrode as an electron beam, and an electron beam extracted by the extraction electrode An accelerating electrode that accelerates, an electron optical system that focuses an electron beam accelerated by the accelerating electrode, and a transmissive target that emits X-rays when the electron beam focused by the electron optical system is incident; A vacuum vessel provided with the target, having an X-ray transmission window that transmits X-rays emitted from the target, and containing the electron source, suppression electrode, extraction electrode, acceleration electrode, and electron optical system; X-ray source,
A first power source that heats the electron source; and a second power source that heats the electron source independently of the first power source; and a power supply unit that supplies power to the X-ray source. It is characterized by that.

FIG. 1 is a schematic configuration diagram illustrating an X-ray apparatus according to an embodiment. FIG. 2 is a graph showing changes in filament current, voltages Eacc, Eext, Esup, and Egl with respect to time in the X-ray apparatus. FIG. 3 is a graph showing changes in filament current with respect to time after the start of operation of the X-ray apparatus. FIG. 4 is a graph showing a change in filament current with respect to time after the operation stop of the X-ray apparatus.

Hereinafter, an X-ray apparatus according to an embodiment will be described in detail with reference to the drawings.
As shown in FIG. 1, the X-ray apparatus is a soft X-ray apparatus. The X-ray apparatus includes an X-ray source 10 and a power supply unit 50.

  The X-ray source 10 is used for measuring substances that need to be measured with low energy X-rays (soft X-rays) such as a resin having a minute shape and relatively high X-ray transmittance, for example, as an X-ray tomography apparatus. The present invention can be used for a stereoscopic image forming apparatus having an X-ray CT (Computed Tomography) apparatus.

  The X-ray source 10 includes an electron source (hot cathode) 16, a suppression electrode 17, an extraction electrode 21, an acceleration electrode 25, a lens electrode 29 that is a gun lens as an electron optical system, an aperture electrode 30, and a target. 13 and a vacuum vessel 11.

  The electron source 16 is made of a conductive material in a cone shape, and the tip of the electron source 16 is formed in a needle shape. Liquid zirconium is placed on the surface of the electron source 16. The electron source 16 is provided with a filament. Heaters 44 and 45 for heating the electron source 16 are connected to the electron source 16. A power supply unit 50 (DC stabilized power supply) is connected to the heaters 44 and 45. The electron source 16 is heated by the heaters 44 and 45 and emits electrons (thermal electrons) when a voltage is applied by the power supply unit 50.

  The suppression electrode 17 is formed in a bowl shape with a conductive material, and has a through hole 17h into which the tip of the electron emission side of the electron source 16 is inserted or through which the electron emitted from the tip passes. The through hole 17 h is formed so as to penetrate the bottom wall of the suppression electrode 17. The through hole 17h is circular. A negative voltage is applied to the suppression electrode 17 with respect to the electron source 16. The suppression electrode 17 suppresses the amount of electrons emitted from the peripheral portion other than the tip portion of the electron source 16.

  The extraction electrode 21 is disposed opposite to the suppression electrode 17 with a predetermined interval, and is formed of a conductive material. The extraction electrode 21 is formed in a plate shape, specifically a disc shape. The extraction electrode 21 has a through hole 21h opposed to the through hole 17h. The through hole 21h is circular. In this embodiment, the extraction electrode 21 is positioned such that the extension line of the central axis of the through hole 21h matches the extension line of the central axis of the through hole 17h. A positive voltage is applied to the extraction electrode 21. The extraction electrode 21 extracts electrons suppressed by the suppression electrode 17 as an electron beam 15.

  The acceleration electrode 25 is located on the opposite side of the suppression electrode 17 with respect to the extraction electrode 21, is arranged at a predetermined interval from the extraction electrode 21, and is formed of a conductive material. The acceleration electrode 25 is formed in a disk shape. The acceleration electrode 25 has a through hole 25h facing the through hole 21h. The through hole 25h is circular. In the direction along the central axis of the through hole 25h, the acceleration electrode 25 is positioned so that the through hole 25h overlaps the through hole 21h. The acceleration electrode 25 is preferably positioned so that the extension line of the central axis of the through hole 25h matches the extension line of the central axis of the through hole 21h. The acceleration electrode 25 is given a positive voltage that is even greater than that of the extraction electrode 21. The acceleration electrode 25 accelerates the electron beam 15 extracted by the extraction electrode 21.

  The lens electrode 29 is located on the opposite side of the extraction electrode 21 with respect to the acceleration electrode 25, is disposed at a predetermined interval from the acceleration electrode 25, and is formed of a conductive material. The lens electrode 29 is provided so as to surround the trajectory of the electron beam 15 from the through hole 25 h of the acceleration electrode 25 toward the target 13. The lens electrode 29 has a through hole 29h facing the through hole 25h. The through hole 29h is circular. The lens electrode 29 is positioned such that the extension line of the central axis of the lens electrode 29 coincides with the extension line of the central axis of the through hole 25h. A positive voltage is applied to the lens electrode 29. The lens electrode 29 focuses the electron beam 15 accelerated by the acceleration electrode 25.

  The aperture electrode 30 is located between the lens electrode 29 and the target 13. The aperture electrode 30 has a through hole 30h opposed to the through hole 29h. The through hole 29h is circular, and its aperture is set to 1 mm or less. The aperture electrode 30 removes unnecessary components of the electron beam 15 focused by the lens electrode 29 and causes the electron beam 15 to enter the target 13. Thereby, overheating of the target 13 by an unnecessary electron beam can be prevented.

  The target 13 is located on the opposite side of the lens electrode 29 with respect to the aperture electrode 30, and is disposed at a predetermined interval from the lens electrode 29. The target 13 is made of tungsten, for example. The target 13 is formed very thin in order to emit the X-ray 37 generated by the incidence of the electron beam 15 to the outside without being attenuated. In this embodiment, the target 13 has a circular shape. The target 13 is in close contact with an X-ray transmission window 14 described later, and is integrated with the X-ray transmission window 14. The target 13 is set to the ground potential. The target 13 is an X-ray transmission type target, and emits X-rays to the X-ray transmission window 14 side when an electron beam having passed through the through hole 30h is incident.

The vacuum vessel 11 has an X-ray transmission window 14 and houses an electron source 16, a suppression electrode 17, an extraction electrode 21, an acceleration electrode 25, a lens electrode 29, an aperture electrode 30, a target 13, and heaters 44 and 45. . The inside of the vacuum vessel 11 is maintained in a vacuum state. The X-ray transmissive window 14 is made of, for example, beryllium as a metal material having a small attenuation of the X-ray 37 having conductivity. As described above, the target 13 is provided in the X-ray transmission window 14, and the X-ray transmission window 14 transmits X-rays radiated from the target 13.
The X-ray source 10 is formed as described above.

  The power supply unit 50 includes a control power supply 60, a control computer 70 as a control unit, a first power supply Ef1, a second power supply Ef2, and a switching module 90. The switching module 90 has a first switch SW1 and a second switch SW2. The control power supply 60 has a computer 61 as a drive unit and an electrode power supply unit 62. The electrode power supply unit 62 has power supplies 63, 64, 65 and 66.

  The power source 63 is connected between the first switch SW1 and the suppression electrode 17. The power source 64 is connected between the first switch SW1 and the extraction electrode 21. The power source 65 is connected between the first switch SW1 and the lens electrode 29. The power source 66 is connected between the first switch SW 1 and the acceleration electrode 25, the aperture electrode 30, and the X-ray transmission window 14. The acceleration electrode 25, the aperture electrode 30, and the X-ray transmission window 14 are set to the ground potential.

  The power source 63 applies a voltage Esup and a current Isup to the suppression electrode 17. The power supply 64 applies a voltage Eext and a current Iext to the extraction electrode 21. The power supply 65 applies a voltage Egl and a current Igl to the lens electrode 29. The power source 66 applies a voltage Eacc and a current Iacc to the acceleration electrode 25, the aperture electrode 30 and the X-ray transmission window 14. The computer 61 controls the operation of the electrode power supply unit 62. That is, the power supplies 63 to 66 are controlled and driven by the computer 61.

  In the first switch SW1, one is connected to the heater 44, and the other is connectable to the first power supply Ef1 or the second power supply Ef2. In the second switch SW2, one is connected to the heater 45, and the other is connectable to the first power supply Ef1 or the second power supply Ef2.

  As described above, the switching module 90 is connected between the first power source Ef1 and the second power source Ef2, and the electron source 16, and switches the connection state between the first power source Ef1, the second power source Ef2, and the electron source 16. The switched connection state can be maintained.

  The computer 61 is connected to the switching module 90, acquires information on the current (filament current) flowing through the electron source 16, and controls the switching operation of the switching module 90 based on the information. The computer 61 operates one of the first power supply Ef1 and the second power supply Ef2. The first power supply Ef1 heats the electron source 16 together with the heaters 44 and 45. The second power supply Ef2 heats the electron source 16 independently of the first power supply Ef1.

  As described above, the electron source 16, the suppression electrode 17, the extraction electrode 21, the acceleration electrode 25, the lens electrode 29, the aperture electrode 30, the target 13, and the X-ray transmission window 14 are connected to independent DC power sources, respectively, and feedback stable It is controlled. The power sources 63 to 66 and the second power source Ef2 are controlled by the computer 61 in the control power source 60 based on the data of the time sequence pattern input by the control computer 70. The second power source Ef2 is a DC power source controlled by the control power source 60, but the first power source Ef1 is another DC power source that is not controlled by the control power source 60 connected by the switching module 90 that can be switched by the control computer 70. .

Next, the operation of the X-ray apparatus according to the one embodiment will be described.
Electrons generated from the electron source 16 while the emission amount is suppressed by the suppression electrode 17 are extracted as the electron beam 15 by the extraction electrode 21 and accelerated by the acceleration electrode 25. When the electron beam 15 is focused to a small diameter by the lens electrode 29 and passes through the through hole of the aperture electrode 30 and is irradiated onto the target 13, X-rays 37 are emitted from the target 13.

  When transmission imaging with X-rays 37 is performed, the X-ray source 10 having a smaller aperture has a higher imaging resolution capability. Therefore, it is desired to reduce the aperture of the electron beam 15 to be focused and focused by the lens electrode 29. is doing.

  As described above, the activation of the X-ray source 10 that requires a plurality of electrodes needs to be operated at a time-optimal value as shown in FIG. 2, and therefore, the power supplies 63 to 66 and the second power supply Ef2 are It is necessary to control with high accuracy by using the control power supply 60 incorporating the computer 61 and the control computer 70 for exchanging information with the operator.

  As shown in FIG. 3, it is necessary to control the filament current If with a predetermined current change from room temperature to a predetermined temperature, and to stably control the electron source 16 with a predetermined current value. Further, at the time of stopping, as shown in FIG. 4, it is necessary to lower the filament current If from the current value in the operating state and lower the temperature of the electron source 16 in a predetermined period. Thus, the current value and voltage value of each electrode need to be controlled by the computer 61 or the like.

  However, after the filament current If is controlled to the rated value, an operation is performed in which a high voltage is applied to the extraction electrode 21, the acceleration electrode 25, and the lens electrode 29 to generate the electron beam 15. In some cases, a gas such as hydrogen or oxygen is generated from this structure, and a large-current discharge (overcurrent) is generated between electrodes to which a high voltage is applied. This overcurrent stops the computer 61 in the control power supply 60. For this reason, the supply of voltage and current to the suppression electrode 17, the extraction electrode 21, the acceleration electrode 25, the lens electrode 29, the aperture electrode 30, the X-ray transmission window 14, and the second power supply Ef2 is stopped. Due to this stop, the temperature of the electron source 16 also drops rapidly.

  Therefore, the filament current If controlled at a constant value other than the start or stop of the operation of the X-ray source 10 is given from the first power supply Ef1 that is not controlled by the computer 61 in the control power supply 60, and the filament current If becomes constant control. If this happens, the switching module 90 switches between the first power supply Ef1 and the second power supply Ef2. That is, the first switch SW1 and the second switch SW2 are switched from the state connected to the second power source Ef2 to the state connected to the first power source Ef1.

  Thus, after operating the electron source 16 with the first power supply Ef1 not controlled by the computer 61 in the control power supply 60, a DC high voltage is applied to each electrode. From the above, it is possible to prevent a rapid temperature drop of the electron source 16 even when an overcurrent occurs. And even if the computer 61 in the control power supply 60 stops due to the occurrence of overcurrent, the temperature of the electron source 16 can be kept constant.

  According to the X-ray apparatus according to the embodiment configured as described above, the X-ray apparatus includes the X-ray source 10 and the power supply unit 50 that supplies power to the X-ray source 10. The power supply unit 50 includes a first power supply Ef1 that heats the electron source 16 and a second power supply Ef2 that heats the electron source 16 independently of the first power supply Ef1. In the operation start period or the operation stop period of the X-ray source 10, the filament current If is supplied from the second power source Ef 2 to the electron source 16. Except for the operation start period and the operation stop period of the X-ray source 10, the first power supply Ef <b> 1 supplies the filament current If controlled at a constant value to the electron source 16.

Therefore, even if a large current discharge (overcurrent) occurs between the electrodes of the X-ray source 10 and the computer 61 stops, the filament current If is applied to the electron source 16 from the first power supply Ef1. Thereby, a rapid temperature drop of the electron source 16 can be prevented.
From the above, it is possible to obtain a power supply unit 50 that supplies power to the X-ray source 10 and an X-ray apparatus including the power supply unit 50 so that the X-ray source 10 can emit normal X-rays 37.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

  For example, the power supply unit 50 may include two control power supplies. For example, the power supply unit 50 includes a first control power supply that operates one of the first power supply Ef1 and the second power supply Ef2, and a second control power supply that operates the other of the first power supply Ef1 and the second power supply Ef2. May be.

The configurations of the X-ray source 10 and the power supply unit 50 are not limited to the above embodiment, and can be variously modified.
The present invention is not limited to the power supply unit 50 and the X-ray apparatus, but can be applied to various power supply units 50 and various X-ray apparatuses.

  DESCRIPTION OF SYMBOLS 10 ... X-ray source, 11 ... Vacuum container, 13 ... Target, 13 ... Lens electrode, 14 ... X-ray transmission window, 16 ... Electron source, 17 ... Suppression electrode, 21 ... Extraction electrode, 25 ... Acceleration electrode, 29 ... Lens Electrode, 30 ... Aperture electrode, 44, 45 ... Heater, 50 ... Power supply unit, 60 ... Control power supply, 61 ... Computer, 62 ... Electrode power supply unit, 63, 64, 65, 66 ... Power supply, 70 ... Control computer, 90 ... Switching module, Ef1 ... first power supply, Ef2 ... second power supply, SW1 ... first switch, SW2 ... second switch, If ... filament current.

Claims (7)

An electron source that emits electrons, a suppression electrode that suppresses the amount of electron emission from the electron source, an extraction electrode that extracts electrons suppressed by the suppression electrode as an electron beam, and an electron beam extracted by the extraction electrode An accelerating electrode that accelerates, an electron optical system that focuses an electron beam accelerated by the accelerating electrode, and a transmissive target that emits X-rays when the electron beam focused by the electron optical system is incident; A vacuum vessel provided with the target, having an X-ray transmission window that transmits X-rays emitted from the target, and containing the electron source, suppression electrode, extraction electrode, acceleration electrode, and electron optical system; In the power supply unit that supplies power to the X-ray source
A first power source for heating the electron source;
And a second power source for heating the electron source independently of the first power source.   A switching module connected between the first power source and the second power source and the electron source, capable of switching a connection state between the first power source and the second power source and the electron source, and maintaining the switched connection state; The power supply unit according to claim 1, further comprising:   It further comprises a control power source that is connected to the switching module, acquires information on the current flowing through the electron source, and has a drive unit that controls the switching operation of the switching module based on the information. The power supply unit according to claim 2.   The power supply unit according to claim 3, wherein the driving unit operates one of the first power supply and the second power supply. The control power supply further comprises an electrode power supply unit connected to the suppression electrode, extraction electrode, acceleration electrode, and electron optical system,
The power supply unit according to claim 3 or 4, wherein the driving unit controls the operation of the electrode power supply unit. A first control power source for operating one of the first power source and the second power source;
The power supply unit according to claim 1, further comprising a second control power supply that operates the other of the first power supply and the second power supply. An electron source that emits electrons, a suppression electrode that suppresses the amount of electron emission from the electron source, an extraction electrode that extracts electrons suppressed by the suppression electrode as an electron beam, and an electron beam extracted by the extraction electrode An accelerating electrode that accelerates, an electron optical system that focuses an electron beam accelerated by the accelerating electrode, and a transmissive target that emits X-rays when the electron beam focused by the electron optical system is incident; A vacuum vessel provided with the target, having an X-ray transmission window that transmits X-rays emitted from the target, and containing the electron source, suppression electrode, extraction electrode, acceleration electrode, and electron optical system; X-ray source,
A first power source that heats the electron source; and a second power source that heats the electron source independently of the first power source; and a power supply unit that supplies power to the X-ray source. An X-ray apparatus characterized by that.

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