X-ray generation device

Abstract

To provide an X-ray generation device capable of continuing suitable X-ray generation even in the occurrence of discharge between a cathode electrode and an adjustment electrode.SOLUTION: An X-ray generation device 1 includes a cathode electrode 5 that emits an electron E, an adjustment electrode 7 that adjusts the amount of releasing electrons from the cathode electrode 5, a control electrode 8 that controls an orbit of the electron E from the cathode electrode 5, a target 9 that generates X-rays R by the incidence of the electron E, a discharge detection unit 21 that detects discharge between the cathode electrode 5 and the adjustment electrode 7, and a bias switching unit 22 that switches the bias state of the electron E toward the target 9 so that the focal position of the electron E at the target 9 at the discharge detection is off from the focal position of the electron E at the target 9 at the normal operation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to x-ray generating devices. [Background technology]

[0002] An example of a conventional X-ray generating device is a radiation generating unit described in Patent Document 1. This conventional radiation generating unit includes a cathode electrode heated by a heater, an extraction electrode that extracts electrons from the heated cathode electrode, a heater power supply connected to the heater, an electrode power supply connected to the extraction electrode, and a target that receives electrons from the cathode electrode and generates radiation.

[0003] In the X-ray generator described above, discharges caused by various factors become a problem. For example, the X-ray generator described in Patent Document 2 focuses on discharges occurring within the casing. When a discharge occurs within the casing, the voltage (tube voltage) applied between the cathode electrode and the target drops instantaneously. At this time, if the bias voltage applied from the Wehnelt is kept at a constant value, the focal area of ​​the X-rays formed on the target is excessively narrowed, damaging the target. The X-ray generator of Patent Document 2 includes a means for detecting discharges occurring within the casing, and when a discharge is detected, the bias voltage applied from the Wehnelt is controlled so that the focal area of ​​the X-rays does not become smaller than the allowable limit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-130732 A [Patent Document 2] Japanese Patent Application Publication No. 8-94546 Summary of the Invention [Problem to be solved by the invention]

[0005] Discharge in the X-ray tube may also occur at a specific location in the casing. For example, when an adjustment electrode for adjusting the amount of electrons emitted from the cathode electrode is disposed in the X-ray tube, it is possible that a part of the material constituting the cathode electrode may fly from the cathode electrode heated by a heater and adhere to the adjustment electrode. When the adhesion accumulates on the adjustment electrode, the gap between the cathode electrode and the adjustment electrode narrows, and the inherent voltage resistance characteristic decreases, making it easier for discharge to occur. When discharge occurs between the cathode electrode and the adjustment electrode, the cathode electrode and the adjustment electrode have the same potential during discharge, so that the amount of electrons emitted from the cathode electrode, which was performed by the potential difference between the cathode electrode and the adjustment electrode, cannot be controlled temporarily. In this case, electrons from the cathode electrode are emitted without control according to the potential difference between the cathode electrode and the target, so there is a risk of excessive electron emission from the cathode electrode. When excessive electrons are emitted from the cathode electrode, excessive electrons are incident on the target, which may damage the target.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an X-ray generating device that can continue to generate appropriate X-rays even when a discharge occurs between the cathode electrode and the adjustment electrode. [Means for solving the problem]

[0007] An X-ray generating device according to one aspect of the present disclosure includes a cathode electrode that emits electrons, an adjustment electrode that adjusts the amount of electrons emitted from the cathode electrode, a control electrode that controls the trajectory of electrons from the cathode electrode, a target that generates X-rays by the incidence of electrons, a discharge detection unit that detects a discharge between the cathode electrode and the adjustment electrode, and a deflection switching unit that switches the deflection state of electrons toward the target so that the focal position of the electrons at the target during discharge detection deviates from the focal position of the electrons at the target during normal operation.

[0008] In this X-ray generator, when a discharge between the cathode electrode and the adjustment electrode is detected, the deflection state of the electrons toward the target is switched, thereby controlling the electron trajectory so that the focal position of the electrons on the target deviates from the focal position on the target during normal operation. This makes it possible to avoid damage to the target due to excessive electrons being incident on the focal position of the electrons during normal operation, i.e., the target region that is the X-ray generation region during normal operation, even if excessive electrons are emitted from the cathode electrode due to a discharge between the cathode electrode and the adjustment electrode. Therefore, in this X-ray generator, appropriate X-ray generation can be continued even if a discharge occurs between the cathode electrode and the adjustment electrode.

[0009] In the X-ray generating device, the driving power of the deflection switching unit may be adjusted during at least one of normal operation and discharge detection, whereby the deflection state of electrons toward the target can be precisely switched.

[0010] The deflection switching unit may direct electrons from the cathode electrode toward the target in a straight line during normal operation, and deflect the electrons from the cathode electrode toward the target when a discharge is detected. In this case, it becomes easy to grasp the focal position of the electrons on the target during normal operation, that is, the focal position of the X-rays during normal operation, and it becomes easy to adjust the optical axis of the X-ray generator.

[0011] The deflection switching unit may deflect electrons traveling from the cathode electrode toward the target during normal operation, and may direct the electrons traveling from the cathode electrode toward the target when a discharge is detected. In this case, it becomes easy to grasp the focal position of the electrons in the target when a discharge is detected, and it becomes easy to grasp a target region that is not preferable as the focal position of the electrons in the target during normal operation.

[0012] The deflection switching unit may switch the electron deflection state so that the focal position of the electrons on the target during discharge detection deviates from the focal position of the electrons on the target during normal operation by a distance equal to or greater than the focal dimension of the electrons. This makes it possible to more reliably avoid damage to the target due to excessive incidence of electrons on the focal position of the electrons during normal operation, i.e., the target region that is the X-ray generation region during normal operation.

[0013] The deflection switching unit may be configured with a deflection coil, in which case the deflection state of the electrons heading toward the target can be suitably switched.

[0014] The deflection switching unit may be configured with a deflection electrode, in which case the deflection state of the electrons heading toward the target can be suitably switched. Effect of the Invention

[0015] According to the present disclosure, even if a discharge occurs between the cathode electrode and the adjustment electrode, appropriate X-ray generation can be continued. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of an X-ray generating device according to an embodiment of the present disclosure. [Diagram 2] 1A is a diagram showing an example of the operation of the deflection switching unit during normal operation and when a discharge is detected, and FIG. 1B is a diagram showing another example of the operation of the deflection switching unit during normal operation and when a discharge is detected. [Diagram 3] 10 is a schematic diagram showing the relationship between the focal position of electrons during normal operation and the focal position of electrons after deflection when detecting a discharge. FIG. [Figure 4] FIG. 13 is a schematic diagram showing the configuration of an X-ray generating device according to a modified example. [Diagram 5] 5(a) to (c) are diagrams illustrating the operation of a deflection switching unit in the X-ray generating device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, a preferred embodiment of an X-ray generating device according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0018] 1 is a schematic diagram showing a configuration of an X-ray generator according to an embodiment of the present disclosure. As shown in the figure, the X-ray generator 1 includes an X-ray tube 2 and a driving circuit 3. The X-ray tube 2 is a transmission type X-ray tube, and includes a cathode electrode 5, a heater 6, an adjustment electrode 7, a control electrode 8, and a target 9 in a vacuum housing 4. The cathode electrode 5, the heater 6, the adjustment electrode 7, and the control electrode 8 constitute an electron gun EG.

[0019] The vacuum housing 4 is formed into a hollow cylinder by airtightly joining a head portion made of, for example, a metal material and a valve portion made of an insulating material. Examples of the metal material constituting the head portion include stainless steel, nickel alloy, copper, copper alloy, and iron alloy. Examples of the insulating material constituting the valve portion include glass and ceramic. A window member 10 is provided at the tip of the head portion. The window member 10 is formed into a plate shape with the tube axis as the center line, and is made of an X-ray transparent material such as beryllium, aluminum, or diamond.

[0020] The cathode electrode 5 is an electrode that emits electrons E. The cathode electrode 5 emits electrons E when heated by a heater 6 in an energized state. The heater 6 is a part that heats the cathode electrode 5. The heater 6 is composed of a filament that generates heat when energized. The electrons E emitted from the cathode electrode 5 pass through the electron passing hole 7a of the adjustment electrode 7 and the electron passing hole 8a of the control electrode 8, and proceed toward the target 9.

[0021] The adjustment electrode 7 is a first grid electrode that adjusts the amount of electrons emitted from the cathode electrode 5. The amount of electrons emitted from the cathode electrode 5 refers to the amount of electrons E that pass through the adjustment electrode 7 and proceed to the target 9, among the electrons E emitted from the cathode electrode 5 by the heating of the heater 6. The adjustment electrode 7 controls the amount of electrons emitted from the cathode electrode 5 based on the voltage applied to the adjustment electrode 7. The adjustment electrode 7 has an electron passing hole 7a having, for example, a circular cross section. The electron passing hole 7a allows the electrons E emitted from the cathode electrode 5 to pass to the control electrode 8 side.

[0022] The control electrode 8 is a second grid electrode that controls the trajectory of the electrons E from the cathode electrode 5 by forming an electrostatic lens. The control electrode 8 also functions as an extraction electrode that forms an electric field for extracting electrons from the cathode electrode 5. The control electrode 8 focuses the electrons E emitted from the cathode electrode 5 and passing through the adjustment electrode 7, and focuses them on the target 9 as an electron beam. The control electrode 8 has an electron passing hole 8a that has, for example, a circular cross section. The electron passing hole 8a is disposed coaxially with the electron passing hole 7a of the adjustment electrode 7, and allows the electrons E that have passed through the electron passing hole 7a to pass toward the target 9.

[0023] The target 9 is a portion that generates X-rays R by the incidence of electrons E. The target 9 is provided on the inner (vacuum side) surface of the window member 10 on the tube axis of the vacuum housing 4. The target 9 is, for example, a film formed on the inner surface of the window member 10. Examples of materials that make up the target 9 include tungsten, molybdenum, and copper. The target 9 is electrically connected to the head of the vacuum housing 4. The potential of the target 9 is, for example, ground potential.

[0024] 1, the drive circuit 3 includes a heater power supply 11, a cathode electrode power supply 12, an adjusting electrode power supply 13, and a control electrode power supply 14. The heater power supply 11 is electrically connected to the heater 6 and supplies a voltage to the heater 6. The cathode electrode power supply 12 is electrically connected to the cathode electrode 5 and supplies a voltage to the cathode electrode 5. The adjusting electrode power supply 13 is electrically connected to the adjusting electrode 7 and supplies a voltage to the adjusting electrode 7. The control electrode power supply 14 is electrically connected to the control electrode 8 and supplies a voltage to the control electrode 8.

[0025] In the X-ray generator 1 having the above configuration, during normal operation in which X-rays R are output from the target 9, a negative high voltage of, for example, about -100 kV is applied to the electron gun EG with the potential of the target 9 as a reference (ground potential). The X-ray tube 2 of this embodiment is a so-called triode X-ray tube that has, in addition to the above-mentioned cathode electrode 5 and target 9, electrodes such as the adjustment electrode 7 and control electrode 8 that control the electrons E emitted from the cathode electrode 5 and directed toward the target 9, and these electrodes 5, 7, and 8 control the parameters of the electrons E emitted from the cathode electrode 5 and the X-rays R generated from the target 9.

[0026] In the X-ray generating device 1, electrons E are emitted from the cathode electrode 5 by application of heat from the heater 6. The amount of electrons emitted from the cathode electrode 5 is controlled by the potential difference between the cathode electrode 5 and the adjustment electrode 7. The initial speed of the electrons E is controlled by the potential difference between the cathode electrode 5 and the control electrode 8. The electrons E that reach the control electrode 8 are accelerated by the potential difference between the control electrode 8 and a target 9 (here, ground potential) and collide with the target 9.

[0027] The potential of the control electrode 8 forms an electrostatic lens that controls the trajectory of the electrons E. The size (focal size) of the focal point F of the electrons E on the target 9 is controlled by the initial velocity of the electrons E and the action of the electrostatic lens. The focal size of the electrons E on the target 9 refers to the size of the incidence area of ​​the electrons E on the electron incidence surface 9a of the target 9. During normal operation, the potential difference between the cathode electrode 5 and the control electrode 8 is controlled so that the focal size of the electrons E on the target 9 is minimized. The X-rays R generated on the target 9 by the collision of the electrons E are emitted to the outside of the X-ray tube 2 through the window member 10. The brightness (tube current value) of the X-rays R is controlled by the potential of the adjustment electrode 7. The energy (acceleration voltage value) of the X-rays R is controlled by the potential of the control electrode 8.

[0028] In the above-mentioned X-ray generating device 1, discharge may occur inside the X-ray tube 2. In the X-ray generating device 1 in which the adjustment electrode 7 for adjusting the amount of electron emission from the cathode electrode 5 is arranged in the X-ray tube 2, it is considered that, for example, a part of the material constituting the cathode electrode 5 may fly from the cathode electrode 5 heated by the heater 6 and adhere to the adjustment electrode 7. In addition, various foreign matter such as the material constituting the heater 6 may adhere to the adjustment electrode 7, not limited to the material constituting the cathode electrode 5. When the adhesion accumulates on the adjustment electrode 7, the gap between the cathode electrode 5 and the adjustment electrode 7 is narrowed, and the inherent withstand voltage characteristics are reduced, making it easier for discharge to occur. When discharge occurs between the cathode electrode 5 and the adjustment electrode 7, the cathode electrode 5 and the adjustment electrode 7 have the same potential during the discharge, so that the amount of electron emission from the cathode electrode 5, which was performed by the potential difference between the cathode electrode 5 and the adjustment electrode 7, cannot be controlled temporarily. In this case, electrons from the cathode electrode 5 are emitted without control according to the potential difference between the cathode electrode 5 and the target 9, and there is a risk of excessive electron emission from the cathode electrode 5. If excessive electron emission from the cathode electrode 5 occurs, excessive electrons E will be incident on the target 9, and there is a risk of the target 9 being damaged.

[0029] Therefore, in the X-ray generator 1, the drive circuit 3 is provided with a discharge detection unit 21 that detects the discharge between the cathode electrode 5 and the adjustment electrode 7, and a deflection switching unit 22 that switches the deflection state of the electrons E toward the target 9 so that the focal position F1 of the electrons E on the target 9 during discharge detection deviates from the focal position F0 of the electrons E on the target 9 during normal operation. The focal position of the electrons E on the target 9 is the incident position of the electrons E on the electron incident surface 9a of the target 9, in other words, the target region that becomes the X-ray generation region.

[0030] The discharge detection unit 21 is composed of, for example, a current transformer or a resistor with a relatively small electric resistance. The discharge detection unit 21 monitors the current flowing through the cathode electrode 5, and when the current exceeds a predetermined threshold, detects that a discharge has occurred between the cathode electrode 5 and the adjustment electrode 7, and outputs a signal (detection signal) indicating the detection result to the control unit 23 described later. The connection position of the discharge detection unit 21 may be any position where a discharge current flows from the cathode electrode 5, and is not limited to the example of FIG. 1. In the example of FIG. 1, the discharge detection unit 21 is connected between the cathode electrode 5 and the cathode electrode power supply 12 (the positive terminal side of the cathode electrode power supply 12), but the discharge detection unit 21 may be connected between the cathode electrode power supply 12 and the control electrode power supply 14 (the negative terminal side of the cathode electrode power supply 12). The connection position of the discharge detection unit 21 may be between the control electrode power supply 14 and a reference potential (ground potential) (the negative terminal side of the control electrode power supply 14).

[0031] The deflection switching unit 22 is composed of a control unit 23 and a deflection coil 24. The control unit 23 is physically configured to include a processor such as a CPU, and a storage medium such as a RAM and a ROM. The control unit 34 may be a smartphone or tablet terminal integrally equipped with a display unit and an input unit, and may be composed of a microcomputer, an FPGA (Field-Programmable Gate Array), or the like.

[0032] The control unit 23 is functionally a part that controls the operation of the deflection coil 24. The control unit 23 has a current source or a voltage source electrically connected to the deflection coil 24. The control unit 23 adjusts the driving power, including supplying or stopping the supply of a driving current or voltage to the deflection coil 24, based on a detection signal from the discharge detection unit 21. The deflection coil 24 is a part that receives the supply of a driving current or voltage and deflects the trajectory of the electrons E. As shown in FIG. 1, the deflection coil 24 is disposed near the X-ray tube 2. The position of the deflection coil 24 in the axial direction of the trajectory of the electrons E is, for example, between the control electrode 8 and the target 9.

[0033] 2(a), the deflection switching unit 22 may be configured to make the electrons E traveling straight from the cathode electrode 5 toward the target 9 during normal operation, and to deflect the electrons E traveling from the cathode electrode 5 toward the target 9 when a discharge is detected. For example, when a focal position F0 of the electrons E on the target 9 is located on a predetermined axis (e.g., the tube axis) during normal operation, the deflection switching unit 22 controls the focal position F1 of the electrons E to be a position deviated in any direction within the plane of the target 9 from the aforementioned predetermined axis when a discharge is detected.

[0034] During normal operation, if there is no element that deflects electrons E from the cathode electrode 5 toward the target 9, the control unit 23 does not supply a driving current or voltage to the deflection coil 24 during normal operation, but supplies a driving current or voltage to the deflection coil 24 for a certain period of time when a detection signal is received from the discharge detection unit 21. During normal operation, if there is an element that deflects electrons E toward the target 9 (for example, a magnetic field due to a permanent magnet or the like is always present), the control unit 23 supplies a driving current or voltage to the deflection coil 24 during normal operation, but does not supply a driving current or voltage to the deflection coil 24 for a certain period of time when a detection signal is received from the discharge detection unit 21.

[0035] 2(b), the deflection switching unit 22 may be configured to deflect the electrons E traveling from the cathode electrode 5 toward the target 9 during normal operation, and to cause the electrons E traveling from the cathode electrode 5 toward the target 9 to travel in a straight line during discharge detection. In this case, the deflection switching unit 22 performs control so that, for example, during normal operation, the focal position F0 of the electrons E on the target 9 is located at a position deviated in any direction within the plane of the target 9 from the above-mentioned predetermined axis (e.g., the tube axis), and so that, during discharge detection, the focal position F1 of the electrons E is located on the above-mentioned predetermined axis within the plane of the target 9.

[0036] The control unit 23 supplies a driving current or voltage to the deflection coil 24 during normal operation, and stops the supply of the driving current or voltage to the deflection coil 24 for a certain period of time when a detection signal is received from the discharge detection unit 21. During normal operation, if there is no element that deflects the electrons E from the cathode electrode 5 toward the target 9, the control unit 23 does not supply a driving current or voltage to the deflection coil 24 during normal operation, and does not supply a driving current or voltage to the deflection coil 24 for a certain period of time when a detection signal is received from the discharge detection unit 21.

[0037] In both of the aspects of FIG. 2(a) and FIG. 2(b), it is preferable that the deflection switching unit 22 switches the deflection state of the electrons E so that the focal position F1 of the electrons E during discharge detection is deviated from the focal position F0 of the electrons E during normal operation by a distance equal to or greater than the focal dimension of the electrons E. The focal dimension of the electrons E is the size of the incidence area of ​​the electrons E on the electron incidence surface 9a of the target 9, in other words, the size of the target area that becomes the X-ray generation area. For example, as shown in FIG. 3, when the focal dimension (here, focal diameter) of the electrons E is r and the shortest distance between the electrons E during normal operation and the electrons E after deflection during discharge detection is K, it is preferable that K≧r. From the viewpoint of more reliably separating the electrons E during normal operation and the electrons E after deflection during discharge detection, it is more preferable that K≧10×r.

[0038] The focal position F1 of the electrons E after deflection during discharge detection may be located within the area of ​​the target 9 or outside the area of ​​the target 9, so long as it is deviated from the focal position F0 of the electrons E during normal operation. When the focal position F1 of the electrons E after deflection during discharge detection is located outside the area of ​​the target 9, a member having absorbency for the electrons E or a member with low efficiency of X-ray generation by the electrons E may be disposed inside the vacuum housing 4 so as to correspond to the focal position F1.

[0039] As described above, when the X-ray generator 1 detects a discharge between the cathode electrode 5 and the adjustment electrode 7, it switches the deflection state of the electrons E toward the target 9, thereby controlling the trajectory of the electrons E so that the focal position F1 of the electrons E on the target 9 deviates from the focal position F0 on the target 9 during normal operation. This makes it possible to avoid damage to the target due to excessive incidence of the electrons E on the focal position F0 of the electrons E during normal operation, that is, the target region that becomes the X-ray generation region during normal operation, even if excessive electrons are emitted from the cathode electrode 5 due to a discharge between the cathode electrode 5 and the adjustment electrode 7. Therefore, the X-ray generator 1 can continue to generate appropriate X-rays R even if a discharge occurs between the cathode electrode 5 and the adjustment electrode 7.

[0040] This embodiment includes an aspect in which the driving power in the deflection switching unit 22 is adjusted at least one of during normal operation and during discharge detection. In this case, the deflection state of the electrons E toward the target 9 can be precisely switched. When the deflection switching unit 22 is driven during discharge detection, the trajectory of the electrons E can be quickly returned to the trajectory during normal operation simply by stopping the supply of driving power after the discharge has ceased. When the deflection switching unit 22 is driven during normal operation, the trajectory of the electrons E can be quickly changed to the trajectory during discharge detection simply by stopping the supply of driving power when a discharge occurs.

[0041] This embodiment includes an aspect in which the electrons E traveling from the cathode electrode 5 toward the target 9 are made to travel in a straight line during normal operation, and the electrons E traveling from the cathode electrode 5 toward the target 9 are deflected when a discharge is detected. According to this aspect, it becomes easy to grasp the focal position F0 of the electrons E on the target 9 during normal operation, that is, the focal position of the X-rays during normal operation, and it becomes easy to adjust the optical axis of the X-ray generating device 1.

[0042] Furthermore, this embodiment includes an aspect in which the electrons E traveling from the cathode electrode 5 toward the target 9 are deflected during normal operation, and the electrons E traveling from the cathode electrode 5 toward the target 9 are made to travel in a straight line when a discharge is detected. According to such an aspect, it becomes easy to grasp the focal position F1 of the electrons E on the target 9 when a discharge is detected, and it becomes easy to grasp a target region that is not preferable as the focal position F0 of the electrons E on the target 9 during normal operation.

[0043] In this embodiment, the deflection switching unit 22 is configured by the deflection coil 24. By configuring the deflection switching unit 22 by the deflection coil 24, the deflection state of the electrons E heading toward the target 9 can be suitably switched.

[0044] Either a current source or a voltage source may be used to drive the deflection coil 24. When a current source is used to drive the deflection coil 24, a large current is passed through the deflection coil 24, and the deflection state of the electrons E can be switched in a short time compared to when a voltage source is used. When a discharge occurs between the cathode electrode 5 and the adjustment electrode 7, the focal position F1 of the electrons E is quickly displaced from the focal position F0 during normal operation, so that the focal position F0 of the electrons E during normal operation on the target 9 can be more reliably protected from excessive concentration of the electrons E. On the other hand, when a voltage source is used to drive the deflection coil 24, the current flowing through the cathode electrode 5 can be stabilized in a short time when the deflection state of the electrons E is switched. Therefore, after the discharge is terminated, the X-ray generator 1 can be quickly restored to normal operation.

[0045] FIG. 4 is a schematic diagram showing the configuration of an X-ray generator according to a modified example. As shown in the figure, an X-ray generator 31 according to a modified example differs from the X-ray generator 1 in that the deflection switching unit 22 includes a deflection electrode 32, in that the deflection switching unit 22 includes a deflection coil 24. Specifically, in the X-ray generator 31, a pair of deflection electrodes 32A and 32B are provided behind the electron passing hole 8a of the control electrode 8 (on the target 9 side) so as to sandwich the orbital axis of the electron E. Here, both of the deflection electrodes 32A and 32B are plate-shaped electrodes. In addition, the drive circuit 3 is provided with a deflection power supply 33 that supplies a voltage to the deflection electrode 32. In the example of FIG. 4, the drive circuit 3 is provided with a pair of deflection power supplies 33A and 33B that supply voltages to the deflection electrodes 32A and 32B, respectively.

[0046] In this X-ray generating device 31, as shown in Fig. 5(a), when the discharge detection unit 21 detects that a discharge has occurred between the cathode electrode 5 and the adjustment electrode 7, a detection signal is output from the discharge detection unit 21 to the control unit 23. The control unit 23, which has received the detection signal, drives the deflection power supplies 33A and 33B, and applies a positive voltage Va to the deflection electrode 32A and a negative voltage Vb to the deflection electrode 32B, as shown in Fig. 5(b) and Fig. 5(c). The deflection electrodes 32A and 32B generate a deflection electric field between the deflection electrodes 32A and 32B due to the voltage application from the deflection power supplies 33A and 33B, and deflect the electrons E from the cathode electrode 5 toward the target 9.

[0047] The manner in which the electrons E are deflected by the deflection electrodes 32A, 32B may be similar to that of the X-ray generating device 1, in which the electrons E traveling from the cathode electrode 5 toward the target 9 are caused to travel in a straight line during normal operation, and the electrons E traveling from the cathode electrode 5 toward the target 9 are deflected when a discharge is detected, or the electrons E traveling from the cathode electrode 5 toward the target 9 are deflected during normal operation, and the electrons E traveling from the cathode electrode 5 toward the target 9 are caused to travel in a straight line when a discharge is detected (see Figures 2(a) and 2(b)).

[0048] In the X-ray generating device 31, similarly to the above embodiment, when a discharge between the cathode electrode 5 and the adjustment electrode 7 is detected, the deflection state of the electrons E toward the target 9 is switched, thereby controlling the trajectory of the electrons E so that the focal position F1 of the electrons E on the target 9 deviates from the focal position F0 on the target 9 during normal operation. This makes it possible to avoid damage to the target due to excessive incidence of the electrons E on the focal position F0 of the electrons E on the target 9 during normal operation, that is, the target region that becomes the X-ray generation region during normal operation, even if excessive electrons are emitted from the cathode electrode 5 due to a discharge between the cathode electrode 5 and the adjustment electrode 7. Therefore, appropriate generation of X-rays R can be continued.

[0049] In this embodiment, the deflection switching unit 22 is composed of deflection electrodes 32A and 32B. By configuring the deflection switching unit 22 with the deflection electrodes 32A and 32B, the deflection state of the electrons E toward the target 9 can be suitably switched. The deflection electrode 32 does not necessarily have to be composed of a pair of deflection electrodes 32A and 32B, and may be composed of only one of the deflection electrodes 32A and 32B. In this case, one of the deflection power supplies 33A and 33B can also be omitted, and therefore the configuration of the drive circuit 3 can be simplified.

[0050] The present disclosure is not limited to the above embodiment. For example, in the above embodiment, a transmission type X-ray tube is exemplified as the X-ray tube 2, but the X-ray tube 2 may be a reflection type X-ray tube. In addition, in the above embodiment, a sealed tube structure in which the vacuum housing 4 is sealed as a vacuum tube is exemplified as the X-ray tube 2, but the X-ray tube 2 may be an open tube structure equipped with an exhaust pump or the like. In addition, in the above embodiment, a hot cathode structure equipped with a heater 6 is exemplified as the electron gun EG, but the electron gun EG may be a cold cathode structure. The potential relationship applied to the electron gun EG and the target 9 may be such that the electrons E are directed toward the target when X-rays are generated, and an electrode other than the target 9 may be a reference potential (ground potential).

[0051] The position of the discharge detection unit 21 is not limited to between the cathode electrode 5 and the cathode electrode power supply 12, and may be provided, for example, between the adjusting electrode 7 and the negative terminal of the adjusting electrode power supply 13. In this case, the discharge detection unit 21 detects the current flowing from the adjusting electrode 7 to the negative terminal of the adjusting electrode power supply 13 (the current flowing through the adjusting electrode 7) as the current during discharge. The discharge detection unit 21 may be provided between the positive terminal of the adjusting electrode power supply 13 and the cathode electrode 5. In this case, the discharge detection unit 21 detects the current flowing from the positive terminal of the adjusting electrode power supply 13 to the cathode electrode 5 as the current during discharge. The discharge detection unit 21 may be provided between the target 9 and a ground potential. In this case, the discharge detection unit 21 detects the current flowing through the target 9 as the current during discharge.

[0052] In the above embodiment, only the deflection switching unit 22 used for dealing with discharge detection is provided, but a deflection unit that changes the incident position of the electrons E during normal operation (i.e., changes the focal position of the X-rays R during normal operation) may be provided separately from the deflection switching unit 22. Also, in the above embodiment, the deflection switching unit 22 is driven either during normal operation or during discharge detection, but the degree of deflection may be changed between normal operation and discharge detection, so that the deflection state of the electrons E heading toward the target 9 may be switched while constantly driving the deflection switching unit 22.

[0053] The gist of the present disclosure is as follows: [1] to [6] [1] An X-ray generating device comprising: a cathode electrode that emits electrons; an adjustment electrode that adjusts the amount of electrons emitted from the cathode electrode; a control electrode that controls the trajectory of the electrons from the cathode electrode; a target that generates X-rays when the electrons are incident on it; a discharge detection unit that detects a discharge between the cathode electrode and the adjustment electrode; and a deflection switching unit that switches the deflection state of the electrons toward the target so that the focal position of the electrons in the target at the time of discharge detection is deviated from the focal position of the electrons in the target during normal operation. [2] The X-ray generating device according to [1], wherein the driving power in the deflection switching unit is adjusted during at least one of the normal operation and the discharge detection. [3] The X-ray generating device according to [1] or [2], wherein the deflection switching unit causes the electrons traveling from the cathode electrode toward the target to travel in a straight line during normal operation, and deflects the electrons traveling from the cathode electrode toward the target when the discharge is detected. [4] The X-ray generating device according to [1] or [2], wherein the deflection switching unit deflects the electrons traveling from the cathode electrode toward the target during normal operation, and causes the electrons traveling from the cathode electrode toward the target to travel in a straight line when the discharge is detected. [5] An X-ray generating device according to any one of [1] to [4], wherein the deflection switching unit switches the deflection state of the electrons so that the focal position of the electrons at the target during discharge detection deviates from the focal position of the electrons at the target during normal operation by a distance equal to or greater than the focal dimension of the electrons. [6] The X-ray generating device according to any one of [1] to [5], wherein the deflection switching unit is constituted by a deflection coil. [7] The X-ray generating device according to any one of [1] to [5], wherein the deflection switching unit is constituted by a deflection electrode. [Explanation of symbols]

[0054] 1,31...X-ray generator, 5...cathode electrode, 7...adjustment electrode, 8...control electrode, 9...target, 21...discharge detection unit, 22...deflection switching unit, 23...control unit, 24...deflection coil, 32 (32A, 32B)...deflection electrode, E...electrons, F0...electron focal position during normal operation, F1...electron focal position when discharge is detected, R...X-rays.

Claims

1. a cathode electrode that emits electrons; an adjustment electrode for adjusting the amount of electrons emitted from the cathode electrode; a control electrode for controlling a trajectory of the electrons from the cathode electrode; a target that generates X-rays when the electrons are incident on the target; a discharge detection unit that detects a discharge between the cathode electrode and the adjustment electrode; and a deflection switching unit that switches the deflection state of the electrons toward the target so that the focal position of the electrons at the target during discharge detection deviates from the focal position of the electrons at the target during normal operation.

2. 2. The X-ray generating apparatus according to claim 1, wherein the driving power of the deflection switching unit is adjusted during at least one of the normal operation and the discharge detection.

3. The X-ray generating device according to claim 1 , wherein the deflection switching unit causes the electrons traveling from the cathode electrode toward the target to travel straight ahead during the normal operation, and deflects the electrons traveling from the cathode electrode toward the target when the discharge is detected.

4. 2 . The X-ray generating device according to claim 1 , wherein the deflection switching unit deflects the electrons traveling from the cathode electrode toward the target during the normal operation, and causes the electrons traveling from the cathode electrode toward the target to travel in a straight line when the discharge is detected.

5. 2. The X-ray generating device according to claim 1, wherein the deflection switching unit switches the deflection state of the electrons so that the focal position of the electrons at the target during discharge detection deviates from the focal position of the electrons at the target during normal operation by a distance equal to or greater than the focal dimension of the electrons.

6. 6. The X-ray generating device according to claim 1, wherein the deflection switching unit is constituted by a deflection coil.

7. 6. The X-ray generating device according to claim 1, wherein the deflection switching section is constituted by a deflection electrode.

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