JP2012003995A - X-ray tube and radiographic x-ray apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent partial discharge between a receptacle and a plug and overheat of a cathode and an insulator in a bushing of an X-ray tube.SOLUTION: The X-ray tube has a cathode having a bushing and an anode. The bushing includes: a plug 202 with a filament 206 connected to a tip portion thereof; a receptacle 201 in which the plug 202 is inserted; a fluid inflow port 218 for injecting an insulative fluid; a fluid discharge port 219 for discharging the insulative fluid; a fluid inflow passage 216 for leading the insulative fluid from the fluid inflow port 218 to the tip portion of the plug 202; and a fluid discharge passage 217 for leading the insulative fluid from the tip portion of the plug 202 to the fluid discharge port 219. The fluid inflow passage 216 and fluid discharge passage 217 are formed between the plug 202 and receptacle 201 and connected with each other at the tip portion of the plug 202. The bushing further includes an insulative fluid circulation apparatus 220 for circulating the insulative fluid.

Description

  The present invention relates to an X-ray tube used in an X-ray imaging apparatus, and more particularly to a cathode insulation technique.

  A medical X-ray CT apparatus will be described as an example of an X-ray imaging apparatus equipped with an X-ray tube. The X-ray CT apparatus includes an X-ray tube that generates an X-ray beam, an X-ray detector (hereinafter referred to as “detector”) disposed at a position facing the X-ray tube with the subject interposed therebetween, and a scanner. The object is irradiated with a fan-shaped X-ray beam from an X-ray tube, the X-ray transmitted through the object is detected by a detector, and the detected X-ray data is image-processed to obtain a tomographic image of the object It is something to shoot. The detector is composed of several hundred or more detection elements arranged in an arc shape, and a number of X-ray passages corresponding to the number of detection elements are radially distributed. The scanner is composed of an X-ray tube, a detector, a scanner turntable on which these are mounted, and the like. When the scanner rotates 360 degrees around the subject, the detector detects the transmitted X-rays of the subject at every fixed angle.

  In the X-ray CT apparatus, it is necessary to supply a high voltage and a large current to the X-ray tube in order to continuously generate X-rays while rotating the scanner. In addition, the rotational speed tends to increase more and more.

  In such a high-speed rotation type X-ray CT apparatus, the X-ray dose irradiated by the X-ray tube per one rotation of the scanner is reduced, so that the noise of the captured image may increase. Therefore, in order to increase the amount of X-ray irradiation per unit time of the X-ray tube, it is necessary to increase the power supplied to the X-ray tube.

  In the X-ray CT apparatus, the anode is heated by the colliding electrons, but an anode-grounded X-ray tube that easily cools the anode is used in order to suppress overheating due to a large current. An example of a grounded anode X-ray tube is described in Patent Document 1.

  Further, in the bushing of the X-ray CT X-ray tube, if there is an air gap between the receptacle and the plug, partial discharge may occur. In order to prevent such partial discharge, it is necessary to fill the insulating grease with no gap between the plug and the receptacle. As this method, for example, a technique described in Patent Document 2 is known.

JP 2009-266622 A JP 2003-7158 A

  As described above, in recent X-ray CT X-ray tubes, an anode grounded X-ray tube that easily cools the anode is used. In the anode-grounded X-ray tube, electrons colliding with the anode are reflected, and the reflected electrons collide with the cathode again, thereby heating the cathode. The anode grounded type has more electrons returning to the cathode than the neutral point grounded type, and the cathode and the insulator may be overheated. Such overheating accelerates the thermal deterioration of insulating grease and rubber plugs, and remarkably deteriorates the insulation reliability. Therefore, in the anode grounded X-ray tube, prevention of overheating of the cathode insulating portion is a problem.

  An object of the present invention is to prevent partial discharge between the receptacle and the plug and prevent overheating of the cathode and the insulator in the bushing of the X-ray tube.

  The present invention solves the above-mentioned problems, and the means thereof will be described below.

  The first means includes a cathode having a bushing and a filament, and an anode. When a high voltage is applied to the cathode, electrons are emitted from the filament, and X-rays are generated by the electrons hitting the anode. An X-ray tube, wherein the bushing discharges the insulating fluid, a plug having the filament connected to a tip, a receptacle into which the plug is inserted, a fluid inlet for injecting an insulating fluid, and the plug. A fluid discharge port; a fluid inflow passage formed between the plug and the receptacle; allowing the insulating fluid to reach from the fluid inlet to the tip of the plug; and between the plug and the receptacle A fluid discharge channel formed to reach the insulating fluid from the tip of the plug to the fluid discharge port, and the fluid inflow channel and the fluid discharge The road, characterized in that it is connected at the distal end of the plug. Further, the X-ray tube includes an insulating fluid circulation device for circulating the insulating fluid through the bushing.

  The second means is the X-ray tube in the first means, wherein the fluid inflow channel and the fluid discharge channel are formed in a spiral shape.

  The third means is the X-ray tube in the first means, wherein the fluid inflow channel and the fluid discharge channel are formed by a protrusion provided in a spiral shape on the outer surface of the plug. Features.

  The fourth means is the X-ray tube in the first means, wherein the fluid inflow channel and the fluid discharge channel are formed by grooves spirally formed on the inner surface of the receptacle. And

  A fifth means is an X-ray tube according to any one of the first to fourth means, wherein the insulating fluid is an insulating liquid.

  The sixth means is an X-ray imaging apparatus comprising the X-ray tube in any one of the first to fourth means.

  According to the present invention, the cathode and insulator of the bushing can be cooled to prevent overheating, and partial discharge between the plug and the receptacle can be prevented. Therefore, an X-ray tube and an X-ray imaging apparatus with high insulation reliability can be obtained. realizable.

2 is a cross-sectional view of an X-ray tube bushing in Embodiment 1. FIG. Sectional drawing in the cross section 212 of the bushing of the X-ray tube in Example 1. FIG. Sectional drawing in the cross section 213 of the bushing of the X-ray tube in Example 1. FIG. Sectional drawing of the bushing of the X-ray tube in Example 2. FIG. Sectional drawing in the cross section 213 of the bushing of the X-ray tube in Example 2. FIG. Sectional drawing of the bushing of the X-ray tube in Example 3. FIG. FIG. 6 is a configuration diagram of an X-ray imaging apparatus in Embodiment 4.

  First, a conventional typical bushing structure will be described. The bushing includes a plug and a receptacle, and is connected to a high voltage generator by a multicore cable.

  The multi-core cable includes two core wires to which a high voltage is applied, an external conductor, an internal insulator that insulates the core wire from the external conductor, and an external insulator that further insulates the external conductor from the outside. In the bushing, the outer conductor is connected to the electric field relaxation ring. The electric field relaxation ring is made of conductive rubber. The multi-core cable from which the internal insulator is exposed is formed into a plug having a generally truncated cone shape by rubber molding.

  The plug has a connector electrode attached to the tip. The connector electrode is connected to the filament through a conducting wire penetrating the receptacle. One end of the filament is electrically connected to a metal converging body.

  The receptacle is generally a truncated cone in the shape of the internal space so that it can be tightly connected to the plug. A receptacle consists of insulators, such as ceramics, the cathode which consists of a filament or a converging body is connected to the front-end | tip part, and the housing | casing which is a grounding potential is connected to the other end. The housing is electrically connected to the outer conductor via the electric field relaxation ring. In the case of an X-ray tube, the housing also serves as a vacuum container.

  In such a configuration, for example, when a voltage obtained by adding −150 kV to one core wire and −150 kV to several tens of volts is applied to the other core wire, the filament is heated and thermoelectrons are emitted toward the anode.

  In the bushing having such a configuration, an important point from the viewpoint of electrical insulation is to prevent a gap from being formed between the receptacle and the plug. The receptacle and the plug are made of an insulator having a relative dielectric constant of 1 or more. For example, alumina ceramic, which is a receptacle material, has a relative dielectric constant of about 9, and rubber, which is a plug material, has a relative dielectric constant of about 4. In such a configuration, if there is an air gap between the receptacle and the plug, the electric field may concentrate in this gap and partial discharge may occur. When time elapses in a state where partial discharge has occurred, the insulator near the gap may deteriorate and lead to conduction.

  In the X-ray tube according to the present invention, the insulating fluid flows through a channel provided between the bushing plug and the receptacle, thereby cooling the cathode and the insulator to prevent overheating. Furthermore, the partial discharge between the plug and the receptacle is prevented by filling the gap between the plug and the receptacle with an insulating fluid.

  In the following embodiments, an X-ray imaging apparatus using the X-ray tube according to the present invention will be described when the X-ray tube according to the present invention is applied to an anode grounded X-ray tube. The X-ray tube according to the present invention is not limited to an anode grounded X-ray tube, but can be applied to a neutral point grounded X-ray tube and other X-ray tubes.

  As the insulating fluid, an insulating liquid or gas can be used. In the following examples, an example in which an insulating liquid is used as the insulating fluid will be described. Insulating liquid has higher insulating performance than insulating gas and has a high effect of preventing partial discharge.

  A first embodiment of an X-ray tube according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of an X-ray tube bushing in the present embodiment. 2 is a cross-sectional view taken along the cross-section 212 of FIG. 1, and FIG. 3 is a cross-sectional view taken along the cross-section 213.

  The bushing shown in FIG. 1 will be described. The bushing includes a plug 202 and a receptacle 201, and is connected to a high voltage generator (not shown) by a multicore cable.

  The multicore cable includes core wires 204A and 204B to which a high voltage is applied, an external conductor 210, an internal insulator 203 that insulates the core wires 204A and 204B and the external conductor 210, and an external that further insulates the external conductor 210 from the outside. An insulator 211 is formed. In the bushing, the outer conductor 210 is connected to the electric field relaxation ring 209.

  The electric field relaxation ring 209 can be made of conductive rubber or other conductive material. Of the volume resistivity of the receptacle 201 and the plug 202, it may be made of a material having a volume resistivity of 1/10 or less of the lower one.

  The multicore cable from which the internal insulator 203 is exposed is formed into a plug 202 having a generally truncated cone shape by rubber molding.

  The plug 202 does not need to be made of rubber, and may be made of an insulating organic material whose main component is epoxy, polyethylene, or the like, or an insulating inorganic material whose main component is alumina ceramics. Connector electrodes 205A and 205B are attached to the tip of the plug 202. Connector electrodes 205 </ b> A and 205 </ b> B are connected to filament 206 through a conducting wire penetrating receptacle 201. Therefore, the filament 206 is connected to the tip end portion of the plug 202 via the connector electrodes 205A and 205B and the conductive wires. One end of the filament 206 is electrically connected to a metal converging body 207.

  The receptacle 201 is a truncated cone having a generally internal shape so that the plug 202 can be inserted. Between the plug 202 and the receptacle 201, a fluid inflow channel 216 and a fluid discharge channel 217 through which an insulating liquid can flow are provided. The insulating liquid is supplied from an insulating fluid circulation device 220 provided outside the bushing. The fluid inlet channel 216 and the fluid outlet channel 217 are connected at the tip of the plug 202. Therefore, the insulating liquid flows from the fluid inflow channel 216 to the fluid discharge channel 217 via the tip of the plug 202.

  As shown in the cross-sectional view of FIG. 3, the fluid inflow channel 216 and the fluid discharge channel 217 are separated by the protrusion 230 of the plug 202. The protrusion 230 is in close contact with the receptacle 201. The protrusion 230 is in contact with the receptacle 201 at the top of the protrusion 230, and reduces the contact area with the receptacle 201, thereby forming a flow path while preventing bubbles and the like from being formed at the contact portion. is there.

  Returning to FIG. 1, the description will be continued. The receptacle 201 is made of an insulating material such as ceramics, a cathode composed of a filament 206 and a converging body 207 is connected to the tip, and a casing 208 that is a ground potential is connected to the other end. The receptacle 201 is preferably made of an insulating inorganic material whose main component is alumina ceramics or the like, but may be made of an insulating organic material whose main component is epoxy, polyethylene or the like.

  The casing 208 is electrically connected to the outer conductor 210 via the electric field relaxation ring 209. In the case of an X-ray tube, the housing 208 also serves as a vacuum container.

  As shown in the cross-sectional view of FIG. 2, the electric field relaxation ring 209 is provided with a fluid inflow hole 214 and a fluid discharge hole 215. As shown in FIG. 1, the bushing is provided with a fluid inlet 218 and a fluid outlet 219. The fluid inlet 218 and the fluid outlet 219 are connected to the insulating fluid circulation device 220. The fluid inlet channel 216 and the fluid outlet channel 217 communicate with the fluid inlet 218 and the fluid outlet 219 via the fluid inlet hole 214 and the fluid outlet hole 215, respectively.

  With such a structure, the insulating liquid supplied from the insulating fluid circulation device 220 includes the fluid inlet 218, the fluid inlet hole 214, the fluid inlet channel 216, the tip of the plug 202, the fluid outlet channel 217, the fluid It flows in the order of the discharge hole 215 and the fluid discharge port 219. In the present embodiment, the fluid inflow channel 216 and the fluid discharge channel 217 are provided so as to connect the tip end portion and the other end portion of the plug 202 substantially linearly along the surface of the plug 202.

  The insulating liquid is mainly composed of mineral oil, insulating oil based on alkylbenzene, insulating oil based on polybutene, insulating oil based on alkylnaphthalene, and alkyldiphenylalkane. Insulating oil, insulating oil mainly composed of silicone oil, oil derived from plants or animals, liquid mainly composed of chlorofluorocarbon, liquid mainly composed of fluorocarbon, liquid mainly composed of hydrochlorofluorocarbon, hydrofluorocarbon It is desirable to use a liquid selected from a liquid containing a main component, a liquid containing halon as a main component, and water. Or the mixture of said liquid may be sufficient. When such an insulating liquid is used as the insulating fluid, in addition to being easy to handle, stable partial discharge prevention performance between the plug 202 and the receptacle 201 can be obtained.

  In the above description, the insulating liquid is made to flow between the plug 202 and the receptacle 201. However, in the X-ray tube according to the present invention, partial discharge between the plug 202 and the receptacle 201 can be prevented. If it is not liquid, the gas supplied from the outside may flow. Examples of the flowing gas include air, nitrogen, sulfur hexafluoride, oxygen, carbon dioxide, and the like. If such a gas is used, a high pressure with an improved withstand voltage in order to prevent partial discharge. It is good to use in a state. Moreover, you may flow the gas selected from what vaporized said liquid. In the following, description will be made assuming that the insulating liquid is made to flow as a representative.

  The insulating liquid can be made to flow into and out of the bushing by the insulating fluid circulation device 220 provided outside the bushing. The insulating fluid circulation device 220 preferably has a function of circulating the fluid and a function of cooling the fluid. As the insulating fluid circulation device 220, a fluid circulation device mounted on an X-ray imaging apparatus may be used also for cooling the anode and the high voltage power source. In this case, you may make it the structure which supplies a part or all of the circulating fluid to a bushing.

  In the configuration of the bushing of the X-ray tube as in this embodiment, the insulating liquid flows through the flow path provided between the plug 202 and the receptacle 201, thereby cooling the cathode and the insulator to prevent overheating. it can. Further, by filling the space between the plug 202 and the receptacle 201 with an insulating liquid, partial discharge between the plug 202 and the receptacle 201 can be prevented.

  A second embodiment of the X-ray tube according to the present invention will be described with reference to FIGS. FIG. 4 is a cross-sectional view of the bushing of the X-ray tube in the present embodiment. 4, the same reference numerals as those in FIG. 1 denote the same or common components as the bushing shown in FIG. FIG. 5 is a cross-sectional view at the cross-section 213.

  Since the bushing of the X-ray tube in the present embodiment has a configuration similar to the bushing in the first embodiment, only portions different from the bushing in the first embodiment will be described below.

  As shown in FIG. 4, the bushing in this embodiment is an insulating material supplied from the insulating fluid circulation device 220 between the plug 202 and the receptacle 201 as in the bushing of the first embodiment (FIG. 1). A fluid inflow channel 216 and a fluid discharge channel 217 through which a liquid can flow are provided. The fluid inlet channel 216 and the fluid outlet channel 217 are connected at the tip of the plug 202. Therefore, the insulating liquid flows from the fluid inflow channel 216 to the fluid discharge channel 217 via the tip of the plug 202.

  In the present embodiment, the fluid inflow channel 216 and the fluid discharge channel 217 are formed in a double spiral shape along the outer surface of the generally conical trapezoidal plug 202 so as to connect the leading end and the other end of the plug 202. Is provided.

  As shown in the cross-sectional view of FIG. 5, the fluid inflow channel 216 and the fluid discharge channel 217 are separated by the protrusion 230 of the plug 202. The protrusion 230 is in close contact with the receptacle 201. In this embodiment, the protrusion 230 is provided on the outer surface of the plug 202 in a double spiral shape, and the double spiral is formed by the spiral fluid inflow channel 216 and the spiral fluid discharge channel 217. Is forming.

  4 has the same shape as the cross section shown in the cross sectional view of FIG. 2, and the electric field relaxation ring 209 is provided with a fluid inflow hole 214 and a fluid discharge hole 215. Further, as shown in FIG. 4, the bushing is provided with a fluid inlet 218 and a fluid outlet 219. The fluid inlet 218 and the fluid outlet 219 are connected to the insulating fluid circulation device 220. The fluid inlet channel 216 and the fluid outlet channel 217 communicate with the fluid inlet 218 and the fluid outlet 219 via the fluid inlet hole 214 and the fluid outlet hole 215, respectively.

  With such a structure, the insulating liquid supplied from the insulating fluid circulation device 220 includes the fluid inlet 218, the fluid inlet hole 214, the fluid inlet channel 216, the tip of the plug 202, the fluid outlet channel 217, the fluid It flows in the order of the discharge hole 215 and the fluid discharge port 219. As described above, in this embodiment, the insulating liquid is formed by the double surface formed by the spiral fluid inflow channel 216 and the spiral fluid discharge channel 217 on the outer surface of the generally frustoconical plug 202. It flows along a spiral channel.

  As the insulating liquid, the same liquid as in Example 1 can be used. The gas may be flowed instead of the insulating liquid as in the first embodiment.

  In the configuration of the bushing of the X-ray tube as in the present embodiment, the insulating liquid passes through one flow channel (fluid inflow channel 216) from the fluid inlet 218 among the double spiral channels. It reaches the tip of the plug 202 and is discharged from the fluid discharge port 219 through another channel (fluid discharge channel 217). Accordingly, it is possible to efficiently exchange heat between the cathode and the insulator and the insulating liquid, and the cathode and the insulator are more effective in cooling than the first embodiment. In addition, by making the flow path of the insulating liquid into a double helix shape, there is no part where the insulating liquid stays, bubbles that cause discharge are efficiently discharged, and the non-uniform part of the insulating liquid is effective. Can be reduced. Furthermore, it is possible to use common parts for the receptacle 201.

  A third embodiment of the X-ray tube according to the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view of the bushing of the X-ray tube in the present embodiment. In FIG. 6, the same reference numerals as those in FIG. 1 denote the same or common components as the bushings shown in FIG.

  Since the bushing of the X-ray tube in the present embodiment has a configuration similar to the bushing in the second embodiment, only portions different from the bushing in the second embodiment will be described below.

  In the bushing in the present embodiment, the fluid inflow channel 216 and the fluid discharge channel 217 have a double spiral shape along the surface of the conical trapezoidal plug 202 in the same manner as the bushing in the second embodiment. It is provided so that the front-end | tip part and other end part of 202 may be tied. The difference from the bushing of the second embodiment is that the fluid inflow channel 216 and the fluid discharge channel 217 are formed by grooves provided on the inner surface of the receptacle 201. That is, a groove is formed in a double spiral shape on the inner surface of the receptacle 201, and an insulating liquid flows through the groove to cool the cathode and the insulator.

  In the configuration of the bushing of the X-ray tube as in the present embodiment, the same effect as in the second embodiment can be obtained. Further, since the flow path of the insulating fluid is provided on the inner surface of the receptacle 201, it is only necessary to change the flow path structure of the receptacle 201 for X-ray tubes having different calorific values. Can be used.

  An embodiment of an X-ray imaging apparatus using an X-ray tube according to the present invention will be described with reference to FIG. FIG. 7 is a configuration diagram of the X-ray imaging apparatus in the present embodiment.

  The frequency converter 2 that is supplied with power from the commercial power supply 1 outputs high-frequency alternating current. The high frequency alternating current output by the frequency converter 2 is sent to the power transmission brush 3. The power transmission brush 3 is in contact with a power transmission slip ring 5 fixed to the scanner turntable 4, and is electrically connected even if the scanner turntable 4 is rotating. The power transmission slip ring 5 is connected to a high voltage generator 6, and the high voltage generator 6 converts high frequency alternating current into high voltage direct current. The X-ray tube 7 is supplied with a high voltage direct current, generates an electron beam therein, hits the target, and generates an X-ray beam 8. The X-ray beam 8 passes through the subject 10 placed on the bed 9, and the intensity of the X-ray beam 8 is converted into an electric signal by the detector 11. This electrical signal is converted into a digital signal by the data acquisition system 12 and sent to the image reconstruction device 15 via the data transmission slip ring 13 and the data transmission brush 14. The image reconstruction device 15 reconstructs an image based on the obtained X-ray intensity data and outputs tomographic image data of the subject 10. The tomographic image data is sent to the computer 16. The computer 16 can display a tomographic image of the subject 10 on the image display device 17 and store the tomographic image data in the image recording device 18.

  The X-ray tube 7 is the one to which the bushing shown in Example 1, Example 2, or Example 3 is applied, and an insulating fluid circulation device 220 that circulates an insulating liquid is connected to the X-ray tube 7. The insulating fluid circulation device 220 plays the same role as the insulating fluid circulation device 220 in the first to third embodiments.

  It is desirable that the insulating fluid circulation device 220 is mounted on the scanner turntable 4 and rotates around the subject 10 like the X-ray tube 7 and the high voltage generator 6. When electric power is required to operate the insulating fluid circulation device 220, it is desirable to supply electric power via the power transmission slip ring 5 or a slip ring provided separately, although not shown in FIG.

  In the configuration of the X-ray imaging apparatus as in the present embodiment, since the X-ray tube in the first, second, or third embodiment is mounted, the cooling and insulation reliability of the cathode and insulator of the X-ray tube are mounted. And the reliability of the entire X-ray imaging apparatus can be secured.

  DESCRIPTION OF SYMBOLS 1 ... Commercial power supply, 2 ... Frequency converter, 3 ... Power transmission brush, 4 ... Scanner rotating disk, 5 ... Power transmission slip ring, 6 ... High voltage generator, 7 ... X-ray tube, 8 ... X-ray beam , 9 ... Bed, 10 ... Subject, 11 ... Detector, 12 ... Data collection system, 13 ... Data transmission slip ring, 14 ... Data transmission brush, 15 ... Image reconstruction device, 16 ... Computer, 17 ... Image Display device, 18 ... Image recording device, 101 ... Cathode, 102 ... Anode, 103 ... Rotor, 104 ... Stator, 105 ... Insulator, 106 ... Housing, 201 ... Receptacle, 202 ... Plug, 203 ... Internal insulator, 204A , 204B ... core wire, 205A, 205B ... connector electrode, 206 ... filament, 207 ... converging body, 208 ... housing, 209 ... electric field relaxation ring, 210 ... outer conductor, 21 DESCRIPTION OF SYMBOLS External insulator, 212, 213 ... Cross section, 214 ... Fluid inflow hole, 215 ... Fluid discharge hole, 216 ... Fluid inflow channel, 217 ... Fluid discharge channel, 218 ... Fluid inflow port, 219 ... Fluid discharge port, 220 ... Insulating fluid circulation device, 230 ... Projection.

Claims (6)

An X-ray tube comprising a cathode having a bushing and a filament, and an anode, wherein when a high voltage is applied to the cathode, electrons are emitted from the filament and the electrons hit the anode to generate X-rays. ,
The bushing is
A plug with the filament connected to the tip;
A receptacle into which the plug is inserted;
A fluid inlet for injecting an insulating fluid;
A fluid outlet for discharging the insulating fluid;
A fluid inflow channel formed between the plug and the receptacle and allowing the insulating fluid to reach from the fluid inlet to the tip of the plug;
A fluid discharge passage formed between the plug and the receptacle and allowing the insulating fluid to reach from the tip of the plug to the fluid discharge port;
The fluid inflow channel and the fluid discharge channel are connected at the tip of the plug,
And an insulating fluid circulation device for circulating the insulating fluid through the bushing,
An X-ray tube characterized by that.   The X-ray tube according to claim 1, wherein the fluid inflow channel and the fluid discharge channel are formed in a spiral shape.   2. The X-ray tube according to claim 1, wherein the fluid inflow channel and the fluid discharge channel are formed by a protrusion provided in a spiral shape on an outer surface of the plug.   The X-ray tube according to claim 1, wherein the fluid inflow channel and the fluid discharge channel are formed by grooves provided in a spiral shape on an inner surface of the receptacle.   The X-ray tube according to any one of claims 1 to 4, wherein the insulating fluid is an insulating liquid.   An X-ray imaging apparatus comprising the X-ray tube according to claim 1.

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