Emitter structure and electron gun

Abstract

To provide an emitter structure and an electron gun that are capable of suppressing occurrence of distortion in an emitter.SOLUTION: An emitter structure includes: an emitter extending in a plate like shape and having an electron emission surface and a heat release surface; a pair of support rod materials located so as to sandwich the electron emission surface and the heat release surface in an extension direction, the support rod materials fixing the emitter; a first insulator attached to one of the pair of support rod materials; a second insulator attached to the other of the pair of support rod materials; and a thermal expansion member extending in the extension direction. The thermal expansion member has an opposite surface that is opposite to the heat release surface across a gap therebetween and that receives radiant heat from the heat release surface. The thermal expansion member is electrically insulated from the pair of support rod materials by the first insulator and the second insulator. When the temperature of the opposite surface has risen upon receiving radiant heat from the heat release surface, the thermal expansion member expands in the extension direction and thereby causes a force to act on the pair of support rod materials.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Embodiments of the present invention relate to an emitter structure and an electron gun.

Background Art

[0002] X-ray tubes are used for X-ray imaging diagnosis applications, non-destructive inspection applications, and the like. As X-ray tubes, there are fixed anode type X-ray tubes and rotating anode type X-ray tubes, and the one corresponding to the application is used. For example, rotating anode type X-ray tubes are generally used for medical diagnosis applications. An X-ray tube includes an anode target, a cathode electron gun, and an envelope. The anode target forms a focal point that emits X-rays when an electron beam is incident thereon. The cathode electron gun includes an emitter that emits electrons, a focusing electrode (electron focusing cup), and the like. The emitter is heated by supplying current and emits electrons. At this time, it is known that the emitter deforms due to thermal expansion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present embodiment provides an emitter structure and an electron gun capable of suppressing the occurrence of strain in the emitter.

Means for Solving the Problems

[0005] The emitter structure according to one embodiment includes an emitter that extends in a plate shape and has an electron emission surface for emitting electrons and a heat emission surface located on the side opposite to the electron emission surface and generating heat radiation, a pair of support bars that are located sandwiching the electron emission surface and the heat emission surface in the extending direction in which the emitter extends, are electrically connected to the emitter, and fix the emitter, a first insulator attached to one of the pair of support bars, a second insulator attached to the other of the pair of support bars, and a thermal expansion member extending in the extending direction. The thermal expansion member faces the heat emission surface with a gap therebetween and has a facing surface for receiving radiant heat from the heat emission surface. The thermal expansion member is electrically insulated from the pair of support bars by the first insulator and the second insulator. When the temperature of the facing surface rises upon receiving radiant heat from the heat emission surface, the thermal expansion member expands in the extending direction and applies a force to the pair of support bars.

[0006] Also, the emitter structure according to one embodiment includes an emitter that extends in a plate shape and has an electron emission surface for emitting electrons and a heat emission surface located on the side opposite to the electron emission surface and generating heat radiation, a pair of support bars that are located sandwiching the electron emission surface and the heat emission surface in the extending direction in which the emitter extends, are electrically connected to the emitter, and fix the emitter, a first insulator attached to one of the pair of support bars, and a thermal expansion member extending in the extending direction. The thermal expansion member faces the heat emission surface with a gap therebetween and has a facing surface for receiving radiant heat from the heat emission surface. The thermal expansion member is electrically insulated from one of the pair of support bars by the first insulator. When the temperature of the facing surface rises upon receiving radiant heat from the heat emission surface, the thermal expansion member expands in the extending direction and applies a force to the pair of support bars.

[0007] Further, an electron gun according to an embodiment includes an emitter having an electron emission surface that extends in a plate shape and emits electrons, and a heat emission surface that is located on the side opposite to the electron emission surface and generates heat radiation, a pair of support bars that are located sandwiching the electron emission surface and the heat emission surface in the extending direction in which the emitter extends and are electrically connected to the emitter to fix the emitter, a first insulator attached to one of the pair of support bars, a second insulator attached to the other of the pair of support bars, and a thermal expansion member that extends in the extending direction, an emitter structure including the above; a support member that supports the pair of support bars via the first insulator and the second insulator and is electrically insulated from the pair of support bars by the first insulator and the second insulator; and a convergence electrode that fixes the support member and converges electrons from the electron emission surface. The thermal expansion member faces the heat emission surface with a gap therebetween, has a facing surface that receives radiant heat from the heat emission surface, is electrically insulated from the pair of support bars by the first insulator and the second insulator, and expands in the extending direction and applies a force to the pair of support bars when the temperature rises due to receiving radiant heat from the heat emission surface on the facing surface.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0009] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. Note that the disclosure is merely an example, and those that can be easily conceived by those skilled in the art with appropriate modifications while maintaining the gist of the invention are naturally included in the scope of the present invention. Also, for the sake of clarity in the drawings and description, the width, thickness, shape, etc. of each part may be schematically represented compared to the actual state, but this is merely an example and does not limit the interpretation of the present invention. Further, in this specification and each figure, the same reference numerals may be assigned to the same elements as those described above with respect to the previously shown figures, and detailed descriptions may be appropriately omitted.

[0010] First, the basic concept of the embodiment of the present invention will be described. The X-ray tube includes an anode target, a cathode electron gun, an enclosure, etc. The cathode electron gun has an emitter, a focusing electrode, etc. When a high voltage of several tens to several hundreds of kV is applied between the anode target and the cathode electron gun, the electrons emitted from the emitter are accelerated toward the anode target. At this time, the focusing electrode serves as an electron lens and converges the electrons traveling toward the anode target.

[0011] Normally, the X-ray tube has two focal spots: a large focal spot with a large size and capable of inputting a large current, and a small focal spot with a small size, less input, but high resolution. Some X-ray tubes have three focal spots. The size of each of these focal spots depends on the respective shapes and positional relationships of the emitter and the focusing electrode and is usually fixed. When using the large focal spot or the small focal spot, the imaging conditions are determined by judging the spatial resolution and the input current (which affects contrast and noise) according to the diagnostic application, and the large focal spot and the small focal spot are used appropriately.

[0012] However, with only two focal points, the imaging conditions may be discontinuous and it may not be possible to obtain the images required for X-ray image diagnosis. In particular, when performing continuous imaging in the axial direction of the subject, such as helical scanning in an X-ray CT apparatus, the continuity of the image quality cannot be maintained with the variable input due to the discontinuous two focal points, and accurate image diagnosis may not be possible. Also, it is necessary to adjust the amount of X-rays radiated according to each patient being imaged. For example, the amount of X-rays radiated to a patient with a large build is more than the amount of X-rays radiated to a small child. Since this amount of X-rays depends on the current supplied to the emitter of the cathode electron gun, the structure of the cathode electron gun and the device for the emitter become important.

[0013] When using a conventional filament coil as an electron emission source, there are various problems such as large current, current control performance, and control performance of the focal spot size. In order to solve the above problems, it has become increasingly common to use a plate-shaped emitter (flat emitter) as an electron emission source. Since the plate-shaped emitter has a plane and emits electrons from the above plane, it becomes easy to control the electron beam bundle forming the focal spot size. For this reason, it is possible to increase the area for emitting electrons, and large current can also be realized.

[0014] On the other hand, when current is supplied, the temperature of the emitter rises. As a result, there is a problem that the shape of the emitter is deformed. The amount of electrons (electron amount) emitted from the emitter depends on the distance between the emitter and the focusing electrode. That is, when the emitter is distorted due to thermal expansion, the amount of electrons emitted from the emitter changes. In response to the change in the amount of emitted electrons, the amount of X-rays emitted from the focal point changes, and the performance of an image evaluation apparatus such as an X-ray CT apparatus changes. Therefore, in the embodiment of the present invention, it is possible to obtain an emitter structure and an electron gun capable of suppressing the occurrence of strain in the emitter when the temperature of the emitter rises, which improves such problems.

[0015] (First Embodiment) FIG. 1 is a cross-sectional view showing an X-ray tube device according to the first embodiment. As shown in FIG. 1, the X-ray tube device includes a rotating anode type X-ray tube (hereinafter also referred to as "rotating anode type X-ray tube") 1, a stator coil 2 as a coil for generating a magnetic field, a housing 3 that houses the rotating anode type X-ray tube 1 and the stator coil 2, and a coolant 4 filled in the housing 3.

[0016] The rotating anode type X-ray tube 1 includes a rotation mechanism 5, an anode target 50, a cathode electron gun (hereinafter also simply referred to as "electron gun") 80, and an envelope 70. The rotation mechanism 5 has a fixed shaft 10, a rotating body 20, a bearing 30, and a rotor 40. The fixed shaft 10 is formed in a cylindrical shape and extends along the rotation axis a. The fixed shaft 10 is formed of a metal such as an Fe (iron) alloy or a Mo (molybdenum) alloy. The rotating body 20 is configured to be rotatable about the fixed shaft 10. The rotating body 20 is formed of a metal such as an Fe alloy or a Mo alloy.

[0017] The bearing 30 is formed between the fixed shaft 10 and the rotating body 20. The bearing 30 rotatably supports the rotating body 20 about the fixed shaft 10. In one example, the bearing 30 has ball bearings 31 and 32. The ball bearings 31, 32 are fixed between the fixed shaft 10 and the rotating body 20. A method of fixing the ball bearings 31, 32 is, for example, shrink fitting in which the ball bearings 31, 32 are provided on the fixed shaft 10, then the rotating body 20 is heated, and thereafter the fixed shaft 10 and the ball bearings 31, 32 are press-fitted into the rotating body 20.

[0018] Note that the bearing 30 is not limited to the ball bearings 31, 32, and may be configured as a sliding bearing having radial bearing surfaces on the outer peripheral surface of the fixed shaft 10 and the inner peripheral surface of the rotating body 20, for example. In this case, a liquid metal is filled between the fixed shaft 10 and the rotating body 20 as a lubricant. The rotor 40 extends along the rotation axis a and is formed in a cylindrical shape, and is fixed to the outer peripheral surface of the rotating body 20. A method of fixing the rotor 40 to the rotating body 20 is, for example, brazing.

[0019] The anode target 50 is formed in a substantially disk shape like an umbrella and is provided coaxially with the fixed shaft 10 and the rotating body 20. The anode target 50 has an anode target body 51 and a target layer 52 provided on a part of the outer surface of the anode target body 51. The anode target body 51 is formed of molybdenum, tungsten, or a metal using these. The melting point of the metal forming the target layer 52 is the same as or higher than the melting point of the metal forming the anode target body 51. For example, the anode target body 51 is formed of a molybdenum alloy, and the target layer 52 is formed of a tungsten alloy. The anode target 50 is rotatable together with the rotating body 20. When electrons collide with the target surface S52 of the target layer 52, a focal point is formed on the target surface S52. Thereby, the anode target 50 emits X-rays from the focal point.

[0020] The electron gun 80 is spaced from the target layer 52 of the anode target 50 and is disposed opposite to the target layer 52. The electron gun 80 is supported by a cathode support portion 60 fixed to the outer container 70. The electron gun 80 has an emitter structure 81. The electron gun 80 emits electrons toward the anode target 50 when a high voltage is applied. The cathode support portion 60 has a cavity through which a wiring 61 connecting the electron gun 80 and a power source (not shown) passes. Details of the electron gun 80 and the emitter structure 81 will be described later in the descriptions of FIGS. 2, 3, and 4.

[0021] The outer container 70 is formed in a cylindrical shape. The outer container 70 is formed of glass, ceramic, and metal. In the outer container 70, the outer diameter of the portion facing the anode target 50 is larger than the outer diameter of the portion facing the rotor 40. The outer container 70 has an opening 71 and an X-ray transmission window 72 that transmits X-rays. The outer container 70 is sealed, houses the anode target 50 and the electron gun 80, and fixes the fixed shaft 10. The inside of the outer container 70 is maintained in a vacuum state (reduced pressure state).

[0022] The stator coil 2 is provided so as to surround the outside of the outer casing 70 facing the outer peripheral surface of the rotor 40. The shape of the stator coil 2 is annular. The stator coil 2 generates a magnetic field applied to the rotor 40 (rotating body 20) to rotate the rotating body 20 and the anode target 50. The housing 3 is formed in a cylindrical shape. The housing 3 is formed of a brittle material such as, for example, an aluminum casting. A lead plate for shielding X-rays is attached to the inner surface of the housing 3. The cooling liquid 4 is filled in the space between the rotating anode type X-ray tube 1 and the housing 3. As the cooling liquid 4, insulating oil or a water-based cooling liquid can be used.

[0023] Figure 2 is a plan view of the electron gun 80 as viewed in the direction of arrow A in Figure 1. Figure 3 is a cross-sectional view of the electron gun 80 taken along line B-B in Figure 2. Figure 4 is a perspective view showing the emitter structure 81 and the support member 82 shown in Figure 3. As shown in Figures 2, 3, and 4, the electron gun 80 includes an emitter structure 81, a support member 82, and a focusing electrode 83. The emitter structure 81 includes an emitter 84, a pair of support bars 85, 86, a first insulator 87, a second insulator 88, a thermal expansion member 89, and a sleeve 90. The emitter 84 extends in a plate shape and has an electron emission surface 84a that emits electrons, a heat emission surface 84b that is located on the side opposite to the electron emission surface 84a and generates heat radiation, and a plurality of slits 84c. The electron emission surface 84a faces the anode target 50. The heat emission surface 84b is, in one example, a plane parallel to the electron emission surface 84a.

[0024] The plurality of slits 84c penetrate from the electron emission surface 84a to the heat emission surface 84b and form a current path for the current flowing through the emitter 84. More specifically, the plurality of slits 84c form a current path in the electron emission surface 84a, the heat emission surface 84b, and the region between the electron emission surface 84a and the heat emission surface 84b. The emitter 84 further has one end surface 84f in a direction parallel to the electron emission surface 84a and orthogonal to the extending direction X, and the other end surface 84g on the side opposite to the one end surface 84f. In one example, the plurality of slits 84c are composed of a first slit 84c1 formed by recessing the one end surface 84f and a second slit 84c2 formed by recessing the other end surface 84c2. The first slit 84c1 and the second slit 84c2 are, in one example, arranged alternately along the extending direction X. Thereby, in the region having the electron emission surface 84a and the heat emission surface 84b of the emitter 84, a zigzag continuous current path is formed, and the area of the electron emission surface 84a for emitting electrons can be ensured. The emitter 84 is formed of, for example, tungsten. The coefficient of thermal expansion of tungsten is about 5.2×10 -6 / K. The emitter 84 further has connecting portions 84d and 84e positioned sandwiching the electron emission surface 84a and the heat emission surface 84b in the extending direction X in which the emitter 84 extends, and fitting holes H1 formed in the connecting portions 84d and 84e. The fitting hole H1 is a hole formed to penetrate in the orthogonal direction Y orthogonal to the electron emission surface 84a.

[0025] The support bar 85 extends in the orthogonal direction Y and is formed in a columnar shape, and has a large-diameter portion 85a and a small-diameter portion 85b. The support bar 86 extends in the orthogonal direction Y and is formed, and has a large-diameter portion 86a and a small-diameter portion 86b. A pair of support bars 85 and 86 are positioned sandwiching the electron emission surface 84a and the heat emission surface 84b in the extending direction X, are electrically connected to the emitter 84, and fix the emitter 84. The pair of support bars 85 and 86 have a first groove portion G1 and a second groove portion G2. The first groove portion G1 is formed by recessing the upper surfaces of the large-diameter portions 85a and 86a. The first groove portion G1 houses the connection portions 84d and 84e. The second groove portion G2 is formed by recessing the upper surface of the first groove portion G1 and is a groove extending in the extending direction X. Both ends of the second groove portion G2 in the extending direction X are formed in an arc shape in a plan view. Note that the second groove portion G2 is not limited to a groove having both ends formed in an arc shape, and for example, it may be a rectangular groove in a plan view. The second groove portion G2 is used when positioning the emitter 84 with respect to the support bars 85 and 86.

[0026] The support bars 85 and 86 fix the emitter 84 by joining the large-diameter portion 85a to the connection portion 84d and joining the large-diameter portion 86a to the connection portion 84e. Also, the support bars 85 and 86 are electrically connected to the emitter 84 by the large-diameter portion 85a contacting the connection portion 84d and the large-diameter portion 86a contacting the connection portion 84e. The material of the pair of support bars 85 and 86 is, for example, molybdenum. Also, the emitter 84 is fixed to the pair of support bars 85 and 86 in a state where a tensile load in the extending direction X is generated at room temperature. The procedure for fixing the emitter 84 to the pair of support bars 85 and 86 will be described later in the description of FIG. 5. Note that the emitter 84 may be fixed to the pair of support bars 85 and 86 in a state where no tensile load is generated.

[0027] The first insulator 87 is composed of three insulators 87a, 87b, and 87c. The first insulator 87 is attached to one of the pair of support bars 85 and 86 (the support bar 85 in FIG. 2). The first insulator 87 is formed of a ceramic material such as alumina (aluminum oxide), zirconia (zirconium oxide), or silicon nitride and has electrical insulation properties. Each of the insulators 87a, 87b, and 87c has a through hole H2 formed to penetrate in the orthogonal direction Y. The small-diameter portion 85b of the support bar 85 is inserted into the through hole H2.

[0028] The second insulator 88 is composed of three insulators 88a, 88b, and 88c. The second insulator 88 is attached to the other one of the pair of support bars 85 and 86 (support bar 86 in FIG. 2). The second insulator 88 is formed of a ceramic material such as alumina, zirconia, or silicon nitride and has electrical insulation properties. Each of the insulators 88a, 88b, and 88c has a through-hole H3 formed to penetrate in the orthogonal direction Y. The reduced-diameter portion 86b of the support bar 86 is inserted into the through-hole H3.

[0029] The thermal expansion member 89 extends in the extending direction X, has a facing surface 89a that faces the heat dissipation surface 84b with a gap therebetween and receives radiant heat from the heat dissipation surface 84b. The facing surface 89a is parallel to the heat dissipation surface 84b. The thermal expansion member 89 further has a connecting portion 89b, a connecting portion 89c, a through-hole H4 formed in the connecting portion 89b, and a through-hole H5 formed in the connecting portion 89c. The connecting portion 89b and the connecting portion 89c are positioned with the facing surface 89a therebetween. The through-hole H4 is a hole formed to penetrate in the orthogonal direction Y in the connecting portion 89b. The through-hole H5 is a hole formed to penetrate in the orthogonal direction Y in the connecting portion 89c.

[0030] The thermal expansion member 89 is fixed to the pair of support bars 85 and 86 via the first insulator 87 and the second insulator 88. Specifically, the thermal expansion member 89 is fixed to the pair of support bars 85 and 86 such that the connecting portion 89b of the thermal expansion member 89 is sandwiched between the insulator 87a and the insulator 87b, the inner peripheral surface of the through-hole H4 contacts the outer peripheral surface of the insulator 87a, the connecting portion 89c is sandwiched between the insulator 88a and the insulator 88b, and the inner peripheral surface of the through-hole H5 contacts the outer peripheral surface of the insulator 88a. Note that the thermal expansion member 89 is not limited to being fixed to the support bars 85 and 86, and for example, it may be attached to the support bars 85 and 86 so as to be slightly movable. Further, the thermal expansion member 89 is electrically insulated from the pair of support bars 85 and 86 by the first insulator 87 and the second insulator 88. The thermal expansion coefficient of the thermal expansion member 89 is larger than that of the emitter 84. The thermal expansion member 89 is formed of, for example, copper (Cu) or a copper-based alloy. In this case, the thermal expansion coefficient of the thermal expansion member 89 is 15×10 -6 to 17×10 -6 / K.

[0031] The sleeves 90 are provided one each on the support bar 85 and the support bar 86. The sleeves 90 extend in the orthogonal direction Y and are formed in a cylindrical shape, and have a cylindrical portion 90a and a flange portion 90b formed on the outer peripheral surface of the cylindrical portion 90a. The cylindrical portion 90a of the sleeve 90 provided on the support bar 85 is located surrounding the reduced-diameter portion 85b and is fixed to the reduced-diameter portion 85b. The cylindrical portion 90a of the sleeve 90 provided on the support bar 86 is located surrounding the reduced-diameter portion 86b and is fixed to the reduced-diameter portion 86b. The sleeve 90 is fixed to the support bars 85 and 86 by the joining of the cylindrical portion 90a to the reduced-diameter portions 85b and 86b.

[0032] The flange portion 90b is in contact with the insulators 87c and 88c. Thereby, the sleeve 90 fixes the first insulator 87 to the support bar 85 and fixes the second insulator 88 to the support bar 86. Note that the flange portion 90b may be joined to the insulators 87c and 88c. The flange portion 90b suppresses the movement of the insulators 87c and 88c in the orthogonal direction Y.

[0033] The sleeve 90 may be configured without the cylindrical portion 90a, and may be configured of, for example, only the flange portion 90b. Note that when it is configured of only the flange portion 90b, the position of the flange portion 90b will shift when the support bars 85 and 86 thermally expand in the orthogonal direction Y. When having the cylindrical portion 90a, since the cylindrical portion 90a expands together with the support bars 85 and 86, the shift of the position of the flange portion 90b can be suppressed. Therefore, it is preferable for the sleeve 90 to have the cylindrical portion 90a.

[0034] The support member 82 extends in the extending direction X and has through holes H6 and H7 formed therethrough in the orthogonal direction Y. The through hole H6 is located surrounding the first insulator 87 and the support bar 85. The through hole H7 is located surrounding the second insulator 88 and the support bar 86. The support member 82 supports a pair of support bars 85 and 86 via the first insulator 87 and the second insulator 88, and is electrically insulated from the pair of support bars 85 and 86 by the first insulator 87 and the second insulator 88. The support member 82 is formed of a metal such as nickel (Ni), stainless steel (SUS), or kovar (KOV). In this case, the coefficient of thermal expansion of the support member 82 is 4×10 -6 to 14×10 -6 / K.

[0035] In one example, the support member 82 fixes the first insulator 87 by contact between the inner peripheral surface of the through hole H6 and the outer peripheral surface of the insulator 87c. That is, the support member 82 fixes one of the pair of support bars 85 and 86 (support bar 85 in one example) via the first insulator 87. In the extending direction X, there is a gap between the inner peripheral surface of the through hole H7 of the support member 82 and the outer peripheral surface of the second insulator 88. In other words, the support member 82 does not contact the second insulator 88 in the extending direction X. The through hole H7 is, for example, a long hole extending in the extending direction X. Further, the support member 82 has a movement restricting portion 82a inside the through hole H7, which faces the second insulator 88 on the side opposite to the first insulator 87 in the extending direction X.

[0036] The convergence electrode 83 controls the electrons emitted from the emitter 84. More specifically, the convergence electrode 83 converges the electrons from the electron emission surface 84a. For example, when a current is supplied, the convergence electrode 83 converges the electrons emitted from the emitter 84 to a focal point on the anode target 50. In one example, the convergence electrode 83 is formed in an annular shape and has a housing hole 83a for housing the emitter 84 therein. The support member 82 is fixed to the inner surface of the convergence electrode 83. That is, the convergence electrode 83 fixes the support member 82.

[0037] The coefficient of thermal expansion of the support member 82 is equal to that of the converging electrode 83. The converging electrode 83 may be formed of the same material as the support member 82, such as nickel or stainless steel, for example. Note that the coefficient of thermal expansion of the converging electrode 83 does not necessarily have to be equal to that of the support member 82. In this case, the converging electrode 83 is formed of iron, for example. The X-ray tube device according to the first embodiment is configured as described above.

[0038] In the operation of the electron gun 80 of the X-ray tube device, when a current is supplied to the emitter 84 via a pair of support bars 85 and 86, the emitter 84 emits electrons from the electron emission surface 84a toward the anode target 50. At this time, the temperature of the emitter 84 rises, and the emitter 84 expands in the extending direction X. On the other hand, heat radiation occurs at the heat radiation surface 84b, and the opposing surface 89a of the thermal expansion member 89 receives the radiant heat from the heat radiation surface 84b. At this time, the temperature of the thermal expansion member 89 rises, and the thermal expansion member 89 expands in the extending direction X.

[0039] As a result, the thermal expansion member 89 applies a force to the pair of support bars 85 and 86 via the first insulator 87 and the second insulator 88. That is, when the temperature of the thermal expansion member 89 rises due to the opposing surface 89a receiving the radiant heat from the heat radiation surface 84b, the thermal expansion member 89 expands in the extending direction X and applies a force to the pair of support bars 85 and 86. Then, the support bar 86 moves in the extending direction X according to the amount of expansion of the thermal expansion member 89. Note that when the thermal expansion member 89 expands excessively, the movement of the support bar 86 is restricted by the contact between the movement restricting portion 82a of the support member 82 and the second insulator.

[0040] Here, an example of the procedure for fixing the emitter 84 to the support bars 85 and 86 will be described. FIG. 5 is a cross-sectional view showing a state before the emitter 84 is fixed to the support bars 85 and 86. As shown in FIG. 5, first, the emitter 84, a pair of support bars 85 and 86 to which the thermal expansion member 89 is fixed, and pins P1 and P2 are prepared, and the emitter 84 is accommodated in the first groove portion G1. Next, the pin P1 is inserted into the fitting hole H1 of the connecting portion 84d and the second groove portion G2 of the large-diameter portion 85a, and the position of the emitter 84 with respect to the support bar 85 is determined by moving the pin P1 along the extending direction X along the second groove portion G2 of the large-diameter portion 85a. Then, the connecting portion 84d and the large-diameter portion 85a are joined. Next, the pin P2 is inserted into the fitting hole H1 of the connecting portion 84e and the second groove portion G2 of the large-diameter portion 86a, a tensile load in the extending direction X is applied to the emitter 84, and the position of the emitter 84 with respect to the pair of support bars 85 and 86 is determined by moving the pin P2 along the second groove portion G2 of the large-diameter portion 86a. Then, the connecting portion 84e and the large-diameter portion 86a are joined, and the pins P1 and P2 are pulled out from the fitting hole H1 and the second groove portion G2 to complete the fixing of the emitter 84 to the support bars 85 and 86. Note that the pin P1 may be pulled out when the connecting portion 84d and the large-diameter portion 85a are joined.

[0041] The effects of the first embodiment will be described. According to the emitter structure and the electron gun according to the first embodiment configured as described above, the emitter structure 81 includes the emitter 84, a pair of support bars 85 and 86, a first insulator 87, a second insulator 88, and a thermal expansion member 89. The thermal expansion member 89 has an opposing surface 89a that receives radiant heat from the heat dissipation surface 84b of the emitter 84, and when the temperature rises due to receiving radiant heat at the opposing surface 89a, it expands in the extending direction X and applies a force to the pair of support bars. The electron gun 80 includes, in addition to the emitter structure 81, a support member 82 and a converging electrode 83. The support member 82 supports the pair of support bars 85 and 86, and the converging electrode 83 fixes the support member 82. The emitter 84 has a plurality of slits 84c. As a result, when the temperature of the emitter 84 rises, it is possible to obtain an emitter structure 81 and an electron gun 80 that can suppress the occurrence of strain in the emitter 84. Further, it is possible to suppress the narrowing of the slit 84c in the extending direction X, and it is possible to maintain the amount of electrons emitted from the emitter 84.

[0042] The thermal expansion member 89 is fixed to the pair of support bars 85 and 86. The support member 82 fixes one of the pair of support bars 85 and 86. As a result, when the emitter structure 81 and the electron gun 80 are used in an X-ray CT apparatus, it is possible to suppress deformation and movement of the emitter 84 when subjected to a centrifugal acceleration.

[0043] The thermal expansion coefficient of the thermal expansion member 89 is larger than the thermal expansion coefficient of the emitter 84. The emitter is fixed to the pair of support bars 85 and 86 in a state where a tensile load in the extending direction X is generated at room temperature. As a result, even when the temperature of the emitter 84 is lower than the temperature of the thermal expansion member 89, the stress generated by the thermal expansion of the emitter 84 can be relaxed, and the strain generated in the emitter 84 can be suppressed.

[0044] The support member 82 has a movement restriction portion 82a that faces the second insulator 88 on the side opposite to the first insulator 87 in the extending direction X. Thereby, it is possible to prevent the emitter 84 from expanding too much in the extending direction X. The thermal expansion coefficient of the support member 82 is equal to the thermal expansion coefficient of the convergence electrode 83. If the support member 82 fixes the support bar 85, even when the support member 82 and the convergence electrode 83 thermally expand, the relative positional relationship between the support bar 85 and the convergence electrode 83 can be maintained.

[0045] (Second Embodiment) Next, the second embodiment will be described. FIG. 6 is a cross-sectional view of the electron gun 80 according to the second embodiment. The electron gun 80 is configured in the same manner as the first embodiment except for the configuration described in the second embodiment. As shown in FIG. 6, the electron gun 80 includes an emitter structure 81, a support member 82, and a focusing electrode 83. The emitter structure 81 includes an emitter 84, a pair of support bars 85 and 86, a first insulator 87, a thermal expansion member 89, and a sleeve 90. That is, the emitter structure 81 is configured without the second insulator 88.

[0046] The connecting portion 89c of the thermal expansion member 89 is fixed to the support bar 86. Specifically, the inner peripheral surface of the through hole H5 of the thermal expansion member 89 contacts the outer peripheral surface of the support bar 86, so that the thermal expansion member 89 is fixed to the support bar 86. Note that the thermal expansion member 89 may be joined to the support bar 86. The support member 82 is fixed to the focusing electrode 83 and supports the support bar 85 via the first insulator 87. In one example, the support member 82 fixes the support bar 85 via the first insulator 87. The support member 82 is configured without the through hole H7 and the movement restricting portion 82a and does not support the support bar 86.

[0047] The operation of the electron gun 80 will be described. The thermal expansion member 89 is electrically insulated from one of the support bars 85. Therefore, when a current is supplied to the emitter 84 via the pair of support bars 85 and 86, no current flows through the thermal expansion member 89. Similar to the first embodiment, the temperature of the thermal expansion member 89 rises by receiving radiant heat from the emitter 84. Since the thermal expansion member 89 is fixed to the pair of support bars 85 and 86, the thermal expansion member 89 acts on the pair of support bars 85 and 86 with a force. As a result, the support bar 86 moves in the extending direction X by the amount of expansion of the thermal expansion member 89.

[0048] According to the emitter structure according to the second embodiment configured as described above, the emitter structure 81 includes an emitter 84, a pair of support bars 85 and 86, a first insulator 87, and a thermal expansion member 89. As a result, the number of components can be reduced, and an inexpensive emitter structure 81 can be obtained.

[0049] Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope. It is also possible to combine a plurality of embodiments as necessary.

Explanation of Reference Numerals

[0050] 1…Rotating anode X-ray tube, 80…Electron gun, 81…Emitter structure, 82…Support member, 82a…Movement restriction portion, 83…Converging electrode, 84…Emitter, 84a…Electron emission surface, 84b…Heat dissipation surface, 84c…Slit, 84c1…First slit, 84c2…Second slit, 84f…One end surface, 84g…The other end surface, 85, 86…Support bars, 87…First insulator, 88…Second insulator, 89…Thermal expansion member, 89a…Opposing surface, X…Extending direction.

Claims

1. An emitter having an electron emission surface that extends in a plate shape and emits electrons, and a heat emission surface that is located on the side opposite to the electron emission surface and generates heat radiation. A pair of support bars that are located sandwiching the electron emission surface and the heat emission surface in the extending direction in which the emitter extends, are electrically connected to the emitter, and fix the emitter. A first insulator attached to one of the pair of support bars. A second insulator attached to the other of the pair of support bars. And a thermal expansion member that extends in the extending direction. The thermal expansion member Faces the heat emission surface with a gap, and has a facing surface that receives radiant heat from the heat emission surface. Is electrically insulated from the pair of support bars by the first insulator and the second insulator. When the temperature rises due to the facing surface receiving radiant heat from the heat emission surface, it expands in the extending direction and acts on the pair of support bars with a force. An emitter structure.

2. The thermal expansion member is fixed to the pair of support bars via the first insulator and the second insulator. The emitter structure according to claim 1.

3. The thermal expansion coefficient of the thermal expansion member is larger than the thermal expansion coefficient of the emitter. The emitter structure according to claim 1 or 2.

4. The emitter is fixed to the pair of support bars in a state where a tensile load in the extending direction is generated at room temperature. The emitter structure according to claim 2.

5. The emitter has one end face in a direction parallel to the electron emission surface and orthogonal to the extending direction, the other end face on the side opposite to the one end face, and a plurality of slits that penetrate from the electron emission surface to the heat emission surface and form a current path for the current flowing through the emitter. The plurality of slits are composed of a first slit formed by recessing the one end face and a second slit formed by recessing the other end face. The emitter structure according to claim 1 or 4.

6. An emitter that extends in a plate shape and has an electron emission surface that emits electrons and a heat emission surface that is located on the side opposite to the electron emission surface and generates heat radiation. A pair of support bars that are located sandwiching the electron emission surface and the heat emission surface in the extending direction in which the emitter extends, are electrically connected to the emitter, and fix the emitter. A first insulator attached to one of the pair of support bars. A thermal expansion member extending in the extending direction, and is provided. The thermal expansion member Faces the heat emission surface with a gap, and has a facing surface that receives radiant heat from the heat emission surface. Is electrically insulated from one of the pair of support bars by the first insulator. When the facing surface receives radiant heat from the heat emission surface and the temperature rises, it expands in the extending direction and acts on the pair of support bars with a force. Emitter structure.

7. An emitter that extends in a plate shape and has an electron emission surface that emits electrons and a heat emission surface that is located on the side opposite to the electron emission surface and generates heat radiation, a pair of support bars that are located sandwiching the electron emission surface and the heat emission surface in the extending direction in which the emitter extends, are electrically connected to the emitter, and fix the emitter, a first insulator attached to one of the pair of support bars, a second insulator attached to the other of the pair of support bars, and a thermal expansion member extending in the extending direction, and an emitter structure including the same. A support member that supports the pair of support bars via the first insulator and the second insulator and is electrically insulated from the pair of support bars by the first insulator and the second insulator; A converging electrode that fixes the support member and converges electrons from the electron emission surface; and The thermal expansion member has a facing surface that faces the heat dissipation surface with a gap therebetween and receives radiant heat from the heat dissipation surface; is electrically insulated from the pair of support bars by the first insulator and the second insulator; when the facing surface receives radiant heat from the heat dissipation surface and the temperature rises, it expands in the extending direction and applies a force to the pair of support bars; An electron gun. **Claim 8** The thermal expansion member is fixed to the pair of support bars via the first insulator and the second insulator. The electron gun according to claim 7. **Claim 9** The thermal expansion coefficient of the thermal expansion member is larger than the thermal expansion coefficient of the emitter. The electron gun according to claim 7 or 8. **Claim 10** The emitter is fixed to the pair of support bars in a state where a tensile load in the extending direction is generated at normal temperature. The electron gun according to claim 8. **Claim 11** The emitter has an end face in a direction parallel to the electron emission surface and orthogonal to the extending direction, the other end face opposite to the end face, and a plurality of slits that penetrate from the electron emission surface to the heat dissipation surface and form a current path of the current flowing through the emitter. The plurality of slits are composed of a first slit formed by recessing the end face and a second slit formed by recessing the other end face. The emitter structure according to claim 1 or 4. **Claim 12** The support member fixes one of the pair of support bars via the first insulator. The electron gun according to claim 7 or 8.

13. The support member has a movement restricting portion that faces the second insulator on the side opposite to the first insulator in the extending direction. The electron gun according to claim 12.

14. The coefficient of thermal expansion of the support member is equal to the coefficient of thermal expansion of the converging electrode. The electron gun according to claim 12.

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