Patent Publication Number: US-2022238292-A1

Title: X-ray module

Description:
TECHNICAL FIELD 
     One aspect of the present disclosure relates to an X-ray module. 
     BACKGROUND 
     An X-ray module has been known which includes a cathode which irradiates an electron beam, a target which is irradiated by the electron beam and generates X-rays, and a magnet portion which moves the irradiation position of the electron beam that is irradiated on the target by means of a magnetic field of a permanent magnet (for example, refer to Japanese Unexamined Patent Publication No. 2004-265602). In the X-ray module described in Japanese Unexamined Patent Publication No. 2004-265602, when the target has deteriorated at a current irradiation position, the irradiation position can be moved to extend the lifespan of the target. 
     In the above-described X-ray module, since an efficiency of conversion of the electron beam into the X-ray in the target is approximately 1%, and approximately 99% of the incident electron beam becomes heat, a large amount of heat can be generated in the target. When the heat is transferred to the permanent magnet, there is concern that the permanent magnet is heated and the magnetic force decreases. In this case, the amount of deflection of the electron beam is changed, and the position of an X-ray focal point (irradiation point of the electron beam on the target) is changed. For example, when the position of the X-ray focal point is changed during continuous imaging by computed tomography (CT) or the like, there is concern that an acquired image is blurred. 
     SUMMARY 
     Therefore, an object of one aspect of the present disclosure is to provide an X-ray module capable of stably outputting an X-ray. 
     According to one aspect of the present disclosure, there is provided an X-ray module including: a housing; an electron gun that emits an electron beam inside the housing; a target disposed inside the housing and fixed to the housing, to generate an X-ray when the electron beam is incident on the target; and a deflection unit including a permanent magnet and disposed outside the housing, to deflect the electron beam by means of a magnetic force of the permanent magnet. The deflection unit includes a heat insulating member disposed at least between the permanent magnet and the housing. A thermal conductivity of the heat insulating member is lower than a thermal conductivity of the permanent magnet. 
     In the X-ray module, the deflection unit includes the heat insulating member disposed at least between the permanent magnet and the housing, and the thermal conductivity of the heat insulating member is lower than the thermal conductivity of the permanent magnet. Accordingly, even when heat generated in the target is transferred to the deflection unit, the transfer of the heat to the permanent magnet can be suppressed by the heat insulating member, and as a result, the heating of the permanent magnet by the heat generated in the target can be suppressed. Therefore, the X-ray module is capable of stably outputting the X-ray. 
     The thermal conductivity of the heat insulating member may be lower than a thermal conductivity of a portion of the housing, the portion being in contact with the deflection unit. In this case, even when heat generated in the target is transferred to the deflection unit via the housing, the transfer of the heat to the permanent magnet can be suppressed by the heat insulating member. 
     The heat insulating member may house the permanent magnet inside. In this case, the transfer of heat generated in the target to the permanent magnet can be effectively suppressed. 
     The heat insulating member may extend to partition between the permanent magnet and the housing. In this case, the transfer of heat generated in the target to the permanent magnet can be effectively suppressed. 
     The deflection unit may further include a holding member holding the permanent magnet, and a thermal conductivity of the holding member may be higher than the thermal conductivity of the permanent magnet. In this case, heat transferred to the deflection unit can be released to the holding member. 
     The heat insulating member may isolate the permanent magnet from the holding member. In this case, the transfer of heat from the holding member to the permanent magnet can be suppressed. 
     When viewed in a direction perpendicular to a path along which the electron beam emitted from the electron gun travels to the target, the deflection unit may include a portion overlapping the path. In this case, the electron beam can be satisfactorily deflected by the deflection unit. 
     The X-ray module according to one aspect of the present disclosure may further include a heat radiating unit having a higher thermal conductivity than the thermal conductivity of the permanent magnet and being thermally connected to the deflection unit. In this case, heat transferred to the deflection unit can be released to the heat radiating unit. 
     The heat radiating unit may include a plurality of fins. In this case, heat radiation by the heat radiating unit can be improved. 
     The heat radiating unit may be formed in a pipe shape. In this case, heat radiation by the heat radiating unit can be improved. 
     According to one aspect of the present disclosure, it is possible to provide the X-ray module capable of stably outputting the X-ray. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of an X-ray generation device according to an embodiment. 
         FIG. 2  is a cross-sectional view of an X-ray tube. 
         FIG. 3  is an exploded perspective view of the X-ray tube. 
         FIG. 4  is a cross-sectional view illustrating a periphery of a protrusion. 
         FIG. 5  is a cross-sectional view illustrating a periphery of a target. 
         FIG. 6  is a cross-sectional view of the X-ray tube. 
         FIG. 7  is a cross-sectional view illustrating a periphery of a deflection unit. 
         FIG. 8  is a cross-sectional view of an X-ray generation device according to a first modification example. 
         FIG. 9  is a cross-sectional view of an X-ray generation device according to a second modification example. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings. In the following description, the same reference signs are used for the same or corresponding elements, and duplicated descriptions will be omitted. 
     [X-ray Generation Device] 
     An X-ray generation device (X-ray module)  100  illustrated in  FIG. 1  is, for example, a microfocus X-ray source used for an X-ray non-destructive inspection in which an internal structure of an inspection object is observed. The X-ray generation device  100  includes an X-ray tube  1 , a heat radiating unit  7 , a case  110 , and a power source unit  120 . 
     As illustrated in  FIG. 2 , the X-ray tube  1  is a transmission type X-ray tube that emits an X-ray XR from an X-ray-emitting window  5  in a direction along an incident direction of an electron beam B, the X-ray XR being generated when the electron beam B from an electron gun  3  is incident on a target  4  and transmitting through the target  4  itself. The X-ray tube  1  is a vacuum-sealed x-ray tube that includes a housing  2  having an internal space R in a vacuum state and does not require component replacement or the like. In the following description, it is assumed that a direction parallel to a tube axis AX of the X-ray tube  1  is an axial direction A, one side (upper side in the drawings) in the axial direction A is a first side S 1 , and the other side (side opposite the first side S 1 ) in the axial direction A is a second side S 2 . In the X-ray tube  1 , an optical axis of the electron beam B coincides with an optical axis the X-ray XR. 
     The housing  2  has a substantially columnar outer shape. The housing  2  includes a head portion  21  made of a metal material and an insulating valve  22  made of an insulating material such as glass. The target  4  and the X-ray-emitting window  5  are fixed to the head portion  21 . 
     The electron gun  3  is fixed to the insulating valve  22 . The electron gun  3  emits the electron beam B in the internal space R. For example, the electron gun  3  is configured such that a heater  31 , a cathode  32 , a first grid electrode  33 , and a second grid electrode  34  are disposed side by side in order from the second side S 2 . The heater  31  is formed of a filament that is energized to generate heat. The cathode  32  is heated by the heater  31  to emit electrons. The first grid electrode  33  and the second grid electrode  34  are formed in a cylindrical shape. The first grid electrode  33  is provided to control the amount of electrons emitted from the cathode  32 , and the second grid electrode  34  is provided to focus the electrons, which have passed through the first grid electrode  33 , toward the target  4 . The heater  31 , the cathode  32 , the first grid electrode  33 , and the second grid electrode  34  are electrically connected to a plurality of stein pins SP provided to penetrate through a bottom portion  22   a  of the insulating valve  22 . 
     The case  110  includes a cylindrical member  111  and a power source unit case  112 . The case  110  is made of a metal material. The cylindrical member  111  is formed in a substantially cylindrical shape, and includes an opening  111   a  and an opening  111   b  at both ends in the axial direction A. The X-ray tube  1  is inserted into the opening  111   a  such that the head portion  21  protrudes from the opening  111   a . An attachment flange  23   c  of the X-ray tube  1  is fixed to an end portion on the first side S 1  of the cylindrical member  111 . Accordingly, the X-ray tube  1  seals the opening  111   a . An insulating oil K that is a liquid insulating substance is sealed in the cylindrical member  111 . 
     The power source unit  120  supplies electric power to the X-ray tube  1 . The power source unit  120  is housed in the power source unit case  112 . The power source unit  120  seals the opening  111   b  of the cylindrical member  111 . The power source unit  120  includes a high-voltage power supply portion  121  including a connector  121   a  having a cylindrical shape. The high-voltage power supply portion  121  is electrically connected to the X-ray tube  1 . Specifically, a tip portion of the connector  121   a  is electrically connected to the stein pins SP protruding from the bottom portion  22   a  of the insulating valve  22 . In this example, with the target  4  (anode) having a ground potential, and a negative high voltage (for example, −10 kV to −500 kV) is supplied from the power source unit  120  to the electron gun  3  via the high-voltage power supply portion  121 . 
     [X-ray Tube] 
     As illustrated in  FIGS. 1 to 7 , the X-ray tube  1  includes the housing  2 , the electron gun  3 , the target  4 , the X-ray-emitting window  5 , and a deflection unit  6 . As described above, the housing  2  includes the head portion  21  and the insulating valve  22 . The head portion  21  corresponds to an anode of the X-ray tube  1  in terms of electrical potential. The head portion  21  includes a body portion  23  and a lid portion  24 . The body portion  23  is made of, for example, stainless steel (for example, SUS304), copper, an iron alloy, a copper alloy, or the like in a substantially cylindrical shape coaxial with the tube axis AX, and includes openings  23   a  and  23   b  at both ends in the axial direction A. The opening  23   a  is closed by the lid portion  24 . The lid portion  24  is fixed to an edge portion of the opening  23   a . The body portion  23  communicates with the insulating valve  22  through the opening  23   b , the insulating valve  22  having a substantially cylindrical shape coaxial with the tube axis AX. An outer peripheral surface of the body portion  23  is provided with the attachment flange  23   c  that is formed in a substantially annular plate shape concentric with the body portion  23 . 
     The lid portion  24  is made of, for example, molybdenum in a substantially circular plate shape coaxial with the tube axis AX, and closes the opening  23   a  of the body portion  23 . A protrusion  26  protruding to the first side S 1  with respect to a surface  24   a  of the lid portion  24  on the first side S 1  is formed on the surface  24   a . The surface  24   a  has a circular shape, and the protrusion  26  is formed in a columnar shape concentric with the lid portion  24 . An opening portion  27  penetrating through the lid portion  24  along the axial direction A is formed in the protrusion  26 . 
     As illustrated in  FIGS. 4 to 6 , the opening portion  27  includes a first portion  27   a  that is open to a surface  26   a  of the protrusion  26  on the first side S 1 , and a second portion  27   b  that communicates with the first portion  27   a  and that is open to a surface  24   b  of the lid portion  24  on the second side S 2 . Each of the first portion  27   a  and the second portion  27   b  is formed in a circular shape in cross section which is concentric with the protrusion  26 . A diameter of the first portion  27   a  is larger than a diameter of the second portion  27   b , and a depth of the first portion  27   a  is shallower than a depth of the second portion  27   b . In other words, the first portion  27   a  is a recess formed in the surface  26   a  of the protrusion  26 , and the second portion  27   b  is a through-hole formed in a bottom surface of the first portion  27   a . The first portion  27   a  functions as a disposition portion in which the target  4  and the X-ray-emitting window  5  are disposed. The second portion  27   b  functions as an electron beam passage hole through which the electron beam B to be incident on the target  4  passes. An end portion of the second portion  27   b  on the second side S 2  is provided with a widening portion  27   ba  of which the diameter increases toward the second side S 2 , and is chamfered in a curved surface shape so as not to form a corner. 
     The target  4  and the X-ray-emitting window  5  are disposed in the first portion  27   a . The target  4  is made of, for example, tungsten, and includes an electron-incident surface  4   a  and an X-ray-emitting surface  4   b  on a side opposite the electron-incident surface  4   a . The target  4  transmits an X-ray generated when the electron beam B is incident on the electron-incident surface  4   a , and emits the X-ray from the X-ray-emitting surface  4   b . In this example, the target  4  is formed in a film shape on an entirety of a surface on the second side S 2  of the X-ray-emitting window  5 . Namely, the target  4  is integrally formed with the X-ray-emitting window  5 . The target  4  is disposed such that the electron-incident surface  4   a  faces the second side S 2  and the X-ray-emitting surface  4   b  faces the first side S 1 . A thickness of the target  4  is, for example, approximately several μm. 
     The X-ray-emitting window  5  is made of, for example, a highly radiolucent material such as diamond or beryllium in a circular plate shape. The X-ray-emitting window  5  is disposed coaxially with the tube axis AX on the bottom surface of the first portion  27   a  of the opening portion  27 , is fixed to the bottom surface by a joining member such as a brazing material (not illustrated), and seals the opening portion  27 . The X-ray-emitting window  5  is in thermal contact with the bottom surface of the first portion  27   a  via the target  4 . In this example, a surface  5   a  of the X-ray-emitting window  5  on the first side S 1  is located on substantially the same plane as the surface  26   a  of the protrusion  26  on the first side S 1 . The X-ray-emitting window  5  faces the electron gun  3  in the axial direction A, transmits the X-ray XR emitted from the target  4 , and emits the X-ray XR to the first side S 1  in the axial direction A. As illustrated in  FIG. 5 , the X-ray XR is generated at an X-ray focal point F that is an irradiation point of the electron beam B on the target  4 , and is emitted while spreading around the X-ray focal point F. The target  4  may be provided in only a region exposed to the second portion  27   b  on the surface of the X-ray-emitting window  5 , or a part of the target  4  may also be provided on a wall surface of the second portion  27   b . In addition, the target  4  and the X-ray-emitting window  5  may be provided away from each other. 
     As illustrated in  FIGS. 2 and 7 , the deflection unit  6  includes a plurality of permanent magnets  61 , a holding member  62 , and a heat insulating member  63 . The deflection unit  6  includes a pair of the permanent magnets  61  facing each other in a radial direction. The pair of permanent magnets  61  are disposed such that different poles face each other in the radial direction. The permanent magnet  61  is formed of, for example, a ferrite magnet, a neodymium magnet, a samarium cobalt magnet, an alnico magnet, or the like. 
     The holding member  62  is made of, for example, a metal material such as aluminum in a flat cylindrical shape (annular shape) coaxial with the tube axis AX, and holds the permanent magnets  61 . In addition, a thermal conductivity of the holding member  62  is higher than a thermal conductivity of the permanent magnet  61 , and the holding member  62  can be utilized as a part of the heat radiating unit  7 . The holding member  62  is disposed outside the housing  2 , and is fixed to the attachment flange  23   c  in a state where the holding member  62  is in contact with a surface of the attachment flange  23   c  of the body portion  23  on the first side S 1 . The holding member  62  overlaps a part of the body portion  23  in the radial direction, and is disposed close to the body portion  23  to cover a part of the outer peripheral surface of the body portion  23 . The holding member  62  is slightly separated from the body portion  23  in the radial direction, but may be in contact with the body portion  23 . In addition, the holding member  62  may be formed of a plurality of members instead of being a cylindrical (annular) integrated member. 
     The heat insulating member  63  is made of, for example, a resin material such as silicone resin, epoxy resin, acrylic resin, polyimide resin, polyphenylene sulfide (PPS) resin, polyetheretherketone resin (PEEK). In order to suppress a decrease in the magnetic force of the permanent magnets  61  caused by a heat treatment when the heat insulating member  63  is cured, silicone resin, epoxy resin, and acrylic resin that is curable at room temperature are preferably used as the material of the heat insulating member  63 . 
     The heat insulating member  63  houses the permanent magnet  61  inside. Namely, the permanent magnet  61  is disposed inside the heat insulating member  63  in a state where the permanent magnet  61  is surrounded by the heat insulating member  63 . For example, the heat insulating member  63  is fixed to the holding member  62 , and the holding member  62  holds the permanent magnet  61  via the heat insulating member  63 . The heat insulating member  63  isolates the permanent magnet  61  from the holding member  62 . A surface  63   a  of the heat insulating member  63  on the second side S 2  is in contact with the surface of the attachment flange  23   c  of the body portion  23  on the first side S 1 . An outer surface other than the surface  63   a  in the heat insulating member  63  is covered with the holding member  62 . Namely, the heat insulating member  63  is provided such that the heat insulating member  63  is embedded in the holding member  62  and only the surface  63   a  is exposed from the holding member  62 . In such a manner, the heat insulating member  63  includes a portion disposed between the permanent magnet  61  and the attachment flange  23   c  of the body portion  23 . 
     The deflection unit  6  deflects the electron beam B by means of the magnetic force of the permanent magnets  61  to change the position of the X-ray focal point F. When viewed in a direction (radial direction) perpendicular to a path P along which the electron beam B emitted from the electron gun  3  travels to the target  4 , the deflection unit  6  includes a portion overlapping the path P. Accordingly, the magnetic force of the permanent magnets  61  can be suitably applied to the electron beam B. In this example, an entirety of the deflection unit  6  overlaps the path P when viewed in the radial direction. The deflection unit  6  is attached to the attachment flange  23   c  such that an imaginary line connecting the pair of permanent magnets  61  facing each other is substantially orthogonal to the tube axis AX. The deflection unit  6  may be rotatable around the tube axis AX. In this case, the position of the X-ray focal point F can be moved by rotating the deflection unit  6 . 
     A thermal conductivity of the holding member  62  is higher than a thermal conductivity of the permanent magnet  61 . A thermal conductivity of the heat insulating member  63  is lower than a thermal conductivity of the body portion  23  of the housing  2  (portion of the housing  2  in contact with the deflection unit  6 ). Namely, heat insulation of the heat insulating member  63  is higher than heat insulation of the body portion  23 . In addition, the thermal conductivity of the heat insulating member  63  is lower than the thermal conductivity of each of the permanent magnet  61  and the holding member  62 . When the body portion  23  is made of SUS304, the thermal conductivity of the body portion  23  is, for example, 16.7 W/m·K. The thermal conductivity of the permanent magnet  61  is, for example, approximately 1 to 50 W/m·K, the thermal conductivity of the holding member  62  is, for example, approximately 100 to 400 W/m·K, and the thermal conductivity of the heat insulating member  63  is, for example, approximately 0.1 to 0.5 W/m·K. The thermal conductivity can be measured by general measurement methods such as a heat flow meter method, a laser flash method, and a hot wire method. 
     As illustrated in  FIGS. 1, 3, 4, and 6 , the heat radiating unit  7  includes a heat sink  70  that radiates heat generated in the target  4 , and a cooling unit  80  that cools the heat sink  70 , and is disposed outside the housing  2 . The heat sink  70  is made of, for example, a metal material such as aluminum. A thermal conductivity of the heat sink  70  is higher than the thermal conductivity of each of the body portion  23  and the permanent magnet  61 . The thermal conductivity of the heat sink  70  is, for example, approximately 100 to 400 W/m·K. The heat sink  70  includes a first portion  71  and a second portion  72 . 
     The first portion  71  is formed in a circular plate shape coaxial with the tube axis AX, and includes an opening  71   b  in a central portion thereof. The first portion  71  extends perpendicularly to the tube axis AX along the surface  24   a  of the lid portion  24 , and the protrusion  26  is disposed in the opening  71   b . The first portion  71  surrounds the protrusion  26  when viewed in the axial direction A. A surface of the first portion  71  on the second side S 2  is in contact with the surface  24   a  of the lid portion  24  via a heat conducting member  8  having a sheet shape. Accordingly, the first portion  71  is thermally connected to the surface  24   a  of the lid portion  24 . The heat conducting member  8  is, for example, a silicone sheet made of a silicone having a high thermal conductivity in a circular sheet shape, is disposed between an entirety of the surface  24   a  and the first portion  71 , and is in close contact with the surface  24   a  and the first portion  71 . Since the heat conducting member  8  intervenes between the first portion  71  and the lid portion  24 , heat conduction between the first portion  71  and the lid portion  24  can be more promoted than when the first portion  71  and the lid portion  24  that are made of a metal material are in direct contact with each other. 
     As illustrated in  FIG. 4 , the first portion  71  is slightly separated from the protrusion  26  in the radial direction. A distance L 1  between the first portion  71  and the protrusion  26  in the radial direction is smaller than a protrusion height L 2  of the protrusion  26  from the surface  24   a  of the lid portion  24  in the axial direction A, and is smaller than a diameter L 3  of the protrusion  26  (width of the protrusion  26  in the radial direction). The first portion  71  may be in contact with the protrusion  26 . The first portion  71  does not protrude to the first side S 1  with respect to the protrusion  26 . In other words, when a surface  71   a  of the first portion  71  on the first side S 1  and the surface  26   a  of the protrusion  26  on the first side S 1  are flat, the surface  71   a  is located on the same plane as the surface  26   a  or is located closer to the second side S 2  than the surface  26   a . In this example, the surface  71   a  is located on the same plane as the surface  26   a . In addition, the surface  71   a  is located on the same plane as the surface  5   a  of the X-ray-emitting window  5  on the first side S 1 . 
     The second portion  72  is formed in a substantially cylindrical shape concentric with the first portion  71 , and extends from an outer edge of the first portion  71  to the second side S 2 . The second portion  72  is located outside an outer edge of the surface  24   a  of the lid portion  24  when viewed in the axial direction A, and is located closer to the second side S 2  in the axial direction A than the surface  24   a . In this example, an entirety of the second portion  72  is located closer to the second side S 2  than the surface  24   a , but only a part of the second portion  72  may be located closer to the second side S 2  than the surface  24   a . The second portion  72  overlaps a part of the body portion  23  in the radial direction, and covers a part of the outer peripheral surface of the body portion  23 . The second portion  72  is slightly separated from the body portion  23  in the radial direction, but may be in contact with the body portion  23 . A surface  72   b  of the second portion  72  on the second side S 2  is in contact with a surface on the first side S 1  of the holding member  62  of the deflection unit  6 , and is thermally connected to the deflection unit  6 . 
     A plurality of fins  72   a  are formed in an outer peripheral surface of the second portion  72 . Each of the fins  72   a  is formed in a substantially circular plate shape concentric with the second portion  72 . The plurality of fins  72   a  are disposed parallel to each other and side by side at equal intervals along the axial direction A. Air from a cooling fan  84  to be described later is supplied to the fins  72   a.    
     The cooling unit  80  includes an air blowing unit  81  and a surrounding portion  82  formed in a substantially cylindrical shape to surround the heat sink  70 . The air blowing unit  81  includes a hood portion  83  and the cooling fan  84 . The hood portion  83  covers one side of the cylindrical member  111  in the direction perpendicular to the axial direction A, and forms a space  83   a . The cooling fan  84  is disposed in the space  83   a . A plurality of through-holes are formed as a ventilation portion  83   b  in the hood portion  83 . The cooling fan  84  sends outside air to the surrounding portion  82  as cooling air, the outside air being suctioned from the ventilation portion  83   b.    
     The surrounding portion  82  includes an upper wall portion  82   a  and a side wall portion  82   b . The upper wall portion  82   a  is formed in an annular shape, and defines an opening  82   c  on the first side S 1  of the surrounding portion  82 . The surrounding portion  82  is disposed such that the surface  71   a  of the first portion  71  on the first side S 1  is exposed from the opening  82   c . The side wall portion  82   b  is formed in a cylindrical shape, and surrounds the plurality of fins  72   a , together with the upper wall portion  82   a . The surrounding portion  82  forms a flow path through which the cooling air sent from a communication portion between the air blowing unit  81  and the surrounding portion  82  circulates so as to flow through spaces between the plurality of fins  72   a  in a circumferential direction. Accordingly, a heat radiation efficiency of the heat sink  70  can be improved. Incidentally, the cooling air is exhausted from a ventilation portion (not illustrated) provided in the side wall portion  82   b . Accordingly, it is possible to make it difficult for the exhausted cooling air to flow to an inspection object side, and an influence of exhausting during imaging can be suppressed. In addition, the cooling fan  84  may operate to suction outside air from the ventilation portion provided in the side wall portion  82   b  and to exhaust the outside air from the ventilation portion  83   b  provided in the hood portion  83 . 
     [Function and Effects] 
     In the X-ray generation device  100 , the deflection unit  6  includes the heat insulating member  63  disposed at least between the permanent magnet  61  and the housing  2 , and the thermal conductivity of the heat insulating member  63  is lower than the thermal conductivity of the permanent magnet  61 . Accordingly, even when heat generated in the target  4  is transferred to the deflection unit  6 , the transfer of the heat to the permanent magnet  61  can be suppressed by the heat insulating member  63 , and as a result, the heating of the permanent magnet  61  by the heat generated in the target  4  can be suppressed. Therefore, the X-ray generation device  100  is capable of stably outputting the X-ray. 
     The thermal conductivity of the heat insulating member  63  is lower than the thermal conductivity of the body portion  23  of the housing  2  (portion of the housing  2  which is in contact with the deflection unit  6 ). Accordingly, even when heat generated in the target  4  is transferred to the deflection unit  6  via the housing  2 , the transfer of the heat to the permanent magnet  61  can be suppressed by the heat insulating member  63   
     The heat insulating member  63  houses the permanent magnet  61  inside. Accordingly, the transfer of heat generated in the target  4  to the permanent magnet  61  can be effectively suppressed. 
     The deflection unit  6  includes the holding member  62  holding the permanent magnet  61 , and the thermal conductivity of the holding member  62  is higher than the thermal conductivity of the permanent magnet  61 . Accordingly, heat transferred to the deflection unit  6  can be released to the holding member  62 . 
     The heat insulating member  63  isolates the permanent magnet  61  from the holding member  62 . Accordingly, the transfer of heat from the holding member  62  to the permanent magnet  61  can be suppressed. 
     The deflection unit  6  includes a portion overlapping the path P when viewed in the direction perpendicular to the path P along which the electron beam B emitted from the electron gun  3  travels to the target  4 . Accordingly, the electron beam B can be satisfactorily deflected by the deflection unit  6 . 
     The heat radiating unit  7  is provided which has a higher thermal conductivity than the thermal conductivity of the permanent magnet  61  and which is thermally connected to the deflection unit  6 . Accordingly, heat transferred to the deflection unit  6  can be released to the heat radiating unit  7 . 
     The heat sink  70  includes the plurality of fins  72   a . Accordingly, heat radiation by the heat sink  70  can be improved. 
     The target  4  includes the electron-incident surface  4   a  and the X-ray-emitting surface  4   b , transmits the X-ray XR generated when the electron beam B is incident on the electron-incident surface  4   a , and emits the X-ray XR from the X-ray-emitting surface  4   b . In such a transmission type configuration, the target  4  is more easily disposed close to the X-ray-emitting window  5  and the focus to object distance (FOD) (distance from the X-ray focal point F to the inspection object) can be more reduced than in a reflection type configuration in which an electron-incident surface also serves as an X-ray-emitting surface. When the FOD is small, observation at a high magnification ratio can be performed. Alternatively, when it is assumed that the magnification ratio remains equal, an X-ray imaging element can be disposed close to an X-ray source, so that a bright image can be acquired. 
     The X-ray generation device  100  (X-ray module) includes the housing  2 ; the electron gun  3  that emits the electron beam B inside the housing  2 ; the target  4  that is disposed inside the housing  2 , is fixed to the housing  2 , and generates the X-ray XR when the electron beam B is incident on the target  4 ; the permanent magnet  61  that is disposed outside the housing  2  and deflects the electron beam B by means of a magnetic force; and the heat radiating unit  7  that has a higher thermal conductivity than the thermal conductivity of the permanent magnet  61  and is thermally connected to the permanent magnet  61 . In such a manner, the X-ray generation device  100  is provided with the heat radiating unit  7  that has a higher thermal conductivity than the thermal conductivity of the permanent magnet  61  and that is thermally connected to the permanent magnet  61 . Accordingly, even when heat generated in the target  4  is transferred to the permanent magnet  61 , the transferred heat can be released to the heat radiating unit  7 , and as a result, the heating of the permanent magnet  61  by the heat generated in the target  4  can be suppressed. Therefore, the X-ray generation device  100  is capable of stably outputting the X-ray XR. 
     The permanent magnet  61  includes a portion overlapping the path P when viewed in the direction perpendicular to the path P along which the electron beam B emitted from the electron gun  3  travels to the target  4 . Accordingly, the electron beam B can be satisfactorily deflected by the permanent magnet  61 . 
     The thermal conductivity of the holding member  62  holding the permanent magnet  61  is higher than the thermal conductivity of the permanent magnet  61 . Accordingly, heat transferred to the permanent magnet  61  can be released to the holding member  62  as a part of the heat radiating unit  7 , and can be released to the heat radiating unit  7  via the holding member  62 . 
     The heat radiating unit  7  is thermally connected to the holding member  62 . Accordingly, heat transferred to the permanent magnet  61  can be effectively released to the heat radiating unit  7  via the holding member  62 . 
     The heat insulating member  63  is disposed at least between the permanent magnet  61  and the housing  2 , and the thermal conductivity of the heat insulating member  63  is lower than the thermal conductivity of the permanent magnet  61 . Accordingly, heat transferred to the housing  2  can be prevented from being transferred to the permanent magnet  61 . 
     The heat insulating member  63  houses the permanent magnet  61  inside. Accordingly, heat transferred to the housing  2  can be effectively prevented from being transferred to the permanent magnet  61 . 
     MODIFICATION EXAMPLES 
     In a first modification example illustrated in  FIG. 8 , the heat insulating member  63  is formed in an annular plate shape concentric with the holding member  62 . The heat insulating member  63  extends in a plate shape to partition between the permanent magnet  61  and the attachment flange  23   c  of the body portion  23 , and isolates the permanent magnet  61  and the holding member  62  from the attachment flange  23   c . The heat sink  70  includes only the second portion  72  without including the first portion  71 , and is not in contact with the housing  2 , but may be in contact with the housing  2 . In addition, the heat insulating member  63  may extend to partition between the permanent magnet  61  and the attachment flange  23   c  of the body portion  23 , and is not limited to a plate-shaped member. The heat insulating member  63  may be formed, for example, by applying and then solidifying a liquid material. 
     Also in the first modification example, similarly to the above embodiment, the X-ray XR can be stably output. In addition, since the heat insulating member  63  extends in a plate shape to partition between the permanent magnet  61  and the housing  2 , heat transferred to the housing  2  can be effectively prevented from being transferred to the permanent magnet  61 . 
     In a second modification example illustrated in  FIG. 9 , the heat radiating unit  7  is formed in a pipe shape. The heat radiating unit  7  is in contact with the surface of the holding member  62  of the deflection unit  6  on the first side S 1 , and is thermally connected to the permanent magnet  61 . The heat radiating unit  7  forms a heat pipe, and a hydraulic fluid is sealed inside. Alternatively, the heat radiating unit  7  may form a cooling water pipe through which cooling water flows. The deflection unit  6  is configured similarly to that in the first modification example. 
     Also in the second modification example, similarly to the above embodiment, the X-ray XR can be stably output. In addition, since the heat radiating unit  7  is formed in a pipe shape, the heat radiating unit  7  can be used as a heat pipe, a cooling water pipe, or the like, and heat radiation by the heat radiating unit  7  can be improved. 
     The present disclosure is not limited to the above embodiment. For example, the material and the shape of each configuration are not limited to the material and the shape described above, and various materials and shapes can be adopted. The holding member  62  may be omitted. In this case, the permanent magnet  61  is held by the heat insulating member  63 . The heat insulating member  63  may be omitted. The heat radiating unit  7  may be a cooling mechanism other than the above-described example. The heat radiating unit  7  and the holding member  62  may be integrally formed, or may be formed of one member. The heat radiating unit  7  may be omitted. The protrusion  26  may not be formed on the surface  24   a  of the housing  2 , and an entirety of the surface  24   a  may be flat. In addition, at least a part of the deflection unit  6  or the heat radiating unit  7  may be integrated with the X-ray tube  1 . In the above embodiment, the X-ray module forms the X-ray generation device  100 ; however, the X-ray module may not necessarily form the X-ray generation device, and may include, for example, only the X-ray tube  1  and the heat radiating unit  7  (heat sink  70 ).