A supporting member supports an anode target at one end thereof and is provided with an attachment portion around the outer circumference of the other end. The attachment portion is attached to the inner circumferential surface of the cylindrical portion of the second vacuum envelope member so that the heat conductivity from the supporting member to the second vacuum envelope member can be improved by means of the attachment portion. A terminal is provided at the end surface portion on the side of the other end of the second vacuum envelope member for applying a voltage to the anode target. The terminal is positioned away from the attachment portion so that the temperature of the insulating material that insulates the terminal can be kept low and the insulating characteristics can be ensured over the long term.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an X-ray tube, and more specifically to a fixed-anode-type X-ray tube whose anode is fixed.

2. Description of the Related Art

In conventional technologies, typical X-ray tubes include a fixed-anode-type X-ray tube. In the fixed-anode-type X-ray tube, electrons are generated by a filament of its cathode. These electrons are accelerated toward the anode target by a high-voltage electric field, and the high-energy electrons collide with the anode target to produce X-rays.

Heat is generated when the high-energy electrons collide with the anode target. The fixed-anode-type X-ray tube is provided with a cooling system of an insulating oil immersion type, a liquid forced cooling type, an air forced cooling type or the like in order to dissipate the generated heat into the outside.

In an X-ray tube of the insulating oil immersion type, a cathode assembly and an anode assembly are vacuum-sealed in an outer glass casing. The vacuum envelope is arranged inside a housing that is filled with insulating oil. The insulating oil serves as an electrical isolator and also as an absorber of heat generated in the anode assembly. The heat absorbed by the insulating oil is dissipated through the outer wall of the housing into the air.

In addition, as disclosed in Jpn. UM Appln. KOKOKU Publication No. H1-32720, for example, an anode target in an X-ray tube of a liquid forced cooling type is supported by a cylindrical anode supporting member. A cooling path is constituted by the inner space of the anode supporting member, through which a cooling liquid can flow to cool the anode portion.

Furthermore, as disclosed in Jpn. PCT National Publication No. 2001-504988, in an X-ray tube of an air forced cooling type, a vacuum envelope is constituted by an outer vacuum casing provided at one end thereof and an outer insulating casing provided at the other end. The anode supporting member has one end supporting the anode target and the other end extending from the other end of the outer insulating casing to the outside. A lead for supplying a high voltage to the anode target is connected to the other end of this anode supporting member. The outer surface of the outer insulating casing and the other end of the anode supporting member are wrapped with a potting material, namely molded material. For the purpose of cooling the anode portion, air is forced to travel outside the potting material.

BRIEF SUMMARY OF THE INVENTION

A conventional X-ray tube of an insulating oil immersion type requires a housing that is larger than X-ray tubes of other cooling systems do. Introduction of the insulating oil immersion type is an obstacle to miniaturizing the X-ray tube. Furthermore, the use of insulating oil in the insulating oil immersion type makes it difficult to assemble, repair, and disposal of the X-ray tube.

In addition, a conventional X-ray tube of a forced liquid cooling type utilizes an insulating oil and purified water as an insulating liquid that serves as a cooling liquid to cool the anode portion. This requires a closed-loop cooling system including a heat exchanger, circulating pump and hose specifically designed for the system. As a result, the cost is increased, and reliability is lowered. Especially when purified water is used, a filter formed of a special ion exchanging resin is required in order to prevent the electric conductivity of purified water from increasing during the use. Because such a filter is needed, problems of a labor of maintenance and management and increased cost arise.

Moreover, the above problems in the insulating oil immersion type and the forced liquid cooling type do not reside in an X-ray tube of a forced air cooling type. However, the forced liquid cooling type does not have sufficient thermal dissipation characteristics because heat is conducted from the anode supporting member to the potting material, which is low in heat conductivity. Thus, there is a problem that the heat load of the anode target is not sufficiently reduced. Furthermore, the heat dissipating member that dissipates heat from the anode supporting member to the potting material is arranged in the vicinity of the high-voltage supplying member to which a high-voltage supplying lead is connected. Insufficient thermal dissipation increases the temperature of the potting material, creating a problem that the electrical insulating function of the potting material is degraded at a relatively early stage.

The purpose of the present invention is to offer an X-ray tube that maintains excellent heat dissipating characteristics and ensures the insulating characteristics over the long term.

According to an aspect of the present invention, there is provided an X-ray tube comprising: a cylindrical vacuum envelope including a first vacuum envelope member formed at one end and provided with an output window through which X-rays pass and a second vacuum envelope member formed at the other end and having electrically insulating characteristics; an anode target arranged inside the first vacuum envelope member; a cathode arranged inside the first vacuum envelope member for releasing electrons to the anode target; a supporting member arranged inside the vacuum envelope and having one end provided with an attachment portion for being attached to an inner surface of the second vacuum envelope member and the other end supporting the anode target; a terminal substantially thermally separated from the supporting member by way of a gap and arranged for supplying a voltage to the supporting member; and a connecting portion for electrically connecting the supporting member to the terminal.

DETAILED DESCRIPTION OF THE INVENTION

Fixed-anode-type X-ray tubes according to the embodiments of the present invention will be explained below with reference to the drawings.

As an X-ray tube,FIGS. 1 and 2show an X-ray tube11of a fixed anode type. The X-ray tube11comprises a vacuum envelope12which keeps the inside under vacuum. The vacuum envelope12is constituted by a first vacuum envelope member13that is formed of a metal and arranged at one end of the X-ray tube11in the shaft direction along the axis of the tube and a second vacuum envelope member14that is arranged at the other end and forms an insulating member.

The first vacuum envelope member13is formed into the shape of a cap (cylinder) in such a manner that the outer diameter of its tip gradually decreases. The tip surface of the first vacuum envelope member13is flattened. The flat portion is provided with an output window15through which X-rays pass. The output window15is formed of a material in which X-rays attenuate less, such as beryllium (Be), to have a thickness of tens to hundreds of micrometers.

The second vacuum envelope member14is formed into a close-ended cylinder by use of an insulating material prepared with an electrically insulating ceramics such as alumina. In other words, the second vacuum envelope member14has a cylindrical portion14aone end of which is an opening for being connected to the first vacuum envelope member13and an end surface portion14bwhich is the close-end portion formed on the other end of the cylindrical portion14a. A mounting hole14cis provided in the center of the end surface portion14bto mount a terminal.

In addition, an anode target21is arranged inside the first vacuum envelope member13so as to oppose the output window15. A focusing electrode22is arranged around the circumference of the anode target21, and a cathode23is arranged outside the circumference of the focusing electrode22. The cathode23is secured onto the external portion of the focusing electrode22.

Moreover, a supporting member25is arranged in the center of the vacuum envelope12to support the anode target21. The supporting member25is formed of a conductive material, for example, copper or a copper-base alloy, to have one end having a smaller diameter and the other end having a larger diameter. The one end is positioned inside the focusing electrode22, with its tip supporting the anode target21. The circumferential surface of the other end is attached to the inner circumferential surface of the cylindrical portion14aof the second vacuum envelope member14. The tip surface of the anode target21is coated with a tungsten layer.

The surface of the other end of the supporting member25is not in direct contact with the end surface portion14bof the second vacuum envelope member14, but there is a gap29therebetween to separate them from each other. Further, a hole portion30is formed along the direction of the shaft to open in the other end of the supporting member25. In addition, a hole portion31is formed along the direction of the diameter at a position closer to the one end with respect to the attachment portion28so as to communicate with the hole portion30. The gap29and the hole portions30and31create an exhaust path32that runs from the inside of the first vacuum envelope member13through the mounting hole14cof the second vacuum envelope member14.

Moreover, a tipped exhaust pipe34is provided in the mounting hole14cformed in the end surface portion14bof the second vacuum envelope member14. The exhaust pipe34serves as a sealing component for vacuum-sealing after air is exhausted from the vacuum envelope12through the exhaust path32that runs inside the supporting member25. The exhaust pipe34is provided with a mounting member35, with which the exhaust pipe34is attached into the mounting hole14cof the second vacuum envelope member14.

Further, a high-voltage cable37is connected to the exhaust pipe34to apply a high voltage to the anode target21. In other words, the exhaust pipe34serves as a sealing component to seal the vacuum envelope12and also has a function as a terminal38to which the high-voltage cable37is connected so as to apply a high voltage to the anode target21. In addition, the terminal38is located at a position away from the attaching position of the attachment portion28inside the second vacuum envelope member14.

A metalized layer39is formed on the second vacuum envelope member14to electrically connect the attachment portion28to the terminal38. The metalized layer39is provided on the inner surface of the second vacuum envelope member14. The metalized layer39includes a supporting-member-side connecting portion40and a terminal-side connecting portion41. The supporting-member-side connecting portion40is arranged between the second vacuum envelope member14and the attachment portion28so as to make an electrical connection to the attachment portion28. On the other hand, the terminal-side connecting portion41is arranged between the terminal38and the mounting hole14cof the second vacuum envelope member14so as to make an electrical connection to the terminal38.

The outer surface of the end surface portion14bof the second vacuum envelope member14, the terminal38and the high-voltage cable37are covered with an insulating material42made of an insulating molded resin that has insulation characteristics, such as a silicone resin.

Further, a heat dissipating member44that serves as a heat dissipating unit is attached onto the outer circumferential surface of the cylindrical portion14aof the second vacuum envelope member14in such a manner as to oppose the attachment portion28. The heat dissipating member44is made with a metallic material that has higher thermal conductivity than ceramics and formed into a cylindrical shape. A metalized layer, namely a metal layer film, is disposed on the outer circumferential surface of the cylindrical portion14aof the second vacuum envelope member14as an interface between the ceramic and metallic layers, although it is not shown in the drawing, and the outer circumferential surface of the cylindrical portion14ais attached to the inner surface of the heat dissipating member44. Multiple fins45are arranged on the outer circumferential surface of the heat dissipating member44at intervals in the circumferential direction of the heat dissipating member44to have widths along the shaft direction of the heat dissipating member44in such a manner as to protrude in the direction of the external diameter.

The inner circumferential surface of the heat dissipating member44is formed to have projections and depressions so as to ease the thermal stress at high temperature. In other words, multiple projections47are formed with multiple depressions46formed along the shaft and circumferential directions and serving as divisions along the shaft and circumferential directions.

Moreover, the X-ray tube11includes a not-shown forced cooling system that forcibly cools at least the heat dissipating member44by use of a fluid. For this forced cooling system, air cooling which utilizes air as a fluid or liquid cooling which utilizes liquid such as an antifreeze solution that contains water as the main element may be chosen in accordance with the heat generation of the X-ray tube11. It is preferable, however, to employ air cooling, for which operation and maintenance is easier.

Next, the operation of the X-ray tube11is explained with reference toFIGS. 1 and 2.

Under the operation of the X-ray tube11, a high voltage is applied between the cathode23and the anode target21contained in the vacuum envelope12so that electrons are released from the cathode23. The electrons are accelerated by a difference in potentials of the cathode23and the anode target21and collide with the anode target21. As a result, X-rays are generated, and the generated X-rays are emitted through the output window15.

Heat is generated by the collision of the electrons with the anode target21, and this heat is conducted to the supporting member25. The heat that is conducted to the supporting member25is transferred to the second vacuum envelope member14via the attachment portion28. The heat transferred to the second vacuum envelope member14is transferred to the heat dissipating member44. The heat transferred to the heat dissipating member44is forcefully dissipated by the fluid of the not-shown forced cooling system that acts on the heat dissipating member44.

In the X-ray tube11, the attachment portion28of the supporting member25is attached to the inner circumferential surface of the cylindrical portion14aof the second vacuum envelope member14. The large contact area improves the thermal conductivity from the supporting member25to the second vacuum envelope member14, which increases the heat dissipating characteristics.

Furthermore, the terminal38is positioned away from the attachment portion28, in other words, on the end surface portion14bof the second vacuum envelope member14. Thus, the temperature of the insulating material42that surrounds this terminal38by means of insulation-molding can be kept low, and the insulating characteristics can be ensured over the long term.

The supporting member25and the terminal38are not brought into direct contact with each other, but are separated by the gap29that are provided therebetween. However, the supporting member25and the terminal38are electrically connected to each other by the metalized layer39deposited on the second vacuum envelope member14.

In addition, the terminal38is constituted by the exhaust pipe34which also serves as a vacuum-sealing component for the vacuum envelope12. This reduces the number of components and thereby simplifies the structure.

Further, the surface of the supporting member25in the vicinity of the attachment portion28is designed to have projections and depressions, and the attachment portion28is constituted by the projections27. Thus, the thermal expansion of the supporting member25produced by high temperature is absorbed by elastic deformation of the projection-depression portion, and the thermal stress can be thereby eased.

Similarly, the inner circumferential surface of the heat dissipating member44is designed to have projections and depressions. Thus, the thermal expansion of the heat dissipating member44produced by high temperature is absorbed by elastic deformation of the projection-depression portion, and the thermal stress can be thereby eased.

Further, the heat dissipating member44, which is formed with a metallic material that has higher thermal conductivity than ceramics, has excellent heat dissipating characteristics. Moreover, because of the multiple fins45arranged on the outer circumferential surface of the heat dissipating member44, the heat dissipating member44has a large surface area, which improves the heat dissipating characteristics.

In addition, the not-shown forced cooling system forcefully cools the outer circumferential surface of the second vacuum envelope member14by means of a fluid. The heat dissipating characteristics of this forced cooling system can be further improved by the heat dissipating member44.

Next,FIGS. 3 and 4illustrate an X-ray tube according to the second embodiment of the present invention.

InFIGS. 3 and 4, the elements the same as those inFIGS. 1 and 2are provided with the same reference numbers, and the explanation thereof is omitted.

Multiple fins45are provided circularly on the outer circumferential surface of the heat dissipating member44along the circumferential direction of the heat dissipating member44at intervals in the shaft direction of the heat dissipating member44in such a manner as to protrude in the direction of the outer diameter. In such a cooling structure, the heat dissipating member44is designed to have a large surface area, which increases the heat dissipating characteristics.

Next,FIGS. 5 and 6illustrate an X-ray tube according to the third embodiment of the present invention.

In a similar manner to the explanation ofFIGS. 3 and 4, the elements inFIGS. 5 and 6that are the same as those inFIGS. 1 and 2are provided with the same reference numbers, and the explanation thereof is omitted.

A flexible component51that is formed of a metal into a shape of a cylinder is arranged between the attachment portion28and the inner circumferential surface of the cylindrical portion14aof the second vacuum envelope member14. The inner circumferential surface of the flexible component51is designed to be a curved surface without any projections or depressions. On the other hand, the outer circumferential surface of the flexible component51is designed to have projections and depressions in order to ease the thermal stress caused by the thermal expansion at high temperature. In other words, multiple projections53are formed by the multiple depressions52formed along the shaft direction and the circumferential direction and serving as divisions in the shaft direction and the circumferential direction. The surfaces of the projections53are attached to the inner circumferential surface of the cylindrical portion14aof the second vacuum envelope member14.

Heat is conducted from the attachment portion28to the second vacuum envelope member14via the flexible component51. Furthermore, the thermal expansion of the supporting member25produced at high temperature is absorbed by the elastic deformation of the flexible component51, and the thermal stress is thereby eased.

Next,FIGS. 7 and 8show an X-ray tube according to the fourth embodiment of the present invention.

The elements inFIGS. 7 and 8that are the same as those inFIG. 1are provided with the same reference numbers, and the explanation thereof is omitted.

The other end of the supporting member25is connected to the inner surface of the end surface portion14bof the second vacuum envelope member14. The surface of the other end of the supporting member25is designed to have projections and depressions so as to ease thermal stress at high temperature. In other words, as illustrated inFIG. 8, multiple projections27are formed with multiple depressions26formed into a grid and serving as a division. The surfaces of the multiple projections27are configured to function as an attachment portion28which is attached to the inner surface of the end surface portion14bof the second vacuum envelope member14. Furthermore, an exhaust path32is formed on the circumferential surface portion of the supporting member25along the shaft direction thereof.

In addition, a mounting hole14cis formed in the cylindrical portion14aof the second vacuum envelope member14. A tipped exhaust pipe34, which functions as a vacuum-sealing component and a terminal38, is attached the mounting hole14c. A high-voltage cable37is connected to the exhaust pipe34. The terminal38is arranged sufficiently away from the position where the attachment portion28is attached to the second vacuum envelope member14.

A metalized layer39is formed on the second vacuum envelope member14to electrically connect the attachment portion28to the terminal38. The metalized layer39is deposited on the inner surface of the second vacuum envelope member14. The metalized layer39includes a supporting-body-side connecting portion40and a terminal-side connecting portion41. The supporting-body-side connecting portion40is positioned between the second vacuum envelope member14and the attachment portion28to make an electrical connection to the attachment portion28. On the other hand, the terminal-side connecting portion41is positioned between the terminal38and the mounting hole14cof the second vacuum envelope member14to make an electrical connection to the terminal38.

The outer surface of the cylindrical portion14aof the second vacuum envelope member14, the terminal38, the high-voltage cable37and the like are coated with an insulating material42.

Moreover, one end of the heat dissipating member44is connected by means of soldering57to the outer surface of the end surface portion14bof the second vacuum envelope member14which opposes the attachment portion28. Multiple fins45are provided on the other end of the heat dissipating member44in such a manner as to protrude toward the outside. The surface of the one end of the heat dissipating member44is designed to have projections and depressions in order to ease thermal stress at high temperature. In other words, multiple projections47are defined by multiple depressions46that are formed into a grid and serve as a division. In addition, the X-ray tube11includes a not-shown forced cooling system that forcefully cools the heat dissipating member44by use of a fluid.

During the operation of the X-ray tube11, a high voltage is applied between the cathode23and the anode target21contained in the vacuum envelope12so that electrons are released from the cathode23. These electrons are accelerated by a difference in potentials of the cathode23and the anode target21and collide with the anode target21, and as a result, X-rays are emitted. The X-rays are released through the output window15.

When the electrons collide with the anode target21, heat is generated. This heat is transferred to the supporting member25. The heat transferred to the supporting member25is conducted to the second vacuum envelope member14by way of the attachment portion28. The heat conducted to the second vacuum envelope member14is conducted to the heat dissipating member44. The heat conducted to the heat dissipating member44is forced dissipated by the fluid of the not-shown forced cooling system that acts on the heat dissipating member44.

The X-ray tube11, in which the attachment portion28is attached to the inner surface of the end surface portion14bof the second vacuum envelope member14, has a large contact area. Thus, thermal conductivity from the supporting member25to the second vacuum envelope member is kept high, and the heat dissipating characteristics is improved.

Furthermore, the terminal38is arranged away from the attachment portion28, in other words, on the cylindrical portion14aof the second vacuum envelope member14. Thus, the temperature of the insulating material42that surrounds the terminal38by means of insulation molding can be kept low, and the insulation characteristics can be ensured over the long term.

The supporting member25and the terminal38are positioned away from each other with the gap29therebetween, but are electrically connected by means of the metalized layer39.

Further, the terminal38is constituted by the exhaust pipe34which also serves as a vacuum-sealing component for the vacuum envelope12. Thus, the number of components is reduced, and the structure is simplified.

Furthermore, the surface of the supporting member25attached to the inner surface of the end surface portion14bof the second vacuum envelope member14is designed to have projections and depressions in the vicinity of the attachment portion28. The attachment portion28is defined by the projections27. The thermal expansion of the supporting member25produced at high temperature is absorbed by the elastic deformation of this projection-depression portion, and the thermal stress is thereby eased.

Similarly, the surface of the one end of the heat dissipating member44is designed to have projections and depressions. Hence, the thermal expansion of the heat dissipating member44produced at high temperature is absorbed by the elastic deformation of the projection-depression portion, and the thermal stress is thereby eased.

Further, as described above, the heat dissipating member44, which is made of a metallic material that has higher thermal conductivity than ceramics, is excellent in heat dissipating characteristics. In addition, because of the multiple fins45arranged on the other end of the heat dissipating member44, the heat dissipating member44is provided with a large surface area, which increases the heat dissipating characteristics. Still further, the not-shown forced cooling system forcefully cools the heat dissipating member44by means of a fluid.

Next,FIG. 9illustrates an X-ray tube according to the fifth embodiment of the present invention.

Any elements inFIG. 9that are the same as those inFIG. 7are provided with the same reference numbers, and the explanation thereof is omitted.

The basic structure of the X-ray tube11where the attachment portion28is attached to the inner surface of the end surface portion14bof the second vacuum envelope member14is the same as the structure of the fourth embodiment.

Multiple fins45are arranged on the outer circumferential surface of the heat dissipating member44in the circumferential direction of the base portion of the heat dissipating member44to protrude in the direction of the outer diameter. The fins45are formed circularly around the circumference of the base of the heat dissipating member44and positioned at intervals along the shaft direction of the heat dissipating member44. In such as structure, the heat dissipating member44is provided with a large surface area, and the heat dissipating characteristics are thereby further improved.

Next,FIG. 10illustrates an X-ray tube according to the sixth embodiment of the present invention.

Any elements inFIG. 10that are the same as those inFIG. 7are provided with the same reference numbers, and the explanation thereof is omitted. The basic structure of the X-ray tube where the attachment portion28is attached to the inner surface of the end surface portion14bof the second vacuum envelope member14is the same as the structure of the fourth embodiment.

In the forced cooling system61that cools the heat dissipating member44, a pipe62through which a fluid flows is connected to the base of the heat dissipating member44. When liquid such as an antifreeze solution or the like that contains water as the main element is supplied as a fluid so as to flow through the pipe62, heat conducted to the heat dissipating member44is forcefully cooled by heat exchange with the liquid through the pipe62. The forced cooling system61that adopts liquid for the fluid improves the heat dissipating characteristics.

Next,FIG. 11illustrates an X-ray tube according to the seventh embodiment of the present invention.

Any elements inFIG. 11that are the same as those inFIG. 10are provided with the same reference numbers, and the explanation thereof is omitted. The basic structure of the X-ray tube where the attachment portion28is attached to the inner surface of the end surface portion14bof the second vacuum envelope member14, as well as the forced cooling system61, is the same as the sixth embodiment.

The attachment portion28and the inner surface of the end surface portion14bof the second vacuum envelope member14are connected to each other by way of a flexible component51arranged therebetween, which is formed of a metal disk. The surface of one end of the flexible component51attached to the attachment portion28is designed to be a curved surface without any projections or depressions. On the other hand, the surface of the other end of the flexible component51attached to the inner surface of the end surface portion14bof the second vacuum envelope member14is designed to have projections and depressions to ease the thermal stress produced at high temperature. In other words, multiple projections53are defined by multiple depressions52that are formed into a grid and serve as a division. The surfaces of these projections53are attached to the inner surface of the end surface portion14bof the second vacuum envelope member14.

Heat is conducted from the attachment portion28to the second vacuum envelope member14by way of the flexible component51arranged between the attachment portion28and the inner surface of the end surface portion14bof the second vacuum envelope member. Further, the thermal expansion of the supporting member25produced at high temperature is absorbed by the elastic deformation of the flexible component51, and the thermal stress is thereby eased.

Next,FIG. 12illustrates an X-ray tube according to the eighth embodiment of the present invention.

Any elements inFIG. 12that are the same as those inFIG. 7are provided with the same reference numbers, and the explanation thereof is omitted. The basic structure of the X-ray tube11where the attachment portion28is attached to the inner surface of the end surface portion14bof the second vacuum envelope member14is the same as the fourth embodiment.

As illustrated inFIG. 12, the heat dissipating member44is fixed to the base60in an integrated fashion. To this base60, the forced cooling system61that cools the heat dissipating unit44is detachably fixed to the base60by means of screws. This forced cooling system61further improves the heat dissipating characteristics. In addition, the forced cooling system61, which is secured by screws, can be readily detached and replaced.

Next,FIG. 13illustrates an X-ray tube according to the ninth embodiment of the present invention.

Any elements inFIG. 13that are the same as those inFIG. 12are provided with the same reference numbers, and the explanation thereof is omitted. The basic structure of the X-ray tube11where the attachment portion28is attached to the inner surface of the end surface portion14bof the second vacuum envelope member14, as well as the forced cooling system61, is the same as the eighth embodiment. In a similar manner to the structure illustrated inFIG. 13, the forced cooling system61is detachably fixed to the base60by means of screws.

A metal cylinder70is secured to the base60in such a manner as to cover the outer circumference of the second vacuum envelope member14. An insulating material42is arranged between the metal cylinder70and the outer circumference of the second vacuum envelope member14, and the entire outer circumference of the cylindrical portion14aof the second vacuum envelope member14, the terminal38, the high-voltage cable37and the like are covered with the insulating material42. In such a structure where the entire outer circumference of the cylindrical portion14aof the second vacuum envelope member14is covered with the insulating material42, excellent insulating characteristics can be realized. For the insulating material42, a material in which alumina or aluminum nitride is mixed into a silicone resin is used.

Next,FIG. 14illustrates an X-ray tube according to the tenth embodiment of the present invention.

Any elements inFIG. 14that are the same as those inFIG. 1are provided with the same reference numbers, and the explanation thereof is omitted. The basic structure of the X-ray tube11where the attachment portion28is attached to the inner surface of the cylindrical portion14aof the second vacuum envelope member14is the same as the first embodiment.

One end of the heat dissipating unit44is connected to the cylindrical portion14aof the second vacuum envelope member14. Moreover, the other end of the heat dissipating member44is extended so as to cover the insulating material42, and the base60is arranged on the other end. The forced cooling system61is secured to the base60by means of screws.

According to the present embodiment, the insulating material42can dissipate heat by means of the heat dissipating member44. Thus, the heat dissipating characteristics can be improved, and the insulating characteristics can be ensured over the long term. Especially because the heat dissipating unit44is cooled directly by the forced cooling system61, the X-ray tube can be efficiently cooled. Furthermore, the forced cooling system61that is secured by screws can be readily detached and replaced.

It should be noted that the present invention is not limited to the above embodiments, but may be realized by modifying the structural elements without departing from the gist at the stage of implementation. Moreover, by suitably combining structural elements disclosed in the above embodiments, various inventions can be attained. In addition, a structure in which, for instance, some structural elements are omitted from the elements of the entire structure indicated in any of the embodiments is conceivable. Further, the structural embodiments described in different embodiments may be suitably combined.

Of course, in addition to the above, the present invention can be realized by making various modifications without departing from the gist of the present invention.

The present invention offers an X-ray tube that maintains excellent heat dissipating characteristics and ensures the insulating characteristics of the insulating material over the long term.