Embodiments described herein relate generally to an X-ray tubes and a method of manufacturing the X-ray tube.
In X-ray tubes for analysis and other applications, the envelope, which maintains a vacuum inside, is made of metal and an insulator such as ceramics, glass or the like. Each of the members of the X-ray tube is joined by brazing, welding, or glass sealing during the assembly process to create a structure that maintains a vacuum. In particular, brazing or welding is used to join ceramic and metal components, and to join metal components to each other.
For each component, the dimensional tolerance is set, but, particularly, in engaging parts and joint parts, backlashes are created. Further, as the dimensional tolerances and the backlashes accumulate in accordance with the number of assembled parts, the focal error with respect to the anode target and the backlash in the distance to the cathode electron gun become significant in the finished shape, which may result in large variations in the shape of the focal point.
The shape of the focal point affects not only the analysis performance but also the lifetime of the X-ray tube. For example, if the focal point is smaller than a necessary size, the X-ray intensity and resolution as analytical performance enhances, but the temperature of the focal plane rises, which accelerates the melting of the focal plane and shortens the lifetime of the X-ray tube. On the other hand, if the focal point is large, the lifetime of the X-ray tube becomes longer, but the X-ray intensity and resolution as resolution performance become lower.
Under these circumstances, there has been a demand for an X-ray tube that can reduce the variation in the shape of the focal point in an anode target spot shape, and a method of manufacturing such an X-ray tube.
One of embodiments described herein aims to provide an X-ray tube that can absorb the effects of the dimensional tolerances of parts and the backlashes during assembly, and reduce the variation of the focal shape in the anode target, and a method of manufacturing such an X-ray tube.
In general, according to one embodiment, an X-ray tube comprises an outer envelope that maintains a vacuum inside, an anode target provided inside the envelope and generating X-rays by collision of thermal electrons, and a cathode electron gun provided inside the envelope and emits thermal electrons toward the anode target, and the X-ray tube also comprises a cathode assembly including a metal-made support which holds the cathode electron gun at a distal end thereof, and an envelope assembly including a support fixing portion which fixes the support of the cathode assembly and constituting the envelope, and the support fixing portion being made of a metal into a cylindrical shape, and the support of the cathode assembly being fixed to an inner circumferential side thereof by welding.
According to another embodiment, a method of manufacturing an X-ray tube comprising an outer envelope that maintains a vacuum inside, an anode target provided inside the envelope and generating X-rays by collision of thermal electrons, and a cathode electron gun provided inside the envelope and emits thermal electrons toward the anode target, the X-ray tube comprising: a cathode assembly including a metal-made support which holds the cathode electron gun at a distal end thereof; an envelope assembly including a metal-made support fixing portion which fixes the support of the cathode assembly and a ceramic-made cylindrical envelope body, one end of the envelope body and an outer circumferential surface of the support fixing portion being joined together by a metal-made joint member; and an anode assembly including a metal-made bottomed cylindrical portion which constitutes a part of the envelope, holding the anode target on an inner bottom surface of the bottomed cylindrical portion, and including an X-ray transmission window on a side surface of the bottomed cylindrical portion, and the method comprises an insertion step of inserting the cathode assembly into the support fixing portion of the envelope assembly from the distal end thereof into the envelope assembly, a cathode assembly positioning step of positioning the cathode assembly by, after the insertion step, positioning the distal end of the cathode assembly at a predetermined position, a cathode assembly welding step of fixing by welding, after the cathode assembly positioning step, a rear end of the support of the cathode assembly to the support fixing portion of the envelope assembly.
An X-ray tube and a method of manufacturing the X-ray tube according to one embodiment will be described in detail below with reference to the accompanying drawings. In addition, in some cases, in order to make the description clearer, the widths, thicknesses, shapes, etc., of the respective parts are schematically illustrated in the drawings, compared to the actual modes. However, the schematic illustration is merely an example, and adds no restrictions to the interpretation of the invention. Besides, in the specification and drawings, the same or similar elements as or to those described in connection with preceding drawings or those exhibiting similar functions are denoted by like reference numerals, and a detailed description thereof is omitted unless otherwise necessary.
As shown in
The X-ray tube 1 is constituted by three assemblies: an envelope assembly 11, a cathode assembly 13, and an anode assembly 15.
As shown in
The envelope body 17 is made of ceramics into a cylindrical shape. On one end 17a and the other end 17b of the main body 17, metallizing portions 18 are formed respectively to be formed into metal surfaces.
The support fixing portion 19 is made of stainless steel or the like into a cylindrical shape. As shown in
The first joint member 21 is made of a metal such as Kovar (KOV) and is placed between the one end 17a of the envelope body 17 and an outer circumferential surface 19b of the support fixing section 19, so as to seal the space therebetween as a part of the envelope 3 (see
An end (inner circumferential end) 21a of the first joint member 21 on a support fixing section 19 side is brazed to the outer circumferential surface 19b of the support fixing section 19. Another end (outer circumferential end) 21b of the first joint member 21 on an envelope body 17 side is brazed to the one end 17a of the envelope body.
Further, to the other end 17b of the envelope body 17, one end 23a of the second joint member 23 is brazed. The second joint member 23 is made of a metal such as Kovar (KOV), and is formed into an annular shape along the form of the other end 17b of the envelope body 17, and here in this embodiment, it has a ring-like shape.
As shown in
The support 27 is made of a metal such as stainless steel into a cylindrical shape, and holds the cathode electron gun 7 at a distal end 27a thereof. As shown in
The distal end 27a of the support 27 has a concave electron gun holding section 27c, where the cathode electron gun 7 is placed, and is flush with the distal end of the cathode electron gun 7 or either side protrudes.
The support 27 has a cylindrical shape, and a ceramic sealing member 29 is provided inside the cylinder at a position corresponding to the support fixing section 19 of the envelope assembly 11. Wires 7a and 7b of the cathode electron gun 7 pass through the sealing member 29 inside the support 27, and are withdrawn out from the envelope 3.
As shown in
As shown in
Next, a method of manufacturing the X-ray tube 1 of this embodiment will be described.
First, the manufacturing of each of the assemblies 11, 13 and 15 will be described.
As shown in
Next, the cylindrical support fixing section 19 is slid into the one end (inner circumferential end) 21a of the first joint member 21 and positioned at a predetermined position using a jig or the like. Here, the support fixing section 19 is positioned so that a distance H2 between the other end 17b of the envelope body 17 and the outer end 19c of the support fixing section 19 becomes a predetermined distance.
After positioning the support fixing portion 19, the one end 17a of the cylindrical envelope body 17 and the other end 21b of the first joint member 21 are brazed together, and so are between the other end 17b of the envelope body 17 and the one end 23a of the second joint member 23, and between the one end 21a of the first joint member 21 and the outer circumferential surface 19b of the support fixing section 19, to be fixed.
As shown in
As shown in
Next, the assembling of each of the assemblies 11, 13 and 15 will be described.
As shown in
More specifically, as shown in
Next, as indicated by a reference symbol B in
As shown in
Next, as shown in
In the above-described manner, the envelope assembly 11, the cathode assembly 13, and the anode assembly 15 are assembled to manufacture the X-ray tube 1.
The function of the X-ray tube 1 will now be described.
As shown in
The effect of the X-ray tube 1 in this embodiment will now be described.
As shown in
In particular, by positioning the cathode electron gun 7 directly with respect to the anode target 5, the influence of the dimensional tolerance, if any, on the distance H1 of the ceramic-made envelope body 17 can be reduced.
The positioning of the support 27 that holds the cathode electron gun 7 can be achieved by placing the distal end 27a of the support 27 to abut on the positioning jig 35 corresponding to the position of the anode target 5, thereby making it easy to carry out the positioning.
According to this embodiment, the X-ray tube can be manufactured so accurately that the distance between the cathode electron gun 7 and the anode target 5, which affects the shape of the focal point of the X-ray tube is set within an error range of 0.1 mm.
As shown in
In the X-ray tube 1 of this embodiment, among the parts related to the distance H3 between the cathode electron gun 7 and the anode target 5, which affects the shape of the focal point, those other than the envelope body 17, which is made of ceramics, are all metal parts. Therefore, precise processing and jointing can be easily achieved.
According to this embodiment, the X-ray tube 1 is constituted by three assemblies: an envelope assembly 11, a cathode assembly 13, and an anode assembly 15, and it is assembled while positioning each of the assemblies 11, 13, and 15. Therefore, it is possible to carry out efficient manufacturing.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
---|---|---|---|
2019-203791 | Nov 2019 | JP | national |
2020-011831 | Jan 2020 | JP | national |
This application is a Continuation application of PCT Application No. PCT/JP2020/027168, filed Jul. 10, 2020 and based upon and claiming the benefit of priority from Japanese Patent Application No. 2019-203791, filed Nov. 11, 2019; and No. 2020-011831, filed Jan. 28, 2020, the entire contents of all of which are incorporated herein by reference.
Number | Date | Country | |
---|---|---|---|
Parent | PCT/JP2020/027168 | Jul 2020 | US |
Child | 17657958 | US |