X-ray tube with high-stability luminous flux

Abstract

The utility model relates to the technical field of X-ray tubes, in particular to an X-ray tube with high-stability luminous flux, which comprises a tube shell, a cathode assembly, an anode assembly and a window assembly, and is characterized in that the anode assembly comprises an anode cap, an anode rod and an anode target assembly; the anode cap comprises an expansion part, a partition part and a necking part which are sequentially connected in the axial direction of the anode cap, the expansion part wraps the focusing piece from the bottom and the circumferential direction of the focusing piece, an electron beam incidence hole is formed in the partition part, and a packaging cavity extending in the axial direction and an X-ray outlet penetrating in the radial direction are formed in the necking part; the potential of the anode assembly is higher than that of the cathode assembly; along the axial direction of the X-ray tube, the distance H between the bottom of the focusing part and the top of the expansion part is greater than the distance D1 between the bottom of the focusing part and the partition part, so that stray electrons and secondary electrons generated by the stray electrons and overflow electrons and secondary electrons generated by the overflow electrons are absorbed after repeated back bombardment in the expansion part, and the secondary electrons are completely prevented from bombarding a tube shell, thereby improving the efficiency of the X-ray tube. And the high stability of the X-ray luminous flux is ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of X-ray tubes, in particular to the technical field of X-ray tubes used in the field of scientific instruments, and in particular to an X-ray tube with high-stability luminous flux. Background Art

[0002] High-end X-ray scientific instruments, such as X-ray fluorescence spectrometers (XRF), high-performance X-ray diffractometers (XRD), micro-area X-ray fluorescence analyzers (MicroXRF), and X-ray absorption spectrometers (XAFS), feature X-ray tubes and sources with micron-scale focal spots. These instruments are widely used in fields such as materials science, biology, chemistry, environmental science, geology, and archaeology, as well as in industries such as semiconductors, new energy, electronic devices, thin films, and forensic analysis, for micro-area trace and micro-analysis, qualitative and quantitative phase analysis, stress and texture analysis, strain analysis, and crystallite size analysis. While traditional industrial and medical X-ray tubes and sources typically require X-ray flux stability of ≤3% / 4 hours, these high-end X-ray scientific instruments have even higher requirements, typically ≤0.1% / 72 hours. Furthermore, unlike traditional industrial and medical X-ray tubes, these high-end X-ray scientific instruments have stringent requirements for the physical stability of the focal spot, typically requiring fluctuations within ±1μm. During operation, X-ray tubes can experience unstable luminous flux due to factors such as unstable high-voltage electric field structures, scattered secondary electrons between the cathode and anode, and the accumulation of excited secondary electrons. During operation, over 99% of the input energy is converted into heat, causing the anode temperature of the X-ray tube to rise and fluctuate. Thermal expansion and contraction cause fluctuations in the focal position, leading to unstable luminous flux entering the X-ray optical device. Therefore, maintaining a constant anode temperature (typically 20-24°C, with fluctuations within ±0.2°C) is crucial.

[0003] Some existing X-ray tubes have various heat dissipation methods designed for their anodes, such as those disclosed in Chinese patent documents Nos. 202210167293.7, 201780063975.0, 201920164824.0, 202222416302.X, 202011184705.5, and 202010552652.1. However, these existing designs are all intended to reduce the temperature of the anode or anode target, prevent melting of the anode target surface, or increase the lifespan of the X-ray tube. They do not address heat dissipation from the anode cap that wraps the anode head, nor do they address constant temperature control of the X-ray tube anode temperature, nor can they maintain a constant anode temperature. Therefore, these existing designs cannot achieve high stability in the spatial position of the focal spot, and cannot meet the requirements of high-performance X-ray scientific instruments for high X-ray flux stability. Moreover, this type of X-ray tube has the disadvantage that the distance between the focus of the X-ray anode target surface and the anode tail end is too long, which will lead to an increase in thermal expansion length and a too long thermal equilibrium time of the anode temperature, resulting in a long waiting time for stability during testing.

[0004] To address the above issues, Chinese patent application No. 201510464658.2 proposes enclosing the anode target within the cathode shield of the electron gun. This reduces the risk of secondary electrons bouncing off the glass insulating shell, causing accumulation within the shell and leading to unstable high-voltage tubes, thus causing unstable X-ray flux. However, this structure, with an X-ray outlet on the cathode shield, cannot completely prevent secondary electrons from bombarding the insulating shell. This structure remains unchanged from traditional X-ray tube design. The anode target directly faces the electron beam from the cathode, and electrons that are bombarded by the electrons, while those that are not effectively intercepted, scatter in all directions and bombard the insulating shell, easily generating interference currents that can cause system miscontrol and ultimately lead to unstable flux. Furthermore, electrons that are drawn back by the anode high voltage can re-bombard the anode, generating unintended stray X-rays and affecting flux stability. Furthermore, because an effective high-voltage insulation length is required, the distance between the X-ray anode target focus and the anode tail end is too long. This increases thermal expansion and prolongs the anode temperature thermal equilibrium time, resulting in a long wait time for stability during testing. This structure in which the anode target is wrapped in a tube shell also makes it difficult to perform wrapped heat dissipation on the anode target to meet the low and constant anode temperature. There is also a disadvantage that the position where the X-rays leave the tube shell is too far from the focal point, and the X-rays diverge, resulting in a low luminous flux density per unit area and less X-rays collected by the X-ray optical device.

[0005] Furthermore, in the X-ray tube disclosed in the Chinese patent document with application number 202080052348.9, the probability of the insulating shell being bombarded by X-rays is reduced, and the risk of sparks is reduced by shielding the X-rays with the cathode cover, that is, the focusing electrode. However, in most actual applications, since the electron-emitting material is a spiral tungsten wire, the electron focus on the cathode and anode target surfaces is also a long strip, rather than a point focus, so it is difficult for the X-rays to be completely blocked by the protrusions of the focusing electrode. In addition, the transmission target of this structure (currently in the existing patent document) Figure 3 7 ) cannot be used in X-ray scientific instruments due to the dispersion of the X-ray flux. Other reflective target structures do not solve the shortcomings of the Chinese patent document with application number 201510464658.2, such as the anode target surface being directly opposite to the electron beam and being blocked, the distance between the focus and the anode tail end being too long, the anode target being difficult to perform wrapped heat dissipation, and the X-ray window being too far from the focus. Therefore, it is difficult to meet the high stability requirements of the X-ray flux. Utility Model Content

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an X-ray tube with highly stable luminous flux, which can completely avoid electron bombardment of the tube shell, control the physical drift of the focal point spatial position, and ensure high stability of the X-ray luminous flux.

[0007] To achieve the above object, the utility model provides an X-ray tube with high stability of light flux, comprising a tube shell, a cathode assembly, an anode assembly, and a window assembly;

[0008] The tube shell has a tube cavity for forming a vacuum environment;

[0009] The cathode assembly is arranged in the tube cavity, and the cathode assembly includes an electron emitting element for emitting an electron beam and a focusing element for focusing the electron beam;

[0010] The anode assembly includes an anode cap, an anode rod, and an anode target assembly provided with an anode target; the anode cap is sealed at one end of the tube shell, the anode cap includes an expansion portion, a partition portion, and a neck portion connected in sequence along its axial direction, the expansion portion wraps the focusing member from the bottom and circumferential direction of the focusing member, the partition portion is provided with an electron beam entrance hole for allowing the electron beam to pass through, the inner diameters of the expansion portion, the inner diameters of the neck portion, and the aperture of the electron beam entrance hole gradually decrease; the neck portion is provided with an axially extending packaging cavity and a radially through X-ray outlet, the anode rod is sealed in the packaging cavity, the anode target assembly is sealed at one end of the anode rod facing the partition portion, the anode target is opposite to the electron emitting member and the focusing member along the axial direction of the anode cap through the electron beam entrance hole, the anode target is aligned with the X-ray outlet along the radial direction of the anode cap, the anode cap forms a cap inner cavity between the partition portion, the neck portion, and the anode target assembly, the electron beam entrance hole and the X-ray outlet are both connected to the cap inner cavity;

[0011] The window assembly is arranged in the X-ray outlet;

[0012] The potential of the anode assembly is higher than that of the cathode assembly. The electron beam emitted by the electron emitting element of the cathode assembly is accelerated by the accelerating electric field between the focusing element and the anode cap to form a focused electron beam. The focused electron beam enters the inner cavity of the cap through the electron beam inlet hole and bombards the anode target, generating diffuse X-rays. The diffuse X-rays are emitted through the X-ray outlet. During this process, some electrons in the focused electron beam leave and form stray electrons. Some rebound electrons that bombard the surface of the anode target overflow from the inner cavity of the cap through the electron beam inlet hole into the expansion portion and form overflow electrons. The stray electrons and overflow electrons bombard the inner surface of the anode cap to form secondary electrons.

[0013] Along the axial direction of the X-ray tube, the distance H between the bottom of the focusing element and the top of the expansion portion is greater than the distance D1 between the bottom of the focusing element and the partition portion, so that the secondary electrons are absorbed after multiple bounces in the expansion portion.

[0014] Furthermore, the distance H between the bottom of the focusing member and the top of the expansion portion is 2-10 times the distance D1 between the bottom of the focusing member and the partition portion.

[0015] Furthermore, the distance H between the bottom of the focusing member and the top of the expansion portion is 3-5 times the distance D1 between the bottom of the focusing member and the partition portion.

[0016] Furthermore, the distance D2 between the outer periphery of the focusing member and the inner periphery of the expansion portion is 1-2 times the distance D1 between the bottom of the focusing member and the partition portion.

[0017] Furthermore, the cathode assembly also includes a first electrode, a second electrode, a third electrode, a first support rod electrically connected to the first electrode, and a second support rod electrically connected to the second electrode. The first electrode, the second electrode and the third electrode are electrically isolated from each other and are all installed on the tube shell. The first support rod and the second support rod are both electrically connected to the electron emission component, and the third electrode is electrically connected to the focusing component.

[0018] Furthermore, the cathode assembly also includes insulating beads, insulating parts, and a transition connecting tube fixed in the tube shell. The first electrode, the second electrode and the third electrode are electrically isolated from each other by the insulating beads. The first support rod and the second support rod are both installed in the transition connecting tube. The first support rod and the transition connecting tube, as well as the second support rod and the transition connecting tube, are electrically isolated by the insulating parts. The third electrode is electrically connected to the focusing part through the transition connecting tube.

[0019] Furthermore, an operation hole is opened on the transition connecting pipe, and the connection part between the first electrode and the first support rod, and the connection part between the second electrode and the second support rod are exposed from the operation hole.

[0020] Furthermore, the X-ray tube with high-stability luminous flux also includes a getter disposed in the tube cavity, one of the first electrode and the second electrode is a common electrode, and both ends of the getter are respectively connected to the common electrode and the third electrode.

[0021] Furthermore, the anode target assembly also includes a target base arranged at one end of the anode rod facing the partition portion, and a base flange fixed on the end face of the target base facing the anode rod, an annular fixing groove is opened on the end face of the anode rod facing the target base, the base flange is sealed in the annular fixing groove, and the anode target is fixed on the end face of the target base facing the partition portion.

[0022] Furthermore, the target base is made of copper or diamond.

[0023] Furthermore, an axially penetrating rod through-hole is provided in the anode rod, and the rod through-hole extends to the target base. The hole wall of the rod through-hole and the outer surface of the target base form a liquid cooling cavity, and the liquid cooling cavity is used to accommodate a cooling medium.

[0024] Furthermore, the window assembly includes a window piece, a window flange and a transition flange, the transition flange is sealed in the X-ray outlet of the neck portion, the window flange is sealed in the transition flange, a step portion is provided on the inner surface of the window flange, and the window piece is sealed in the window flange at the step portion.

[0025] As described above, the X-ray tube with high-stability luminous flux involved in the present invention has the following beneficial effects:

[0026] First, the stray electrons repelled from the focused electron beam and the secondary electrons generated by the stray electrons bombarding the expansion part are absorbed back into the anode cap because the potential on the anode cap is higher than the potential of the focusing member. Combined with the fact that the distance H between the bottom of the focusing member and the top of the expansion part is much greater than the distance D1 between the bottom of the focusing member and the partition part, and the structural setting that the expansion part wraps the focusing member from the bottom and circumferential direction, the stray electrons and the secondary electrons generated are gradually depleted and absorbed after multiple back-bombardments on the inner surface of the anode cap. At the same time, the overflow electrons overflowing from the inner cavity of the cap and the secondary electrons generated by the overflow electrons bombarding the expansion part are also gradually depleted and absorbed after multiple back-bombardments on the inner surface of the anode cap. Therefore, the present application can completely avoid the secondary electrons bombarding the tube shell, thereby avoiding the interference current generated thereby, and ultimately preventing the X-ray source from being misadjusted due to the detection of the interference current, thus reliably ensuring the high stability of the X-ray flux.

[0027] Second, stray electrons and the secondary electrons generated by them, as well as overflow electrons and the secondary electrons generated by them, are absorbed after multiple back-bombardments in the expansion portion, completely avoiding the accumulation of charge on the tube shell due to the secondary electrons bombarding the tube shell, thereby avoiding the instability of the X-ray flux caused by sparks.

[0028] Third, the part where the stray electrons and the secondary electrons generated thereby, as well as the overflow electrons and the secondary electrons generated thereby bombard the anode cap is the inner surface of the expansion part, and the window assembly is arranged in the contraction part, and the partition part is blocked between the contraction part and the expansion part, so that the window assembly is away from the part bombarded by the stray electrons, the overflow electrons and the secondary electrons, and is blocked by the partition part of the anode cap. Then, the stray X-rays generated by the electrons bombarding the inner surface of the expansion part will not enter the X-ray outlet, thereby reliably improving the quality and stability of the X-ray beam emitted by the window assembly.

[0029] Fourth, the anode target assembly is located inside the neck portion of the anode cap and is wrapped by the neck portion, so it is easy to adopt an effective heat dissipation method to dissipate the heat of the anode target assembly, the anode rod and the neck portion of the anode cap. That is, it is easy to accurately control the temperature rise of the anode target assembly, the anode rod and the neck portion of the anode cap at a lower temperature, reduce the problem of focus space drift caused by temperature rise of the anode target focus, meet the requirement within ±1μm, effectively control the physical drift of the focus space position, and thus effectively avoid the problem of X-ray light flux instability caused by focus space drift. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structure of an X-ray tube with high-stability luminous flux in the present application, which is a top view.

[0031] Figure 2 for Figure 1 AA section view.

[0032] Figure 3 for Figure 2 Schematic diagram of the structure of the anode assembly.

[0033] Figure 4 for Figure 2 Schematic diagram of the structure of the anode cap.

[0034] Figure 5 for Figure 2 Schematic diagram of the structure of the anode rod and anode target assembly.

[0035] Component number description

[0036] 10 tube shell

[0037] 11 Lumen

[0038] 20 cathode assembly

[0039] 21 Electron emitter

[0040] 22 Focusing parts

[0041] 23. First electrode

[0042] 24 Second electrode

[0043] 25 Third electrode

[0044] 26 First support rod

[0045] 27 Second support rod

[0046] 28 Insulation Beads

[0047] 29 Insulation

[0048] 210 transition pipe

[0049] 211 operation hole

[0050] 30 Anode assembly

[0051] 31 Anode cap

[0052] 311 Expansion Department

[0053] 312 Partition

[0054] 313 Neck Shrinkage

[0055] 314 electron beam entrance hole

[0056] 315 package cavity

[0057] 316 X-ray outlet

[0058] 317 cap cavity

[0059] 32 Anode rod

[0060] 321 annular fixing groove

[0061] 322 Rod Through Hole

[0062] 33 Anode target assembly

[0063] 331 anode target

[0064] 332 target base

[0065] 333 base flange

[0066] 40 Window Components

[0067] 41 Window

[0068] 42 Window flange

[0069] 421 Steps

[0070] 43 Transition flange

[0071] 50 Liquid cooling chamber

[0072] e1 stray electrons

[0073] e2 rebound electron

[0074] e3 overflow electron DETAILED DESCRIPTION

[0075] The following describes the implementation of the present invention through specific embodiments. People familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0076] It should be noted that the structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification for the understanding and reading of those familiar with this technology, and are not used to limit the conditions for the implementation of the present invention. Therefore, they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose of the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be considered as the scope of the implementation of the present invention without substantially changing the technical content.

[0077] It should also be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or indirectly connected to the other element through an intervening element.

[0078] In addition, the descriptions of "first", "second", etc. in this application are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0079] The utility model provides an X-ray tube and an X-ray source including the X-ray tube, wherein the X-ray tube has a high stability of light flux. Figure 1 and Figure 2 As shown, the X-ray tube with high stability of light flux involved in the present invention includes a tube shell 10, a cathode assembly 20, an anode assembly 30 and a window assembly 40. The structure of each assembly is described as follows.

[0080] like Figure 2 As shown, the tube shell 10 is a hollow shell having a tube cavity 11 therein for forming a vacuum environment. The tube shell 10 is an insulating shell made of an insulating material, which may be electronic glass or ceramic. The tube shell 10 supports the cathode assembly 20 and the anode assembly 30 and provides electrical insulation and vacuum sealing between the cathode assembly 20 and the anode assembly 30.

[0081] like Figure 2 As shown, the cathode assembly 20 is arranged in the tube cavity 11 of the tube shell 10. The cathode assembly 20 includes an electron emitting element 21 for emitting an electron beam and a focusing element 22 for focusing the electron beam. The focusing element 22 is arranged at one end of the cathode assembly 20 close to the anode assembly 30.

[0082] like Figures 2 to 4As shown, the anode assembly 30 includes an anode cap 31, an anode rod 32, and an anode target assembly 33 equipped with an anode target 331. The tube shell 10, the anode cap 31, and the anode rod 32 are coaxially arranged. The anode cap 31 is sealed at one end of the tube shell 10 and includes an expansion portion 311, a partition portion 312, and a constriction portion 313, which are sequentially connected along the axial direction. The expansion portion 311 wraps around the focusing element 22 from the bottom and circumference of the focusing element 22. The end surface of the focusing element 22 facing the anode assembly 30 and the outer circumference of the focusing element 22 are completely covered by the expansion portion 311. The partition portion 312 defines an axially extending electron beam entrance hole 314, which allows the electron beam emitted by the cathode assembly 20 to pass through. The inner diameter of the expanded portion 311 , the inner diameter of the constricted portion 313 , and the aperture of the electron beam incident hole 314 gradually decrease, and the outer diameter of the expanded portion 311 is larger than the outer diameter of the constricted portion 313 . The necking portion 313 is provided with a packaging cavity 315 extending along its axial direction and an X-ray outlet 316 passing through it radially. One end of the packaging cavity 315 extends to the partition portion 312. The anode rod 32 is sealed in the packaging cavity 315. The anode target assembly 33 is sealed at the end of the anode rod 32 facing the partition portion 312. The anode target 331 is opposite to the electron emitting element 21 and the focusing element 22 along the axial direction of the anode cap 31 through the electron beam incident hole 314. The anode target 331 is aligned with the X-ray outlet 316 along the radial direction of the anode cap 31. The anode cap 31 forms a cap inner cavity 317 between the partition portion 312, the necking portion 313 and the anode target assembly 33. The cap inner cavity 317 is part of the packaging cavity 315. The electron beam incident hole 314 and the X-ray outlet 316 are both connected to the cap inner cavity 317.

[0083] like Figure 2 As shown, the window assembly 40 is provided in the X-ray outlet 316 , and the window assembly 40 is used to isolate the inner and outer vacuums of the X-ray tube.

[0084] During the operation of the above X-ray tube, Figure 2As shown, the electron beam emitted by the electron emitting element 21 of the cathode assembly 20 is accelerated by the accelerating electric field between the focusing element 22 and the anode cap 31 to form a focused electron beam. The focused electron beam enters the cap cavity 317 through the electron beam entrance hole 314 and bombards the anode target 331 to generate diffuse X-rays. The diffuse X-rays are emitted through the X-ray outlet 316, and the diffuse X-rays directly pass through the window assembly 40 and are collected by the X-ray optical device of the X-ray source. During the operation of the above-mentioned X-ray tube, due to the mutual repulsive force between electrons in the focused electron beam, some electrons will leave the focused electron beam, and these electrons leaving the focused electron beam will form stray electrons e1. The stray electrons e1 are attracted by the potential on the anode cap 31 and bombard the inner surface of the anode cap 31, thereby forming secondary electrons. At the same time, the anode target 331 of the anode target assembly 33 is opposite to the focusing member 22 through the electron beam entrance hole 314. Most of the rebound electrons e2 bombarding the surface of the anode target 331 are directly blocked by the cap cavity 317 of the anode cap 31. The small number of rebound electrons e2 bombarding the surface of the anode target 331 overflow from the cap cavity 317 of the anode cap 31 and overflow into the expansion part 311 through the electron beam entrance hole 314 of the partition part 312, thereby forming overflow electrons e3. The overflow electrons e3 are attracted by the potential on the anode cap 31 and bombard the inner surface of the anode cap 31, thereby forming secondary electrons.

[0085] In particular, Figure 2 As shown, along the axial direction of the X-ray tube, the distance between the bottom of the focusing element 22 and the partition 312 is D1. This distance D1 is related to the potential difference between the focusing element 22 and the anode cap 31, as well as the dimensions and structures of the focusing element 22 and the anode cap 31. The potential difference between the focusing element 22 and the anode cap 31 is the tube voltage of the X-ray tube. Typically, distance D1 is 3-25 mm. The distance between the bottom of the focusing element 22 and the top of the expansion portion 311 is H. In this application, the distance H between the bottom of the focusing element 22 and the top of the expansion portion 311 is much larger than the distance D1 between the bottom of the focusing element 22 and the partition 312. The distance H between the bottom of the focusing element 22 and the top of the expansion portion 311 should satisfy the following requirement: secondary electrons generated by stray electrons e1 and overflow electrons e3 bombarding the inner surface of the anode cap 31 are absorbed within the expansion portion 311 after multiple back-bombardments. Furthermore, during operation of the X-ray tube, the potential of the anode assembly 30 is higher than that of the cathode assembly 20. The X-ray tube of the present application has the following advantages after being configured in this way.

[0086] First, the stray electrons e1 repelled from the focused electron beam, as well as the secondary electrons generated by the stray electrons e1 bombarding the expansion portion 311, are absorbed back into the anode cap 31 because the potential on the anode cap 31 is higher than the potential of the focusing element 22. Furthermore, the distance H between the bottom of the focusing element 22 and the top of the expansion portion 311 is much greater than the distance D1 between the bottom of the focusing element 22 and the partition portion 312, and the expansion portion 311 wraps around the focusing element 22 from the bottom and circumference. As a result, the stray electrons e1 and, in particular, the secondary electrons generated, are gradually depleted and absorbed after multiple back-bombardments on the inner surface of the anode cap 31. Simultaneously, the overflow electrons e3 from the cap cavity 317, as well as the secondary electrons generated by the overflow electrons e3 bombarding the expansion portion 311, are also gradually depleted and absorbed after multiple back-bombardments on the inner surface of the anode cap 31. Therefore, the present application can completely prevent secondary electrons from bombarding the tube shell 10, thereby avoiding the interference current generated thereby, and ultimately preventing the X-ray source from being misadjusted due to the detection of the interference current, thereby reliably ensuring the high stability of the X-ray flux.

[0087] Second, the stray electrons e1 and the secondary electrons generated thereby, as well as the overflow electrons e3 and the secondary electrons generated thereby, are absorbed within the expansion portion 311 after multiple back-bombardments, thereby completely preventing the secondary electrons from bombarding the tube shell 10 and forming charge accumulation on the tube shell 10, thereby avoiding instability of the X-ray flux caused by sparks.

[0088] Third, the part where the stray electrons e1 and the secondary electrons generated thereby, as well as the overflow electrons e3 and the secondary electrons generated thereby bombard the anode cap 31 is the inner surface of the expansion portion 311, and the window assembly 40 is arranged in the constricted portion 313. The partition portion 312 blocks the constricted portion 313 and the expansion portion 311, that is, blocks the window assembly 40 and the part of the anode cap 31 that is bombarded by the electrons. This makes the window assembly 40 away from the part that is bombarded by the stray electrons e1, the overflow electrons e3 and the secondary electrons, and is blocked by the partition portion 312 of the anode cap 31. Therefore, the stray X-rays generated by the electrons bombarding the inner surface of the expansion portion 311 will not enter the X-ray outlet 316, thereby reliably improving the quality and stability of the X-ray beam emitted by the window assembly 40.

[0089] Fourth, the anode target assembly 33 is located inside the neck portion 313 of the anode cap 31 and is wrapped by the neck portion 313. It is easy to adopt an effective heat dissipation method to dissipate heat from the anode target assembly 33, the anode rod 32 and the neck portion 313 of the anode cap 31. That is, it is easy to accurately control the temperature rise of the anode target assembly 33, the anode rod 32 and the neck portion 313 of the anode cap 31 at a relatively low temperature, thereby reducing the focus space drift problem caused by the temperature rise of the focus of the anode target 331, meeting the requirement within ±1 μm, effectively controlling the physical drift of the focus space position, and thereby effectively avoiding the problem of X-ray flux instability caused by the focus space drift.

[0090] Fifth, after the anode target 331 is provided with the partition portion 312, the partition portion 312 is blocked between the anode target 331 and the tube shell 10. The partition portion 312 plays a blocking role, reducing the X-rays on the target surface from entering the expansion portion 311, and can completely prevent the X-rays on the target surface from bombarding the tube shell 10, thereby ensuring the high stability of the X-ray flux.

[0091] Furthermore, the distance H between the bottom of the focusing member 22 and the top of the expansion portion 311 is 2-10 times, preferably 3-5 times, the distance D1 between the bottom of the focusing member 22 and the partition portion 312 .

[0092] Further, if Figure 2 As shown, along the radial direction of the X-ray tube, the distance between the outer periphery of the focusing piece 22 and the inner periphery of the expansion portion 311 is D2, and the distance D2 is greater than the distance D1 between the bottom of the focusing piece 22 and the partition portion 312; preferably, the distance D2 between the outer periphery of the focusing piece 22 and the inner periphery of the expansion portion 311 is 1-2 times the distance D1 between the bottom of the focusing piece 22 and the partition portion 312, so as to meet the high-voltage insulation requirements between the outer side of the focusing piece 22 and the inner side of the anode cap 31, and prevent the risk of unstable X-ray flux caused by sparks.

[0093] Furthermore, the preferred structure of the cathode assembly 20 is as follows: Figure 2 As shown, cathode assembly 20 further includes a first electrode 23, a second electrode 24, a third electrode 25, a first support rod 26 electrically connected to first electrode 23, and a second support rod 27 electrically connected to second electrode 24. First electrode 23 and second electrode 24 are both used to connect to an external power source. First support rod 26 and second support rod 27 are both metal rods. First electrode 23, second electrode 24, and third electrode 25 are electrically isolated from each other and are all mounted on tube housing 10. First support rod 26 and second support rod 27 are all electrically connected to electron emission element 21, and third electrode 25 is electrically connected to focusing element 22. The connection between first electrode 23 and first support rod 26, between second electrode 24 and second support rod 27, between first support rod 26 and electron emission element 21, and between second support rod 27 and electron emission element 21 is preferably achieved by various welding methods, such as resistance welding, argon arc welding, and laser welding. The third electrode 25 is electrically connected to the focusing element 22, and the third electrode 25 is electrically isolated from the electron emitting element 21. In this way, the third electrode 25 can give the focusing element 22 a different potential relative to the electron emitting element 21, thereby controlling the focusing of the electron beam by the focusing element 22 and obtaining focal points of different sizes.

[0094] Preferably, when the X-ray tube is in operation, the potential of the focusing element 22 can be controlled to be lower than the potential of the electron emitting element 21, thereby blocking the electrons emitted by the electron emitting element 21 to stop generating X-rays; when X-rays are needed, the potential on the focusing element 22 is restored, so that the X-ray tube is switched to pulse mode to generate X-rays.

[0095] Preferably, if Figure 2 As shown, the cathode assembly 20 also includes insulating beads 28, insulating parts 29, and a transition connecting tube 210 fixed in the tube shell 10. The first electrode 23, the second electrode 24 and the third electrode 25 are electrically isolated from each other by the insulating beads 28. The first support rod 26 and the second support rod 27 are both installed in the transition connecting tube 210. The first support rod 26 and the transition connecting tube 210, as well as the second support rod 27 and the transition connecting tube 210 are electrically isolated by the insulating part 29. The transition connecting tube 210 is a metal tube. The third electrode 25 is electrically connected to the focusing member 22 through the transition connecting tube 210. In addition, a pair of diametrically opposed operating holes 211 are provided on the transition connecting tube 210, and the connection parts between the first electrode 23 and the first support rod 26, as well as the connection parts between the second electrode 24 and the second support rod 27 are exposed from the operating holes 211. By providing the operating holes 211, it is convenient to form an electrical connection between the first electrode 23, the first support rod 26, the second electrode 24, the second support rod 27 and the electron emission element 21, thereby supplying power to the electron emission element 21.

[0096] Furthermore, the X-ray tube with highly stable luminous flux also includes a getter disposed within the tube cavity 11, with one of the first electrode 23 and the second electrode 24 serving as a common electrode. Within the X-ray tube housing 10, the two ends of the getter are connected to the common electrode and the third electrode 25, respectively. Thus, the getter can be activated, etc., so that after the X-ray tube forms a sealed space, the getter can absorb residual gas within the X-ray tube housing 10 or gas released during operation. This improves the vacuum level of the X-ray tube housing 10, reduces the risk of ignition, improves the stability of the X-ray tube, and thus enhances the stability of the X-ray luminous flux.

[0097] Preferably, if Figure 3 and Figure 4 As shown, the inner surface of the expansion portion 311 includes a conical segment and a cylindrical segment connected in sequence along the direction away from the partition portion 312, the aperture of the conical segment gradually increases along the direction away from the partition portion 312, and the cylindrical segment extends to the top of the expansion portion 311.

[0098] Further, if Figure 3 and Figure 5As shown, the anode target assembly 33 also includes a target base 332 disposed at the end of the anode rod 32 facing the barrier portion 312, and a base flange 333 fixed to the end surface of the target base 332 facing the anode rod 32. An annular fixing groove 321 is defined on the end surface of the anode rod 32 facing the target base 332. The base flange 333 is sealingly connected to the annular fixing groove 321. The anode target 331 is fixed to the end surface of the target base 332 facing the barrier portion 312. Preferably, the anode rod 32 and the constricted portion 313, as well as the base flange 333 and the wall of the annular fixing groove 321, are brazed to achieve a vacuum-tight connection. Furthermore, the provision of the annular fixing groove 321 on the end surface of the anode rod 32 prevents the risk of vacuum leakage caused by loss of molten solder during welding, while also increasing the welding area and ensuring weld strength.

[0099] Furthermore, the material of the anode target 331 can be various materials, such as Al, Mg, W, Mo, Cu, Ti, Cr, Fe, Co, Ag, Rh, Au, and Pt. The material of the anode target 331 is bonded to the target base 332 by brazing, magnetron sputtering, or other methods. The target base 332 can be made of various materials with high thermal conductivity, such as copper or diamond, preferably diamond, to enhance the heat dissipation capacity of the target surface, increase the power of the electron beam bombardment on the target surface, and thus increase the X-ray flux density generated by the electron bombardment. The target base 332 is tightly connected to the base flange 333 by brazing with or without a transition layer. This ensures that over 99% of the heat generated by the electron bombardment of the anode target 331 material is promptly dissipated, reducing the temperature rise of the anode target 331 and thereby alleviating the problem of X-ray flux instability caused by focus drift.

[0100] Further, if Figure 2 and Figure 3As shown, the anode rod 32 has an axially extending rod through-hole 322 extending to the target base 332. The wall of the rod through-hole 322 and the outer surface of the target base 332 define a liquid cooling chamber 50, which is used to contain a cooling medium, which can be a coolant. This allows the cooling medium to flow directly into the liquid cooling chamber 50 and reach the bottom of the base flange 333, effectively dissipating heat from the anode target 331 and reducing the temperature of the anode target 331, thereby alleviating X-ray flux instability caused by focus drift. Furthermore, the anode rod 32 and the anode target assembly 33 are both wrapped around the neck portion 313 of the anode cap 31. Thus, while the cooling medium cools the anode target assembly 33, it also wraps around the neck portion 313 of the anode cap 31 and cools the neck portion 313 of the anode cap 31. This simultaneously controls and stabilizes the temperature rise of the anode rod 32, the anode target assembly 33, and the neck portion 313 of the anode cap 31, thereby reducing the problem of X-ray flux instability caused by focus drift. Liquid cooling structures that introduce cooling medium into the liquid cooling chamber 50 are prior art, and reference can be made to the anode liquid-cooled X-ray tube disclosed in Chinese Utility Model Patent Application No. 202410503371.5.

[0101] Further, if Figure 3 As shown, the window assembly 40 includes a window piece 41, a window flange 42, and a transition flange 43. The transition flange 43 is vacuum-tightly connected to the X-ray outlet 316 of the constricted neck 313 by brazing. The window flange 42 is sealed within the transition flange 43. The window flange 42 and transition flange 43 are vacuum-tightly connected at their tops by argon arc welding or laser welding. A step 421 is provided on the inner surface of the window flange 42. The window piece 41 is vacuum-tightly connected to the window flange 42 by brazing at the step 421. Preferably, the window piece 41 is made of a material with low X-ray filtering properties, such as beryllium, diamond, or titanium, with beryllium being particularly preferred. The step 421 within the window flange 42 is a thin step, forming the welding area between the window flange 42 and the window piece 41. The thin step is used to relieve stress during welding and prevent the risk of vacuum leaks. The present application achieves an airtight seal between the window assembly 40 and the neck portion 313 of the anode cap 31, and allows X-rays to directly pass through the window assembly 40 into a non-vacuum environment, so that the distance D3 from the window piece 41 to the focal point of the anode target 331 is smaller than that of a traditional X-ray tube, thereby increasing the X-ray flux per unit area at the window piece 41, that is, increasing the flux density. At the same time, the X-ray optical device that focuses the X-rays can be brought closer to the window assembly 40 to collect as much X-rays as possible, thereby increasing the flux density of the X-ray optical device after focusing, that is, increasing the brightness of the X-rays to reach the level of synchrotron radiation.

[0102] Furthermore, during operation of the X-ray tube, the anode assembly 30 is set to ground potential, and the cathode assembly 20 is set to negative high-voltage mode. This not only facilitates bringing the X-ray optical device closer to the window, avoiding high-voltage sparking issues, but also more effectively dissipates heat from the anode target assembly 33, the anode rod 32, and the neck portion 313 of the anode cap 31. Furthermore, while insulating media such as insulating oil and deionized water can be used as cooling media, non-insulating media such as plant water can also be used as heat dissipation media, reducing the cooling medium requirements for the X-ray tube and increasing user-friendliness. Furthermore, grounding the anode assembly 30 also reduces the design requirements for the cooling system, allowing the high-voltage cooling system to be at ground potential, reducing the requirements for high-voltage insulation and safety protection.

[0103] In addition, based on the grounding method of the anode assembly 30, the X-ray outlet 316 on the neck portion 313 can be close to the tail end of the anode rod 32, and a long distance from the anode rod 32 is no longer required to provide an insulation distance for the tube shell 10. The focus can be very close to the tail end of the anode rod 32, which effectively reduces the heat capacity of the anode part and shortens the time to reach temperature equilibrium. High-end X-ray scientific instruments using the X-ray tube of this application can perform detection operations without a long waiting time.

[0104] In summary, the X-ray tube having the above structure has the following beneficial effects.

[0105] The X-ray tube provided by the present invention completely prevents stray electrons e1 repelled from the focused electron beam from bombarding the tube housing 10 by virtue of the focusing member 22 being enclosed by the expansion portion 311 of the anode cap 31 and the reasonable setting of the distance H between the bottom of the focusing member 22 and the top of the expansion portion 311. This also completely avoids the problem of X-ray flux instability caused by X-ray tube instability due to accumulated charge in the tube housing 10.

[0106] The X-ray tube provided by the present invention has a partition portion 312 with an electron beam entrance hole 314 disposed between the constricted neck portion 313 and the expanded portion 311 of the anode cap 31, so that the anode target 331 of the anode target assembly 33 and the focusing element 22 are opposite each other through the partition portion 312. Combined with the fact that the focusing element 22 is enclosed by the expanded portion 311 of the anode cap 31 and the reasonable setting of the distance H between the bottom of the focusing element 22 and the top of the expanded portion 311, the rebound electrons e2 from the target surface of the anode target 331 are completely prevented from bombarding the insulating tube shell 10. In addition, the problem of X-ray light flux instability caused by X-ray tube instability caused by accumulated charge in the tube shell 10 is completely avoided. The instability problem caused by X-rays from the target surface of the anode target 331 bombarding the tube shell 10 can also be avoided.

[0107] In the X-ray tube of the present invention, the neck portion 313 of the anode cap 31 wraps around the anode target assembly 33, and the outer surface of the target base 332 constitutes the bottom surface of the liquid-cooling chamber 50, so that the bottom of the anode target assembly 33 is in direct contact with the cooling medium. This makes it easy to accurately control the temperature rise of the anode target assembly 33, the anode rod 32, and the neck portion 313 of the anode cap 31 at a relatively low temperature, thereby reducing the problem of focal spot spatial drift caused by temperature rise of the focus of the anode target 331, meeting the requirement of within ±1 μm, and effectively avoiding the problem of unstable X-ray flux caused by focal spot spatial drift.

[0108] In the X-ray tube of the present invention, the constricted neck portion 313 of the anode cap 31 wraps around the anode target assembly 33, and X-rays are emitted from the side of the constricted neck portion 313 of the anode cap 31, that is, from the bottom side of the anode assembly 30. Compared with an X-ray tube with a center beam emission and a method of grounding the anode assembly 30, the present application effectively shortens the length of the anode rod 32 and the constricted neck portion 313 of the anode cap 31, reduces the heat capacity of the anode assembly 30, thereby reducing the thermal equilibrium time and the waiting time during application testing.

[0109] The X-ray tube of the present invention facilitates heat dissipation by fully enclosing the anode rod 32, the anode target assembly 33, and the neck portion 313 of the anode cap 31. The anode target assembly 33 is made of a material with high thermal conductivity, and heat is directly dissipated from the bottom of the anode target assembly 33. This can increase the electron beam density per unit area of the focus of the anode target assembly 33, thereby increasing the X-ray yield, that is, increasing the X-ray luminous flux density.

[0110] The X-ray tube of the present invention adopts a beam-emitting method at the bottom side of the anode assembly 30, and the anode assembly 30 is grounded, so that the X-ray optical device can be as close as possible to the center of the anode target 331, thereby collecting and focusing X-rays to the greatest extent, thereby increasing the X-ray flux density, that is, the brightness, to the level of synchrotron radiation.

[0111] The X-ray tube of the present invention can be applied to high-end X-ray scientific instruments such as X-ray fluorescence spectrometers, micro-area X-ray fluorescence spectrometers, high-performance X-ray diffractometers and X-ray absorption spectrometers, which require high X-ray flux density and high long-term stability of the X-ray flux.

[0112] In summary, the X-ray tube of the present invention effectively solves the problem of high-stability X-ray flux in X-ray tubes and X-ray sources used in high-end scientific instruments. It features advantages such as complete non-bombardment of the tube housing 10 by stray electrons e1 and overflow electrons e3, easy envelopment of the anode target assembly 33 by the cooling medium, minimal physical position drift of the anode assembly 30 focal point, controllable temperature of the anode assembly 30 under low-temperature requirements, a short thermal equilibrium time for the anode assembly 30, and a short distance from the anode assembly 30. These advantages reliably ensure high X-ray flux stability. Furthermore, the X-ray tube of the present invention also features a short distance between the X-ray outlet 316 and the focal point of the anode target assembly 33, high X-ray flux density, easy collection of X-rays by the X-ray optical device, and high brightness.

[0113] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0114] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed in the present invention are intended to be covered by the claims of the present invention.

Claims

1. An X-ray tube with high stability of light flux, characterized by: It comprises a tube shell (10), a cathode assembly (20), an anode assembly (30), and a window assembly (40); The tube shell (10) has a tube cavity (11) for forming a vacuum environment; The cathode assembly (20) is arranged in the tube cavity (11), and the cathode assembly (20) includes an electron emitting element (21) for emitting an electron beam, and a focusing element (22) for focusing the electron beam; The anode assembly (30) comprises an anode cap (31), an anode rod (32), and an anode target assembly (33) provided with an anode target (331); the anode cap (31) is sealed at one end of the tube shell (10); the anode cap (31) comprises an expansion portion (311), a partition portion (312), and a neck portion (313) connected in sequence along its axial direction; the expansion portion (311) wraps the focusing member (22) from the bottom and circumferential direction of the focusing member (22); the partition portion (312) is provided with an electron beam incident hole (314) for allowing the electron beam to pass through; the inner diameter of the expansion portion (311), the inner diameter of the neck portion (313), and the aperture of the electron beam incident hole (314) gradually decrease; the neck portion (313) is provided with an axially extending sealing portion (311). The anode rod (32) is sealed in the packaging cavity (315), and the anode target assembly (33) is sealed at one end of the anode rod (32) facing the partition portion (312). The anode target (331) is opposite to the electron emitting element (21) and the focusing element (22) along the axial direction of the anode cap (31) through the electron beam incident hole (314). The anode target (331) is aligned with the X-ray outlet (316) along the radial direction of the anode cap (31). The anode cap (31) forms a cap inner cavity (317) between the partition portion (312), the neck portion (313) and the anode target assembly (33). The electron beam incident hole (314) and the X-ray outlet (316) are both connected to the cap inner cavity (317). The window assembly (40) is arranged in the X-ray outlet (316); The potential of the anode assembly (30) is higher than that of the cathode assembly (20); the electron beam emitted by the electron emitting element (21) of the cathode assembly (20) is accelerated by the accelerating electric field between the focusing element (22) and the anode cap (31) to form a focused electron beam; the focused electron beam enters the cap inner cavity (317) through the electron beam entrance hole (314) and bombards the anode target (331), generating diffuse X-rays, which are emitted through the X-ray outlet (316); during this process, some electrons in the focused electron beam leave and form stray electrons (e1); some rebound electrons (e2) that bombard the surface of the anode target (331) overflow from the cap inner cavity (317) through the electron beam entrance hole (314) into the expansion portion (311) and form overflow electrons (e3); the stray electrons (e1) and the overflow electrons (e3) bombard the inner surface of the anode cap (31) to form secondary electrons; Along the axial direction of the X-ray tube, the distance H between the bottom of the focusing member (22) and the top of the expansion portion (311) is greater than the distance D1 between the bottom of the focusing member (22) and the partition portion (312), so that the secondary electrons are absorbed after multiple back-bombardments in the expansion portion (311).

2. The X-ray tube with high light flux stability according to claim 1, characterized in that: The distance H between the bottom of the focusing member (22) and the top of the expansion portion (311) is 2-10 times the distance D1 between the bottom of the focusing member (22) and the partition portion (312).

3. The X-ray tube with high-stability luminous flux according to claim 2, characterized in that: The distance H between the bottom of the focusing member (22) and the top of the expansion portion (311) is 3-5 times the distance D1 between the bottom of the focusing member (22) and the partition portion (312).

4. The X-ray tube with high light flux stability according to claim 1, characterized in that: The distance D2 between the outer periphery of the focusing member (22) and the inner periphery of the expansion portion (311) is 1-2 times the distance D1 between the bottom of the focusing member (22) and the partition portion (312).

5. The X-ray tube with high light flux stability according to claim 1, characterized in that: The cathode assembly (20) further comprises a first electrode (23), a second electrode (24), a third electrode (25), a first support rod (26) electrically connected to the first electrode (23), and a second support rod (27) electrically connected to the second electrode (24); the first electrode (23), the second electrode (24), and the third electrode (25) are electrically isolated from each other and are all mounted on the tube shell (10); the first support rod (26) and the second support rod (27) are both electrically connected to the electron emission element (21); and the third electrode (25) is electrically connected to the focusing element (22).

6. The X-ray tube with high-stability luminous flux according to claim 5, characterized in that: The cathode assembly (20) further includes insulating beads (28), insulating members (29), and a transition connecting tube (210) fixed in the tube shell (10); the first electrode (23), the second electrode (24), and the third electrode (25) are electrically isolated from each other by the insulating beads (28); the first support rod (26) and the second support rod (27) are both installed in the transition connecting tube (210); the first support rod (26) and the transition connecting tube (210), as well as the second support rod (27) and the transition connecting tube (210), are electrically isolated by the insulating member (29); and the third electrode (25) is electrically connected to the focusing member (22) via the transition connecting tube (210).

7. The X-ray tube with high light flux stability according to claim 6, characterized in that: An operating hole (211) is provided on the transition connecting pipe (210), and a connection portion between the first electrode (23) and the first support rod (26), and a connection portion between the second electrode (24) and the second support rod (27) are exposed from the operating hole (211).

8. The X-ray tube with high-stability luminous flux according to claim 5, characterized in that: It also includes a getter arranged in the tube cavity (11), one of the first electrode (23) and the second electrode (24) is a common electrode, and two ends of the getter are respectively connected to the common electrode and the third electrode (25).

9. The X-ray tube with high light flux stability according to claim 1, characterized in that: The anode target assembly (33) further comprises a target base (332) provided at one end of the anode rod (32) facing the partition portion (312), and a base flange (333) fixed on the end surface of the target base (332) facing the anode rod (32). An annular fixing groove (321) is provided on the end surface of the anode rod (32) facing the target base (332). The base flange (333) is sealed in the annular fixing groove (321). The anode target (331) is fixed on the end surface of the target base (332) facing the partition portion (312).

10. The X-ray tube with high-stability luminous flux according to claim 9, characterized in that: The target base (332) is made of copper or diamond.

11. The X-ray tube with high-stability luminous flux according to claim 9, characterized in that: The anode rod (32) is provided with an axially penetrating rod through hole (322), and the rod through hole (322) extends to the target base (332). The hole wall of the rod through hole (322) and the outer surface of the target base (332) form a liquid cooling cavity (50), and the liquid cooling cavity (50) is used to accommodate a cooling medium.

12. The X-ray tube with high light flux stability according to claim 1, characterized in that: The window assembly (40) includes a window piece (41), a window flange (42) and a transition flange (43); the transition flange (43) is sealed and connected to the X-ray outlet (316) of the neck portion (313); the window flange (42) is sealed and connected to the transition flange (43); a step portion (421) is provided on the inner surface of the window flange (42); and the window piece (41) is sealed and connected to the window flange (42) at the step portion (421).

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