CN118888412A - An X-ray tube with high stability of light flux - Google Patents

Abstract

The invention 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, wherein 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 along the axial direction of the anode cap, the expansion part wraps the focusing part from the bottom and the circumferential direction of the focusing part, an electron beam entering hole is formed in the partition part, and an axially extending packaging cavity and a radially penetrating X-ray outlet 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 element and the top of the expanding part is larger than the distance D1 between the bottom of the focusing element and the partition part, so that stray electrons, secondary electrons generated by the stray electrons, overflowing electrons, secondary electrons generated by overflowing electrons and secondary electrons generated by overflowing electrons are absorbed after being repeatedly bombarded in the expanding part, secondary electrons are completely prevented from bombarding the tube shell, and the high stability of X-ray luminous flux is ensured.

Description

An X-ray tube with high stability of light flux

Technical Field

The present invention 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

High-end X-ray scientific instruments such as X-ray fluorescence spectrometer (XRF), high-performance X-ray diffractometer (XRD), micro-area X-ray fluorescence analyzer (MicroXRF) and X-ray absorption spectrometer (XAFS), with micron-level focus X-ray tubes and X-ray sources, are widely used in scientific fields such as materials, biology, chemistry, environment, geology and archaeology, as well as in industries such as semiconductors, new energy, electronic equipment, thin films and forensic identification for micro-area trace and trace analysis of materials, qualitative and quantitative analysis of physical phases, stress and texture analysis, strain and crystallite size analysis, etc. Traditional industrial and medical X-ray tubes and X-ray sources usually require the stability of X-ray light flux to be ≤3%/4h, but such high-end X-ray scientific instruments have higher requirements for light flux stability, usually requiring ≤0.1%/72h. In addition, unlike traditional industrial and medical X-ray tubes, X-ray tubes and X-ray sources used in high-end X-ray scientific instruments have very high requirements for the stability of the physical position of the focus, and the fluctuation is usually required to be within ±1μm. When the X-ray tube is working, the light flux of the X-ray tube will be unstable due to factors such as the unstable high-voltage electric field structure, the accumulation of scattered secondary electrons and excited secondary electrons between the cathode and anode, etc. When the X-ray tube is working, more than 99% of the input energy is converted into heat, which causes the temperature of the anode of the X-ray tube to rise and fluctuate. Due to thermal expansion and contraction, the focus position fluctuates, resulting in unstable light flux entering the X-ray optical device. Therefore, the constant temperature of the anode of the X-ray tube (usually required to be 20-24℃, and the fluctuation is allowed to be within ±0.2℃) is also very important.

Some existing X-ray tubes have various heat dissipation methods designed for their anode parts, such as the X-ray tubes disclosed in Chinese patent documents with application numbers 202210167293.7, 201780063975.0, 201920164824.0, 202222416302.X, 202011184705.5 and 202010552652.1. However, the purpose of these existing designs is to reduce the temperature on the anode or anode target, prevent the melting of the anode target surface or increase the life of the X-ray tube, but they do not involve the heat dissipation of the anode cap that wraps the anode head, nor the constant temperature control of the anode temperature of the X-ray tube, nor can they control the constancy of the anode temperature. Therefore, these existing designs cannot control the high stability of the spatial position of the focus, and cannot meet the requirements of high-performance X-ray scientific instruments for high stability of X-ray light flux. Moreover, this type of X-ray tube has the disadvantage that the distance between the focus of the X-ray anode target and the tail end of the anode 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.

In response to the above problems, the Chinese patent document with application number 201510464658.2 proposes that the anode target be wrapped by the cathode cover of the electron gun, which can reduce the risk of rebound secondary electrons bombarding the glass insulating shell, causing the shell to accumulate and lead to unstable high voltage of the light tube, thereby causing unstable X-ray flux. However, this structure is provided with an X-ray outlet on the cathode cover, which cannot completely avoid the secondary electrons bombarding the insulating shell; this structure does not depart from the traditional X-ray tube design, the anode target surface is directly opposite to the electron beam from the cathode, and is bombarded by electrons, but those that are not effectively intercepted are scattered in all directions and bombard the insulating shell, which is easy to generate interference current that causes system miscontrol, and ultimately leads to unstable light flux; and the heat dissipation electrons absorbed by the anode high voltage bombard the anode again, which will also generate unexpected stray X-rays, affecting the stability of the light flux. Further, because an effective high-voltage insulation length is required, there is also a disadvantage that the distance between the focus of the X-ray anode target surface and the tail end of the anode is too long, which will lead to an increase in the thermal expansion length and a too long thermal equilibrium time of the anode temperature, resulting in a long waiting time to achieve 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 temperature of the anode. 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.

Furthermore, in the X-ray tube disclosed in the Chinese patent document with application number 202080052348.9, the probability of the insulating tube shell being bombarded by X-rays is reduced, and the risk of ignition 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 in the shape of 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 (Figures 3 and 7 of the current existing patent document) cannot be used for X-ray scientific instruments due to the dispersion of the X-ray flux, and other reflective target structures do not solve the problems of the anode target surface being directly opposite to the electron beam and being blocked in the Chinese patent document with application number 201510464658.2, the distance between the focus and the anode tail end is too long, and the anode target is difficult to carry out wrapped heat dissipation, and the X-ray window is too far from the focus. Therefore, it is also difficult to meet the high stability requirements of the X-ray flux.

Summary of the invention

In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide an X-ray tube with high stability of light flux, which can completely avoid electron bombardment of the tube shell, control the physical drift of the focus space position, and ensure the high stability of the X-ray light flux.

To achieve the above object, the present invention provides an X-ray tube with high stability light flux, comprising a tube shell, a cathode assembly, an anode assembly, and a window assembly;

The tube shell has a tube cavity for forming a vacuum environment;

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;

The anode assembly comprises 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 comprises an expansion part, a partition part and a neck part connected in sequence along the axial direction thereof, the expansion part wraps the focusing part from the bottom and circumferential direction of the focusing part, the partition part is provided with an electron beam entrance hole for allowing the electron beam to pass through, the inner diameter of the expansion part, the inner diameter of the neck part, and the aperture of the electron beam entrance hole are gradually reduced; the neck part is provided with an axially extending packaging cavity and a radially penetrating 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 part, the anode target is opposite to the electron emitting part and the focusing part 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 part, the neck part and the anode target assembly, the electron beam entrance hole and the X-ray outlet are both connected to the cap inner cavity;

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

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 entrance hole and bombards the anode target to generate diffuse X-rays. The diffuse X-rays are emitted through the X-ray outlet. In this process, part of the electrons in the focused electron beam leave and form stray electrons. Part of the rebound electrons bombarding the surface of the anode target overflow from the inner cavity of the cap through the electron beam entrance hole into the expansion part and form overflow electrons. The stray electrons and overflow electrons bombard the inner surface of the anode cap to form secondary electrons.

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.

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.

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.

Furthermore, a 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.

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.

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, and the third electrode is electrically connected to the focusing part through the transition connecting tube.

Furthermore, an operation hole is provided on the transition connecting pipe, and a connection portion between the first electrode and the first supporting rod, and a connection portion between the second electrode and the second supporting rod are exposed from the operation hole.

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 two ends of the getter are respectively connected to the common electrode and the third electrode.

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 sealingly connected in the annular fixing groove, and the anode target is fixed on the end face of the target base facing the partition portion.

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

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 surface 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.

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

As described above, the X-ray tube with high stability light flux according to the present invention has the following beneficial effects:

First, the stray electrons repelled from the focused electron beam and the secondary electrons generated by the bombardment of the expansion part by the stray electrons 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 larger 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 of the focusing member, the energy of the stray electrons and the secondary electrons generated in particular is gradually depleted and absorbed after multiple back-bombardments on the inner surface of the anode cap; at the same time, the overflowing electrons overflowing from the inner cavity of the cap and the secondary electrons generated by the bombardment of the expansion part by the overflowing electrons will also be gradually depleted and absorbed after multiple back-bombardments on the inner surface of the anode cap. Therefore, the present application can completely avoid the bombardment of the secondary electrons onto the tube shell, thereby avoiding the interference current generated thereby, and ultimately avoiding 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 light flux.

Second, stray electrons and secondary electrons generated thereby, as well as overflow electrons and secondary electrons generated thereby are absorbed in the expansion portion after multiple back-bombardments, completely avoiding the accumulation of charge on the tube shell due to the bombardment of the secondary electrons onto the tube shell, thereby avoiding the instability of the X-ray light flux caused by sparking.

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, so that 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.

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 relatively low temperature, thereby reducing the problem of focal space drift of the anode target focus due to temperature rise, meeting the requirement within ±1μm, effectively controlling the physical drift of the focal space position, and thereby effectively avoiding the problem of X-ray flux instability due to focal space drift.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of an X-ray tube with high-stability luminous flux according to the present application, which is a top view.

Fig. 2 is a cross-sectional view taken along the line A-A of Fig. 1 .

FIG. 3 is a schematic structural diagram of the anode assembly in FIG. 2 .

FIG. 4 is a schematic structural diagram of the anode cap in FIG. 2 .

FIG. 5 is a schematic structural diagram of the anode rod and anode target assembly in FIG. 2 .

Component number description

10 Tube shell

11 Lumen

20 Cathode assembly

21. Electron emitter

22 Focusing parts

23. First electrode

24 Second electrode

25 Third electrode

26 First support rod

27 Second support rod

28 Insulation beads

29 Insulation

210 Transition pipe

211 Operation hole

30 Anode assembly

31 Anode cap

311 Expansion Department

312 Partition

313 Neck Shrinkage

314 Electron beam entrance hole

315 Encapsulation Cavity

316 X-ray Exit

317 Cap cavity

32 Anode rod

321 Annular fixing groove

322 Rod Through Hole

33 Anode target assembly

331 Anode Target

332 Target base

333 Base flange

40 Window Components

41 Window

42 Window flange

421 Steps

43 Transition flange

50 Liquid cooling chamber

e1 Stray electrons

e2 Rebound Electron

e3 overflow electron

DETAILED DESCRIPTION

The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

It should be noted that the structures, proportions, sizes, etc. drawn in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by 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. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

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

In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. 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.

The present invention provides an X-ray tube and an X-ray source including the X-ray tube, wherein the X-ray tube is an X-ray tube with high stability light flux. As shown in FIG1 and FIG2 , the X-ray tube with high stability light flux according to the present invention comprises a tube shell 10, a cathode assembly 20, an anode assembly 30 and a window assembly 40, and the structures of the components are described as follows.

As shown in Fig. 2, the tube shell 10 is a hollow shell, and a tube cavity 11 for forming a vacuum environment is provided in the tube shell 10. The tube shell 10 is an insulating shell made of an insulating material, and the insulating material of the tube shell 10 can be electronic glass or ceramic. The tube shell 10 supports the cathode assembly 20 and the anode assembly 30, and plays the role of electrical insulation and vacuum sealing between the cathode assembly 20 and the anode assembly 30.

As shown in FIG. 2 , the cathode assembly 20 is disposed 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 disposed at one end of the cathode assembly 20 close to the anode assembly 30 .

As shown in FIGS. 2 to 4 , the anode assembly 30 includes an anode cap 31, an anode rod 32, and an anode target assembly 33 provided 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. The anode cap 31 includes an expansion portion 311, a partition portion 312 and a neck portion 313 which are sequentially connected along the axial direction thereof. The expansion portion 311 wraps the focusing member 22 from the bottom and circumferential direction of the focusing member 22, and the end surface of the focusing member 22 facing the anode assembly 30 and the outer circumferential surface of the focusing member 22 are completely covered by the expansion portion 311. An axially through electron beam incident hole 314 is provided in the partition portion 312, and the electron beam incident hole 314 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 greater than the outer diameter of the constricted portion 313 . A packaging cavity 315 extending along the axial direction and an X-ray outlet 316 passing through the neck portion 313 are provided in the neck portion 313. 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 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. A cap inner cavity 317 is formed on the anode cap 31 between the partition portion 312, the neck portion 313 and the anode target assembly 33. The cap inner cavity 317 is a 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.

As shown in FIG. 2 , the window assembly 40 is disposed in the X-ray outlet 316 , and the window assembly 40 is used to isolate the inner and outer vacuum of the X-ray tube.

During operation of the above-mentioned X-ray tube, as shown in FIG2 , 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 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 repulsion 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, which are attracted by the potential on the anode cap 31 and bombard the inner surface of the anode cap 31 to form 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 incident hole 314, and most of the rebound electrons e2 bombarding the surface of the anode target 331 are directly blocked by the cap inner cavity 317 of the anode cap 31, and a small part of the rebound electrons e2 bombarding the surface of the anode target 331 overflow from the cap inner cavity 317 of the anode cap 31, and overflow into the expansion part 311 through the electron beam incident hole 314 of the partition part 312 to form overflow electrons e3, and the overflow electrons e3 are attracted by the potential on the anode cap 31 to bombard the inner surface of the anode cap 31 to form secondary electrons.

In particular, as shown in FIG2 , along the axial direction of the X-ray tube, the distance between the bottom of the focusing member 22 and the partition portion 312 is D1, and the distance D1 is related to the potential difference between the focusing member 22 and the anode cap 31, and the size structure of the focusing member 22 and the anode cap 31. The potential difference between the focusing member 22 and the anode cap 31 is the tube voltage of the X-ray tube; generally, the distance D1 is 3-25 mm. The distance between the bottom of the focusing member 22 and the top of the expansion portion 311 is H. In the present application, the distance H between the bottom of the focusing member 22 and the top of the expansion portion 311 is much larger than the distance D1 between the bottom of the focusing member 22 and the partition portion 312, and the distance H between the bottom of the focusing member 22 and the top of the expansion portion 311 should satisfy: the secondary electrons formed by the stray electrons e1 and the overflow electrons e3 after bombarding the inner surface of the anode cap 31 are absorbed in the expansion portion 311 after multiple back bombardments. In addition, during the operation of the X-ray tube, the potential of the anode assembly 30 is higher than the potential of the cathode assembly 20. The X-ray tube of the present application has the following advantages after being configured in this way.

First, the stray electrons e1 repelled in the focused electron beam, and the secondary electrons generated by the stray electrons e1 bombarding the expansion part 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 member 22; combined with the fact that the distance H between the bottom of the focusing member 22 and the top of the expansion part 311 is much larger than the distance D1 between the bottom of the focusing member 22 and the partition part 312, and the structural setting that the expansion part 311 wraps the focusing member 22 from the bottom and circumferential direction, the energy of the stray electrons e1 and the secondary electrons generated are gradually exhausted and absorbed after multiple back bombardments on the inner surface of the anode cap 31; at the same time, the overflow electrons e3 overflowing from the cap inner cavity 317, and the secondary electrons generated by the overflow electrons e3 bombarding the expansion part 311, will also be gradually exhausted and absorbed after multiple back bombardments on the inner surface of the anode cap 31. Therefore, the present application can completely avoid secondary electrons 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 light flux.

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 in the expansion portion 311 after multiple back-bombardments, thereby completely avoiding the accumulation of charges on the tube shell 10 due to the secondary electrons bombarding the tube shell 10, thereby avoiding the instability of the X-ray light flux caused by sparking.

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 part 311, and the window assembly 40 is arranged in the contraction part 313, and the partition part 312 blocks between the contraction part 313 and the expansion part 311, that is, blocks between the window assembly 40 and the part bombarded by the electrons in the anode cap 31, so that the window assembly 40 is away from the part bombarded by the stray electrons e1, the overflow electrons e3 and the secondary electrons, and is blocked by the partition part 312 of the anode cap 31, so that the stray X-rays generated by the electrons bombarding the inner surface of the expansion part 311 will not enter the X-ray outlet 316, thereby reliably improving the quality and stability of the X-rays emitted by the window assembly 40.

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 the heat of 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, reduce the focus space drift problem caused by the temperature rise of the focus of the anode target 331, meet the requirement within ±1μm, effectively control the physical drift of the focus space position, and thus effectively avoid the problem of X-ray flux instability caused by the focus space drift.

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

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 .

Furthermore, as shown in FIG2 , 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 requirement 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.

Further, the preferred structure of the cathode assembly 20 is as follows: as shown in FIG. 2 , the 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 the first electrode 23, and a second support rod 27 electrically connected to the second electrode 24, the first electrode 23 and the second electrode 24 are both used to connect to an external power source, the first support rod 26 and the second support rod 27 are both metal rods, the first electrode 23, the second electrode 24 and the third electrode 25 are electrically isolated from each other and are all installed 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. The connection method between the first electrode 23 and the first support rod 26, the second electrode 24 and the second support rod 27, the first support rod 26 and the electron emission element 21, and the second support rod 27 and the electron emission element 21 is preferably 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 emission element 21. In this way, the third electrode 25 can be used to give the focusing element 22 a different potential relative to the electron emission element 21, thereby controlling the focusing of the electron beam by the focusing element 22 to obtain focal points of different sizes.

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.

Preferably, as shown in Figure 2, 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, and 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 connecting parts of the first electrode 23 and the first support rod 26, as well as the connecting parts of 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, so as to supply power to the electron emission element 21.

Furthermore, the X-ray tube with high stability luminous flux also includes a getter disposed in the tube cavity 11, and one of the first electrode 23 and the second electrode 24 is a common electrode; in the tube shell 10 of the X-ray tube, the two ends of the getter are respectively connected to the common electrode and the third electrode 25. In this way, the getter can be activated and other operations can be performed, so that after the X-ray tube forms a closed space, the getter can absorb the residual gas in the tube shell 10 of the X-ray tube or the gas released when the X-ray tube is working, thereby improving the vacuum degree of the tube shell 10 of the X-ray tube, reducing the risk of ignition, and providing the stability of the X-ray tube, thereby improving the stability of the X-ray luminous flux.

Preferably, as shown in Figures 3 and 4, the inner surface of the expansion portion 311 includes a conical segment and a cylindrical segment connected in sequence along a 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.

Further, as shown in FIG3 and FIG5, the anode target assembly 33 also includes a target base 332 disposed 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 sealedly connected in the annular fixing groove 321, and the anode target 331 is fixed on the end surface of the target base 332 facing the partition portion 312. Preferably, the anode rod 32 and the neck portion 313, and the base flange 333 and the groove wall of the annular fixing groove 321 are brazed and fixed, so as to achieve a vacuum-tight connection. In addition, the provision of the annular fixing groove 321 on the end surface of the anode rod 32 can prevent the risk of vacuum leakage caused by the loss of solder when it melts during welding, while increasing the welding area and ensuring the welding strength.

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, Pt, etc. The material of the anode target 331 is combined on the target base 332 by brazing, magnetron sputtering, etc. The target base 332 can be various materials with high thermal conductivity such as copper and diamond, preferably a diamond material with high thermal conductivity, so as 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 light flux density of the X-rays generated by the electron bombardment. The target base 332 and the base flange 333 are tightly connected by brazing with or without a transition layer, so that more than 99% of the heat generated by the electron bombardment of the anode target 331 material can be promptly conducted away, reducing the temperature rise of the anode target 331, thereby reducing the problem of unstable X-ray light flux caused by focus drift.

Further, as shown in Fig. 2 and Fig. 3, an axially penetrating rod through hole 322 is provided in the anode rod 32, and the rod through hole 322 extends to the target base 332. The hole wall surface 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 contain a cooling medium, and the cooling medium can be a coolant. In this way, after the cooling medium flows into the liquid cooling cavity 50, it can directly reach the bottom of the base flange 333, thereby more effectively dissipating the heat of the anode target 331, reducing the temperature of the anode target 331, and thus reducing the problem of X-ray flux instability caused by focus drift. In addition, the anode rod 32 and the anode target assembly 33 are both wrapped by the neck 313 of the anode cap 31, so that the cooling medium cools the anode target assembly 33 while also wrapping the neck 313 of the anode cap 31 and cooling the neck 313 of the anode cap 31, thereby simultaneously controlling the temperature rise of the anode rod 32, the anode target assembly 33 and the neck 313 of the anode cap 31 and maintaining stability, thereby reducing the problem of X-ray flux instability caused by focus drift. The liquid cooling structure of introducing the cooling medium into the liquid cooling chamber 50 is a prior art, and reference can be made to an anode liquid-cooled X-ray tube disclosed in the Chinese invention patent application number 202410503371.5.

Further, as shown in FIG3 , the window assembly 40 includes a window sheet 41, a window flange 42 and a transition flange 43. The transition flange 43 is vacuum-sealed in the X-ray outlet 316 of the neck portion 313 by brazing, and the window flange 42 is sealed in the transition flange 43. The window flange 42 and the transition flange 43 are vacuum-sealed at the top by argon arc welding or laser welding. A step portion 421 is provided on the inner surface of the window flange 42, and the window sheet 41 is vacuum-sealed in the window flange 42 by brazing at the step portion 421. Preferably, the window sheet 41 is made of a material with little X-ray filtering, such as a beryllium sheet, a diamond sheet, and a titanium sheet, and is particularly preferably a beryllium sheet. The step portion 421 in the window flange 42 is a thin step, which is the welding area between the window flange 42 and the window sheet 41. The thin step is used to release the stress during welding and prevent the risk of vacuum leakage. The present application realizes an airtight connection 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 conventional 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 many 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.

Furthermore, during the operation of the X-ray tube, the anode assembly 30 is set to the ground potential, and the cathode assembly 20 is set to the negative high voltage mode. In this way, it is convenient to bring the X-ray optical device closer to the window to avoid the problem of high voltage sparking; and it is more effective to dissipate heat from the anode target assembly 33, the anode rod 32 and the neck portion 313 of the anode cap 31. In addition, while insulating media such as insulating oil and deionized water can be used as cooling media, non-insulating media such as factory water can also be used as heat dissipation media, which reduces the cooling medium requirements of the X-ray tube and increases user friendliness. At the same time, the way the anode assembly 30 is grounded also reduces the design requirements of the cooling system, and can make the pressure cooling system also at ground potential, reducing the requirements for high-voltage insulation and safety protection.

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.

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

The X-ray tube provided by the present invention completely avoids the bombardment of the tube shell 10 by the stray electrons e1 rejected in the focused electron beam by the focusing member 22 being wrapped 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, and also completely avoids the problem of X-ray light flux instability caused by the instability of the X-ray tube caused by the accumulated charge of the tube shell 10.

The X-ray tube provided by the present invention is provided with a partition portion 312 with an electron beam incident hole 314 between the neck portion 313 and the expansion portion 311 of the anode cap 31, so that the anode target 331 of the anode target assembly 33 is opposite to the focusing member 22 through the partition portion 312. In combination with the fact that the focusing member 22 is wrapped by the expansion portion 311 of the anode cap 31 and the distance H between the bottom of the focusing member 22 and the top of the expansion portion 311 is reasonably set, it is completely avoided that the rebound electrons e2 on the target surface of the anode target 331 bombard the insulating tube shell 10, and the problem of X-ray light flux instability caused by the instability of the X-ray tube caused by the accumulated charge of the tube shell 10 is completely avoided, and the instability problem caused by the X-rays on the target surface of the anode target 331 bombarding the tube shell 10 can also be avoided.

In the X-ray tube of the present invention, the neck portion 313 of the anode cap 31 wraps 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, and 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 of the anode target 331 focus caused by the temperature rise, meeting the requirement within ±1μm, and effectively avoiding the problem of X-ray light flux instability caused by the focus space drift.

In the X-ray tube of the present invention, the neck portion 313 of the anode cap 31 wraps the anode target assembly 33, and emits X-rays from the side of the neck portion 313 of the anode cap 31, that is, emits X-rays from the bottom side of the anode assembly 30. Compared with an X-ray tube with a beam output in the middle and a method of grounding the anode assembly 30, the present application effectively shortens the length of the anode rod 32 and the 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.

The X-ray tube of the present invention is convenient for adopting a method of fully wrapping the anode rod 32, the anode target assembly 33, and the neck portion 313 of the anode cap 31 for heat dissipation. The anode target assembly 33 is made of a material with high thermal conductivity, and the bottom of the anode target assembly 33 is directly cooled, which can increase the electron beam density per unit area of the focus of the anode target assembly 33, thereby increasing the yield of X-rays, that is, increasing the luminous flux density of X-rays.

The X-ray tube of the present invention adopts the beam emitting method at the bottom side of the anode assembly 30, and the anode assembly 30 is grounded at the same time, so that the X-ray optical device can be as close to the center of the anode target 331 as possible, so as to collect and focus the X-rays to the maximum extent, thereby improving the X-ray flux density, that is, the brightness, to reach the level of synchrotron radiation.

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 very high X-ray flux density and high long-term stability of the X-ray flux.

In summary, the X-ray tube of the present invention effectively solves the problem of high stability of the light flux of X-ray tubes and X-ray sources used in high-end scientific instruments, and has the advantages that stray electrons e1 and overflow electrons e3 do not bombard the tube shell 10 at all, the anode target assembly 33 is easily wrapped by the cooling medium, the physical position drift of the focus of the anode assembly 30 is small, the temperature of the anode assembly 30 can be controlled under low temperature requirements, the thermal equilibrium time of the anode assembly 30 is short, and the distance of the anode assembly 30 is short, which reliably guarantees the high stability of the X-ray light flux. At the same time, the X-ray tube of the present invention also has the advantages of a small distance between the X-ray outlet 316 and the focus of the anode target assembly 33, high X-ray light flux density, X-rays are easily collected by X-ray optical devices, and high brightness.

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

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 familiar with 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims (12)

1. An X-ray tube with high stability of light flux, characterized in that 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) comprises 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 and arranged 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) which are connected in sequence along the axial direction; the expansion portion (311) wraps around 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 electron beams 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) are gradually reduced; the neck portion (313) is provided with an axially extending sealing portion (311) and a sealing portion (312) which is provided with a sealing portion (313) which is provided with a sealing portion (314) which is provided with a sealing portion (314) which is provided with a sealing portion (314) which is provided with a sealing portion (311) which is provided with a sealing portion (312) which is provided with a sealing portion (313) which is provided with a sealing portion (314) which is provided with a sealing portion (314) which is provided with a sealing portion (314) which is provided with a sealing portion (314) which is provided with a sealing portion (311) which is provided with a sealing portion (311) which is provided with a sealing portion (312 ... The anode rod (32) is sealed in the packaging cavity (315), 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), and 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 emission 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) to generate diffuse X-rays; the diffuse X-rays are emitted through the X-ray outlet (316); during this process, part of the electrons in the focused electron beam leave and form stray electrons (e1); part of the rebound electrons (e2) bombarding the surface of the anode target (331) overflow from the cap inner cavity (317) through the electron beam entrance hole (314) into the expansion part (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 piece (22) and the top of the expansion part (311) is greater than the distance D1 between the bottom of the focusing piece (22) and the partition part (312), so that the secondary electrons are absorbed after multiple back-bombardments in the expansion part (311). 2. The X-ray tube with high stability luminous flux according to claim 1 is characterized in that the distance H between the bottom of the focusing piece (22) and the top of the expansion part (311) is 2-10 times the distance D1 between the bottom of the focusing piece (22) and the partition part (312). 3. The X-ray tube with high stability luminous flux according to claim 2 is characterized in that the distance H between the bottom of the focusing piece (22) and the top of the expansion part (311) is 3-5 times the distance D1 between the bottom of the focusing piece (22) and the partition part (312). 4. The X-ray tube with high stability luminous flux according to claim 1 is 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 stability luminous flux 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 installed 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 comprises 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) and the second support rod (27) and the transition connecting tube (210) are electrically isolated by the insulating parts (29); and the third electrode (25) is electrically connected to the focusing member (22) through the transition connecting tube (210). 7. The X-ray tube with high stability luminous flux according to claim 6 is characterized in that: an operation hole (211) is opened on the transition connecting tube (210), and the connection part between the first electrode (23) and the first support rod (26) and the connection part between the second electrode (24) and the second support rod (27) are exposed from the operation 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 stability luminous flux according to claim 1 is characterized in that: the anode target assembly (33) further comprises a target base (332) arranged at one end of the anode rod (32) facing the partition portion (312), and a base flange (333) fixedly arranged on the end surface of the target base (332) facing the anode rod (32), an annular fixing groove (321) is opened 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), and 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 material of the target base (332) is copper or diamond. 11. The X-ray tube with high stability luminous flux according to claim 9, characterized in that: an axially penetrating rod through hole (322) is provided in the anode rod (32), the rod through hole (322) extends to the target base (332), and the hole wall surface 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 stability luminous flux according to claim 1, characterized in that: the window assembly (40) comprises a window piece (41), a window flange (42) and a transition flange (43), the transition flange (43) is sealed and connected in the X-ray outlet (316) of the neck portion (313), the window flange (42) is sealed and connected in 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 in the window flange (42) at the step portion (421).