X-ray tube with sheet electron beam and adjustable voltage

Abstract

This invention proposes an X-ray tube with an adjustable voltage for a sheet-like electron beam, belonging to the fields of microwave and medical technology. It includes a cathode, a control electrode, an anode, an accelerating cavity, a beryllium window, a tungsten target, and an energy feed inlet. The control electrode surrounds the cathode, and the anode is located opposite the control electrode outlet, with a gap between them. The anode is connected to the accelerating cavity, which has an energy feed inlet. The cathode emits an electron beam, which, in conjunction with the control electrode and anode, forms a sheet-like electron beam through an electric field. The sheet-like electron beam passes through the anode and enters the accelerating cavity, where it is accelerated to produce a high-energy sheet-like electron beam. This high-energy electron beam strikes the tungsten target, generating X-rays, which then pass through the beryllium window. This invention can achieve effective focal spots at the micron or even nanometer scale, significantly improving imaging resolution and realizing dynamic optimization of penetration capability and resolution, thus possessing broad application value.

Description

Technical Field

[0001] This invention belongs to the field of microwave and medical technology, and particularly relates to a sheet-shaped X-ray tube with adjustable voltage electron beam. Background Technology

[0002] X-rays can penetrate matter and are widely used in medical diagnosis, non-destructive testing, and materials analysis. With the continuous development of technology, industrial CT systems based on X-ray non-destructive testing are increasingly widely used in machinery manufacturing, pressure vessels, aerospace, petroleum, chemical, railway transportation, metallurgy, shipbuilding, and military industries, as well as in special equipment, ships, weaponry, hydraulic engineering equipment, pipelines, and bridge steel structures. As the heart of an X-ray flaw detector, the X-ray tube plays a decisive role in the stability and resolution of the imaging machine and is the key to the entire imaging system.

[0003] Existing X-ray tubes are mainly divided into two types: one type uses DC high voltage X-ray tubes, such as... Figure 1 As shown, its main operating voltage is below 500kV. It directly generates an electron beam using a tungsten filament cathode, compresses and accelerates the electron beam through a focusing electrode and anode, and then produces X-rays upon hitting the target. Because it only uses ceramic insulation to block high voltage, it can only operate at a fixed voltage, and the low operating voltage prevents it from penetrating very deep thicknesses. Another type is the accelerator-driven X-ray tube, such as... Figure 2 As shown, a typical X-ray source uses a linear accelerator with a 3GHz magnetron to generate an electron beam of 2-10 MeV, which is then used to strike a target and produce X-rays. X-rays generated at higher voltages have better penetrating power, but their resolution is insufficient due to the larger X-ray focal spot. X-ray sources using linear accelerators are large and heavy, and their fixed operating voltage makes them unsuitable for flexible application systems.

[0004] Conventional low-voltage X-ray tubes, due to their reliance on ceramic-insulated high voltage, can only operate at fixed voltages, typically 50kV, 160kV, 230kV, 320kV, and 450kV. Since each X-ray tube can only operate at one of these fixed voltages, it is clearly only suitable for imaging steel plates of specific thicknesses.

[0005] X-ray sources using linear accelerators are large and heavy (typically over 2 meters and over 400 kg), and their feed electromagnetic wave power is fixed (otherwise electrons cannot be transmitted to the endpoint, i.e., low feed power will prevent normal operation), resulting in a fixed operating voltage, which cannot adapt to flexible application systems.

[0006] Existing technologies for X-ray tubes struggle to simultaneously achieve high voltage, high resolution, and flexible adjustable operating voltage. Summary of the Invention

[0007] The purpose of this invention is to provide a sheet-shaped electron beam adjustable voltage X-ray tube to solve the technical problem that existing X-ray tubes cannot simultaneously achieve high voltage, high resolution, and flexible adjustable operating voltage.

[0008] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0009] A sheet-shaped electron beam adjustable voltage X-ray tube, the X-ray tube comprising a cathode, a control electrode, an anode, an accelerating cavity, a beryllium window, a tungsten target, and an energy feed inlet;

[0010] The control electrode surrounds the cathode, and the anode is located opposite the control electrode outlet, with a gap between the anode and the control electrode; the anode is connected to the acceleration chamber, and an energy feed inlet is provided on the acceleration chamber.

[0011] The cathode, control electrode, and anode voltages are different. The cathode emits an electron beam, which, in conjunction with the control electrode and anode, is constrained by an electric field and formed into a thin sheet-like electron beam that is wide in the horizontal direction and thin in the vertical direction.

[0012] A thin sheet-like electron beam passes through the anode and enters the acceleration cavity. The acceleration cavity generates an electric field based on the electromagnetic wave excitation entering the energy feed inlet, which accelerates the thin sheet-like electron beam and outputs the accelerated high-energy thin sheet-like electron beam.

[0013] High-energy, thin-film electron beams are fired onto a tungsten target, generating X-rays that pass through a beryllium window.

[0014] Furthermore, the cathode material is made of tungsten wire or barium tungsten metal, and thermionic emission is used. By applying a heating current to the cathode, its temperature is raised, and an electron beam is generated; that is, the current heating increases the energy of electrons inside the material, exceeding the Fermi level, and then they escape from the material surface, forming electron emission.

[0015] Furthermore, the cathode material can be graphene sheets or metal sheets. By applying a voltage between the cathode and anode, field emission is formed, generating an electron beam. That is, when a voltage is applied between the cathode and anode, the potential barrier will be lowered. If the external electric field is further increased to lower the peak of the potential barrier below the Fermi level, then a large number of electrons in the metal will escape, forming field emission.

[0016] Furthermore, the cathode material is made of alkali metal, and photoelectric emission is used to generate an electron beam, that is, electron emission can be generated when irradiated by specific light.

[0017] Furthermore, the control electrode has an elliptical cross-section, and an asymmetric electrostatic field distribution is formed between the control electrode and the anode. The electric field exhibits weak focusing or diverging characteristics on the electron beam in the vertical direction, allowing the electron beam to spread freely in the vertical direction; while it exhibits strong focusing characteristics in the horizontal direction, compressing the electron beam to a very small thickness. In this way, the electron beam emitted by the cathode is shaped into a thin sheet-like electron beam with a rectangular cross-section.

[0018] Furthermore, the accelerating cavity is made of oxygen-free copper or stainless steel, and a beam channel matching the cross-sectional shape of the sheet-like electron beam is formed inside the accelerating cavity; the accelerating cavity is used to receive the sheet-like electron beam and apply an axial accelerating electric field to the sheet-like electron beam through the electromagnetic wave fed in through the energy feed inlet.

[0019] Furthermore, a microwave window is connected to the lower end of the energy feed inlet. The microwave power generated by the external microwave source is fed into the acceleration cavity through the microwave window and the energy feed inlet, establishing an axial standing wave acceleration electric field in the acceleration cavity.

[0020] Furthermore, an extended interaction cavity structure is adopted as the acceleration cavity.

[0021] Furthermore, the accelerating cavity employs a folded waveguide structure, with an energy feed inlet on each of its upper and lower sides. One energy feed inlet is connected to the electromagnetic wave input, while the other is connected to the load to absorb the electromagnetic wave.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] 1) High dose output: By using sheet-like electron beams, while maintaining a very small thickness, a larger beam cross-section and beam power can be obtained by increasing the width dimension, thereby generating sufficient dose of X-rays to meet the needs of rapid imaging or high-penetration scenarios.

[0024] 2) High-resolution imaging: The thickness of the thin-film electron beam is extremely small. When it bombards the target material at a large tilt angle, the size of the X-ray focal spot in the spatial resolution sensitive direction is determined by the thickness of the electron beam. This can achieve effective focal spots at the micron or even nanometer scale, significantly improving imaging resolution.

[0025] 3) Flexible and adjustable operating voltage: By changing the electromagnetic wave power fed into the accelerating cavity, the final energy of the electron beam can be easily adjusted, allowing the X-ray tube to flexibly select the optimal operating voltage according to the material and thickness of the object being inspected, thus achieving dynamic optimization of penetration capability and resolution.

[0026] 4) The X-ray tube structure of this invention, compared to conventional high-voltage X-ray tubes, adds an intermediate adjustment cavity (i.e., acceleration cavity). By varying the input electromagnetic waves, the output electron voltage can be adjusted, thereby achieving imaging of different thicknesses. For example, it can achieve an operating voltage of 50-250kV, or 250kV to 450kV, thus enabling imaging of steel plates of different thicknesses. By adjusting the voltage, the voltage with the highest imaging clarity, i.e., the optimal operating voltage, can also be selected.

[0027] 5) The X-ray tube of this invention has a similar volume and weight to a low-pressure X-ray tube (approximately 0.4 meters in length and less than 10 kg in weight). Its operating voltage can be adjusted by the power of the fed electromagnetic wave, thus it clearly has a wider range of applications. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of a conventional low-voltage X-ray tube structure in the prior art.

[0030] Figure 2 This is a schematic diagram of the high-pressure X-ray tube structure of a linear accelerator in the prior art.

[0031] Figure 3 This is a schematic diagram of the overall structure of the adjustable X-ray tube of the tungsten filament cathode sheet electron beam accelerator according to an embodiment of the present invention.

[0032] Figure 4 This is a schematic diagram of the adjustable X-ray tube of the tungsten filament cathode sheet electron beam accelerator according to an embodiment of the present invention.

[0033] Figure 5 This is a schematic diagram of an adjustable X-ray tube for a field emission cathode sheet electron beam extended interaction acceleration cavity, according to an embodiment of the present invention.

[0034] Figure 6 This is a schematic diagram of an adjustable X-ray tube with a barium-tungsten cathode sheet electron beam folded waveguide accelerating cavity, according to an embodiment of the present invention.

[0035] The following are the labels in the figure: 1-Cathode, 2-Control electrode, 3-Anode, 4-Acceleration cavity, 5-Beryllium window, 6-Tungsten target, 7-Energy feed inlet. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a sheet-shaped electron beam adjustable voltage X-ray tube, such as... Figure 3-4 As shown, the X-ray tube includes a cathode 1, a control electrode 2, an anode 3, an acceleration cavity 4, a beryllium window 5, a tungsten target 6, and an energy feed inlet 7.

[0039] The cathode emits electrons, the control electrode surrounds the cathode, and the anode is located opposite the control electrode outlet. The cathode, control electrode, and anode have different voltages. The cathode emits the electron beam and, in conjunction with the control electrode and anode, uses an electric field to constrain the emitted electron beam, forming a thin, sheet-like electron beam that is wide horizontally and extremely thin vertically. The electron beam passing through the anode enters the accelerating cavity, where it is further accelerated based on the energy of the input electromagnetic wave. The electron beam exiting the accelerating cavity strikes a tungsten target, generating X-rays. To minimize the X-ray beam area, the tungsten target is tilted, with the tilt direction matching the wide side of the thin electron beam. The generated X-rays also exit through a beryllium window along this wide side.

[0040] The cathode is a thermionic emission type, specifically a tungsten filament cathode. Applying a heating current to the cathode raises its temperature, generating electron emission. The control electrode has a near-elliptical cross-section, thus creating an asymmetric electrostatic field distribution between it and the anode. This electric field exhibits weak focusing or diverging characteristics in the vertical direction, allowing the electron beam to spread freely in that direction; while in the horizontal direction it exhibits strong focusing characteristics, compressing the electron beam to a very small thickness. In this way, the initial electron beam emitted from the cathode is shaped into a thin, rectangular electron beam.

[0041] The anode and the accelerating cavity are integrally formed. After the thin-film electron beam enters the accelerating cavity, the electric field inside the accelerating cavity is generated by the electromagnetic wave excitation entering through the energy feed inlet, which accelerates or decelerates the electron beam according to the input electromagnetic wave.

[0042] The accelerating cavity is made of oxygen-free copper or stainless steel. Inside the accelerating cavity is a beam channel that matches the cross-sectional shape of the thin-film electron beam (i.e., the cross-section is rectangular, chamfered, or elliptical with a high aspect ratio). In this example, the accelerating cavity has a rectangular cross-section thin electron beam channel. The accelerating cavity is used to receive the thin-film electron beam and apply an axial accelerating or decelerating electric field to it.

[0043] An energy feed inlet is provided on the accelerating cavity, and a microwave window is connected to the lower end of the energy feed inlet. Microwave power generated by an external microwave source is fed into the accelerating cavity through the microwave window and the energy feed inlet, establishing an axial standing wave accelerating or decelerating electric field within the accelerating cavity. The energy feed inlet is coupled to the accelerating cavity to feed electromagnetic waves into the accelerating cavity to establish the axial accelerating or decelerating electric field. This allows the sheet-like electron beam to continuously receive energy for acceleration or deceleration. By adjusting the output power of the external microwave source, the electric field strength within the accelerating cavity can be changed, thereby accelerating or decelerating the sheet-like electron beam to the desired energy level. For example, for the detection of thin steel plates, the accelerating voltage can be adjusted to 0.5 MeV; for the detection of thick steel plates, the accelerating voltage can be adjusted to 2 MeV or higher.

[0044] The high-energy, thin-film electron beam, after acceleration or deceleration, forms an angle with the normal to the tungsten target surface. Because the electron beam thickness (h) is extremely small, the effective projection size of the X-ray focal spot onto the imaging plane through the beryllium window (d = h / sinθ) remains very small, resulting in extremely high imaging resolution. Simultaneously, because the electron beam maintains a relatively large size in the width direction (W), the total power and current of the electron beam are guaranteed, ensuring sufficient X-ray dose output.

[0045] Example 2

[0046] The main difference between this embodiment and Embodiment 1 lies in the selection of the cathode and the operating mode of the accelerating cavity 3. In this embodiment, the cathode uses wedge-shaped graphite field emission, which, combined with the control electrode and the anode, forms a thin-film electron beam, such as... Figure 5 As shown in the diagram. In this structure, there is no need to heat the cathode. By applying a high voltage of several thousand volts between the cathode and anode, an extremely strong electric field can be formed at the tip of the wedge-shaped graphite, emitting electrons through the quantum tunneling effect. By precisely designing the voltage of the control electrode, the emitted electron beam can also be shaped into a thin sheet-like electron beam. Field emission has the advantages of fast start-up and high instantaneous current density, making it suitable for X-ray tubes operating in pulsed mode.

[0047] The generated sheet-like electron beam enters the accelerating cavity. In this embodiment, an extended interaction cavity (EIC) structure is used as the accelerating cavity. In this structure, a standard waveguide is used as the energy feed inlet, and the extended interaction cavity is naturally suitable for sheet-like electron beams. Similar to Embodiment 1, different feed energies will result in different electric fields established in the extended interaction cavity, thereby allowing the sheet electrons to obtain different energies.

[0048] Example 3

[0049] The main difference between this embodiment and Embodiment 1 lies in the cathode and the accelerating cavity, such as Figure 6As shown in the diagram. In this embodiment, a barium tungsten thermionic emission cathode is used as the cathode. By controlling the compression of the electrode and anode, a thin sheet-like electron beam is formed. The accelerating cavity adopts a folded waveguide structure with two energy feed ports. One energy feed port is connected to the electromagnetic wave feed, and the other energy feed port is connected to the load to absorb the electromagnetic wave. At this time, the electromagnetic wave advances in the folded waveguide, so that when the electron passes through the gap in the electron beam channel at the center of the folded waveguide, the electromagnetic wave forms an accelerating electric field, accelerating or decelerating the electron beam, similar to a traveling wave accelerator. Finally, the remaining electromagnetic wave energy is absorbed by the load. The electron beam leaving the accelerating cavity, after obtaining sufficient energy, hits the tungsten target and forms X-rays. This structure is more compact and suitable for portable or miniaturized X-ray sources with lower energies (e.g., below 1 MeV).

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sheet-shaped X-ray tube with adjustable electron beam voltage, characterized in that, The X-ray tube includes a cathode, a control electrode, an anode, an accelerating cavity, a beryllium window, a tungsten target, and an energy feed inlet; The control electrode surrounds the cathode, and the anode is located opposite the control electrode outlet, with a gap between the anode and the control electrode; The anode is connected to the acceleration chamber, which is equipped with an energy feed inlet. The cathode, control electrode, and anode voltages are different. The cathode emits an electron beam, which, in conjunction with the control electrode and anode, is constrained by an electric field and formed into a thin sheet-like electron beam that is wide in the horizontal direction and thin in the vertical direction. A thin sheet-like electron beam passes through the anode and enters the acceleration cavity. The acceleration cavity generates an electric field based on the electromagnetic wave excitation entering the energy feed inlet, which accelerates or decelerates the thin sheet-like electron beam, and outputs a high-energy thin sheet-like electron beam after acceleration or deceleration. High-energy, thin-film electron beams are fired onto a tungsten target, generating X-rays that pass through a beryllium window.

2. The sheet-shaped electron beam adjustable voltage X-ray tube according to claim 1, characterized in that, The cathode is made of tungsten wire or barium tungsten metal and uses thermal emission. By applying a heating current to the cathode, its temperature is raised, and an electron beam is generated.

3. The sheet-shaped electron beam adjustable voltage X-ray tube according to claim 1, characterized in that, The cathode is made of graphene sheets or metal sheets. By applying a voltage between the cathode and the anode, field emission is generated to produce an electron beam.

4. The sheet-shaped electron beam adjustable voltage X-ray tube according to claim 1, characterized in that, The cathode is made of alkali metal and uses photoelectric emission to generate an electron beam.

5. The sheet-shaped electron beam adjustable voltage X-ray tube according to claim 1, characterized in that, The control electrode has an elliptical cross-section. An asymmetric electrostatic field distribution is formed between the control electrode and the anode. The electric field exhibits weak focusing or diverging characteristics on the electron beam in the vertical direction, allowing the electron beam to spread freely in the vertical direction. In the horizontal direction, it exhibits strong focusing characteristics, compressing the electron beam to a very small thickness. In this way, the electron beam emitted by the cathode is shaped into a thin sheet-like electron beam with a rectangular cross-section.

6. The sheet-shaped electron beam adjustable voltage X-ray tube according to claim 1, characterized in that, The accelerating cavity is made of oxygen-free copper or stainless steel, and a beam channel matching the cross-sectional shape of the sheet-like electron beam is formed inside the accelerating cavity. The accelerating cavity is used to receive the sheet-like electron beam and apply an axial accelerating or decelerating electric field to the sheet-like electron beam through electromagnetic waves fed in through the energy feed inlet.

7. The sheet-shaped electron beam adjustable voltage X-ray tube according to claim 1, characterized in that, A microwave window is connected to the lower end of the energy feed inlet. The microwave power generated by the external microwave source is fed into the acceleration cavity through the microwave window and the energy feed inlet, establishing an axial standing wave acceleration or deceleration electric field in the acceleration cavity.

8. The sheet-shaped electron beam adjustable voltage X-ray tube according to claim 1, characterized in that, An extended interaction cavity structure is used as the acceleration cavity.

9. The sheet-shaped electron beam adjustable voltage X-ray tube according to claim 1, characterized in that, The accelerating cavity adopts a folded waveguide structure. An energy feed inlet is set on the upper and lower sides of the accelerating cavity. One energy feed inlet is connected to the electromagnetic wave feed, and the other energy feed inlet is connected to the load to absorb the electromagnetic wave.

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