Microwave buncher x-ray tube

Abstract

A microwave bunching X-ray tube comprises: a housing comprising a receiving cavity; a cathode assembly at least partially accommodated in the receiving cavity, the cathode assembly being configured to emit an electron beam; an electromagnetic focusing system comprising at least one microwave resonant cavity, the at least one microwave resonant cavity being located in the receiving cavity, the at least one microwave resonant cavity being arranged on an electron beam transmission path between the cathode assembly and an anode assembly, the microwave resonant cavity being configured to axially bunch the electron beam, the axial direction being a transmission direction of the electron beam; and an anode assembly comprising an anode target, the anode target being located in the receiving cavity, the electron beam being configured to impinge on the anode target after passing through the electromagnetic focusing system to generate X-rays. The technical solution of the present application can effectively improve the X-ray output intensity.

Description

Technical Field

[0001] This invention relates to the field of X-ray tube technology, and more particularly to a microwave focusing X-ray tube. Background Technology

[0002] The X-ray tube is the core X-ray generating component of imaging equipment such as CT scanners and DR systems. Its performance directly determines key imaging indicators such as temporal and spatial resolution. Temporal resolution determines the ability to suppress motion artifacts during scanning of dynamic organs (such as arteries and the heart), while spatial resolution is crucial for accurate screening of early-stage tumors, small nodules, and other small lesions. Both directly affect the accuracy of clinical diagnosis.

[0003] With the development of advanced medical imaging technology, clinical practice has placed core demands on CT equipment, including high imaging resolution, high beam power, and low artifacts. Correspondingly, modern X-ray tubes require more effective electron beam focusing and deflection control, a more stable anode rotation support structure, and higher target surface heat dissipation efficiency. However, existing technologies still have shortcomings in electron beam control; the peak current and pulse dose of the electron beam are insufficient to meet the high temporal resolution requirements of advanced CT equipment. Summary of the Invention

[0004] The technical problem solved by this invention is to provide an improved microwave focusing X-ray tube.

[0005] To address the aforementioned technical problems, embodiments of the present invention provide a microwave-focused X-ray tube, comprising: a housing including a receiving cavity; a cathode assembly, at least partially housed within the receiving cavity, the cathode assembly for emitting an electron beam; an electromagnetic focusing system including at least one microwave resonant cavity located within the receiving cavity, the at least one microwave resonant cavity being disposed on the electron beam transmission path between the cathode assembly and the anode assembly, the microwave resonant cavity axially focusing the electron beam, the axis being the transmission direction of the electron beam; and an anode assembly including an anode target located within the receiving cavity, the electron beam bombarding the anode target after passing through the electromagnetic focusing system to generate X-rays.

[0006] Optionally, the microwave resonant cavity is adapted to establish an axial electromagnetic field in the electron beam transmission path, the phase of which is configured to apply axial velocity modulation to the electron beam so as to compress and focus the electron beam in the axial direction.

[0007] Optionally, the microwave resonant cavity operates in the X-band, Ku-band, or Ka-band; and / or the phase modulation range of the electromagnetic field is (-π / 2, 0).

[0008] Optionally, the electromagnetic focusing system includes at least two microwave resonant cavities connected in series along the transmission direction of the electron beam.

[0009] Optionally, the cavity wall of the microwave resonant cavity is arc-shaped or rectangular.

[0010] Optionally, the cavity wall of the microwave resonant cavity is made of a high-conductivity material.

[0011] Optionally, the cavity wall of the microwave resonant cavity is made of oxygen-free copper or diffused copper.

[0012] Optionally, the microwave resonant cavity wall is provided with a microwave power feed inlet, and an external microwave power source feeds microwave energy into the microwave resonant cavity through a waveguide via the microwave power feed inlet.

[0013] Optionally, an electron collecting section is provided downstream of the microwave resonant cavity along the transmission direction of the electron beam. The electron collecting section is used to collect backscattered electrons reflected from the anode target.

[0014] Optionally, the electromagnetic focusing system further includes a focusing structure disposed around the transmission path of the electron beam, the focusing structure being used to focus the electron beam.

[0015] Optionally, the housing includes a cathode housing, the microwave resonant cavity is located in the cathode housing, and the focusing structure is sleeved on the outer periphery of the cathode housing.

[0016] Optionally, the focusing structure and the microwave resonant cavity are arranged alternately along the transmission path of the electron beam.

[0017] Optionally, the focusing structure includes a first focusing part and a second focusing part, which are spaced apart along the transmission direction of the electron beam.

[0018] Optionally, along the transmission direction of the electron beam, the microwave resonant cavity is located between the first focusing section and the second focusing section.

[0019] Optionally, the first focusing part and the second focusing part each include a magnetic focusing coil, which is adapted to change the magnetic field strength by adjusting the current in order to achieve radial focusing of the electron beam.

[0020] Optionally, the second focusing section also integrates two sets of mutually perpendicular deflection coils to deflect the electron beam in the x and y directions respectively to form a flying focus, wherein the x and y directions are two mutually perpendicular radial directions.

[0021] Optionally, the cathode assembly includes: an electron emitter for emitting an electron beam; and a cathode focusing portion disposed around the electron emitter for initially focusing the electron beam.

[0022] Optionally, the electron emitter may be made of tungsten or its alloys or oxide cathode materials.

[0023] Optionally, the electron emitter is a flat filament structure or a spiral filament structure.

[0024] Optionally, the cathode assembly further includes an insulating support portion, through which the electron emitter is connected to the housing.

[0025] Optionally, the X-ray tube further includes: a bearing assembly including a shaft that extends axially through the anode target and is fixedly connected to both ends of the housing; the anode target rotates about the shaft.

[0026] Optionally, the bearing assembly further includes: a bushing fitted around the outer periphery of the shaft, the anode target being fixedly connected to the outer peripheral surface of the bushing, and a non-zero gap between the bushing and the shaft, the non-zero gap being used to form a filling cavity, the filling cavity being filled with liquid metal.

[0027] Optionally, the shaft, the bushing, and the liquid metal filling the filling cavity form a liquid metal bearing structure.

[0028] Optionally, the shaft and the bushing are provided with herringbone and / or figure-eight texture structures on their corresponding wall surfaces.

[0029] Optionally, the shaft has a hollow structure for the passage of cooling medium.

[0030] Optionally, the hollow structure is provided with a heat dissipation structure, including a honeycomb mesh structure and / or a finned structure.

[0031] Compared with the prior art, the technical solution of the embodiments of the present invention has the following beneficial effects: The technical solution of this application involves arranging a microwave resonant cavity along the electron beam transmission path between the cathode assembly and the anode target. This microwave resonant cavity performs axial focusing of the electron beam, effectively increasing the peak current intensity and instantaneous dose per pulse. This optimizes the temporal resolution of CT equipment and reduces motion artifacts, such as those formed during dynamic organ scanning. The axially focused electron beam has a more concentrated energy distribution when bombarding the anode target, resulting in increased X-ray output intensity, which meets the high beam power requirements of advanced imaging equipment.

[0032] Furthermore, an axial electromagnetic field is constructed along the electron beam transmission path using a microwave resonant cavity. Axial velocity modulation is then applied to the electron beam by matching the phase of the electromagnetic field, achieving axial focusing and compression based on the velocity difference within the electron beam. The focusing process is smooth and uniform, preventing electron beam divergence overload. This allows for a stable increase in the peak electron beam pulse intensity, continuously increasing the instantaneous X-ray output dose and further optimizing imaging quality under dynamic scanning.

[0033] Furthermore, by employing the X-band, Ku-band, or Ka-band as the operating frequency band for the microwave resonant cavity and setting the electromagnetic field phase modulation range to (-π / 2, 0), precise electron beam focusing and compression can be achieved. This frequency band offers concentrated microwave energy and a fast modulation response, avoiding beam divergence issues caused by phase shifts. The focusing parameters have a wider adjustable range, adapting to various clinical scanning conditions and improving the overall imaging stability.

[0034] Furthermore, at least two microwave resonant cavities are arranged in series along the electron beam propagation direction, relying on multi-stage cavities to achieve axial focusing of the electron beam step by step. This can significantly increase the upper limit of the peak electron beam current, distribute the power load of a single cavity, and extend the service life of the resonant cavity. It also allows for fine adjustment of the electron beam pulse waveform through multi-stage segmented modulation, adapting to the differentiated dosage requirements of different clinical scenarios.

[0035] Furthermore, by adding an electron collecting section downstream of the microwave resonant cavity along the electron beam propagation path, backscattered electrons generated by the anode target are efficiently captured. This avoids high-temperature losses caused by backscattered electrons bombarding the cavity and cathode, and also eliminates interference from backscattered electrons on the microwave field within the cavity. This maintains the stable focusing capability of the microwave resonant cavity for a long time, extending the overall lifespan of the X-ray tube.

[0036] Furthermore, by incorporating a focusing structure around the electron beam transmission path, a bidirectional beam modulation mechanism is formed in conjunction with the microwave resonant cavity. The microwave resonant cavity is responsible for compressing the axial length of the electron beam, while the focusing structure constrains the radial diffusion of the electron beam. Together, they reduce the focal spot size of the electron beam bombarding the anode target, effectively improving the spatial resolution of CT equipment and facilitating the clinical identification of small lesions.

[0037] Furthermore, by dividing the focusing structure into a first focusing section and a second focusing section spaced apart along the electron beam path, a two-segment structure is used to correct the electron beam transmission offset. Compared to single-segment focusing, the correction coverage is larger, which can offset the slight radial offset caused by microwave focusing and stably constrain the electron beam trajectory throughout the entire process. Attached Figure Description

[0038] Figure 1 This is a cross-sectional view of an X-ray tube according to an embodiment of the present invention; Figure 2 yes Figure 1 Schematic diagram of the central cathode assembly and electromagnetic focusing system; Figure 3 yes Figure 2 Schematic diagram of a microwave resonant cavity; Figure 4 yes Figure 3 A schematic diagram of a variation of the structure shown; Figure 5 yes Figure 2 A schematic diagram of the electric field distribution inside a microwave resonant cavity; Figure 6 yes Figure 5 A schematic diagram showing the electric field normalized along the axial direction; Figure 7 yes Figure 1 Schematic diagram of the bearing assembly; Figure 8 yes Figure 1 Distribution diagram of the electron beam emitted by the central cathode assembly; Figure 9 yes Figure 1 Distribution diagram of the modulated electron beam in the electromagnetic focusing system. Detailed Implementation

[0039] As mentioned in the background section, existing X-ray tubes still have shortcomings in electron beam control, and the peak current and pulse dose of the electron beam are difficult to meet the high temporal resolution requirements of high-end CT equipment.

[0040] To address the aforementioned technical problems, embodiments of the present invention provide a microwave-focused X-ray tube, comprising: a housing including a receiving cavity; a cathode assembly, at least partially housed within the receiving cavity, the cathode assembly for emitting an electron beam; an electromagnetic focusing system including at least one microwave resonant cavity located within the receiving cavity, the at least one microwave resonant cavity being disposed on the electron beam transmission path between the cathode assembly and the anode assembly, the microwave resonant cavity axially focusing the electron beam, the axis being the transmission direction of the electron beam; and an anode assembly including an anode target located within the receiving cavity, the electron beam bombarding the anode target after passing through the electromagnetic focusing system to generate X-rays.

[0041] The technical solution of this application involves arranging a microwave resonant cavity along the electron beam transmission path between the cathode assembly and the anode target. This microwave resonant cavity performs axial focusing of the electron beam, effectively increasing the peak current intensity and instantaneous dose per pulse. This optimizes the temporal resolution of CT equipment and reduces motion artifacts during dynamic organ scanning. The axially focused electron beam has a more concentrated energy distribution when bombarding the anode target, resulting in enhanced X-ray output intensity, meeting the high beam power requirements of advanced imaging equipment.

[0042] To make the above-mentioned objectives, features and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0043] Figure 1 This is a cross-sectional view of an X-ray tube 100 according to an embodiment of the present invention. Figure 2 yes Figure 1 A schematic diagram of the central cathode assembly 2 and the electromagnetic focusing system 3. Figure 3 yes Figure 2 A schematic diagram of the microwave resonant cavity 31.

[0044] In some embodiments, combined with Figures 1 to 3 The microwave focusing X-ray tube 100 may include: a housing 1, including a receiving cavity 10; a cathode assembly 2, at least partially housed in the receiving cavity 10, the cathode assembly 2 being used to emit an electron beam; an electromagnetic focusing system 3 including at least one microwave resonant cavity 31, the at least one microwave resonant cavity 31 being located within the receiving cavity 10, the at least one microwave resonant cavity 31 being disposed on the electron beam transmission path between the cathode assembly 2 and the anode assembly 4, the microwave resonant cavity 31 axially focusing the electron beam, the axis being the transmission direction of the electron beam; and an anode assembly 4, including an anode target 41, located within the receiving cavity 10, the electron beam bombarding the anode target 41 after passing through the electromagnetic focusing system 3 to generate X-rays.

[0045] Specifically, the housing 1 is the external vacuum-sealed structure of the X-ray tube 100.

[0046] In some embodiments, the housing 1 may be made of a metal material (e.g., stainless steel).

[0047] Furthermore, the housing 1 can achieve the fixation of each internal component and the sealing of the overall vacuum environment through metal sealing process, providing vacuum conditions for the unobstructed transmission of the electron beam, while forming mechanical protection and structural support for the internal components.

[0048] Furthermore, the receiving cavity 10 is defined by the housing 1, and the receiving cavity 10 provides a vacuum accommodating space for internal components such as the cathode assembly 2, the electromagnetic focusing system 3, and the anode assembly 4.

[0049] In some embodiments, the cathode assembly 2 is at least partially housed within the receiving cavity 10. The cathode assembly 2 is the electron source of the X-ray tube 100. When heated, the cathode assembly 2 emits an electron beam, which travels axially (i.e., the direction of electron beam transmission) toward the anode target 41.

[0050] Furthermore, the microwave resonant cavity 31 axially focuses the electron beam propagating along this path; the axial direction refers to the direction of electron beam propagation. Thus, the electron beam is compressed into a high-density bundle arranged along the axial direction as it passes through the microwave resonant cavity 31, providing high-current, high-dose electron beam conditions for subsequent bombardment of the anode target 41.

[0051] Furthermore, the anode assembly 4 includes an anode target 41, which is located within the receiving cavity 10.

[0052] In some embodiments, the anode target 41 may be made of a molybdenum-titanium-zirconium (TZM) alloy, and the diameter of the anode target 41 may be, for example, 150 mm to 220 mm.

[0053] In operation, the electron beam is modulated by the electromagnetic focusing system 3 and then bombards the anode target 41. The kinetic energy of the electron beam is converted into X-rays and radiated outward, thereby generating X-rays for CT imaging.

[0054] In some embodiments, reference Figure 1 The back of the anode target 41 is also provided with a heat storage structure 42 (the heat storage structure 42 can be, for example, a graphite ring). The heat storage structure 42 is used to absorb and store the heat generated by the anode target 41 during operation, thereby alleviating the local heat load of the anode target 41. As a result, the heat storage structure 42 shares the heat capacity of the anode target 41 and extends the service life of the anode target 41 under continuous high power conditions.

[0055] In some embodiments, combined with Figure 2 , Figure 5 and Figure 6 The microwave resonant cavity 31 is adapted to establish an axial electromagnetic field in the electron beam transmission path, the phase of the electromagnetic field being configured to apply axial velocity modulation to the electron beam so as to compress and focus the electron beam in the axial direction.

[0056] Specifically, the microwave resonant cavity 31 establishes an axial electromagnetic field along the electron beam propagation path, and the phase of this axial electromagnetic field is configured to apply axial velocity modulation to the electron beam. Through axial velocity modulation, the traveling electron beam is compressed and focused axially, transforming its previously dispersed state into a high-density bundle arranged along the axial direction. This significantly increases the peak flux of the electron beam, and since the X-ray dose generated by the electron beam is proportional to the flux, it is beneficial for generating high-dose pulsed X-rays and improving the temporal resolution of the image.

[0057] further, Figure 5 The electric field distribution within the microwave resonant cavity 31 is shown. Figure 6 It shows Figure 5The distribution curve of the electric field after axial normalization. By adjusting the phase of the electromagnetic field in the microwave resonant cavity 31, the transmitted electron beam can be compressed axially, solving the problem of low electron beam current in the prior art.

[0058] In a specific application scenario, the peak current of the electron beam can be increased from approximately 2 amperes to approximately 11 amperes, and the transient X-ray dose can be increased by approximately five times or more. Therefore, the increase in peak current and transient X-ray dose is particularly beneficial for rapid scanning of dynamic organs such as the heart and arteries.

[0059] It should be understood that Figure 5 The horizontal axis can, for example, represent the axial position (unit: millimeters), and the vertical axis can, for example, represent the axial electric field intensity (unit: megavolts per meter). Figure 5 Reflects the axial electric field component Spatial distribution along the electron beam propagation direction (i.e., the z-axis). Axial electric field components. The peak value is obtained in the central region of the microwave resonant cavity 31 and gradually decays towards both ends of the cavity. This distribution characteristic makes the electron beam subject to the strongest axial electric field when passing through the center of the cavity.

[0060] according to Figure 5 When the electron beam passes through the microwave resonant cavity 31, electrons at different axial positions experience longitudinal electric fields of varying intensities, resulting in axial velocity modulation (acceleration or deceleration). That is, Figure 5 This illustrates the physical basis of microwave focusing.

[0061] Figure 6 The x-coordinate is also the axial position. (Unit: mm), the vertical axis represents the normalized electric field intensity, i.e., the axial electric field component. With peak electric field The ratio: (Dimensionless).

[0062] Through normalization, the electric field distribution in the microwave resonant cavity 31 under different microwave power feed conditions is comparable, which facilitates the evaluation of the axial modulation efficiency of the microwave resonant cavity 31 for the electron beam. Figure 6 This further confirms Figure 5 The physical basis of microwave focusing is shown.

[0063] In some embodiments, the microwave resonant cavity 31 operates in the X-band, Ku-band, or Ka-band.

[0064] The aforementioned X-band, Ku-band, or Ka-band all belong to the high-frequency microwave band (above 3 GHz). The higher the frequency, the shorter the microwave wavelength, resulting in stronger spatial resolution for electron beam velocity modulation and beam focusing / compression, higher beam focusing and control precision, and making it more suitable for electron beam pulse compression. Therefore, the high-frequency microwave band can establish an electromagnetic field distribution within the microwave resonant cavity 31 that satisfies the requirements for axial compression of the electron beam.

[0065] In one variation, the microwave resonator 31 can also operate in other high-frequency microwave bands, such as K-band, Q-band, V-band, or W-band.

[0066] In some embodiments, the phase modulation range of the electromagnetic field within the microwave resonant cavity 31 can be, for example, (-π / 2, 0).

[0067] In some embodiments, combined with Figure 1 and Figure 2 The electromagnetic focusing system 3 further includes a focusing structure 33, which is disposed around the transmission path of the electron beam, and the focusing structure 33 is used to focus the electron beam.

[0068] Specifically, the focusing structure 33 applies radial focusing to the electron beam during its transmission, causing the electron beam to be converged step by step in the radial direction, gradually reducing the radial size of the electron beam and improving focusing accuracy. Thus, the focusing structure 33, in conjunction with the axial focusing of the microwave resonant cavity 31, allows the electron beam to be controlled simultaneously in both the radial and axial directions, providing beam current conditions for high-precision imaging.

[0069] In some embodiments, combined with Figures 1 to 3 The electromagnetic focusing system 3 includes at least two microwave resonant cavities 31, which are connected in series along the transmission direction of the electron beam.

[0070] Specifically, Figure 3 An example is shown of a dual-cavity structure consisting of two microwave resonant cavities 31.

[0071] In some embodiments, multiple microwave resonant cavities 31 can be connected in series to form a cavity chain. As the electron beam passes through the multi-stage microwave resonant cavities 31 in sequence, its axial velocity is modulated step by step. Each stage of the microwave resonant cavity 31 further densifies the distribution of the clustered electron beam based on the previous stage.

[0072] Therefore, the multi-stage series-connected microwave resonators 31 provide stronger axial focusing force than a single-cavity structure, while avoiding the problems of excessively long electron drift paths and increased electron beam loss caused by an excessive number of cavities, thus achieving a balance between focusing strength and transmission efficiency. In addition, the multi-stage series structure can also distribute the power load of a single microwave resonator 31, extend the service life of the microwave resonator 31, and finely adjust the electron beam pulse waveform through multi-stage segmented modulation to adapt to the differentiated dose requirements of different clinical scenarios.

[0073] In some embodiments, the cavity wall of the microwave resonant cavity 31 can be an arc-shaped structure. The arc-shaped cavity wall can improve the electromagnetic field distribution inside the cavity, making the axial electric field more uniform and concentrated, thereby improving the quality factor of the microwave resonant cavity 31.

[0074] In some embodiments, the cavity wall of the microwave resonant cavity 31 can also be rectangular (square cavity) structure. The machining process of the square cavity structure is relatively simple, which facilitates mass production and is suitable for application scenarios that are sensitive to processing costs.

[0075] In some embodiments, the cavity wall of the microwave resonant cavity 31 is made of a high conductivity material.

[0076] In one specific embodiment, the cavity wall of the microwave resonant cavity 31 is made of oxygen-free copper or diffused copper.

[0077] High-conductivity materials can reduce microwave losses on the cavity wall surface, improving electromagnetic field establishment efficiency and resonance quality. Therefore, by rationally selecting the cavity wall shape and material, a flexible balance can be struck between electromagnetic field quality, processing difficulty, and manufacturing cost to meet the needs of different operating conditions.

[0078] In some embodiments, the cavity wall of the microwave resonant cavity 31 is provided with a microwave power feed inlet 311, and an external microwave power source feeds microwave energy into the microwave resonant cavity 31 through a waveguide via the microwave power feed inlet 311.

[0079] In practical applications, the high-frequency microwave energy generated by the external microwave power source is transmitted through a waveguide to the microwave power feed inlet 311, and then fed into the microwave resonant cavity 31, thereby establishing an axial electromagnetic field within the microwave resonant cavity 31. The phase and amplitude of the electromagnetic field can be precisely controlled by adjusting the output parameters of the external microwave power source, so that a field distribution that meets the axial velocity modulation requirements is formed within the microwave resonant cavity 31. Thus, the microwave power feed inlet 311 realizes the energy coupling channel between the external power source and the microwave resonant cavity 31, making the excitation mode of the microwave resonant cavity 31 flexible and controllable, and facilitating real-time adjustment of the focusing parameters according to the imaging conditions.

[0080] In some embodiments, combined with Figure 1 and Figure 2Along the transmission direction of the electron beam, an electron collecting section 32 is provided downstream of the microwave resonant cavity 31. The electron collecting section 32 is used to collect backscattered electrons reflected from the anode target 41.

[0081] In practical applications, when the electron beam bombards the anode target 41, some backscattered electrons are generated. These backscattered electrons bounce back along the opposite direction of the electron beam transmission path. The electron collection unit 32 is arranged in the bounce path of the backscattered electrons to intercept and collect them.

[0082] Therefore, the electron collection section 32 can avoid backscattered electrons bombarding the microwave resonant cavity 31 and the cathode assembly 2, which would cause high-temperature losses. It can also eliminate the interference of backscattered electrons on the microwave electromagnetic field in the microwave resonant cavity 31, maintain the stable beam focusing ability of the microwave resonant cavity 31 for a long time, and extend the overall service life of the X-ray tube 100.

[0083] In some embodiments, the electron collecting section 32 may be funnel-shaped or horn-shaped, with the larger opening facing one side of the anode target 41.

[0084] In some embodiments, the microwave resonant cavity 31 can be directly enclosed by the inner wall of the cathode housing 11, that is, the local inner wall of the cathode housing 11 constitutes the cavity wall of the microwave resonant cavity 31, without the need for additional independent cavity components, thereby simplifying the assembly structure of the electromagnetic focusing system 3 and reducing the overall volume.

[0085] In other embodiments, the microwave resonant cavity 31 is formed by embedding an independent resonant cavity inside the cathode housing 11. The resonant cavity is independently processed from high conductivity materials such as oxygen-free copper or dispersed copper and then installed inside the cathode housing 11. The cavity wall is fixedly connected to the inner wall of the cathode housing 11.

[0086] In some embodiments, combined with Figure 2 The housing 1 includes a cathode housing 11, the microwave resonant cavity 31 is located in the cathode housing 11, and the focusing structure 33 is sleeved on the outer periphery of the cathode housing 11.

[0087] Specifically, the cathode housing 11 is the cathode-side housing portion of the cavity 10. The microwave resonant cavity 31 is arranged inside the cathode housing 11, while the focusing structure 33 is fitted onto the outer periphery of the cathode housing 11. Thus, the cathode housing 11 simultaneously provides internal mounting space for the microwave resonant cavity 31 and external mounting reference for the focusing structure 33, making the integration of the electromagnetic focusing system 3 on the cathode side more compact and reducing the need for additional support structures to fix the microwave resonant cavity 31 and the focusing structure 33.

[0088] In some embodiments, combined with Figure 2Along the transmission path of the electron beam, the focusing structure 33 and the microwave resonant cavity 31 are arranged alternately.

[0089] Thus, the electron beam alternately (or successively) experiences radial focusing and axial focusing during its journey. The two types of control are spatially staggered to avoid structural interference between the focusing structure 33 and the microwave resonant cavity 31, while ensuring a smooth spatial connection between the radial focusing and axial compression of the electron beam.

[0090] In some embodiments, combined with Figure 2 The focusing structure 33 includes a first focusing part 331 and a second focusing part 332, which are spaced apart along the transmission direction of the electron beam.

[0091] Specifically, the first focusing section 331 is located on the side closer to the cathode assembly 2, and is responsible for electron beam emissivity compensation and initial focusing; the second focusing section 332 is located on the side closer to the anode assembly 4, and is responsible for high-precision focusing and deflection control. Thus, the two focusing sections form a series combination, which converges the electron beam radially step by step, gradually reducing the radial size of the electron beam and improving focusing accuracy.

[0092] In some embodiments, combined with Figure 2 Along the transmission direction of the electron beam, the microwave resonant cavity 31 is located between the first focusing part 331 and the second focusing part 332.

[0093] In practical applications, after the first focusing section 331 completes the initial radial focusing of the electron beam, the electron beam enters the microwave resonant cavity 31 to receive axial focusing, and then enters the second focusing section 332 to receive high-precision radial focusing and deflection control. Thus, the microwave resonant cavity 31 is sandwiched between the two stages of radial focusing sections. The electron beam first undergoes initial radial focusing, then axial compression, and finally fine radial focusing. The control levels are clear, which is beneficial for balancing radial resolution and axial time resolution.

[0094] In some embodiments, combined with Figure 2 The first focusing part 331 and the second focusing part 332 each include a magnetic focusing coil 333, which is adapted to change the magnetic field strength by adjusting the current in order to achieve radial focusing of the electron beam.

[0095] In a specific application scenario, by adjusting the current magnitude of the magnetic focusing coil 333 in the first focusing section 331 and the second focusing section 332, the magnetic field strength can be changed, enabling flexible adjustment of the radial focusing size of the electron beam and thus improving spatial resolution. Furthermore, the real-time current control of the magnetic focusing coil 333 can also compensate for radial defocusing that may occur during axial focusing, ensuring focusing accuracy.

[0096] The following explanation, based on the electron beam motion control equations, illustrates the quantitative mechanism by which axial focusing and radial focusing are achieved within this phase range.

[0097] The axial velocity modulation of the electron beam by the microwave resonant cavity 31 follows the electron beam motion control equation. In the radial direction, the radial momentum of the electron beam bundle... Bound group charge Electric field strength at the location of the bundle Relativistic factor speed of light and the angular magnetic field at the location of the bundle The combined effects of these factors on the radial momentum of the bundle rate of change and bundle charge Electric field strength at the location of the bundle The product is proportional to the bundle axial velocity and is proportional to the bundle axial velocity. and the angular magnetic field at the location of the bundle The product is related to these parameters, among which the relativistic factor and the speed of light These are parameters characterizing the relativistic motion of the electron.

[0098] The longitudinal momentum change of the electron beam bundle along the axial direction. With bundle charge Average electric field in microwave resonant cavity 31 Transit time factor And the axial length of the microwave resonant cavity 31 The product is proportional to the phase of the microwave electromagnetic field. sine function Modulation, and relative velocity with electrons and the speed of light The product is inversely proportional. The quantitative relationship of the above axial bundle convergence can be expressed as:

[0099]

[0100] In the formula, This represents the change in longitudinal momentum of the electron beam bundle. The charge of the cluster. The average electric field intensity in microwave resonant cavity 31 is given by [insert value here]. For the time factor of transit, Let be the axial length of the microwave resonant cavity 31. For microwave electromagnetic field phase, The relative velocity of electrons ( In the formula (The axial velocity of the bundle). It is the speed of light in a vacuum.

[0101] Furthermore, when phase When taking the interval (-π / 2, 0), A negative value indicates the change in longitudinal momentum. The value is negative. This means the electron beam's axial momentum decreases, causing backward electrons to slow down while forward electrons maintain a higher velocity. The electron beam is compressed into a high-density cluster in space, thus achieving axial focusing. Therefore, by precisely controlling the phase of the electromagnetic field... This allows for flexible adjustment of the longitudinal compression of the electron beam. Simultaneously, the radial defocusing that may occur during axial focusing is compensated in real time by the magnetic focusing coil 333 to ensure focusing accuracy.

[0102] further, Figure 9 The distribution pattern of the electron beam after being modulated by the electromagnetic focusing system 3 is shown. Figure 9 middle This indicates the axial observation position corresponding to the distribution map (correspondingly, Figure 8 middle ).

[0103] Figure 9 middle: The horizontal axis represents the vertical axis of the bundle. and according to Scaling (i.e., the actual unit is millimeters); The left side of the vertical axis represents the current intensity. (Unit: Ampere); The right side of the vertical axis represents the change in longitudinal momentum. and according to Scaling (unit: ).

[0104] The blue curve represents the electron beam current intensity, and the colored area represents the distribution of the electron beam in the longitudinal momentum space. After axial velocity modulation by the microwave resonant cavity 31 and radial focusing by the focusing structure 33, the peak current of the electron beam increases from approximately 2 amperes to approximately 11 amperes. The current distribution narrows significantly in the axial direction into a high-density cluster, while the longitudinal momentum change is concentrated within a relatively small area. Therefore, Figure 9 and Figure 8 The comparison clearly shows that the combined effect of axial focusing and radial focusing of the electromagnetic focusing system 3 significantly improves the peak current intensity and beam quality of the electron beam, providing beam conditions for pulsed high-dose X-ray emission.

[0105] In some embodiments, the second focusing part 332 may also integrate two sets of mutually perpendicular deflection coils to respectively deflect the electron beam in the x and y directions to form a flying focus, wherein the x and y directions are two mutually perpendicular radial directions.

[0106] In some embodiments, the second focusing unit 332 may also integrate two sets of mutually perpendicular deflection coils, corresponding to the x and y directions respectively. By adjusting the current parameters of the two sets of deflection coils, the impact position of the electron beam on the target surface of the anode target 41 can be controlled, achieving precise deflection of the electron beam in the x and y directions respectively, thereby forming multiple virtual focal points and realizing the fly-focus function. Thus, the fly-focus function can effectively suppress cone-beam artifacts and improve CT imaging quality. In a variation, the deflection coils can also use a piezoelectric ceramic-driven mechanical deflection structure to replace electromagnetic deflection, which can also achieve precise deflection of the electron beam in the x and y directions and the fly-focus function.

[0107] In a specific application scenario, the electrical parameters of the electromagnetic focusing system 3 can be flexibly adjusted according to the radiation dose requirements of clinical imaging to achieve coordinated control of image temporal resolution, spatial resolution and beam energy.

[0108] For example, by adjusting the current magnitude of the magnetic focusing coil 333 in the first focusing section 331 and the second focusing section 332, the magnetic field strength can be changed, thereby flexibly adjusting the radial focusing size of the electron beam and improving the spatial resolution.

[0109] For example, by adjusting the phase of the electromagnetic field of the microwave resonant cavity 31, the electron beam bundle can be compressed longitudinally. When the phase is (-π / 2, 0), the change in axial momentum of the electron beam is negative, and the electron beam is compressed into a high-density bundle, thereby increasing the peak current intensity.

[0110] Furthermore, by adjusting the current parameters of the two sets of mutually perpendicular deflection coils in the second focusing section 332, precise deflection of the electron beam in the x and y directions is achieved, changing the impact position of the electron beam on the target surface of the anode target 41 and forming multiple virtual focal points, effectively suppressing cone-shaped beam artifacts. Thus, the multi-parameter coordinated control in this application scenario enables the X-ray tube 100 to simultaneously meet the imaging requirements of high temporal resolution, high spatial resolution, and low artifacts.

[0111] In some embodiments, combined with Figure 2 and Figure 8 The cathode assembly 2 includes: an electron emitter 21 for emitting an electron beam; and a cathode focusing part 22, which is sleeved around the electron emitter 21 for initially focusing the electron beam.

[0112] Specifically, the cathode focusing section 22 initially focuses the electron beam in the initial stage after it leaves the electron emitter 21, so that the electron beam completes a radial convergence before entering the electromagnetic focusing system 3. As a result, the cathode focusing section 22 reduces the divergence angle of the initial electron beam, providing a good initial beam state for the subsequent radial focusing and axial focusing of the electromagnetic focusing system 3. Figure 8The distribution pattern of the electron beam emitted by cathode assembly 2 at the exit is shown.

[0113] further, Figure 8 The distribution of the electron beam emitted by the cathode assembly 2 at the exit (i.e., before modulation by the electromagnetic focusing system 3) is shown. Figure 8 Title This indicates the axial observation position corresponding to the distribution map.

[0114] Figure 8 middle: The horizontal axis represents the vertical axis of the bundle (unit: meters); The left side of the vertical axis represents the current intensity. (Unit: Ampere); The right side of the vertical axis represents the change in longitudinal momentum. and according to Scaling (unit: ).

[0115] The blue curve represents the current intensity distribution of the electron beam, and the colored area represents the distribution of the electron beam in the longitudinal momentum space. In the unmodulated initial state, the peak current of the electron beam is about 2 amperes, the current distribution is relatively diffuse in the axial direction, and the longitudinal momentum variation distribution range is relatively wide.

[0116] Combination Figure 8 and Figure 9 It can be seen that at the axial observation position place ( Figure 8 The electron beam, without modulation by the electromagnetic focusing system 3, has a peak current of approximately 2 amperes. The current distribution along the axial direction is relatively diffuse, and the longitudinal momentum change... The distribution range is relatively wide, and the beam quality is in its initial state.

[0117] At the axial observation position place ( Figure 9 The electron beam has passed through the axial velocity modulation of the microwave resonant cavity 31 and the radial focusing of the focusing structure 33 in sequence. The peak current has increased from about 2 amperes to about 11 amperes (an increase of about 4.5 times). The current distribution in the axial direction has significantly narrowed from a diffuse state to a high-density cluster, and the longitudinal momentum has changed. The distribution range has also narrowed significantly and become more concentrated.

[0118] The above comparison shows that, The narrowing of the current distribution is positively correlated with the axial compression of the current distribution—differential velocity modulation of electrons in different phases by the microwave resonant cavity 31 ( The differential distribution of electron beam density (EPD) is the direct cause of the formation of axial density clusters, while the radial focusing of focusing structure 33 further suppresses the radial defocusing that may occur during the focusing process. Thus, the two work together to achieve a dual quality improvement of the electron beam in both the axial and radial directions.

[0119] In some embodiments, the electron emitter 21 may be made of tungsten and tungsten alloys or oxide cathode materials.

[0120] Specifically, the electron emitter 21 may be made of a material with high emission current density and low work function, such as tungsten and tungsten alloys or oxide cathode materials.

[0121] In one variation, the electron emitter 21 may also be made of other high emission current density materials such as tantalum-tungsten alloy.

[0122] In some embodiments, the electron emitter 21 is a flat filament structure or a spiral filament structure.

[0123] In high-power medical X-ray tubes, the flat filament can adopt a circular or rectangular structure; in a variation, the filament structure of the electron emitter 21 can also be selected as an irregularly shaped flat filament according to the working conditions, as long as it can meet the requirements of high-power electron emission.

[0124] In some embodiments, the cathode assembly 2 further includes an insulating support portion 23, through which the electron emitter 21 is connected to the housing 1.

[0125] The insulating support part 23 provides mechanical support for the electron emitter 21 while also providing electrical isolation between the electron emitter 21 and the housing 1, preventing the high voltage potential of the electron emitter 21 from short-circuiting to the housing 1 through the support path.

[0126] In a specific application scenario, the X-ray tube 100 described herein can employ anode grounding technology, with the voltage of the housing 1 set to 0 volts, and the cathode assembly 2 subjected to a negative high voltage. The negative high voltage value of the cathode assembly 2 can be, for example, -160 kV to -140 kV. Thus, the insulating support 23 balances the support reliability and electrical safety of the cathode assembly 2, enabling the cathode assembly 2 to operate stably under negative high voltage conditions.

[0127] In some embodiments, combined with Figure 1 , Figure 7 and Figure 8 The X-ray tube 100 further includes a bearing assembly 5, including a shaft 51, which axially passes through the anode target 41 and is fixedly connected to both ends of the housing 1; the anode target 41 rotates about the shaft 51.

[0128] Specifically, the bearing assembly 5 provides support for the rotation of the anode target 41.

[0129] Furthermore, the shaft 51 extends axially (i.e., in the direction of electron beam transmission) through the anode target 41, and both ends of the shaft 51 are fixedly connected to both ends of the housing 1, thus forming a double-support structure on the housing 1. The anode target 41 rotates at high speed around the shaft 51 as its rotation axis. The position where the electron beam bombards the anode target 41 continuously changes with the rotation of the anode target 41, avoiding local heat accumulation that could lead to target surface melting. Thus, the double-fixed shaft 51 provides double support for the anode target 41. Compared to a single-support cantilever structure, double support significantly reduces vibration under high centrifugal loads, improving rotational stability and imaging quality.

[0130] Furthermore, the X-ray tube 100 may also include a rotor 6, which is fixed to the bearing assembly 5. The rotor 6 generates a rotational torque under the action of an alternating magnetic field and drives the anode target 41 to rotate at high speed around the shaft 51.

[0131] In one specific implementation, the rotor 6 may be made of a high-permeability material (e.g., an iron-based alloy).

[0132] In some embodiments, the rotational speed of the anode target 41 is characterized as 6,000 rpm to 15,000 rpm.

[0133] In some embodiments, combined with Figure 7 The bearing assembly 5 further includes: a bushing 52, which is sleeved on the outer periphery of the shaft 51; the anode target 41 is fixedly connected to the outer peripheral surface of the bushing 52; there is a non-zero gap between the bushing 52 and the shaft 51; the non-zero gap is used to form a filling cavity; the filling cavity is filled with liquid metal.

[0134] Specifically, the liquid metal can be, for example, a low-melting-point, high-thermal-conductivity liquid metal alloy such as indium gallium tin, which forms a fluid lubrication interface between the bushing 52 and the shaft 51.

[0135] Furthermore, the X-ray tube 100 may also include a connecting part 7, which is used to connect the rotor 6 and the bushing 52. The rotor 6 is fixedly connected to the bushing 52 through the connecting part 7, thereby driving the anode target 41 to rotate.

[0136] Furthermore, the anode target 41 is fixedly connected to the outer circumferential surface of the bushing 52, and the rotor 6 is fixed to the bushing 52. When the rotor 6 rotates, it drives the bushing 52, which in turn drives the anode target 41 to rotate at high speed around the shaft 51. Thus, a fluid lubrication interface is formed between the bushing 52 and the shaft 51 by liquid metal filling, which enables the anode target 41 to rotate at high speed and stably. At the same time, the liquid metal has good thermal conductivity, which helps to dissipate heat from the bearing area.

[0137] Furthermore, a convex ring structure 55 is provided between the anode target 41 and the bushing 52. The convex ring structure 55 supports the anode target 41 and securely fixes the anode target 41 to the outer circumferential surface of the bushing 52, dispersing the stress at the connection between the anode target 41 and the bushing 52. Thus, the convex ring structure 55 improves the reliability of the connection between the anode target 41 and the bushing 52, preventing failure of the connection due to stress concentration under high-speed rotation.

[0138] In some embodiments, the bearing assembly 5 may further include a sealing flange 8, which is arranged at the end of the bushing 52 away from the cathode assembly 2. The sealing flange 8 is used to seal the liquid metal in the filling cavity to prevent the liquid metal from leaking from the filling cavity between the bushing 52 and the shaft 51 under high-speed rotation conditions, thereby ensuring the sealing performance and operational reliability of the liquid metal bearing structure.

[0139] In some embodiments, a corresponding sealing structure is also provided at one end of the bushing 52 facing the cathode assembly 2 to prevent leakage of liquid metal.

[0140] In some embodiments, combined with Figure 7 The shaft 51, the bushing 52, and the liquid metal filling the filling cavity form a liquid metal bearing structure.

[0141] Specifically, liquid metal forms a fluid lubricating film between the opposing walls of the shaft 51 and the bushing 52, while simultaneously bearing the load during the rotation of the anode target 41. Thus, the liquid metal bearing structure possesses both high load-bearing capacity and low friction characteristics, enabling the anode target 41 to maintain stable rotation even under high speed and high centrifugal load conditions.

[0142] In some embodiments, the shaft 51 and the bushing 52 are provided with herringbone and / or figure-eight texture structures on their corresponding wall surfaces.

[0143] The textured structure can be etched onto the opposing walls of the shaft 51 and the bushing 52, which can increase the load-bearing capacity of the liquid metal bearing.

[0144] In one variation, the opposing walls of the shaft 51 and the bushing 52 can also be textured with other patterns such as diamond patterns or spiral patterns. This textured structure further enhances the load-bearing capacity of the liquid metal bearing and reduces vibration and image artifacts at high speeds.

[0145] Further reference Figure 1 and Figure 7 The shaft 51 has a hollow structure for the cooling medium to pass through.

[0146] In a preferred embodiment, the cooling medium may be deionized water, which flows through the hollow channel of the shaft 51 and quickly removes the heat accumulated on the anode target 41 through heat exchange.

[0147] In a specific application scenario, the bearing assembly 5 further includes a coolant inlet 53, located on the side of the bearing assembly 5 away from the cathode assembly 2, and connected to the hollow channel of the shaft 51. This allows the cooling medium to enter the hollow channel of the shaft 51, flow axially through it, and then exit from the other end, forming a circulating cooling system. Thus, the hollow cooling structure of the shaft 51, in conjunction with the heat storage structure 42 near the anode target 41, achieves efficient heat removal and uniform heat dissipation from the target surface.

[0148] In some embodiments, combined with Figure 7 The hollow structure is equipped with a heat dissipation structure 54.

[0149] Furthermore, the heat dissipation structure may include a honeycomb mesh structure and / or a finned structure.

[0150] Therefore, the heat dissipation structure 54 increases the contact area between the cooling medium and the inner wall of the shaft 51, thereby enhancing the heat exchange efficiency.

[0151] In one variation, the heat dissipation structure 54 may also be a corrugated or needle-shaped heat dissipation structure.

[0152] Furthermore, in addition to deionized water, highly efficient thermally conductive coolants such as ethylene glycol aqueous solution can also be used as the cooling medium to adapt to different working environments. Thus, the heat dissipation structure 54 enables the target surface heat to be quickly and evenly dissipated, improving the continuous high-power operation capability of the X-ray tube 100.

[0153] In some embodiments, reference Figure 1 The housing 1 may also have a window 9.

[0154] In some embodiments, X-rays generated by the electron beam bombardment of the anode target 41 penetrate the window 9 radially and radiate outwards, so as to be received and imaged by an external CT detector.

[0155] In some embodiments, the window 9 is a through opening, and the opening contour can be adapted to the CT fan-beam imaging requirements, and can be set as a rectangle, an arc trapezoid or a circle; in multi-channel imaging models, the cathode tube shell 11 can open multiple sets of windows 9 at intervals along the circumference to realize synchronous output of X-rays from multiple angles.

[0156] In actual production, a vacuum transmission window can be embedded inside the window 9. The window and the edge of the opening of the cathode tube shell 11 can be sealed by metal brazing to maintain a high vacuum environment inside the cavity 10 of the shell 1 and prevent external air from seeping in and causing electron beam ionization loss.

[0157] By employing the technical solution of this application, a microwave resonant cavity 31 is arranged along the electron beam transmission path between the cathode assembly 2 and the anode target 41. The microwave resonant cavity 31 is used to perform axial focusing of the electron beam, which effectively improves the peak current intensity and the instantaneous dose of a single pulse. This optimizes the temporal resolution of the X-ray tube 100 and reduces motion artifacts formed during dynamic organ scanning. After axial focusing, the energy distribution of the electron beam is more concentrated when it bombards the anode target 41, resulting in enhanced X-ray output intensity, which meets the high beam power requirements of high-end imaging equipment.

[0158] Furthermore, an axial electromagnetic field is constructed in the electron beam transmission path through the microwave resonant cavity 31, and then axial velocity modulation is applied to the electron beam by matching the phase of the electromagnetic field. Axial focusing and compression are achieved by relying on the velocity difference within the electron beam. The focusing process is smooth and uniform, and there is no phenomenon of electron beam divergence overload. As a result, the peak current intensity of the electron beam pulse can be stably increased, the instantaneous output dose of X-rays can be continuously increased, and the imaging quality under dynamic scanning can be further optimized.

[0159] Furthermore, by employing the X-band, Ku-band, or Ka-band as the operating frequency band of the microwave resonator 31, and setting the electromagnetic field phase modulation range to (-π / 2, 0), precise electron beam focusing and compression are achieved. This frequency band offers concentrated microwave energy and a fast modulation response, avoiding beam divergence issues caused by phase shifts. The focusing parameters have a wider adjustable range, adapting to various clinical scanning conditions and improving the overall imaging stability.

[0160] Furthermore, at least two microwave resonant cavities 31 are arranged in series along the electron beam propagation direction, and the electron beam is axially focused step by step by the multi-stage microwave resonant cavities 31. This can significantly increase the upper limit of the peak current of the electron beam, distribute the power load of a single microwave resonant cavity 31, and extend the service life of the microwave resonant cavity 31. It can also finely adjust the electron beam pulse waveform through multi-stage segmented modulation to adapt to the differentiated dose requirements of different clinical scenarios.

[0161] Furthermore, by adding an electron collecting section 32 downstream of the microwave resonant cavity 31 along the electron beam transmission path, backscattered electrons generated by the anode target 41 are efficiently captured. This avoids backscattered electrons bombarding the microwave resonant cavity 31 and cathode, preventing high-temperature losses, and also eliminates interference from backscattered electrons on the microwave field within the microwave resonant cavity 31. This maintains the stable focusing capability of the microwave resonant cavity 31 for a long time, extending the overall service life of the X-ray tube.

[0162] Furthermore, by incorporating a focusing structure 33 around the electron beam transmission path, a bidirectional beam modulation mechanism is formed in conjunction with the microwave resonant cavity 31. The microwave resonant cavity 31 is responsible for compressing the axial length of the electron beam, while the focusing structure 33 constrains the radial diffusion of the electron beam. Together, they reduce the focal spot size of the electron beam bombarding the anode target 41, effectively improving the spatial resolution of the X-ray tube 100 and facilitating the clinical identification of small lesions.

[0163] Furthermore, by dividing the focusing structure 33 into a first focusing section 331 and a second focusing section 332 distributed at intervals along the electron beam path, a two-segment structure is adopted to correct the electron beam transmission offset. Compared with single-segment focusing, the correction coverage is larger, which can offset the slight radial offset caused by microwave focusing and stably constrain the electron beam trajectory throughout the entire process.

[0164] It should be understood that the term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this document indicates that the preceding and following related objects are in an "or" relationship. As used herein, unless explicitly stated otherwise, the term "or" covers all possible combinations unless impractical. For example, if a component is declared to include A or B, then unless explicitly stated otherwise or impractical, the component can include A, or B, or A and B. As a second example, if a component is declared to include A, B, or C, then unless explicitly stated otherwise or impractical, the component can include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0165] In the embodiments of this application, "multiple" refers to two or more.

[0166] Relational terms appearing in the embodiments of this application, such as "first," "second," etc., are used only to distinguish an entity or operation from another entity or operation, without requiring or implying any actual relationship or order between these entities or operations. Furthermore, the words "comprising," "having," and "including," and other similar forms, are intended to be equivalent in meaning and are open-ended; one or more items following any of these words do not imply an exhaustive list of such items or that they are limited to only the listed items. Exemplary embodiments have been disclosed in the drawings and specification. However, many variations and modifications can be made to these embodiments. Therefore, although specific terminology is used, it is used only in a general and descriptive sense and not for limiting purposes.

[0167] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A microwave-focused X-ray tube, characterized in that, include: The housing includes a receiving cavity; A cathode assembly, at least partially housed in the receiving cavity, the cathode assembly being used to emit an electron beam; An electromagnetic focusing system includes at least one microwave resonant cavity located within the receiving cavity. The at least one microwave resonant cavity is disposed on the electron beam transmission path between the cathode assembly and the anode assembly. The microwave resonant cavity performs axial focusing of the electron beam, where the axial direction is the transmission direction of the electron beam. An anode assembly, including an anode target, is located within the receiving cavity, and the electron beam, after passing through the electromagnetic focusing system, bombards the anode target to generate X-rays.

2. The X-ray tube according to claim 1, characterized in that, The microwave resonant cavity is adapted to establish an axial electromagnetic field in the electron beam transmission path, the phase of which is configured to apply axial velocity modulation to the electron beam so as to compress and focus the electron beam in the axial direction.

3. The X-ray tube according to claim 2, characterized in that, The microwave resonant cavity operates in the X-band, Ku-band, or Ka-band; and / or the phase modulation range of the electromagnetic field is (-π / 2, 0).

4. The X-ray tube according to claim 1, characterized in that, The electromagnetic focusing system includes at least two microwave resonant cavities, which are connected in series along the transmission direction of the electron beam.

5. The X-ray tube according to claim 1 or 4, characterized in that, The cavity wall of the microwave resonant cavity is arc-shaped or rectangular; and / or The cavity wall of the microwave resonant cavity is made of a high-conductivity material; and / or The cavity wall of the microwave resonant cavity is made of oxygen-free copper or diffused copper.

6. The X-ray tube according to claim 1, characterized in that, The microwave resonant cavity has a microwave power feed inlet on its cavity wall. An external microwave power source feeds microwave energy into the microwave resonant cavity through a waveguide via the microwave power feed inlet.

7. The X-ray tube according to claim 1, characterized in that, Along the transmission direction of the electron beam, an electron collecting section is provided downstream of the microwave resonant cavity, which is used to collect backscattered electrons reflected from the anode target.

8. The X-ray tube according to claim 1, characterized in that, The electromagnetic focusing system also includes: A focusing structure is disposed around the transmission path of the electron beam, and the focusing structure is used to focus the electron beam.

9. The X-ray tube according to claim 8, characterized in that, The housing includes a cathode tube shell, the microwave resonant cavity is located in the cathode tube shell, and the focusing structure is sleeved on the outer periphery of the cathode tube shell.

10. The X-ray tube according to claim 8, characterized in that, Along the transmission path of the electron beam, the focusing structure and the microwave resonant cavity are arranged alternately.

11. The X-ray tube according to claim 8, characterized in that, The focusing structure includes: The first focusing section and the second focusing section are arranged at intervals along the transmission direction of the electron beam.

12. The X-ray tube according to claim 11, characterized in that, Along the transmission direction of the electron beam, the microwave resonant cavity is located between the first focusing section and the second focusing section.

13. The X-ray tube according to claim 11, characterized in that, The first focusing section and the second focusing section each include a magnetic focusing coil, which is adapted to change the magnetic field strength by adjusting the current in order to achieve radial focusing of the electron beam.

14. The X-ray tube according to claim 13, characterized in that, The second focusing section also integrates two sets of mutually perpendicular deflection coils to deflect the electron beam in the x and y directions to form a flying focus, wherein the x and y directions are two mutually perpendicular radial directions.

15. The X-ray tube according to claim 1, characterized in that, The cathode assembly includes: Electron emitter, used to emit electron beams; The cathode focusing section is sleeved around the electron emitter and is used to initially focus the electron beam.

16. The X-ray tube according to claim 15, characterized in that, The electron emitter uses tungsten and its alloys or oxide cathode materials; and / or The electron emitter is a flat filament structure or a spiral filament structure; and / or The cathode assembly also includes an insulating support portion, through which the electron emitter is connected to the housing.

17. The X-ray tube according to claim 1, characterized in that, Also includes: A bearing assembly includes a shaft that extends axially through the anode target and is fixedly connected to both ends of the housing; The anode target rotates about the shaft.

18. The X-ray tube according to claim 17, characterized in that, The bearing assembly also includes: A bushing is fitted around the outer periphery of the shaft. The anode target is fixedly connected to the outer peripheral surface of the bushing. There is a non-zero gap between the bushing and the shaft. The non-zero gap is used to form a filling cavity, which is filled with liquid metal.

19. The X-ray tube according to claim 18, characterized in that, The shaft and the bushing, along with the liquid metal filling the filling cavity, form a liquid metal bearing structure; and / or The shaft and the bushing are provided with herringbone and / or figure-eight pattern textures on their corresponding wall surfaces.

20. The X-ray tube according to claim 17, characterized in that, The shaft has a hollow structure for the cooling medium to pass through.

21. The X-ray tube according to claim 20, characterized in that, The hollow structure contains a heat dissipation structure, including a honeycomb mesh structure and / or a finned structure.

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