X-ray tube cathode arrangement based on photoelectric effect and field effect

Abstract

The application discloses an X-ray tube cathode device based on photoelectric effect and field effect, and relates to the technical field of electron tubes / discharge devices. The device comprises a concave curved functional layer, a nanometer bristle array grown on a material layer and an ultrathin photocathode material layer sequentially arranged on the surface of the concave curved functional layer; a pixelated control layer is arranged correspondingly and closely below the concave curved functional layer and comprises a plurality of independently programmable pixel electrodes, each pixel electrode corresponds to an emission area of the concave curved functional layer and is used for independently adjusting the potential of the area; an integrated support layer is used for providing mechanical support and vacuum sealing for the concave curved functional layer and the pixelated control layer; and a control system is used for receiving a beam current feedback signal and independently driving each pixel electrode according to the beam current feedback signal, automatically adjusting the electrode voltage of a specific area, changing a local electric field and realizing real-time adaptive shaping of an electron beam, so as to realize dynamic focusing and beam shaping without inertia.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of electron tube / discharge device technology, and more particularly to X-ray tube cathode devices based on photoelectric effect and field effect. Background Technology

[0002] X-ray tubes are core devices in fields such as medical diagnosis, industrial inspection, and scientific research analysis. Their performance depends on the photoelectric effect of traditional photocathodes: specific wavelength light irradiates the photocathode (materials such as metals, alkali metals, alkali metal compounds, and semiconductors) to excite electrons, which are then accelerated to bombard the target material to generate X-rays.

[0003] However, due to the inherent characteristics of photocathode materials, traditional solutions still have many drawbacks, such as low quantum efficiency and energy utilization, poor uniformity of photoelectron emission, poor beam monochromaticity, passive focusing control, weak anti-interference, time response lag, and low system integration. These directly result in X-ray tubes being unable to simultaneously meet the requirements of high brightness, small focal spot, compact size, and high time resolution.

[0004] These shortcomings are particularly prominent in the medical field. For example, low quantum efficiency requires higher radiation doses, increasing the exposure risk to patients (especially children and pregnant women); insufficient time response leads to blurred dynamic organ imaging and inaccurate lesion localization during interventional surgery; and poor beam quality limits the detection rate of early micro-lesions.

[0005] In summary, the performance bottleneck of traditional photocathodes has become the key to breakthroughs in high-end X-ray tube applications, and innovative improvements are urgently needed. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of traditional photocathode X-ray tubes in terms of photocathode properties, and to provide an X-ray tube cathode device based on the photoelectric effect and field effect, which can meet the application scenarios where there are high requirements for the brightness, focal size, and temporal resolution of photocathode X-ray tubes. Examples include: high spatial resolution micro-CT and non-destructive testing; dynamic and ultrafast time-resolved X-ray imaging; and compact / programmable industrial and space application X-ray sources.

[0007] In a first aspect, embodiments of the present invention provide an X-ray tube cathode device based on the photoelectric effect and field effect, comprising:

[0008] A concave curved functional layer, on the surface of which an ultrathin photocathode material layer and a nano-bristle array grown on the ultrathin photocathode material layer are sequentially stacked to form a photoelectric-field synergistic emitter;

[0009] A pixelation control layer is attached to the concave surface functional layer below it and includes multiple independently programmable pixel electrodes. Each pixel electrode corresponds to an emission region of the concave surface functional layer and is used to independently adjust the potential of that region.

[0010] An integrated support layer is used to provide mechanical support and vacuum sealing for the concave surface functional layer and pixelation control layer, and is connected to an external drive circuit.

[0011] The control system, connected to the pixelation control layer, is used to receive beam feedback signals and independently drive each pixel electrode according to the beam feedback signals to achieve real-time adaptive shaping of the electron beam.

[0012] In a preferred embodiment, the radius of curvature of the concave surface functional layer is 1mm to 5mm, and the surface shape is a spherical or aspherical optical surface, used to provide geometric pre-focusing and aberration pre-correction of the electron beam.

[0013] In a preferred embodiment, the ultrathin photocathode material layer has a thickness of less than 50 nm, and the material includes alkali metal compounds or III-V semiconductors. The nanofiber array is zinc oxide nanowires or carbon nanotubes, and the areal density of the zinc oxide nanowires or carbon nanotubes is 10-50 wires / µm², with a diameter of less than 50 nm, which is used to achieve synergistic enhancement of photoelectric excitation and field tunneling.

[0014] In a preferred embodiment, the pixel electrodes are arranged in a hexagonal close-packed array, and each pixel electrode includes at least one central electrode and a plurality of annular electrodes arranged around the central electrode. The electrodes are isolated from each other by insulating trenches, and the electrode material is a transparent conductive oxide.

[0015] In a preferred embodiment, the control system includes:

[0016] The beam profile monitoring module is used to acquire the two-dimensional current density distribution and divergence angle information of the electron beam in real time, as the measured beam shape.

[0017] An adaptive control algorithm module is used to receive the measured beam shape and, based on the difference between the measured beam shape and the preset target beam shape, calculate the voltage compensation value required for each pixel electrode through an iterative optimization algorithm.

[0018] The multi-channel driving module is used to apply corresponding independent voltages to each pixel electrode according to the voltage compensation value, change the local electric field distribution, and adjust the electron trajectory to achieve electron beam focusing, deflection, astigmatism correction, and shape programming.

[0019] In a preferred embodiment, the adaptive control algorithm module supports at least one of the following control modes:

[0020] Dynamic aberration compensation mode is used to correct emission distortion caused by material inhomogeneity or thermal deformation;

[0021] Programmable beam shaping modes for generating ring-shaped, multi-spot, or linear electron beams;

[0022] The emission homogenization mode enhances extraction efficiency by adjusting the local electric field, which is used to compensate for the uneven distribution of quantum efficiency in the photocathode material.

[0023] In a preferred embodiment, a pulsed laser source is also included, the emitted light of which is incident from the back side of the concave surface, and its wavelength matches the photoelectric response peak of the ultrathin photocathode material layer. The pulsed laser source and the pixel electrode work together in the following timing sequence:

[0024] Each pixel electrode is preloaded with a voltage lower than the electron emission threshold; when the pulsed laser arrives, a fast voltage pulse is synchronously applied to the corresponding pixel electrode, causing the local electric field to rise instantaneously to above the emission threshold;

[0025] After the pulsed laser ends, the rapid voltage pulse returns to zero, and the voltage drops back down.

[0026] In a preferred embodiment, a heterojunction or Schottky contact is formed between the nanofiber array and the ultrathin photocathode material layer to enhance the local electric field and promote thermal electron tunneling, thereby improving quantum efficiency and energy concentration.

[0027] In a preferred embodiment, the integrated support layer is made of a metal material with a thermal expansion coefficient that matches that of the concave curved functional layer substrate, and vacuum sealing and high-pressure isolation are achieved through laser sealing.

[0028] Secondly, embodiments of the present invention also provide an X-ray tube, including an X-ray tube cathode device as described in any of the above claims, and an anode target disposed opposite to the X-ray tube cathode device, wherein an adjustable electron optical path is formed between the X-ray tube cathode device and the anode target to support dynamic focusing and scanning imaging.

[0029] Compared with the prior art, the present invention achieves the following beneficial effects:

[0030] (1) This invention pioneers a photoelectric effect and field effect synergistic enhancement mechanism, combined with a concave structure design, to enhance the current density through nano-field enhancement. The concave geometry provides natural pre-focusing, transforming the divergent surface light source into a converging point light source, compressing the electron divergence angle from the source, and significantly improving the brightness of photoelectron emission. An ultra-thin photocathode layer is used to reduce the scattering loss of electrons in the body. Combined with the field enhancement effect to promote thermal electron tunneling, the energy distribution is concentrated, breaking through the traditional limitations in the generation mechanism. The monochromaticity index is better than 0.3eV.

[0031] (2) This invention overturns the traditional passive correction mode, achieves natural pre-focusing with curved surface structure, and integrates pixel electrodes on the cathode surface to replace the bulky external magnetic / electric lens. The electric field can be locally controlled in real time to achieve inertial dynamic focusing and beam shaping. The focusing control is more proactive and flexible. It integrates the dual physical mechanisms of photoelectric effect and field emission, breaks through the material intrinsic limitation of single photoelectric effect, and improves the quantum efficiency by more than an order of magnitude with the help of the local field enhancement effect of nano-tip.

[0032] (3) This invention breaks through the bottleneck of fixed performance of traditional photocathodes. Through the combination of structural design and intelligent algorithm, it realizes the function of adaptive cathode: dynamically optimizes the focal spot size and shape to meet the high resolution requirements of industrial CT, micro-focal imaging and other scenarios; it can compensate for the emission unevenness caused by material differences and performance degradation in real time, eliminate aberrations and other problems, and ensure long-term stability; it supports programmable multimodal output and can flexibly adjust the emission area and pulse form to meet diverse application requirements. Attached Figure Description

[0033] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0034] Figure 1 This is a schematic diagram of the concave curved surface functional layer structure of an X-ray tube cathode device based on photoelectric effect and field effect provided in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the integrated support layer structure of an X-ray tube cathode device based on photoelectric effect and field effect provided in an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the pixelated control layer structure of an X-ray tube cathode device based on photoelectric effect and field effect provided in an embodiment of the present invention;

[0037] Figure 4 This is a three-dimensional structural view of the X-ray tube cathode device based on the photoelectric effect and field effect provided in the embodiment of the present invention;

[0038] Figure 5 This is a flowchart of the operation of an X-ray tube cathode device based on photoelectric effect and field effect provided in an embodiment of the present invention;

[0039] Figure 6 This is a functional diagram of the X-ray tube cathode device based on the photoelectric effect and field effect provided in the embodiment of the present invention. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0041] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations (or steps) can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but it may also have additional steps not included in the figures. The process may correspond to a method, function, procedure, subroutine, subroutine, etc.

[0042] Example 1

[0043] like Figures 1-4 The figures shown are a schematic diagram and a three-dimensional view of the X-ray tube cathode device based on the photoelectric effect and field effect provided in Embodiment 1 of the present invention. Figures 1-4 As shown, the device includes a concave curved surface functional layer, a pixelation control layer, an integrated support layer, and a control system. These components work together to achieve efficient electron beam emission and adaptive control. The specific structure is as follows:

[0044] In a preferred embodiment, the concave curved functional layer comprises, from bottom to top, a transparent substrate, an ultrathin photocathode material layer, and a nanofiber array, constituting a photoelectric-field synergistic emitter, specifically:

[0045] The transparent substrate is made of sapphire or quartz glass and processed into a concave spherical or aspherical optical surface with a curvature radius of 1mm to 20mm (preferably 5mm). This curvature design can provide sufficient electron beam pre-focusing force and avoid the increased difficulty of voltage control due to excessive curvature. The back of the substrate is equipped with a microchannel heat dissipation structure (activated when the working power is ≥10W), and the substrate temperature is controlled to ≤50℃ by circulating fluorinated oil cooling medium to prevent thermal deformation from affecting the curvature stability of the surface.

[0046] The ultrathin photocathode material layer is deposited on the surface of a transparent substrate using a vacuum evaporation process, with a thickness of 20-50nm (preferably 30nm). The material is selected from alkali metal compounds such as antimony cesium bromide or III-V semiconductors such as GaAs. This thickness design takes into account both photoelectric response efficiency and electron transport efficiency, shortening the electron scattering path within the layer and reducing the transport time to ≤50fs, thus laying the foundation for improving monochromaticity.

[0047] The nanofiber array is grown on the surface of an ultrathin photocathode layer using hydrothermal synthesis or chemical vapor deposition (CVD). The material is zinc oxide nanowires or carbon nanotubes with an areal density of 10-50 nanofibers / µm² (preferably 20 nanofibers / µm²) and a diameter of 20-50nm (preferably 30nm). Before growth, the photocathode layer surface is cleaned with argon plasma (power 50-100W, time 5-10min) to improve the adhesion between the array and the substrate. After growth, it is subjected to low-temperature annealing at 200℃ for 1h to enhance the mechanical hardness of the array and prevent it from collapsing. The nanofibers form Schottky contacts with the ultrathin photocathode layer, with a contact barrier height of 0.2-0.5eV, which can significantly enhance the local electric field and promote thermal electron tunneling.

[0048] In summary, the core design logic of this concave curved surface functional layer is to change the traditional planar photocathode into a concave structure, providing a natural pre-focusing function. Combined with the field enhancement effect of the nanofiber array, it realizes the transformation from a divergent surface light source to a converging point light source, compressing the electron divergence angle from the source.

[0049] In a preferred embodiment, a pixelation control layer is disposed adjacent to and below the concave curved surface functional layer, and its specific structure is as follows: Figure 3 As shown, it includes multiple independently programmable pixel electrodes, each corresponding to an emission region of the concave curved surface functional layer, used to independently adjust the potential of that region. The specific structure is as follows:

[0050] The pixel electrodes are made of transparent conductive oxide materials such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO), with a thickness of 100-200nm. These electrodes are arranged in a hexagonal close-packed array (1 pixel in the center, 6 pixels in the first ring, 12 pixels in the second ring, for a total of 19 pixels). Each electrode is isolated from the others by silicon oxide insulating trenches with a width of 5-10µm (thickness of 500nm) to prevent leakage under high voltage.

[0051] The voltage adjustment range of the pixel electrode is -200V to 0V, with a minimum adjustment step of 0.1V. The electron beam deflection angle is linearly related to the pixel voltage difference. For every 1V increase in voltage difference, the deflection angle increases by 0.1-0.5 degrees. During focusing, the center pixel voltage is set to be 5V-10V higher than the edge pixels to form a concave equipotential surface, thereby achieving electron beam focusing.

[0052] Each pixel electrode is connected to a silicon via of the integrated support layer via an independent metal lead. The lead is preferably made of a titanium / gold composite layer to ensure the independence and stability of signal transmission.

[0053] In a preferred embodiment, an integrated support layer is provided to offer mechanical support for the concave curved surface functional layer and the pixelation control layer. This layer connects to the external driving circuit and enables connection and vacuum sealing. The core components include a three-dimensional vertical interconnect system, an integrated microchannel heat sink, and heat dissipation channels. The specific design is as follows:

[0054] The main body of the integrated support layer is a metal encapsulation base, preferably made of Kovar alloy or oxygen-free copper, with a thermal expansion coefficient difference between it and the sapphire / quartz glass substrate of ≤5×10⁻⁶. -6 The temperature is set at ℃ to avoid structural stress damage caused by temperature changes. It is fixed to the transparent substrate by pulsed laser sealing. The support layer integrates high-voltage transmission lines and signal feedback lines. The lines are made of polyimide insulation coating with a withstand voltage rating of ≥200kV to prevent high-voltage breakdown.

[0055] The three-dimensional vertical interconnect system includes through-silicon vias (TSVs) and solder balls. The TSVs are the core interconnect channels between pixel electrodes and external circuits, fabricated in a silicon substrate embedded within a support layer using deep silicon etching. The internal copper filler is electroplated to form vertical conductive channels. Each TSV corresponds one-to-one with an independent pixel electrode in the pixelation control layer, enabling individual addressing and high-voltage signal transmission for each pixel, thus avoiding crosstalk between adjacent channels. Solder balls are located on the side of the integrated support layer away from the concave functional layer and are electrically connected to the bottom of the copper filler layer of the TSVs. High-melting-point, low-resistivity gold-tin alloy solder balls are arranged in the TSV array to form corresponding pads. The solder balls are used for flip-chip bonding to the PCB board of the external driving circuit to ensure rapid voltage signal transmission and reliable mechanical connections.

[0056] The integrated microchannel heat sink is embedded in the integrated support layer on one side near the concave curved functional layer and is tightly attached to the back of the transparent substrate. The heat sink is made of oxygen-free copper and is fabricated using microfabrication technology to create an array of microchannels, which can quickly dissipate the heat generated by the transparent substrate and pixelated control layer.

[0057] The heat dissipation channel, serving as the connection path between the microchannel heat sink and the external cooling system, is located on the side of the integrated support layer and is sealed to the inlet and outlet of the microchannel heat sink via brazing. Preferably, the channel is wrapped with heat insulation cotton to reduce heat diffusion to the outside of the vacuum chamber and prevent condensation. The cooling medium enters the microchannel heat sink through the inlet channel, absorbs heat, and then flows back to the external cooler through the outlet channel, forming a closed-loop heat dissipation circuit.

[0058] In a preferred embodiment, the control system, acting as the "brain" of electron beam control, achieves adaptive shaping of the electron beam through closed-loop feedback. It receives beam feedback signals and independently drives each pixel electrode based on these signals, thus realizing real-time adaptive shaping of the electron beam. Specifically, this includes:

[0059] The beam profile monitoring module uses a 16×16 array-divided anode or fluorescent screen + CCD camera, with a signal acquisition frequency ≥1kHz and spatial resolution ≤1µm. It is used to acquire the two-dimensional current density distribution and divergence angle information of the electron beam in real time as the measured beam morphology.

[0060] An adaptive control algorithm module is used to receive the above-mentioned measured beam shape and, based on the difference between the measured beam shape and the preset target beam shape, calculate the voltage compensation value required for each pixel electrode through an iterative optimization algorithm.

[0061] The multi-channel driving module is used to apply corresponding independent voltages to each pixel electrode according to the above voltage compensation amount, change the local electric field distribution, adjust the electron trajectory, and realize the focusing, deflection, astigmatism correction and shape programming of the electron beam.

[0062] In a preferred embodiment, the adaptive control algorithm supports at least one of the following control modes:

[0063] Dynamic aberration compensation mode is used to correct emission distortion caused by material inhomogeneity or thermal deformation;

[0064] Programmable beam shaping mode generates ring-shaped, multi-spot, or linear electron beams through pre-programmed voltage patterns or user-defined two-dimensional coordinate matrices;

[0065] In the emission homogenization mode, when local dimming of the beam is detected, the pixel voltage in the corresponding area is increased (up to 10V) to compensate for the uneven distribution of quantum efficiency of the photocathode material.

[0066] In a preferred embodiment, to achieve extremely high time response characteristics, the device also includes a pulsed laser source (supporting components). The emitted light is incident from the back side of the transparent substrate of the concave curved functional layer, and a laser with a wavelength of 405nm (blue-violet) and a pulse width of <100fs-10ps is selected. The laser wavelength matches the photoelectric response peak of the ultrathin photocathode material layer, and the pulsed laser source and the pixel electrode work together in the following timing sequence to achieve "emission timing gating":

[0067] Each pixel electrode is preloaded with a voltage lower than the electron emission threshold, so that the emitter is in a ready-to-emit state; when the pulsed laser arrives, a fast voltage pulse is synchronously applied to the corresponding pixel electrode, so that the local electric field is instantaneously raised to above the emission threshold.

[0068] After the pulsed laser ends, the fast voltage pulse returns to zero and the voltage drops back; wherein, the laser pulse arrives 0~5ps earlier than the voltage pulse to ensure that the timing of electron excitation and electric field extraction is matched; the rise time of the voltage pulse is ≤1ns and the fall time is ≤2ns to ensure that the width of the electron pulse is consistent with the width of the laser pulse.

[0069] Through the aforementioned timing gating, the effective time window for electron emission is strictly limited to the duration of the laser pulse, making the width of the output electron pulse essentially determined by the laser pulse width. This fundamentally breaks through the limitation of carrier lifetime on time response in traditional photocathode materials, improving the temporal resolution of electron emission from the nanosecond level to the picosecond or even femtosecond level, providing a key foundation for advanced applications such as ultrafast time-resolved X-ray imaging.

[0070] In a preferred embodiment, this device achieves electron beam trajectory control through the synergistic effect of a vertical extraction field and a transverse control field. The specific process is as follows:

[0071] Establish a vertical extraction field: All pixel electrodes are set with a common base voltage (e.g., -100V), which, together with the anode (0V), forms a main extraction electric field pointing from the cathode surface to the anode, responsible for pulling electrons out of the surface;

[0072] Introducing a lateral control field: When regulation is required, a small voltage difference is formed between the target pixel and its neighboring pixels (e.g., pixel A changes from -100V to -99V, while pixel B remains at -100V), causing the equipotential surface to tilt. When electrons are emitted, they are subjected to a lateral electric field component, and their trajectory deflects toward the electrode region with a higher voltage.

[0073] By coordinating the voltage distribution across the entire pixel array, three core functions can be achieved:

[0074] Astigmatism correction: Enhances the pixel voltage on both sides of the divergence direction, forming an inward squeezing electric field;

[0075] Focusing: Gradually increase the pixel voltage from the edge to the center to form a concave equipotential surface, causing the edge electrons to deflect towards the axis;

[0076] Deflection: Makes the overall pixel voltage on one side higher than that on the other side, and the electron beam deflects to the side with lower voltage.

[0077] Based on the above embodiments, the present invention achieves the following beneficial effects:

[0078] (1) This invention pioneers a synergistic enhancement mechanism of photoelectric effect and field effect, combined with a concave structure design. The current density is increased through nano-field enhancement, and the concave geometry provides natural pre-focusing, transforming the divergent surface light source into a converging point light source. This compresses the electron divergence angle from the source and significantly improves the brightness of photoelectron emission. An ultra-thin photocathode layer is used to reduce the scattering loss of electrons in the body. Combined with the field enhancement effect, thermal electron tunneling is promoted to achieve concentrated energy distribution. This breaks through the traditional limitations in terms of generation mechanism, and the monochromaticity index is better than 0.3eV.

[0079] (2) This invention overturns the traditional passive correction mode, achieves natural pre-focusing with curved surface structure, and integrates pixel electrodes on the cathode surface to replace the bulky external magnetic / electric lens. The electric field can be locally controlled in real time to achieve inertial dynamic focusing and beam shaping. The focusing control is more proactive and flexible. It integrates the dual physical mechanisms of photoelectric effect and field emission, breaks through the material intrinsic limitation of single photoelectric effect, and improves the quantum efficiency by more than an order of magnitude with the help of the local field enhancement effect of nano-tip.

[0080] (3) This invention breaks through the bottleneck of fixed performance of traditional photocathodes. Through the combination of structural design and intelligent algorithm, it realizes the function of adaptive cathode: dynamically optimizes the focal spot size and shape to meet the high resolution requirements of industrial CT, micro-focal imaging and other scenarios; real-time compensation for emission unevenness caused by material differences and performance degradation, eliminates aberrations and ensures long-term stability; supports programmable multimodal output, and can flexibly adjust the emission area and pulse form to meet diverse application requirements.

[0081] Example 2

[0082] The present invention provides an X-ray tube according to Embodiment 2, comprising the X-ray tube cathode device as described in Embodiment 1, and further comprising an anode assembly, a vacuum cavity, an electron optical path control unit, and an X-ray emission window, constituting a complete X-ray generation system, the specific structure of which is as follows:

[0083] Anode assembly: It is set opposite to the cathode device. The anode target material is tungsten (W), molybdenum (Mo) or rhenium-tungsten alloy. The target surface is a curved surface or a flat surface that is adapted to the concave surface of the cathode (to adapt to the pre-focused electron beam). The back of the target material is integrated with a water-cooled or oil-cooled heat dissipation structure with a heat dissipation power of ≥500W, which is used to quickly dissipate the heat generated by electron bombardment and avoid target material melting or performance degradation.

[0084] Vacuum cavity: formed by laser sealing of an integrated support layer and a metal shell, with a vacuum level ≤1×10⁻⁶. -6 Pa; the inner wall of the cavity is coated with a graphite anti-secondary electron emission coating to avoid electron scattering interference with the electron beam trajectory; the cavity is reserved with a vacuum interface for connecting a vacuum maintenance system (such as an ion pump) to ensure vacuum stability during long-term operation.

[0085] Electron optics path control unit: A 0-100KV adjustable high voltage is applied between the cathode device and the anode assembly to form the main accelerating electric field; an auxiliary focusing electrode is provided near the anode to coordinate with the cathode pixel electrode to control the electron beam trajectory and adapt to different imaging distance requirements; by adjusting the high voltage value and the pixel electrode voltage, the electron beam acceleration energy and the focal size can be linked and controlled.

[0086] X-ray exit window: Located in the vacuum cavity corresponding to the radiation direction of the anode target, it is made of beryllium (Be) or borosilicate glass, with a window thickness of 100-300µm (selected according to X-ray energy requirements) to reduce X-ray attenuation and ensure the output dose and purity.

[0087] Combination Figure 5 and Figure 6 As shown, the core workflow of this X-ray tube is as follows:

[0088] System startup: The vacuum chamber is evacuated to the set vacuum level, and the cooling system is activated to reduce the temperature of the cathode substrate and anode target to the working range;

[0089] Triggering and Emission: The pulsed laser is incident from the back side of the cathode, exciting the ultrathin photocathode layer to generate photoelectrons; and the pulsed laser source and the pixel electrode work together in the following timing sequence:

[0090] Each pixel electrode is preloaded with a voltage lower than the electron emission threshold; when the pulsed laser arrives, a fast voltage pulse is synchronously applied to the corresponding pixel electrode, causing the local electric field to rise instantaneously to above the emission threshold;

[0091] When the pulsed laser ends, the rapid voltage pulse returns to zero, and the voltage drops back down;

[0092] Electron beam control: The beam profile monitoring module collects electron beam information in real time, and the control system calculates the voltage adjustment amount through an adaptive algorithm to drive the pixel electrode to adjust the local electric field, thereby realizing electron beam focusing, astigmatism correction and shape shaping.

[0093] Acceleration and Radiation: The modulated electron beam is accelerated by a high-voltage electric field and then bombards the anode target to generate X-rays; by adjusting the cathode control parameters and the anode high voltage, the focal size (adjustable from 1-100µm), radiation dose and pulse frequency of the X-rays can be dynamically changed.

[0094] Closed-loop maintenance: During long-term operation, if the quantum efficiency drops by 20% or more, the control system will automatically activate the emission homogenization mode and maintain performance stability through voltage compensation.

[0095] Based on the above embodiments, the present invention achieves the following beneficial effects:

[0096] (1) This invention pioneers a synergistic enhancement mechanism of photoelectric effect and field effect, combined with a concave structure design. The current density is increased through nano-field enhancement, and the concave geometry provides natural pre-focusing, transforming the divergent surface light source into a converging point light source. This compresses the electron divergence angle from the source and significantly improves the brightness of photoelectron emission. An ultra-thin photocathode layer is used to reduce the scattering loss of electrons in the body. Combined with the field enhancement effect, thermal electron tunneling is promoted to achieve concentrated energy distribution. This breaks through the traditional limitations in terms of generation mechanism, and the monochromaticity index is better than 0.3eV.

[0097] (2) This invention overturns the traditional passive correction mode, achieves natural pre-focusing with curved surface structure, and integrates pixel electrodes on the cathode surface to replace the bulky external magnetic / electric lens. The electric field can be locally controlled in real time to achieve inertial dynamic focusing and beam shaping. The focusing control is more proactive and flexible. It integrates the dual physical mechanisms of photoelectric effect and field emission, breaks through the material intrinsic limitation of single photoelectric effect, and improves the quantum efficiency by more than an order of magnitude with the help of the local field enhancement effect of nano-tip.

[0098] (3) Breaking through the bottleneck of fixed performance of traditional photocathodes, the adaptive cathode function is realized through the combination of structural design and intelligent algorithm: dynamically optimizing the focal spot size and shape to meet the high resolution requirements of industrial CT, micro-focal imaging and other scenarios; real-time compensation for emission unevenness caused by material differences and performance degradation, eliminating aberrations and ensuring long-term stability; supporting programmable multimodal output, and flexibly adjusting the emission area and pulse form to meet diverse application requirements.

[0099] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0100] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that various variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An X-ray tube cathode device based on the photoelectric effect and field effect, characterized in that, include: A concave curved functional layer, on the surface of which an ultrathin photocathode material layer and a nano-bristle array grown on the ultrathin photocathode material layer are sequentially stacked to form a photoelectric-field synergistic emitter; A pixelation control layer is attached to the concave surface functional layer below it and includes multiple independently programmable pixel electrodes. Each pixel electrode corresponds to an emission region of the concave surface functional layer and is used to independently adjust the potential of that region. An integrated support layer is provided to provide mechanical support and vacuum sealing for the concave surface functional layer and the pixelation control layer, and is connected to an external drive circuit. The control system, connected to the pixelation control layer, is used to receive beam feedback signals and independently drive each pixel electrode according to the beam feedback signals to achieve real-time adaptive shaping of the electron beam.

2. The X-ray tube cathode device according to claim 1, characterized in that, The concave surface functional layer has a radius of curvature of 1mm to 5mm and a surface shape of spherical or aspherical optical surface, which is used to provide geometric prefocusing and aberration precorrection of the electron beam.

3. The X-ray tube cathode device according to claim 1, characterized in that, The ultrathin photocathode material layer has a thickness of less than 50 nm and includes alkali metal compounds or III-V semiconductors. The nanofiber array is made of zinc oxide nanowires or carbon nanotubes, with an areal density of 10-50 nanowires / µm² and a diameter of less than 50 nm, used to achieve synergistic enhancement of photoelectric excitation and field tunneling.

4. The X-ray tube cathode device according to claim 1, characterized in that, The pixel electrodes are arranged in a hexagonal close-packed array. Each pixel electrode includes at least one central electrode and multiple annular electrodes surrounding the central electrode. The electrodes are isolated from each other by insulating trenches. The electrodes are made of transparent conductive oxide.

5. The X-ray tube cathode device according to claim 4, characterized in that, The control system includes: The beam profile monitoring module is used to acquire the two-dimensional current density distribution and divergence angle information of the electron beam in real time, as the measured beam shape. An adaptive control algorithm module is used to receive the measured beam shape and, based on the difference between the measured beam shape and the preset target beam shape, calculate the voltage compensation value required for each pixel electrode through an iterative optimization algorithm. The multi-channel driving module is used to apply corresponding independent voltages to each pixel electrode according to the voltage compensation value, change the local electric field distribution, and adjust the electron trajectory to achieve electron beam focusing, deflection, astigmatism correction, and shape programming.

6. The X-ray tube cathode device according to claim 5, characterized in that, The adaptive control algorithm module supports at least one of the following control modes: Dynamic aberration compensation mode is used to correct emission distortion caused by material inhomogeneity or thermal deformation; Programmable beam shaping modes for generating ring-shaped, multi-spot, or linear electron beams; The emission homogenization mode enhances extraction efficiency by adjusting the local electric field, which is used to compensate for the uneven distribution of quantum efficiency in the photocathode material.

7. The X-ray tube cathode device according to claim 1, characterized in that, It also includes a pulsed laser source, whose emitted light is incident from the back side of the concave curved surface, and whose wavelength matches the photoelectric response peak of the ultrathin photocathode material layer. The pulsed laser source and the pixel electrode work together in the following timing sequence. Each pixel electrode is preloaded with a voltage lower than the electron emission threshold; when the pulsed laser arrives, a fast voltage pulse is synchronously applied to the corresponding pixel electrode, causing the local electric field to rise instantaneously to above the emission threshold; After the pulsed laser ends, the rapid voltage pulse returns to zero, and the voltage drops back down.

8. The X-ray tube cathode device according to claim 3, characterized in that, The nanofiber array forms a heterojunction or Schottky contact with the ultrathin photocathode material layer to enhance the local electric field and promote thermal electron tunneling, thereby improving quantum efficiency and energy concentration.

9. The X-ray tube cathode device according to claim 1, characterized in that, The integrated support layer is made of a metal material with a thermal expansion coefficient that matches the concave curved surface functional layer substrate, and vacuum sealing and high-pressure isolation are achieved through laser sealing.

10. An X-ray tube, characterized in that, It includes an X-ray tube cathode device as described in any one of claims 1 to 9, and an anode target disposed opposite to the X-ray tube cathode device, wherein an adjustable electron optical path is formed between the X-ray tube cathode device and the anode target to support dynamic focusing and scanning imaging.

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