Ultrafast pulsed x-ray generation apparatus and method based on deflected electric field chopping modulation

Abstract

This invention discloses an ultrafast pulsed X-ray generation device and method based on deflection electric field chopping modulation, mainly solving the technical problems of existing pulsed X-ray generation devices, such as system complexity, large jitter, difficulty in simultaneously meeting the requirements of high time resolution and high repetition rate, or lack of deep integration with the X-ray output structure. The ultrafast pulsed X-ray generation device of this invention includes a vacuum cavity assembly, a DC high-voltage electron gun, an electron beam focusing and collimation assembly, a deflection electrode assembly, a slit chopping assembly, and an X-ray target assembly. The ultrafast pulsed X-ray generation device of this invention has low time jitter, a simplified system, adjustable pulse width and repetition rate over a wide range, programmable time structure, and is easily integrated with the DC high-voltage electron gun and X-ray target assembly.

Description

Technical Field

[0001] This invention relates to an ultrafast pulse X-ray generation device and method, specifically to an ultrafast pulse X-ray generation device and method based on deflection electric field chopping modulation. Background Technology

[0002] Flash X-ray radiography and pulsed X-ray imaging are important diagnostic tools for studying transient processes such as detonation, shock wave propagation, high-speed fracture, high-energy-density material behavior, and complex phase transition dynamics. By releasing high-intensity pulsed X-rays for an extremely short time, the rapid evolution of a sample can be "frozen," obtaining instantaneous structural information on nanosecond or even picosecond timescales. This is of great significance for non-destructive testing of high-end equipment and cutting-edge scientific research.

[0003] The commonly used methods for generating pulsed X-rays mainly include the following: 1. Flash X-ray machine based on high-voltage pulse power Traditional flash X-ray machines typically employ high-voltage pulse power technologies such as Marx generators, pulse forming lines, and low-inductance capacitive-inductive networks. These technologies release electrical energy into X-ray diodes or high-voltage electron guns within tens of nanoseconds or even shorter timeframes, generating high-current electron pulses that bombard high-Z targets to produce pulsed X-rays. While these devices offer advantages in peak power and single-pulse energy, they suffer from the following drawbacks: (1) The pulse width of pulsed X-rays is generally between 20ns and 100ns, and it is difficult to further shorten it to the picosecond level; (2) The repetition frequency is low, and in most cases it is single or low repetition, which makes it difficult to meet the requirements of high repetition measurement. (3) The system relies on multiple high-voltage switches and a complex pulse forming network. The structure is large and the cost is high. The lifespan and jitter performance of the high-voltage switches directly limit the stability and time resolution of the overall system.

[0004] 2. Ultrafast X-ray source based on ultrafast laser-photocathode To achieve shorter pulse widths, a technique exists that uses femtosecond / picosecond lasers to irradiate metal or semiconductor photocathodes to generate ultrashort electron beams, which are then accelerated by DC or radio frequency before being used to strike a target to obtain ultrafast pulsed X-rays. This approach can achieve sub-picosecond or even shorter time resolutions under laboratory conditions, but it also has the following limitations: (1) It requires a highly stable ultrafast laser system and high-quality photocathode fabrication and maintenance, which makes the system complex and costly; (2) If radio frequency acceleration or radio frequency compression is used, the phase jitter between the radio frequency field and the laser pulse will be converted into random drift of the electron beam emission time and the pulse X-ray arrival time, which limits the effective time resolution that the system can achieve. (3) The overall system is sensitive to the environment and operating conditions, which is not conducive to engineering and long-term stable operation.

[0005] 3. Electron beam chopping technology In fields such as ultrafast electron microscopy, "beam choppers" or "beam gates" exist that use electrostatic deflection plates in conjunction with pinholes or slits to time-modulate continuous electron beams, converting them into ultrashort electron pulses for time-resolved imaging. This technology demonstrates that time slicing of continuous electron beams can be achieved by applying a relatively low-amplitude, high-bandwidth deflection voltage without altering the high-voltage acceleration state of the electron gun. However, the following shortcomings still exist: (1) It mainly serves systems such as transmission electron microscopes, targeting electron beams with tens of kiloelectron volts and low average current; (2) It focuses more on electronic image timing control and single-electron / few-electron imaging, and has not made systematic designs for the application of high-dose electron beam to generate pulsed X-rays; (3) A complete engineering scheme for ultrafast pulsed X-ray source that is organically combined with high Z target material and X-ray output structure has not yet been formed.

[0006] In summary, the existing technology still has the following shortcomings: (1) Pulsed X-ray sources mostly rely on high-voltage pulses or radio frequency acceleration, which makes the system complex and jittery, making it difficult to simultaneously meet the requirements of high time resolution and high repetition frequency. (2) Although deflection chopping technology can achieve electron beam time modulation, it mainly stays at the level of electron imaging and has not been deeply integrated with the X-ray output structure. (3) There is a lack of a compact modular device that can realize ultra-short electron pulses by deflecting electric field chopping based on DC high voltage electron gun, and further convert them into ultrafast pulse X-rays.

[0007] Therefore, there is an urgent need for an ultrafast pulsed X-ray generation device and method based on deflection electric field chopping modulation, which can achieve efficient conversion from continuous electron beam to ultrashort electron pulse and then to ultrafast pulsed X-ray without relying on high-voltage pulse power supply and ultrafast laser. At the same time, it has the characteristics of compact structure, adjustable parameters, high repetition frequency and low jitter. Summary of the Invention

[0008] The purpose of this invention is to solve the technical problems of existing pulsed X-ray generating devices, such as system complexity, large jitter, difficulty in simultaneously meeting the requirements of high time resolution and high repetition frequency, or lack of deep integration with the X-ray output structure, and to provide an ultrafast pulsed X-ray generating device and method based on deflection electric field chopping modulation.

[0009] To achieve the above objectives, the technical solution provided by this invention is as follows: An ultrafast pulsed X-ray generating device based on deflection electric field chopping modulation is characterized by: It includes a vacuum chamber assembly, a DC high-voltage electron gun, an electron beam focusing and collimation assembly, a deflection electrode assembly, a slit chopper assembly, and an X-ray target assembly; The DC high-voltage electron gun is installed at one end of the vacuum chamber assembly, with its input end located outside the vacuum chamber assembly and its output end located inside the vacuum chamber assembly. The DC high-voltage electron gun is used to connect to an external high-voltage power supply through its input end to generate a continuous electron beam, accelerate it to a predetermined energy, and then output it through the output end. The electron beam focusing and collimation assembly is installed inside the vacuum cavity assembly, and its input end is set on the output path of the DC electron gun. It is used to adjust the beam waist position, beam spot size and divergence angle of the electron beam so that the electron beam has the expected lateral size and propagation characteristics in the deflection region of the deflection electrode assembly and forms the expected focal spot on the X-ray target assembly. The deflection electrode assembly is installed inside the electron beam focusing and collimation assembly near its input end. It is used to electrically connect with the external synchronization control module through the external deflection modulation drive module, so as to form a time-varying transverse deflection electric field under the control of the synchronization control module and the drive of the deflection modulation drive module, so that the propagation path of the electron beam will periodically deflect laterally over time. The slit chopper assembly is installed inside the electron beam focusing and collimating assembly near its output end, and has an opening on it for the deflected electron beam to pass through, which is used to time-gated the deflected electron beam to generate ultrashort electron pulses. The X-ray target assembly is installed at the other end of the vacuum cavity assembly and is located at the output end of the electron beam focusing and collimation assembly. It is provided with an output window for generating ultrafast pulsed X-rays under ultrashort electron pulse bombardment and outputting them outward through the output window. The output end of the DC high-voltage electron gun, the input and output ends of the electron beam focusing and collimation assembly, the axis of the deflection electrode assembly, the opening center of the slit chopper assembly, and the output window center of the X-ray target assembly are all located on the same straight line.

[0010] Furthermore, the DC high-voltage electron gun includes a DC high-voltage cable, a high-voltage insulator, a cathode support, a high-voltage connector, a cathode electrode, a cathode cover, a grid, a shielding electrode, and an anode electrode; The outer end of the high-voltage insulating component is mounted on one end of the vacuum chamber assembly via a vacuum flange. The DC high-voltage cable is plugged into the outer end of the high-voltage insulator, with one end placed outside the vacuum cavity assembly for connecting to an external high-voltage power supply, and the other end and the inner end of the high-voltage insulator both placed inside the vacuum cavity assembly. The cathode support is installed on the inner end of the high-voltage insulation component via a high-voltage connector. The cathode electrode and the cathode cover are respectively installed on the cathode support, and the cathode cover covers the output end of the cathode electrode. One end of the shielding electrode is mounted on the cathode support and covered outside the high-voltage connector; one end of the gate is connected to one end of the shielding electrode; the shielding electrode and the gate are respectively electrically connected to the DC high-voltage cable through the high-voltage connector. The anode electrode is installed inside the vacuum cavity assembly and is located downstream of the cathode electrode along the electron beam propagation direction, with a predetermined interval between them; the anode electrode is provided with an anode hole to allow the electron beam to pass through and define the exit cross section of the electron beam.

[0011] Furthermore, the accelerating voltage of the DC high-voltage electron gun is 50kV~300kV; The cathode electrode is a thermal cathode or a field emission cathode; One end of the gate is detachably connected to one end of the shielding electrode via a spring-loaded ball-type positioning and latching mechanism; The cathode support is a hollow ceramic column structure, with one end of it installed inside the high-voltage insulation component via a high-voltage connector. The high-voltage insulation component is made of ceramic.

[0012] Furthermore, the electron beam focusing and collimating assembly includes N-level lenses arranged sequentially along the electron beam propagation direction; N≥1; The lens is a magnetic lens, an electrostatic lens, or a magnetic-electrostatic composite lens; The N-level lenses are respectively installed inside the vacuum cavity assembly, and each of them has a through hole at its center; the through holes of the N-level lenses are connected in sequence, and there is a gap between adjacent two-level lenses; One end of the through hole on the lens of the first stage serves as the input end of the electron beam focusing and collimation assembly and is located on the output path of the DC high voltage electron gun; the other end of the through hole on the lens of the last stage serves as the output end of the electron beam focusing and collimation assembly and is located inside the X-ray target assembly. The deflection electrode assembly is installed in a through hole on the first-stage lens, and the slit chopper assembly is installed in a through hole on the last-stage lens.

[0013] Furthermore, N=2; The first-stage lens is a pre-focusing magnetic lens, used to achieve preliminary adjustment of the beam waist position, beam spot size, and divergence angle of the electron beam; the second-stage lens is a focusing magnetic lens, used to achieve further adjustment of the beam waist position, beam spot size, and divergence angle of the electron beam. All lenses of level 2 include a magnetic pole shoe and a magnetic coil mounted on the magnetic pole shoe; The magnetic pole shoe is installed inside the vacuum chamber assembly, and the through hole is located at the center of the magnetic pole shoe.

[0014] Furthermore, the deflection electrode assembly includes two opposing deflection plates installed inside the electron beam focusing and collimating assembly; The front end of the deflection plate adopts a rounded corner transition structure or a multi-segment curved surface contour structure, with a length of 1mm to 20mm, and the distance between the two opposing deflection plates is 0.1mm to 5mm. The two opposing deflection plates are electrically connected to an external synchronization control module via an external deflection modulation drive module, so as to form a time-varying transverse deflection electric field under the control of the synchronization control module and the drive of the deflection modulation drive module.

[0015] Furthermore, the slit chopper assembly includes a slit support mounted inside the electron beam focusing and collimating assembly, and a slit plate detachably mounted on the slit support. The slit plate is provided with a straight slit or a rectangular hole; the width of the straight slit or rectangular hole is 1μm~1mm, and the height is 0.1mm~5mm.

[0016] Furthermore, the X-ray target assembly is made of tungsten, molybdenum, or gold, and has an output window at its rear or side, with a shielding collimation structure at the output window to draw out and limit the propagation direction of ultrafast pulsed X-rays.

[0017] Furthermore, the vacuum chamber assembly includes a first chamber body, a second chamber body, a vacuum pump interface, and a vacuum pump; One end of the first cavity body is connected to one end of the second cavity body via a hinge mechanism, which allows for opening and closing. The DC high-voltage electron gun is installed inside the first cavity body, the electron beam focusing and collimation assembly is installed inside the second cavity body, and the X-ray target assembly is installed at the other end of the second cavity body; The vacuum pump interface is installed on the side wall of the first cavity body, with its inner end placed inside the first cavity body; the vacuum pump is installed on the outer end of the vacuum pump interface.

[0018] Meanwhile, the present invention also provides a method for generating ultrafast pulsed X-rays based on deflection electric field chopping modulation, which uses the aforementioned ultrafast pulsed X-ray generating device based on deflection electric field chopping modulation, and is characterized by including the following steps: Step 1: A continuous electron beam is generated by a DC high-voltage electron gun, accelerated to a predetermined energy, and then output through the output terminal; Step 2: Adjust the beam waist position, beam spot size and divergence angle of the electron beam through the electron beam focusing and collimating assembly so that the electron beam has the expected lateral size and propagation characteristics in the deflection region of the deflection electrode assembly and forms the expected focal spot on the X-ray target assembly. Step 3: Under the control of the synchronization control module and the drive of the deflection modulation drive module, the deflection electrode assembly forms a time-varying transverse deflection electric field, so that the propagation path of the electron beam is periodically deflected transversely over time. Step 4: Time-gated electron beam after deflection is generated by slit chopper assembly to produce ultrashort electron pulses; Step 5: The X-ray target assembly generates ultrafast pulsed X-rays under ultrashort electron pulse bombardment and outputs them outward through the output window.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: 1. No need for high-voltage pulse power or RF compression structure, resulting in low timing jitter and a simplified system. This invention uses a DC high-voltage electron gun to generate a continuous electron beam and achieves time modulation through deflection-slit chopping. It eliminates the need for a high-voltage pulse generator, pulse forming line, or RF compression cavity, and also eliminates the need to consider the phase synchronization problem between the RF field and the laser, thus greatly simplifying the system structure. Furthermore, since the time modulation is achieved jointly by the electronically driven deflection electric field and the geometric slit, its timing jitter is mainly determined by the electronic drive bandwidth and stability, which is significantly lower than that of high-voltage pulse or RF synchronization schemes.

[0020] 2. Pulse width and repetition frequency can be adjusted within a wide range, and the time structure is programmable. By selecting different driving signal waveforms and frequencies, and combining them with slit openings of different widths and shapes, this invention can achieve pulse width adjustment in the nanosecond to picosecond range, as well as repetition frequency adjustment from kHz to MHz or even higher. Simultaneously, it can achieve various time structure outputs, including single pulses, equally spaced pulse trains, double pulses, multi-pulses, and complex unequal-spaced pulse sequences, meeting the different requirements for time resolution, sampling frequency, and time structure in various application scenarios.

[0021] 3. The deflection electrode assembly and slit chopper assembly are compactly collinear, facilitating integration with the DC high-voltage electron gun and X-ray target assembly. The deflection electrode assembly and slit chopper assembly of this invention are compactly arranged along the electron beam propagation direction without altering the electron beam transmission direction, achieving a collinear layout of "DC high-voltage electron gun outlet - deflection region - slit - target material"; furthermore, they can be directly inserted between the DC high-voltage electron gun and X-ray target assembly via a vacuum flange, exhibiting good compatibility and scalability. Attached Figure Description

[0022] Figure 1This is a front view of an embodiment of the ultrafast pulse X-ray generating device based on deflection electric field chopping modulation of the present invention; Figure 2 This is a side view of the ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to the present invention; Figure 3 This is a cross-sectional view of the ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to the present invention; Figure 4 This is an isoelectric field distribution diagram under a 225kV operating voltage in an embodiment of the ultrafast pulse X-ray generating device based on deflection electric field chopping modulation of the present invention. Figure 5 This is a map showing the distribution of magnetic field lines in the lens region of an embodiment of the ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to the present invention.

[0023] The annotations in the attached figures are explained as follows: 1-Vacuum chamber assembly, 11-First chamber body, 12-Second chamber body, 13-Vacuum pump interface, 14-Vacuum pump, 15-Hinge mechanism; 2-DC high voltage electron gun, 21-DC high voltage cable, 22-high voltage insulation component, 23-cathode support component, 24-high voltage wiring component, 25-cathode electrode, 26-cathode cover, 27-gate, 28-shielding electrode, 29-anode electrode, 210-vacuum flange; 3-Electron beam focusing and collimation assembly; 31-Magnetic pole shoe; 32-Magnetic coil; 4-Deflection electrode assembly; 5-Slit chopper assembly, 51-Slit plate; 6-X-ray target assembly. Detailed Implementation

[0024] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0025] like Figures 1 to 3 As shown in the figure, this embodiment is an ultrafast pulse X-ray generating device based on deflection electric field chopping modulation. The device mainly includes a vacuum cavity assembly 1, a DC high voltage electron gun 2, an electron beam focusing and collimation assembly 3, a deflection electrode assembly 4, a slit chopping assembly 5, and an X-ray target assembly 6.

[0026] The vacuum chamber assembly 1 is mainly used to house and install the other components mentioned above, and to ensure the stable transmission of the electron beam in a high vacuum environment.

[0027] See Figures 1 to 3Specifically, the vacuum chamber assembly 1 mainly includes a first chamber body 11, a second chamber body 12, a vacuum pump interface 13, and a vacuum pump 14.

[0028] One end of the first cavity body 11 is connected to one end of the second cavity body 12 via a hinge mechanism 15. When the two are opened via the hinge mechanism 15, the internal structure of the DC high voltage electron gun 2 can be directly exposed, which facilitates the replacement and maintenance of the internal structure of the DC high voltage electron gun 2, thereby improving maintainability and engineering usability.

[0029] Vacuum pump interface 13 is mounted on the side wall of the first cavity body 11, with its inner end located inside the first cavity body 11; vacuum pump 14 is mounted on the outer end of vacuum pump interface 13. Continuous pumping by vacuum pump 14 maintains a high vacuum environment within the cavity; in this embodiment, a vacuum level of 10⁻⁻⁶ is preferred. 6 Pa level or better, to reduce residual gas scattering and lower the risk of high-voltage discharge.

[0030] In other embodiments of the present invention, a vacuum gauge interface, an observation window, or a beam diagnostic interface (not shown) may also be provided on the first cavity body 11 for status monitoring, assembly and alignment, and operation and maintenance.

[0031] The DC high-voltage electron gun 2 is connected to an external high-voltage power supply through its input terminal to generate a continuous electron beam, which is then accelerated to a predetermined energy and output through the output terminal. The accelerating voltage of the DC high-voltage electron gun 2 can be adjusted between 50kV and 300kV, or extended to higher energies, depending on the application requirements. As long as the trajectory of the electron beam in the deflection region is matched with the electron optics of the slit chopper assembly 5, a similar ultrafast pulse X-ray output effect can be obtained.

[0032] See Figure 3 Specifically, the DC high-voltage electron gun 2 includes a DC high-voltage cable 21, a high-voltage insulation component 22, a cathode support component 23, a high-voltage wiring component 24, a cathode electrode 25, a cathode cover 26, a grid 27, a shielding electrode 28, and an anode electrode 29.

[0033] The high-voltage insulating component 22 is made of ceramic, and its outer end is installed at the other end of the first cavity body 11 via a vacuum flange 210. The high-voltage insulating component 22 is used to achieve electrical insulation and vacuum sealing between the high-voltage end and the vacuum cavity assembly 1, and serves as the mounting base for the "cathode electrode 25-gate electrode 27-shielding electrode 28", allowing it to be assembled, removed, and maintained as a whole.

[0034] The DC high-voltage cable 21 is plugged into the outer end of the high-voltage insulator 22. One end of the cable is placed outside the first cavity body 11 for connecting to the external high-voltage power supply. The other end and the inner end of the high-voltage insulator 22 are both placed inside the vacuum cavity assembly 1, so that the high-voltage power supply can be reliably introduced into the cathode support 23 and electrically connected to the shielding electrode 28 and the grid 27 respectively through the high-voltage connector 24.

[0035] The cathode support 23 is installed on the inner end of the high-voltage insulator 22 via the high-voltage connector 24. The cathode support 23 is preferably a threaded ceramic hollow column structure, which is used to achieve coaxial positioning and electrical insulation support of the cathode system.

[0036] Cathode electrode 25 and cathode cover 26 are respectively mounted on cathode support 23, with cathode cover 26 covering the output end of cathode electrode 25. Cathode electrode 25 can be a hot cathode, field emission cathode, or other continuous emission cathode structure. In this embodiment, a hot cathode is preferred to obtain a stable and continuous electron beam output. Cathode cover 26 is used to define the equipotential boundary near cathode electrode 25 and suppress edge field enhancement, working together with grid 27 to achieve initial confinement and stable emission of the electron beam.

[0037] One end of the shielding electrode 28 is mounted on the cathode support 23 and covered outside the high-voltage connector 24. The main function of the shielding electrode 28 is to weaken the electric field enhancement effect at the three-phase point of "vacuum-cathode support 23-cathode electrode 25" and suppress the risk of field emission and discharge, thereby improving the long-term stability of DC high-voltage operation.

[0038] One end of the gate 27 is detachably connected to one end of the shielding electrode 28 via a spring-loaded ball-type positioning latch mechanism. Specifically, the spring-loaded ball-type positioning latch mechanism includes a receiving hole on the shielding electrode 28 (or its mounting base), a compression spring and a movable spherical positioning element (steel ball) are provided in the receiving hole. Under the action of the compression spring, the steel ball cooperates with the positioning recess / groove on the gate 27 to achieve positioning and locking, and facilitates disassembly and maintenance.

[0039] The anode electrode 29 is grounded or at a low potential, installed inside the first cavity body 11, and located downstream of the cathode electrode 25 along the electron beam propagation direction, with a predetermined interval between them. An anode hole is provided on the anode electrode 29 to allow the electron beam to pass through and to define the electron beam's exit cross-section. A stable DC accelerating electric field exists between the cathode electrode 25 and the anode electrode 29. A continuous electron beam is formed in this DC accelerating electric field and output along the acceleration direction of the DC accelerating electric field.

[0040] The main function of the electron beam focusing and collimating assembly 3 is to adjust the beam waist position, beam spot size and divergence angle of the electron beam so that the electron beam has the expected lateral size and propagation characteristics in the deflection region of the deflection electrode assembly 4 and forms the expected focal spot on the X-ray target assembly 6.

[0041] See Figure 3 Specifically, the electron beam focusing and collimation assembly 3 includes N-level lenses arranged sequentially along the electron beam propagation direction; N≥1. In this embodiment, N=2 and the lenses are magnetic lenses for illustration.

[0042] In other embodiments of the present invention, the lens may also be an electrostatic lens or a magnetic-electrostatic composite lens, as long as the beam waist position of the electron beam can be controlled and the beam spot size can be matched with the width of the straight slit.

[0043] Both stages of the lens include a magnetic pole shoe 31 and a magnetic coil 32 mounted on the magnetic pole shoe 31. The magnetic pole shoe 31 is installed inside the second cavity body 12, and a through hole is provided at the center of the magnetic pole shoe 31. The through holes of the two stages of the lens are connected sequentially, and there is a gap between adjacent stages of the lens.

[0044] The first-stage lens is a pre-focusing magnetic lens, used to achieve preliminary adjustment of the beam waist position, beam spot size and divergence angle of the electron beam, so that the diverging beam tends to be parallel after shaping; one end of the through hole on the first-stage lens serves as the input end of the electron beam focusing and collimation assembly 3, and is set on the output path of the DC high-voltage electron gun 2.

[0045] The second-stage lens is a focusing magnetic lens, used to further adjust the beam waist position, beam spot size, and divergence angle of the electron beam, so that the divergent beam obtains a preset convergence state after shaping. The other end of the through hole on the second-stage lens serves as the output end of the electron beam focusing and collimation assembly 3, and is located inside the X-ray target assembly 6.

[0046] See Figure 3 The deflection electrode assembly 4 includes two opposing deflection plates installed inside the through-hole of the first-stage lens.

[0047] The front end of the deflection plate adopts a rounded corner transition structure or a multi-segment curved surface contour structure to reduce the local electric field peak and improve the vacuum withstand voltage margin. The length of the deflection plate is 1mm~20mm, and the distance between two opposing deflection plates is 0.1mm~5mm.

[0048] Two opposing deflection plates are electrically connected to an external synchronization control module via an external deflection modulation drive module, so that a time-varying transverse deflection electric field is formed under the control of the synchronization control module and the drive of the deflection modulation drive module, causing the propagation path of the electron beam to deflect laterally periodically over time.

[0049] The deflection modulation drive module applies a time-varying deflection voltage signal as a drive signal to the deflection electrode assembly 4. This drive signal can be a sine wave, square wave, pulse train, or any programmable waveform. By adjusting parameters such as the peak value, frequency, duty cycle, rise time, and repetition frequency of the drive signal, the propagation path of the electron beam and its time window across the slit chopper assembly 5 can be controlled, thereby achieving adjustment of the ultrafast pulse X-ray pulse width, repetition frequency, and time structure.

[0050] The synchronization control module controls the operating mode and trigger timing of the deflection modulation drive module, and can synchronize with an external pump excitation source as needed. Through the control of the synchronization control module, various output modes can be achieved, such as single pulse, double pulse, multi-pulse, equally spaced pulse trains, or unequally spaced pulse sequences, to meet the needs of different time-resolved experiments and dynamic diagnostic applications.

[0051] In other embodiments of the present invention, the deflection electrode assembly 4 may also adopt other different structures, such as a parallel plate electrostatic deflector, a stripline deflector with a loaded capacitor, or a smaller integrated deflection unit. As long as sufficient deflection electric field can be generated within the required time scale and the local electric field strength on the surface of the shielding electrode 28 and the gate 27 is within a safe range, a time chopping effect similar to that of the present invention can be achieved.

[0052] See Figure 3 The slit chopper assembly 5 includes a slit support mounted inside the through-hole of the second-stage lens, and a slit plate 51 detachably mounted on the slit support.

[0053] The slit plate 51 is provided with an opening, and the openings of different widths and shapes can be changed according to the requirements of the electron beam energy, beam diameter, expected pulse width and repetition frequency. The opening is usually in the form of a straight slit or a rectangular hole, with a width of 1μm to 1mm and a height of 0.1mm to 5mm.

[0054] In other embodiments of the present invention, the slit plate 51 may also be provided with multiple openings to realize the output of multiple ultrashort electron pulses, which are used to generate ultrafast pulse X-rays at multiple locations simultaneously. As long as the opening position matches the propagation path of the electron beam, effective control of the time window can be achieved.

[0055] The main function of the slit plate 51 is to perform time gating on the deflected electron beam to generate ultrashort electron pulses. That is, by coordinating the time change of the deflection electric field with the spatial position of the fixed straight slit, the electron beam is allowed to pass through only within an extremely short time window when the propagation path of the electron beam coincides with the straight slit. At other times, the electron beam is blocked by the slit plate 51 and cannot pass through, thereby slicing the originally continuous electron beam into ultrashort electron pulses.

[0056] The ultrashort electron pulse is further focused by the second-stage lens and forms a micron-sized focal spot on the X-ray target assembly 6, thereby increasing the target power density per unit time and the instantaneous brightness of the ultrafast pulse X-ray.

[0057] The main function of X-ray target assembly 6 is to generate ultrafast pulsed X-rays under ultrashort electron pulse bombardment and output them outward through the output window. The X-ray target assembly 6 is a high-Z target material, preferably made of tungsten, molybdenum, or gold, and can be designed as a transmission target structure or a reflection target structure according to application requirements. An output window is provided at the rear or side of the X-ray target assembly 6 (the location is determined based on the embodiment of the transmission or reflection target structure). The output window can be made of beryllium, thin metal, or a composite window structure, and a shielding collimation structure is provided at the output window to extract and limit the propagation direction of ultrafast pulsed X-rays, thereby reducing stray radiation and improving effective utilization efficiency.

[0058] See Figure 3 The X-ray target assembly 6 is installed at the other end of the second cavity body 12 and is located at the output end of the electron beam focusing and collimation assembly 3.

[0059] The output end of the DC high-voltage electron gun 2, the input and output ends of the electron beam focusing and collimation assembly 3, the axis of the deflection electrode assembly 4, the opening center of the slit chopper assembly 5, and the window center of the X-ray target assembly 6 are located on the same straight line to ensure collinear transmission of the electron beam; the other related components can be finely adjusted according to the system assembly and adjustment requirements.

[0060] To further clarify the design rationale of this invention in terms of high-voltage stability and electron beam focusing performance, Figure 4 and Figure 5 The electromagnetic field simulation results for the key regions are presented separately.

[0061] like Figure 4 As shown, under the operating condition of a DC high-voltage electron gun 2 with an accelerating voltage of 225kV, the isoelectric field distribution was obtained through simulation using the finite difference method. The simulation results show that the maximum electric field intensity on the surfaces of the shielding electrode 28 and the gate 27 is less than 10MV / m, which is lower than the field emission threshold of commonly used electrode materials in a vacuum environment, effectively suppressing the risk of high-voltage discharge and leakage current. Simultaneously, the isoelectric field distribution between the cathode electrode 25 and the anode electrode 29 is relatively uniform, without significant local distortion, ensuring that the electron beam obtains stable lateral focusing force and low emission during acceleration, providing a high-quality electron source for subsequent deflection and chopping.

[0062] like Figure 5As shown, the distribution of isomagnetic field lines generated by the two-stage magnetic lenses (pre-focusing magnetic lens and focusing magnetic lens) in the electron beam focusing and collimation assembly 3 exhibits high axial symmetry, and the gradient change of the magnetic field along the axial direction is gentle. This magnetic field configuration enables precise control of the beam waist position and beam spot size during electron beam transmission, allowing the electron beam to maintain the expected lateral size when passing through the deflection region of the deflection electrode assembly 4, and ultimately forming a micrometer-scale focal spot on the X-ray target assembly 6 after passing through the slit chopper assembly 5. The excellent magnetic field symmetry also reduces electron beam astigmatism and distortion, which is beneficial for improving the spatial resolution and stability at repetition rates of ultrafast pulsed X-rays.

[0063] In conclusion, Figure 4 The uniformity of the electric field distribution and the withstand voltage reliability of the DC high-voltage electron gun 2 of this invention under 225kV high voltage were verified. Figure 5 The focusing capability of the second-order lens for electron beams was verified. Together, these verifications demonstrate that the present invention can achieve efficient conversion from continuous electron beams to ultrashort electron pulses and then to ultrafast pulsed X-rays through deflection electric field chopping modulation without relying on high-voltage pulsed power supplies or ultrafast lasers.

[0064] Based on the same inventive concept, this embodiment provides a method for generating ultrafast pulsed X-rays based on deflection electric field chopping modulation, specifically including the following steps: Step 1: A continuous electron beam is generated by the DC high-voltage electron gun 2, accelerated to a predetermined energy, and then output through the output terminal.

[0065] Step 2: Adjust the beam waist position, beam spot size and divergence angle of the electron beam through the electron beam focusing and collimating assembly 3 so that the electron beam has the expected lateral size and propagation characteristics in the deflection region of the deflection electrode assembly 4 and forms the expected focal spot on the X-ray target assembly 6.

[0066] Step 3: Under the control of the synchronization control module and the drive of the deflection modulation drive module, the deflection electrode assembly 4 forms a time-varying transverse deflection electric field, causing the propagation path of the electron beam to deflect periodically over time.

[0067] Step 4: Time-gated electron beam is generated by slit chopper assembly 5.

[0068] Step 5: Ultrafast pulsed X-rays are generated by the X-ray target assembly 6 under the bombardment of ultrashort electron pulses and output outward through the output window.

[0069] When time-correlated measurements with external excitation processes are required, the deflection modulation drive signal can be synchronously controlled with the laser, impact loading device or other pump sources through the synchronization control module, so that the ultrafast pulse X-ray generated by this invention can be used as a detection pulse to achieve time-resolved diagnosis of transient processes.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. An ultrafast pulse X-ray generating device based on deflection electric field chopping modulation, characterized in that: It includes a vacuum chamber assembly (1), a DC high-voltage electron gun (2), an electron beam focusing and collimation assembly (3), a deflection electrode assembly (4), a slit chopper assembly (5), and an X-ray target assembly (6); The DC high-voltage electron gun (2) is installed at one end of the vacuum cavity assembly (1), with its input end located outside the vacuum cavity assembly (1) and its output end located inside the vacuum cavity assembly (1); the DC high-voltage electron gun (2) is used to connect to an external high-voltage power supply through its input end to generate a continuous electron beam, accelerate it to a predetermined energy, and output it through the output end; The electron beam focusing and collimation assembly (3) is installed inside the vacuum cavity assembly (1), and its input end is set on the output path of the DC high voltage electron gun (2). It is used to adjust the beam waist position, beam spot size and divergence angle of the electron beam so that the electron beam has the expected lateral size and propagation characteristics in the deflection area of ​​the deflection electrode assembly (4) and forms the expected focal spot on the X-ray target assembly (6). The deflection electrode assembly (4) is installed inside the electron beam focusing and collimation assembly (3) near its input end. It is used to be electrically connected to the external synchronization control module through the external deflection modulation drive module, so as to form a time-varying transverse deflection electric field under the control of the synchronization control module and the drive of the deflection modulation drive module, so that the propagation path of the electron beam will be periodically deflected transversely over time. The slit chopper assembly (5) is installed inside the electron beam focusing and collimating assembly (3) near its output end. It has an opening for the deflected electron beam to pass through, which is used to perform time gating on the deflected electron beam to generate ultra-short electron pulses. The X-ray target assembly (6) is installed at the other end of the vacuum cavity assembly (1) and is located at the output end of the electron beam focusing and collimation assembly (3). It is provided with an output window for generating ultrafast pulse X-rays under ultrashort electron pulse bombardment and outputting them outward through the output window. The output end of the DC high voltage electron gun (2), the input and output ends of the electron beam focusing and collimation assembly (3), the axis of the deflection electrode assembly (4), the opening center of the slit chopper assembly (5), and the output window center of the X-ray target assembly (6) are all on the same straight line.

2. The ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to claim 1, characterized in that: The DC high-voltage electron gun (2) includes a DC high-voltage cable (21), a high-voltage insulator (22), a cathode support (23), a high-voltage connector (24), a cathode electrode (25), a cathode cover (26), a grid (27), a shielding electrode (28), and an anode electrode (29); The outer end of the high-voltage insulating component (22) is mounted on one end of the vacuum chamber assembly (1) via a vacuum flange (210); The DC high voltage cable (21) is plugged into the outer end of the high voltage insulator (22), with one end placed outside the vacuum cavity assembly (1) for connecting to an external high voltage power supply, and the other end and the inner end of the high voltage insulator (22) both placed inside the vacuum cavity assembly (1). The cathode support (23) is installed on the inner end of the high voltage insulator (22) via the high voltage connector (24). The cathode electrode (25) and the cathode cover (26) are respectively installed on the cathode support (23), and the cathode cover (26) covers the output end of the cathode electrode (25). One end of the shielding electrode (28) is mounted on the cathode support (23) and covered outside the high voltage connector (24); one end of the gate electrode (27) is connected to one end of the shielding electrode (28); the shielding electrode (28) and the gate electrode (27) are electrically connected to the DC high voltage cable (21) through the high voltage connector (24); The anode electrode (29) is installed inside the vacuum cavity assembly (1) and is located downstream of the cathode electrode (25) along the electron beam propagation direction, and has a set interval between them; the anode electrode (29) is provided with an anode hole to allow the electron beam to pass through and to define the exit cross section of the electron beam.

3. The ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to claim 2, characterized in that: The accelerating voltage of the DC high-voltage electron gun (2) is 50kV~300kV; The cathode electrode (25) is a hot cathode or a field emission cathode; One end of the gate (27) is detachably connected to one end of the shielding electrode (28) via a spring-loaded bead-type positioning latch mechanism; The cathode support (23) is a ceramic hollow column structure, and one end of it is installed on the inner end of the high voltage insulator (22) through the high voltage connector (24); The high-voltage insulating component (22) is made of ceramic.

4. The ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to any one of claims 1-3, characterized in that: The electron beam focusing and collimation assembly (3) includes N-level lenses arranged sequentially along the electron beam propagation direction; N≥1; The lens is a magnetic lens, an electrostatic lens, or a magnetic-electrostatic composite lens; The N-level lenses are respectively installed inside the vacuum cavity assembly (1), and each of them has a through hole at its center; the through holes of the N-level lenses are connected in sequence, and there is a gap between adjacent two-level lenses; One end of the through hole on the lens of the first stage serves as the input end of the electron beam focusing and collimation assembly (3) and is located on the output path of the DC high voltage electron gun (2); the other end of the through hole on the lens of the last stage serves as the output end of the electron beam focusing and collimation assembly (3) and is located inside the X-ray target assembly (6). The deflection electrode assembly (4) is installed in the through hole on the first-stage lens, and the slit chopper assembly (5) is installed in the through hole on the last-stage lens.

5. The ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to claim 4, characterized in that: The N=2; The first-stage lens is a pre-focusing magnetic lens, used to achieve preliminary adjustment of the beam waist position, beam spot size, and divergence angle of the electron beam; the second-stage lens is a focusing magnetic lens, used to achieve further adjustment of the beam waist position, beam spot size, and divergence angle of the electron beam. The lenses described in the second level all include a magnetic pole shoe (31) and a magnetic coil (32) mounted on the magnetic pole shoe (31); The magnetic pole shoe (31) is installed inside the vacuum cavity assembly (1), and the through hole is located at the center of the magnetic pole shoe (31).

6. The ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to claim 1, characterized in that: The deflection electrode assembly (4) includes two opposing deflection plates installed inside the electron beam focusing and collimation assembly (3); The front end of the deflection plate adopts a rounded corner transition structure or a multi-segment curved surface contour structure, with a length of 1mm to 20mm, and the distance between the two opposing deflection plates is 0.1mm to 5mm. The two opposing deflection plates are electrically connected to an external synchronization control module via an external deflection modulation drive module, so as to form a time-varying transverse deflection electric field under the control of the synchronization control module and the drive of the deflection modulation drive module.

7. The ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to claim 1 or 6, characterized in that: The slit chopper assembly (5) includes a slit support seat installed inside the electron beam focusing and collimating assembly (3), and a slit plate (51) detachably installed on the slit support seat; The slit plate (51) is provided with a straight slit or a rectangular hole; the width of the straight slit or rectangular hole is 1μm~1mm and the height is 0.1mm~5mm.

8. The ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to claim 7, characterized in that: The X-ray target assembly (6) is made of tungsten, molybdenum or gold, and has an output window at its rear or side. A shielding collimation structure is provided at the output window to draw out and limit the propagation direction of ultrafast pulsed X-rays.

9. The ultrafast pulse X-ray generating device based on deflection electric field chopping modulation according to claim 1, characterized in that: The vacuum chamber assembly (1) includes a first chamber body (11), a second chamber body (12), a vacuum pump interface (13), and a vacuum pump (14); One end of the first cavity body (11) is connected to one end of the second cavity body (12) via a hinge mechanism (15); The DC high-voltage electron gun (2) is installed inside the first cavity body (11), the electron beam focusing and collimation assembly (3) is installed inside the second cavity body (12), and the X-ray target assembly (6) is installed at the other end of the second cavity body (12); The vacuum pump interface (13) is installed on the side wall of the first cavity body (11), and its inner end is placed inside the first cavity body (11); the vacuum pump (14) is installed on the outer end of the vacuum pump interface (13).

10. A method for generating ultrafast pulsed X-rays based on deflection electric field chopping modulation, employing the ultrafast pulsed X-ray generating apparatus based on deflection electric field chopping modulation as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1: A continuous electron beam is generated by a DC high-voltage electron gun (1), and after being accelerated to a predetermined energy, it is output through the output terminal; Step 2: Adjust the beam waist position, beam spot size and divergence angle of the electron beam through the electron beam focusing and collimating assembly (3) so that the electron beam has the expected lateral size and propagation characteristics in the deflection area of ​​the deflection electrode assembly (4) and forms the expected focal spot on the X-ray target assembly (6). Step 3: The deflection electrode assembly (4) forms a time-varying transverse deflection electric field under the control of the synchronization control module and the drive of the deflection modulation drive module, so that the propagation path of the electron beam is periodically deflected transversely over time. Step 4: Time-gated electron beam after deflection is generated by slit chopper assembly (5); Step 5: The X-ray target assembly (6) generates ultrafast pulsed X-rays under ultrashort electron pulse bombardment and outputs them outward through the output window.

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