A time-amplified streak-scan based ultrafast electron pulse width measurement system and method

Abstract

The application discloses a kind of ultrafast electron pulse pulse width measurement system and measurement method based on time amplification stripe scanning, solve the existing pulse width measurement technology to the pulse width measurement of ultra-short electron pulse, there is the problem of low measurement precision, complex measurement system and high cost when meeting the measurement demand of the length of ultrafast electron pulse beamlet of electron pulse width less than hundred femtosecond;The method of the application utilizes femtosecond order ultrafast electron pulse itself space charge effect and vacuum dispersion effect to occur time broadening effect, and is broadened to picosecond order that can be detected by traditional stripe scanning method, the time broadening amount of electron pulse can be obtained using space-time broadening theory;Ultrafast electron pulse pulse width after broadening is obtained using stripe scanning deflection method, and the pulse width of ultrafast electron pulse can be obtained by inversion;The method of the application can accurately characterize femtosecond order ultrafast electron pulse pulse, and has high time resolution, simple system principle and easy realization.

Description

Technical Field

[0001] This invention relates to a method for measuring the pulse width of ultrafast electron pulses, specifically to an ultrafast electron pulse width measurement system and method based on time-amplified fringe scanning. Background Technology

[0002] Ultrafast electron pulses are one of the main probes for studying the ultrafast dynamics of atoms or electrons in matter. Their pulse width directly affects the temporal resolution of ultrafast characterization instruments such as ultrafast electron diffraction devices and ultrafast electron microscopes. For a long time, how to generate shorter ultrafast electron pulses has been a cutting-edge and hotly debated area of ​​scientific research, and the corresponding ultrafast electron pulse width measurement technology has also attracted much attention. Currently, the existing technologies in the field of ultrafast electron pulse width measurement mainly include:

[0003] The paper Zhang W, Zhu D, Sui Y, et al. Streak camera calibration for bunchlength measurement at BEPC II[J]. Radiation Detection Technology and Methods, 2021, 5: 466-473. discloses an electron pulse measurement method based on a traditional streak camera. This method utilizes the time-varying deflection electric field on the deflection plate of the streak camera to deflect electrons arriving at different times to different spatial positions, converting the electron pulse time series into a recognizable spatial system. Then, the pulse width of the electron pulse arriving at the deflection plate is obtained by inverting the relationship between the deflection electric field and time. The measurement accuracy of this method mainly depends on the streak camera. However, the time resolution of the most advanced commercial streak cameras is currently 100 fs, which is insufficient to meet the measurement requirements of the bunch length of ultrafast electron pulses with a pulse width of less than 100 femtoseconds.

[0004] The paper Bai Jin, Chen Qushan, and Fan Kuanjun, "Bundle Length Measurement System Based on Radio Frequency Deflection Cavity [J]. Atomic Energy Science and Technology, 2019, 53(09):1607-1611," discloses a bundle length measurement system based on a radio frequency deflection cavity. The radio frequency deflection cavity generates an intrinsic mode electric field under external energy excitation. When an electron pulse passes through the cavity, it is deflected by the cavity's electric field, causing bundle slices with different longitudinal phases to be incident on different positions on the screen. The bundle length can be derived by analyzing the screen signal. This method can currently achieve bundle length diagnosis for tens of femtoseconds. However, the synchronization problem of the radio frequency signal limits the improvement of the measurement accuracy of this scheme. Furthermore, the radio frequency source, cooling system, and signal synchronization system make the system relatively complex and the operating cost relatively high.

[0005] The paper "Pompili R, Cianchi A, Alesini D, et al. First single-shot and non-intercepting longitudinal bunch diagnostics for comb-like beam by means of electro-optic sampling[J]. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2014, 740: 216-221" discloses an electro-optic sampling method for diagnosing electron beam bunches. When electrons pass through an electro-optic crystal, a birefringence effect occurs, and linearly polarized light becomes elliptically polarized light. The ellipticity is proportional to the electric field strength, and the distribution of the bunch's Coulomb electric field reflects the bunch's longitudinal distribution. Although the electro-optic sampling method can achieve very high resolution in diagnosing bunch length, it has strict requirements for laser technology, optical detection technology, etc., resulting in high system complexity, technical threshold, and cost. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of existing pulse width measurement technology when measuring the pulse width of ultrashort (femtosecond or attosecond) electron pulses, such as difficulty in meeting the measurement requirements of ultrafast electron pulse bundle length with electron pulse width less than hundreds of femtoseconds, low measurement accuracy, complex measurement system, and high cost. The invention provides an ultrafast electron pulse width measurement system and method based on time-magnified stripe scanning.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An ultrafast electronic pulse width measurement system based on time-magnified fringe scanning is characterized by the following features:

[0009] It includes a vacuum drift tube, a scanning deflection housing, a parallel deflection plate, a fluorescent screen, an electron bombardment CCD camera, and a deflection control system;

[0010] The input end of the vacuum drift tube is connected to the output end of the ultrafast electron pulse generating device. An ultrafast electron pulse is input and broadened within the vacuum drift tube to obtain a broadened electron pulse. The output end of the vacuum drift tube is connected to the input end of the scanning deflection housing, with a slit between them. The parallel deflection plate is disposed inside the scanning deflection housing. The central axis of the vacuum drift tube is located between and parallel to the two plates of the parallel deflection plate. The slit limits the size of the electron beam spot entering the parallel deflection plate, preventing it from incident on the plate. The vacuum drift tube is used for the time amplification process of the ultrafast electron pulse, i.e., the ultrafast electron pulse undergoes temporal and spatial broadening under its own space charge effect. A femtosecond-level electron pulse can be amplified into a picosecond-level electron pulse through the vacuum chamber, making it a signal detectable by a conventional streak camera.

[0011] The input terminal of the deflection control system is connected to the signal output terminal of the ultrafast electron pulse generator, and the output terminal of the deflection control system is connected to the parallel deflection plate. It is used to collect the electrical signal output by the signal output terminal of the ultrafast electron pulse generator and perform delay modulation to obtain a scanning bias signal that is synchronized with the time of the broadened electron pulse entering the parallel deflection plate. The synchronized scanning bias signal is input into the parallel deflection plate to form a scanning deflection field between the two plates of the parallel deflection plate.

[0012] The fluorescent screen is located at the end of the scanning deflection housing away from the vacuum drift tube, and the outside of the fluorescent screen is connected to the input terminal of the electron bombardment CCD camera.

[0013] Furthermore, the formula for pulse broadening of ultrafast electron pulses by the vacuum drift tube (3) is as follows:

[0014] t x =t0+Δt c ;

[0015] Where t x To broaden the pulse width of the electron pulse, t0 is the pulse width of the ultrafast electron pulse generated by the ultrafast electron pulse generator, Δt c The time extension term is represented as:

[0016]

[0017] Where t represents the electron drift time in the ultrafast electron pulse, v represents the ultrafast electron pulse velocity, N represents the number of electrons in the ultrafast electron pulse, r represents the transverse radius of the ultrafast electron pulse, and m represents the mass of a single electron.

[0018] Furthermore, the deflection control system includes a signal synchronization system and a scanning circuit. The input terminal of the signal synchronization system is connected to the signal output terminal of the ultrafast electron pulse generating device, and the output terminal of the signal synchronization system is sequentially connected to the scanning circuit and the parallel deflection plate. The signal synchronization system is used to acquire the electrical signal output from the signal output terminal of the ultrafast electron pulse generating device and perform time delay modulation to obtain an electrical signal synchronized with the broadened electron pulse entering the parallel deflection plate. The synchronized electrical signal triggers the scanning circuit to generate a scanning bias signal, and the parallel deflection plate is used to generate a scanning deflection field according to the scanning bias signal.

[0019] Furthermore, the ultrafast electron pulse has an emission energy of 200 keV, a longitudinal length of 30 fs, a transverse dimension of 200 μm, and a number of electrons of 10,000.

[0020] Furthermore, the slit width is 20 μm, and the distance from the slit to the parallel deflection plate is 4 mm.

[0021] Furthermore, the outer side of the fluorescent screen is connected to the input terminal of the electron-bombarded CCD camera via optical coupling adhesive.

[0022] Meanwhile, the present invention also provides a method for measuring the pulse width of ultrafast electron pulses based on time-magnified fringe scanning. The method is characterized by the following steps:

[0023] S1. Disconnect the deflection control system, turn on the ultrafast electron pulse generator to generate ultrafast electron pulses, and input them into the vacuum drift tube. Calculate the time broadening term of the ultrafast electron pulse based on its parameters, and use the time broadening term to broaden the ultrafast electron pulse in the vacuum drift tube, then output the broadened electron pulse.

[0024] S2. The broadened electron pulses sequentially pass through the slit and parallel deflection plate and are incident on the fluorescent screen, forming a striped light spot. The image of the striped light spot is acquired by an electron bombardment CCD camera, and the longest dimension σ of the striped light spot is calculated. s ;

[0025] S3. Reconnect to the deflection control system. The deflection control system acquires the output electrical signal of the ultrafast electron pulse generator and delays and modulates the output signal to output a scanning bias signal synchronized with the time of the broadened electron pulse entering the parallel deflection plate. This scanning bias signal is input to the parallel deflection plate, forming a scanning deflection field between the two plates. When the broadened electron pulse is output from the parallel deflection plate, it is deflected and incident on the fluorescent screen, forming a striped spot. An image of the striped spot is acquired by an electron-bombarded CCD camera, and the longest dimension of the striped spot is σ. d ;

[0026] S4, the size σ of the striped light spot s The size of the stripe-like light spot is σ d Calculate the pulse width of the broadened electron pulse, and then calculate the pulse width of the ultrafast electron pulse based on the pulse width of the broadened electron pulse and the time broadening term.

[0027] Furthermore, the specific process of S1 is as follows:

[0028] S11. Disconnect the deflection control system, turn on the ultrafast electronic pulse generator to generate ultrafast electronic pulses, and input them into the vacuum drift tube.

[0029] S12. Calculate the time-spanning term Δt of the ultrafast electron pulse based on its parameters. c The formula is:

[0030]

[0031] Where t represents the electron drift time in the ultrafast electron pulse, v represents the ultrafast electron pulse velocity, N represents the number of electrons in the ultrafast electron pulse, r represents the transverse radius of the ultrafast electron pulse, and m represents the mass of a single electron;

[0032] S13. The ultrafast electron pulse is pulse-widened using a time-spanning term within a vacuum drift tube. The expression is:

[0033] t x =t0+Δt c ;

[0034] Where x is the pulse width of the broadened electron pulse, and t0 is the pulse width of the ultrafast electron pulse generated by the ultrafast electron pulse generator.

[0035] S14, Output pulse width is t x The broadened electron pulse.

[0036] Furthermore, in S4, the size σ of the stripe-like light spot... s The size of the stripe-like light spot is σ d The formula for calculating the pulse width of a broadened electronic pulse is:

[0037]

[0038] Among them, v scan The scanning speed is the speed of the stripe scanning deflection system.

[0039] Furthermore, in S4, the formula for calculating the ultrafast electron pulse width based on the pulse width of the broadened electron pulse and the time broadening term is as follows:

[0040] t0 = t x -Δt c .

[0041] The beneficial effects of this invention are:

[0042] 1. The present invention provides an ultrafast electron pulse width measurement system and method based on time-magnified fringe scanning. Based on the spatiotemporal broadening theory of non-relativistic electron pulses and the traditional fringe scanning deflection method, it can accurately characterize the pulse of femtosecond-level ultrafast electron pulses. It has high time resolution, simple system principle and is easy to implement.

[0043] 2. The present invention provides an ultrafast electronic pulse width measurement system based on time-magnified stripe scanning, which is simple and low in cost and can be widely used in various electronic pulse width measurement experiments. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of an embodiment of an ultrafast electron pulse width measurement system based on time-magnified stripe scanning according to the present invention;

[0045] Figure 2 This is a schematic diagram illustrating the evolution of the ultrafast electron pulse width over time in step S1 of an embodiment of the ultrafast electron pulse pulse width measurement method based on time-amplified stripe scanning according to the present invention.

[0046] In the figure, 1-Ultrafast electron pulse generating device; 2-Ultrafast electron pulse; 3-Vacuum drift tube; 4-Scanning deflection housing; 5-Parallel deflection plate; 6-Fluorescent screen; 7-Electron bombardment CCD camera; 8-Output electrical signal; 9-Signal synchronization system; 10-Scanning circuit; 11-Scanning bias voltage signal; 12-Slit. Detailed Implementation

[0047] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] This embodiment presents an ultrafast electronic pulse width measurement system based on time-magnified fringe scanning, such as... Figure 1 As shown, it includes a vacuum drift tube 3, a scanning deflection housing 4, a parallel deflection plate 5, a fluorescent screen 6, an electron bombardment CCD camera 7, and a deflection control system.

[0049] The input end of the vacuum drift tube 3 receives an ultrafast electron pulse 2 on the order of hundreds of femtoseconds generated by the ultrafast electron pulse generator 1. The ultrafast electron pulse 2 is pulse-broadened inside the vacuum drift tube 3 to obtain a broadened electron pulse. A slit 12 is provided between the output end of the vacuum drift tube 3 and the scanning deflection housing 4. A parallel deflection plate 5 is provided inside the scanning deflection housing 4. The central axis of the vacuum drift tube 3 is located between the two plates of the parallel deflection plate 5 and is parallel to the two plates.

[0050] Among them, the ultrafast electron pulse 2 generated by the ultrafast electron pulse generating device 1 has an output energy of 200keV, a longitudinal length of 30fs, a transverse dimension of 200μm, and a number of electrons of 10000.

[0051] In this embodiment, the vacuum drift tube 3 has a length of 39.5 cm and a diameter of 5 cm; the ultrafast electron pulse is pulse-broadened within the vacuum drift tube 3 using the following formula:

[0052] t x =t0+Δt c ;

[0053] Where t x To broaden the pulse width of the electron pulse, t0 is the pulse width of the ultrafast electron pulse generated by the ultrafast electron pulse generating device 1, Δt c The time extension term is represented as:

[0054]

[0055] Where, Δt c For the time-stretched term, t represents the electron drift time in the ultrafast electron pulse, v represents the ultrafast electron pulse velocity, N represents the number of electrons in the ultrafast electron pulse, r represents the transverse radius of the ultrafast electron pulse, and m represents the mass of a single electron.

[0056] The slit 12 has a width of 20 μm and a distance of 4 mm from the slit 12 to the parallel deflection plate 5.

[0057] The distance between the ultrafast electron pulse 2 and the parallel deflection plate 5 is the vacuum drift distance. In this embodiment, the vacuum drift distance is close to 40cm. After passing through the vacuum drift tube 3, the electron pulse on the order of hundreds of femtoseconds will be broadened to 1-2 picoseconds.

[0058] The parallel deflection plate 5 is 50mm long, 20mm wide, and 2mm apart.

[0059] The input terminal of the signal synchronization system 9 is connected to the output terminal of the ultrafast electronic pulse generator 1. The output terminal of the signal synchronization system 9 is sequentially connected to the scanning circuit 10 and the parallel deflection plate 5. It is used to collect the output electrical signal 8 of the output terminal of the ultrafast electronic pulse generator 1 and obtain an electrical signal that is synchronized with the broadened electronic pulse entering the parallel deflection plate. The synchronized electrical signal triggers the scanning circuit to generate a scanning bias signal, which is input to the parallel deflection plate 5. A scanning deflection field is formed between the two plates of the parallel deflection plate 5 to deflect the broadened electronic pulse entering the parallel deflection plate 5.

[0060] The scanning circuit 10 provides a time-varying scanning electric field with a peak value of 1000V to the parallel deflection plate 5.

[0061] The electron pulse, after exiting from the parallel deflection plate 5, will drift 300mm and be incident on the fluorescent screen 6.

[0062] The end of the scanning deflection housing 4 furthest from the vacuum drift tube 3 is connected to the fluorescent screen 6, and the fluorescent screen 6 is connected to the electron bombardment CCD camera 7 through optical coupling adhesive.

[0063] A method for measuring the pulse width of an ultrafast electron pulse based on time-magnified fringe scanning, comprising the following steps, is based on an ultrafast electron pulse width measurement system using time-magnified fringe scanning:

[0064] S1. Disconnect the deflection control system, turn on the ultrafast electron pulse generator 1 to generate ultrafast electron pulses, and input them into the vacuum drift tube 3. Calculate the time broadening term of the ultrafast electron pulse, use the time broadening term to broaden the ultrafast electron pulse, and output the broadened electron pulse; the specific process is as follows:

[0065] S11. Turn on the ultrafast electron pulse generator 1 to generate ultrafast electron pulse 2 with a pulse width of t0.

[0066] S12. Calculate the time broadening term of the ultrafast electron pulse, using the following formula:

[0067]

[0068] Where, Δt c For time-stretched terms, t represents the electron drift time in the ultrafast electron pulse, v represents the ultrafast electron pulse velocity, N represents the number of electrons in the ultrafast electron pulse, r represents the transverse radius of the ultrafast electron pulse, and m represents the mass of a single electron.

[0069] S13. Time-stretching is performed on the ultrafast electron pulse using a time-stretching term, expressed as follows:

[0070] t x =t0+Δt c ;

[0071] Among them, tx To broaden the pulse width of the electron pulse, t0 is the pulse width of the ultrafast electron pulse generated by the ultrafast electron pulse generating device 1;

[0072] S14, Output pulse width is t x The broadened electron pulse.

[0073] S2. The broadened electron pulses pass sequentially through slit 12 and parallel deflection plate 5 and are incident on fluorescent screen 6, forming a striped light spot. The image of the striped light spot is acquired by electron bombardment CCD camera 7, and the longest dimension σ of the striped light spot is calculated. s ;

[0074] S3. Restore access to the deflection control system. The deflection control system acquires the output electrical signal of the ultrafast electron pulse generator 1, and uses the signal synchronization system 9 to delay and modulate the output electrical signal of the ultrafast electron pulse generator 1, so that the signal is synchronized with the time of the broadened electron pulse entering the parallel deflection plate 5. Then, it is used as a trigger signal input to the scanning circuit 10. The time-varying scanning bias signal 11 generated by the scanning circuit 10 is input to the parallel deflection plate 5, forming a scanning deflection field between the two plates of the parallel deflection plate 5. When the broadened electron pulse in the parallel deflection plate 5 is output, it is deflected and incident on the fluorescent screen 6 to form a stripe-like light spot. The image of the stripe-like light spot is acquired by the electron bombardment CCD camera 7, and the longest size of the stripe-like light spot is calculated as σ. d ;

[0075] S4, the size σ of the striped light spot s The size of the stripe-like light spot is σ d The pulse width of the broadened electronic pulse is calculated based on the correspondence between spatial and temporal information, using the following formula:

[0076]

[0077] Among them, v scan The scanning speed is the speed of the stripe scanning deflection system.

[0078] The ultrafast electron pulse width is calculated based on the pulse width of the broadened electron pulse and the time broadening term; the formula is:

[0079] t0 = t x -Δt c .

[0080] This embodiment employs an ultrafast electron pulse width measurement system and method based on time-amplified fringe scanning to measure ultrafast electron pulses. The evolution of the pulse width during the time amplification process of the ultrafast electron pulse is as follows: Figure 2As shown, the left side of the horizontal axis 700mm represents the evolution of the pulse width of the electron pulse during the acceleration, collimation, focusing, and pulse compression processes inside the ultrafast electron pulse generator; the right side represents the time amplification process of the ultrashort electron pulse during vacuum drift. After a time broadening of 40cm, the pulse width at the deflection plate is 592fs (RMS), or 1.394ps (FWHM). At this point, the pulse width of the broadened electron pulse can be measured using a currently common streak camera, thus meeting the measurement requirements for the length of ultrafast electron pulse bundles less than 100 femtoseconds.

[0081] In this invention, an ultrafast electron pulse width measurement system and method based on time-magnified stripe scanning is proposed. After time-broadening the ultrafast electron pulse with a value of less than 100 femtoseconds, an electric field is applied to deflect the time-broadened ultrafast electron pulse. The light spot information before and after the electric field is applied on the fluorescent screen is collected to calculate the ultrafast electron pulse width. This method can accurately characterize the pulse of ultrafast electron pulses on the femtosecond scale. It has high time resolution, simple system principle, and is easy to implement.

[0082] The above description is merely a specific embodiment of the present invention and a comparison of the effects of the specific embodiments with relevant comparative examples. However, the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A system for measuring the pulse width of ultrafast electron pulses based on time-magnified fringe scanning, characterized in that: It includes a vacuum drift tube (3), a scanning deflection housing (4), a parallel deflection plate (5), a fluorescent screen (6), an electron bombardment CCD camera (7), and a deflection control system; The input end of the vacuum drift tube (3) is used to connect with the output end of the ultrafast electron pulse generating device (1) to input ultrafast electron pulses. After the ultrafast electron pulses are pulse-broadened in the vacuum drift tube (3), broadened electron pulses are obtained. The output end of the vacuum drift tube (3) is connected with the input end of the scanning deflection housing (4), and a slit (12) is provided between the two. The parallel deflection plate (5) is provided inside the scanning deflection housing (4). The central axis of the vacuum drift tube (3) is located between the two plates of the parallel deflection plate (5) and is parallel to the two plates. The input end of the deflection control system is connected to the signal output end of the ultrafast electron pulse generator (1), and the output end is connected to the parallel deflection plate (5). It is used to collect the electrical signal output by the signal output end of the ultrafast electron pulse generator (1) and perform delay modulation to obtain a scanning bias signal that is synchronized with the time of the broadened electron pulse entering the parallel deflection plate (5). The synchronized scanning bias signal is input into the parallel deflection plate (5) to form a scanning deflection field between the two plates of the parallel deflection plate (5). The fluorescent screen (6) is installed at one end of the scanning deflection housing (4) away from the vacuum drift tube (3), and the outside of the fluorescent screen (6) is connected to the input end of the electron bombardment CCD camera (7); The formula for pulse broadening of ultrafast electron pulses by the vacuum drift tube (3) is as follows: t x =t0+Δt c ; Where t x To broaden the pulse width of the electron pulse, t0 is the pulse width of the ultrafast electron pulse generated by the ultrafast electron pulse generating device (1), Δt c The time extension term is represented as: Where t represents the electron drift time in the ultrafast electron pulse, v represents the ultrafast electron pulse velocity, N represents the number of electrons in the ultrafast electron pulse, r represents the transverse radius of the ultrafast electron pulse, m represents the mass of a single electron, and σ s When the deflection control system is disconnected, the electron bombardment CCD camera (7) acquires the longest size of the stripe-like light spot, σ. d To restore access to the deflection control system, when the broadened electronic pulse output in the parallel deflection plate (5) causes deflection, the electron bombardment CCD camera (7) acquires the longest size of the stripe-like light spot, v. scan The scanning speed is the speed of the stripe scanning deflection system.

2. The ultrafast electron pulse width measurement system based on time-magnified fringe scanning according to claim 1, characterized in that: The deflection control system includes a signal synchronization system (9) and a scanning circuit (10). The input terminal of the signal synchronization system (9) is connected to the signal output terminal of the ultrafast electron pulse generator (1). The output terminal of the signal synchronization system (9) is connected in sequence to the scanning circuit (10) and the parallel deflection plate (5). The signal synchronization system (9) is used to collect the electrical signal output from the signal output terminal of the ultrafast electron pulse generator (1) and perform delay modulation to obtain an electrical signal that is synchronized with the broadened electron pulse entering the parallel deflection plate (5). The synchronized electrical signal triggers the scanning circuit (10) to generate a scanning bias signal. The parallel deflection plate (5) is used to generate a scanning deflection field according to the scanning bias signal.

3. The ultrafast electron pulse width measurement system based on time-magnified fringe scanning according to claim 1, characterized in that: The ultrafast electron pulse has an emission energy of 200 keV, a longitudinal length of 30 fs, a transverse dimension of 200 μm, and 10,000 electrons.

4. The ultrafast electron pulse width measurement system based on time-magnified fringe scanning according to claim 1, characterized in that: The slit (12) has a width of 20 μm and a distance of 4 mm from the slit (12) to the parallel deflection plate (5).

5. The ultrafast electron pulse width measurement system based on time-magnified fringe scanning according to claim 1, characterized in that: The outside of the fluorescent screen (6) is connected to the input terminal of the electron bombardment CCD camera (7) via optical coupling adhesive.

6. A method for measuring the pulse width of ultrafast electron pulses based on time-magnified fringe scanning, characterized in that, An ultrafast electron pulse width measurement system based on time-magnified fringe scanning as described in any one of claims 1-5 includes the following steps: S1. Disconnect the deflection control system, turn on the ultrafast electron pulse generator (1) to generate ultrafast electron pulses, and input them into the vacuum drift tube (3). Calculate the time broadening term of the ultrafast electron pulse based on the parameters of the ultrafast electron pulse, and use the time broadening term to broaden the ultrafast electron pulse in the vacuum drift tube (3) to output the broadened electron pulse. S2. The broadened electron pulse passes through the slit (12) and the parallel deflection plate (5) in sequence and is incident on the fluorescent screen (6), forming a striped light spot. The image of the striped light spot is acquired by the electron bombardment CCD camera (7), and the longest dimension σ of the striped light spot is obtained. s ; S3. Reconnect to the deflection control system. The deflection control system collects the output electrical signal of the ultrafast electron pulse generator (1) and performs time delay modulation on the output electrical signal to output a scanning bias signal that is synchronized with the time of the broadened electron pulse entering the parallel deflection plate (5). The scanning bias signal is input to the parallel deflection plate (5) to form a scanning deflection field between the two plates of the parallel deflection plate (5). When the broadened electron pulse in the parallel deflection plate (5) is output, it is deflected and incident on the fluorescent screen (6) to form a stripe-like light spot. The image of the stripe-like light spot is collected by the electron bombardment CCD camera (7), and the longest size of the stripe-like light spot is σ. d ; S4, the size σ of the striped light spot s The size of the stripe-like light spot is σ d Calculate the pulse width of the broadened electron pulse, and then calculate the pulse width of the ultrafast electron pulse based on the pulse width of the broadened electron pulse and the time broadening term.

7. The method for measuring the pulse width of ultrafast electron pulses based on time-magnified fringe scanning according to claim 6, characterized in that, The specific process of S1 is as follows: S11. Disconnect the deflection control system and turn on the ultrafast electron pulse generator (1) to generate ultrafast electron pulses and input them into the vacuum drift tube (3). S12. Calculate the time-spanning term Δt of the ultrafast electron pulse based on its parameters. c The formula is: Where t represents the electron drift time in the ultrafast electron pulse, v represents the ultrafast electron pulse velocity, N represents the number of electrons in the ultrafast electron pulse, r represents the transverse radius of the ultrafast electron pulse, and m represents the mass of a single electron; S13. The ultrafast electron pulse is pulse-widened using a time-spanning term within the vacuum drift tube (3), and the expression is as follows: t x =t0+Δt c ; Among them, t x To broaden the pulse width of the electron pulse, t0 is the pulse width of the ultrafast electron pulse generated by the ultrafast electron pulse generating device (1); S14, Output pulse width is t x The broadened electron pulse.

8. The method for measuring the pulse width of ultrafast electron pulses based on time-magnified fringe scanning according to claim 6, characterized in that, In S4, the size σ of the stripe-like light spot... s The size of the stripe-like light spot is σ d The formula for calculating the pulse width of a broadened electronic pulse is: Among them, v scan The scanning speed is the speed of the stripe scanning deflection system.

9. The method for measuring the pulse width of ultrafast electron pulses based on time-magnified fringe scanning according to claim 8, characterized in that, In S4, the formula for calculating the ultrafast electron pulse width based on the pulse width of the broadened electron pulse and the time broadening term is as follows: t0=t x -Δt c 。

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