Hundred femtosecond pulse length free electron laser generation device and method based on electron beam cutting

Abstract

This invention discloses a device and method for generating a 100-femtosecond pulse-length free-electron laser based on electron beam cutting. The device includes: an electron beam generating device, an electron beam accelerating device, a beam focusing device, an electron beam cutting device, a free-electron laser generating device, an electron beam pulse length measuring device, and a free-electron laser measuring device. This invention can cut an electron beam into a 100-femtosecond electron beam using the electron beam cutting device, thereby obtaining a 100-femtosecond pulse-length free-electron laser. This free-electron laser has good quality and can be used for experimental research on the 100-femtosecond timescale.

Description

Technical Field

[0001] This invention relates to ultrashort laser pulse generation technology in the field of free-electron lasers. Background Technology

[0002] Free-electron lasers (LEX) are currently recognized as a viable technology for fourth-generation light sources. They combine accelerator and laser technologies, offering wide spectral coverage, continuously tunable wavelengths, high peak power and brightness, narrow spectral width, short pulse width, and excellent temporal structure and coherence. These superior characteristics have led to widespread attention and application of LEX in numerous fields. Many intermediate processes in chemical reactions occur on timescales of hundreds of femtoseconds or even shorter. These intermediate processes are typically detected using pump-probe experiments, allowing for a clear view of how a chemical reaction occurs. Therefore, researching how to generate LEX with femtosecond pulse lengths is essential. Summary of the Invention

[0003] The purpose of this invention is to provide a device and method for generating a 100-femtosecond pulse length free electron laser based on electron beam cutting.

[0004] The technical solution of this invention is: a femtosecond pulse length-free electron laser generation device based on electron beam cutting, comprising:

[0005] An electron beam generating device 1 is used to generate a high-quality electron beam with high flux, low emissivity, and low energy dissipation.

[0006] An electron beam accelerator that accelerates the high-quality electron beam generated by the electron beam generating device 1 to a higher energy.

[0007] The focusing device 3 shortens the longitudinal length of the electron beam, thereby increasing the peak current intensity of the electron beam;

[0008] Electron beam cutting device 4, which cuts an electron beam into a hundred femtosecond electron beam;

[0009] Free electron laser generating device 5, which uses a femtosecond electron beam to generate a free electron laser with a pulse length of femtosecond.

[0010] Electron beam pulse length measuring device 6 is used to measure the longitudinal length of the electron beam after it has been cut by electron beam cutting device 4, so as to ensure that the electron beam after passing through electron beam cutting device 4 is a 100 femtosecond electron beam.

[0011] The free electron laser measuring device 7 is used to measure the spectral information and pulse energy information of the free electron laser generated by the femtosecond electron beam in the free electron laser generating device 5, thereby verifying that the free electron laser generated in the free electron laser generating device (5) is a femtosecond pulse length free electron laser.

[0012] Preferably, the electron beam generating device 1 is a photocathode microwave electron gun.

[0013] Preferably, the electron beam acceleration device is an electron linear accelerator, comprising: a first-stage electron beam acceleration device 21 and a second-stage electron beam acceleration device 22.

[0014] Preferably, the focusing device 3 is a magnetic compression system, which consists of four diode magnets 31, from left to right, namely the first to the fourth diode magnets. The second diode magnet is placed at a position 6° away from the first diode magnet. The projected length between the two magnets is 2.2m, and the projected length between the second and third diode magnets is 1.0m. The third and fourth diode magnets are mirror images of the second and first diode magnets in the left-right direction, respectively.

[0015] Preferably, the electron beam cutting device 4 consists of two blocks 41, placed between the second and third diode magnets in the beam-gathering device 3.

[0016] Preferably, the free electron laser generating device 5 is an undulator system, comprising, from left to right: a modulation undulator 51, a dispersion undulator 52, and a radiation undulator 53. The dispersion undulator 52 consists of four diode magnets with the same magnetic field strength, arranged from left to right as the first to the fourth diode magnets. The second diode magnet is positioned 1° away from the first diode magnet. The projected length between the two magnets is 1.32m, and the projected length between the second and third diode magnets is 1.0m. The third and fourth diode magnets are mirror images of the second and first diode magnets, respectively, in the left-right direction. The electron beam undergoes energy modulation in the modulation undulator 51, density modulation in the dispersion undulator 52, and radiates a free electron laser in the radiation undulator 53.

[0017] Preferably, the electron beam pulse length measuring device 6 uses the zero-phase method, which involves introducing longitudinal linear correlation energy dispersion into the electron beam and projecting the energy distribution of the electron beam onto the energy analysis station at the end of the electron beam acceleration device 2. Since the longitudinal distribution of the electron beam along the z-direction corresponds one-to-one with the energy distribution, the longitudinal distribution of the electron beam along the z-direction can be deduced by measuring the energy distribution of the electron beam, thereby obtaining the pulse length of the electron beam.

[0018] Preferably, the free electron laser measuring device 7 includes a variable-pitch grating spectrometer 71 and a photodiode 72. The variable-pitch grating spectrometer 71 is used to measure the spectral information of the free electron laser, and the photodiode 72 is used to measure the pulse energy information of the free electron laser.

[0019] The device, from left to right, includes:

[0020] Electron beam generating device 1, first-stage electron beam accelerating device 21, focusing device 3, second-stage electron beam accelerating device 22, electron beam pulse length measuring device 6, free electron laser generating device 5, free electron laser measuring device 7;

[0021] The beam focusing device 3 consists of a diode magnet 31 and an electron beam cutting device 4, and the electron beam cutting device 4 contains two baffles 41.

[0022] The free electron laser generating device 5 consists of a modulation section undulator 51, a dispersion section 52, and a radiation section undulator 53.

[0023] The free-electron laser measurement device 7 consists of a variable-pitch grating spectrometer 71 and a photodiode 72.

[0024] The method is as follows:

[0025] Electron beam generating device 1 generates a high-current, low-emissivity, and low-energy-dispersion high-quality electron beam. This high-quality electron beam enters the first-stage electron beam accelerator 21 for acceleration and is compressed longitudinally by a focusing device 3. An electron beam cutter 4 is located in the middle of the focusing device 3. Before entering the focusing device 3, the microwave phase in the first-stage electron beam accelerator 21 is adjusted to position the electron beam at a microwave off-peak phase, resulting in an electron beam with low energy at the head and high energy at the tail. This links the longitudinal position information and energy distribution information within the electron beam. After entering the focusing device 3, under the dispersion effect of the first two diode magnets 31, electrons of different energies in the electron beam will be distributed at different horizontal positions. The electron beam cutter 4 then cuts off the portion of the electron beam that does not meet the energy requirements in the horizontal direction. The distribution and longitudinal position distribution are in one-to-one correspondence, which is equivalent to shortening the electron beam in the longitudinal direction, thereby obtaining a 100-femtosecond electron beam. After being accelerated to a higher energy by the second-stage electron beam acceleration device 22, the 100-femtosecond electron beam enters the free electron laser generating device 5 and radiates a 100-femtosecond pulse length free electron laser. The longitudinal length of the electron beam after being cut by the electron beam cutting device 4 is measured using the electron beam pulse length measuring device 6, thereby confirming that the electron beam after being cut by the electron beam cutting device 4 is a 100-femtosecond electron beam. The spectral information and pulse energy information of the free electron laser radiated in the free electron laser generating device are measured using the free electron laser measuring device 7, thereby confirming that the obtained free electron laser pulse length is 100 femtoseconds and the feasibility and effectiveness of the 100-femtosecond pulse length free electron laser generation method based on electron beam cutting.

[0026] The present invention has the following beneficial effects:

[0027] This invention uses an electron beam cutting device 4 to cut an electron beam into a 100-femtosecond electron beam, thereby obtaining a free electron laser with a 100-femtosecond pulse length. Using an electron beam pulse length measuring device 6 to measure the longitudinal length of the cut electron beam ensures that the electron beam cut by the electron beam cutting device 4 is a 100-femtosecond electron beam. Using a free electron laser measuring device 7 to measure the spectral and pulse energy information of the free electron laser emitted in the free electron laser generating device 5 confirms that the obtained free electron laser has a pulse length of 100 femtoseconds and good quality, suitable for experimental research on a 100-femtosecond timescale. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the femtosecond pulse length-free electron laser generation device based on electron beam cutting in an embodiment of the present invention;

[0029] In the diagram: 1. Electron beam generating device; 21. First-stage electron beam accelerating device; 22. Second-stage electron beam accelerating device; 3. Focusing device; 31. Diode magnet; 4. Electron beam cutting device; 41. Stop block; 5. Free electron laser generating device; 51. Modulation section undulator; 52. Dispersion section; 53. Radiation section undulator; 6. Electron beam pulse length measuring device; 7. Free electron laser measuring device; 71. Variable line spacing grating spectrometer; 72. Photodiode. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] A 100-femtosecond pulse length-free electron laser generation device based on electron beam cutting includes:

[0032] Electron beam generating device 1, which is used to generate a high-quality electron beam with high flux, low emissivity and low energy dissipation.

[0033] An electron beam accelerator accelerates the high-quality electron beam generated by electron beam generator 1 to a higher energy.

[0034] The focusing device 3 shortens the longitudinal length of the electron beam, thereby increasing the peak current intensity of the electron beam.

[0035] Electron beam cutting device 4 cuts the electron beam into 100 femtosecond electron beams;

[0036] Free electron laser generating device 5 uses a 100-femtosecond electron beam to generate a free electron laser with a 100-femtosecond pulse length.

[0037] Electron beam pulse length measuring device 6 is used to measure the longitudinal length of the electron beam after it has been cut by electron beam cutting device 4, so as to ensure that the electron beam after passing through electron beam cutting device 4 is a 100 femtosecond electron beam.

[0038] The free electron laser measurement device 7 is used to measure the spectral information and pulse energy information of the free electron laser generated by the femtosecond electron beam in the free electron laser generating device 5.

[0039] The system includes: an electron beam generating device 1, a photocathode microwave electron gun; an electron beam accelerating device, a linear accelerator comprising a first-stage electron beam accelerating device 21 and a second-stage electron beam accelerating device 22; a focusing device 3, a magnetic compression system consisting of four dipole magnets 31; an electron beam cutting device 4, two baffles 41; and a free electron laser generating device 5, an undulator system comprising a modulation section undulator 51, a dispersion section 52, and a radiation section undulator 53. The electron beam undergoes energy modulation in the modulation section undulator 51, density modulation in the dispersion section 52, and radiates a free electron laser in the radiation section undulator 53. Electron beam pulse length measurement is also included. Device 6 uses the zero-phase method, which involves introducing longitudinal linear correlation energy dispersion into the electron beam and projecting the energy distribution of the electron beam onto the energy analysis station at the end of the electron beam acceleration device. Since the longitudinal distribution of the electron beam along the z-direction corresponds one-to-one with the energy distribution, the longitudinal distribution of the electron beam along the z-direction can be deduced by measuring the energy distribution of the electron beam, thereby obtaining the pulse length of the electron beam. The free electron laser measurement device 7 includes a variable-pitch grating spectrometer 71 and a photodiode 72. The variable-pitch grating spectrometer 71 is used to measure the spectral information of the free electron laser, and the photodiode 72 is used to measure the pulse energy information of the free electron laser.

[0040] The generation method is as follows:

[0041] Electron beam generating device 1 generates a high-current, low-emissivity, and low-energy-dispersion high-quality electron beam. This high-quality electron beam then enters the first-stage electron beam accelerator 21 for acceleration, and is compressed longitudinally by a focusing device 3. An electron beam cutter 4 is located in the middle of the focusing device 3. Before entering the focusing device 3, the microwave phase in the electron beam accelerator 21 is adjusted to position the electron beam at a microwave off-peak phase, resulting in an electron beam with low energy at the head and high energy at the tail. This links the longitudinal position information and energy distribution information within the electron beam. After entering the focusing device 3, under the dispersion effect of the first two diode magnets 31, electrons of different energies in the electron beam will be distributed at different horizontal positions. The electron beam cutter 4 then removes the portion of the electron beam that does not meet the energy requirements in the horizontal direction. The distribution and longitudinal position distribution are in one-to-one correspondence, which is equivalent to shortening the electron beam in the longitudinal direction, thus obtaining a 100-femtosecond electron beam. After being accelerated to a higher energy by the second-stage electron beam acceleration device 22, the 100-femtosecond electron beam enters the free electron laser generating device 5 and radiates a 100-femtosecond pulse length free electron laser. The longitudinal length of the electron beam after being cut by the electron beam cutting device 4 is measured using the electron beam pulse length measuring device 6, thereby confirming that the electron beam after being cut by the electron beam cutting device 4 is a 100-femtosecond electron beam. The spectral information and pulse energy information of the free electron laser radiated in the free electron laser generating device are measured using the free electron laser measuring device 7, thereby confirming that the obtained free electron laser pulse length is 100 femtosecond and the feasibility and effectiveness of the 100-femtosecond pulse length free electron laser generation method based on electron beam cutting.

[0042] The measurement results of the 100-femtosecond free-electron laser generated using this method are as follows:

[0043] The emission mode was HGHG. When the electron beam passed through the modulation undulator 51, the seed laser wavelength was 243 nm, the pulse length was 1 ps, and the harmonic conversion order was 2. The length of the cut electron beam was shorter than the seed laser length, and the emission time should be consistent with the electron beam length. Therefore, the emitted free electron laser should be 100 femtosecond light. The relevant measurement information of the free electron laser is summarized in Table 1. The measurement results show that the pulse energy of the electron beam emitted in 100 femtoseconds is 4.2 μJ, and the spectral distribution is relatively ideal, with the center wavelength at 121.333 nm and the full width at half maximum (FWHM) of the spectrum at 156.2 cm. -1 Based on an electron beam length (FWHM) of 150 fs, the corresponding Fourier transform bandwidth is 98.0 cm. -1Therefore, the spectral bandwidth of the electron beam emitted in 100 femtoseconds is about 1.6 times the Fourier transform limit bandwidth. This indicates that the pulse length of the free electron laser emitted by the cut electron beam is 100 femtoseconds and has good quality, which can be used for experimental research on the 100 femtosecond timescale.

[0044] Table 1. Measurement results of free electron laser during electron beam picosecond and femtosecond laser emission.

[0045]

[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A device for generating a 100-femtosecond pulse length-free electron laser based on electron beam cutting, characterized in that, include: An electron beam generating device (1) is used to generate a high-quality electron beam with high flux, low emissivity, and low energy dissipation. An electron beam accelerator accelerates a high-quality electron beam generated by an electron beam generating device (1) to a higher energy. A beam-focusing device (3) shortens the longitudinal length of the electron beam, thereby increasing the peak current of the electron beam. Electron beam cutting device (4), which cuts the electron beam into 100 femtosecond electron beams; Free electron laser generating device (5), which uses a femtosecond electron beam to generate a free electron laser with a pulse length of a femtosecond; Electron beam pulse length measuring device (6) is used to measure the longitudinal length of the electron beam after it has been cut by the electron beam cutting device (4) to ensure that the electron beam after it has been cut by the electron beam cutting device (4) is a 100 femtosecond electron beam. Free electron laser measuring device (7), the free electron laser measuring device (7) is used to measure the spectral information and pulse energy information of the free electron laser generated by the femtosecond electron beam in the free electron laser generating device (5), thereby verifying that the free electron laser generated in the free electron laser generating device (5) is a femtosecond pulse length free electron laser; The focusing device (3) is a magnetic compression system, which consists of four polar magnets (31) with the same magnetic field strength. From left to right, they are the first to the fourth polar magnets. The second polar magnet is placed at a position 6° away from the first polar magnet. The projected length between the two magnets is 2.2m, and the projected length between the second and third polar magnets is 1.0m. The third and fourth polar magnets are mirror images of the second and first polar magnets in the left and right directions, respectively. The electron beam cutting device (4) consists of two blocks (41) placed between the second and third diode magnets in the beam-gathering device (3); The free electron laser generating device (5) is an undulator system, which includes, from left to right, a modulation section undulator (51), a dispersion section (52), and a radiation section undulator (53). The dispersion section (52) consists of four polar magnets with the same magnetic field strength, which are the first to the fourth polar magnets from left to right. The second polar magnet is placed at a position 1° away from the first polar magnet. The projected length between the two magnets is 1.32m, and the projected length between the second and third polar magnets is 1.0m. The third and fourth polar magnets are mirror images of the second and first polar magnets, respectively. The electron beam is modulated in energy in the modulation section undulator (51), modulated in density in the dispersion section (52), and radiates a free electron laser in the radiation section undulator (53).

2. The femtosecond pulse length-free electron laser generation device based on electron beam cutting according to claim 1, characterized in that, The electron beam generating device (1) is a photocathode microwave electron gun.

3. The femtosecond pulse length-free electron laser generation device based on electron beam cutting according to claim 1, characterized in that, The electron beam acceleration device is an electron linear accelerator, comprising: a first-stage electron beam acceleration device (21) and a second-stage electron beam acceleration device (22).

4. The femtosecond pulse length-free electron laser generation device based on electron beam cutting according to claim 1, characterized in that, The electron beam pulse length measuring device (6) uses the zero-phase method.

5. The femtosecond pulse length-free electron laser generation device based on electron beam cutting according to claim 1, characterized in that, The free electron laser measurement device (7) includes a variable line spacing grating spectrometer (71) and a photodiode (72). The variable line spacing grating spectrometer (71) is used to measure the spectral information of the free electron laser, and the photodiode (72) is used to measure the pulse energy information of the free electron laser.

6. The femtosecond pulse length-free electron laser generation device based on electron beam cutting according to claim 1, characterized in that: The device, from left to right, includes an electron beam generating device (1), a first-stage electron beam accelerating device (21), a beam focusing device (3), a second-stage electron beam accelerating device (22), an electron beam pulse length measuring device (6), a free electron laser generating device (5), and a free electron laser measuring device (7). The beam focusing device (3) consists of a diode magnet (31) and an electron beam cutting device (4), and the electron beam cutting device (4) has two stops (41); The free-electron laser generating device (5) consists of a modulation section undulator (51), a dispersion section (52), and a radiation section undulator (53); the free-electron laser measuring device (7) consists of a variable-pitch grating spectrometer (71) and a photodiode (72).

7. A method for generating a 100-femtosecond pulse-length free-electron laser based on electron beam cutting using the apparatus described in any one of claims 1-6, characterized in that, The method is as follows: An electron beam generating device (1) generates a high-current, low-emissivity, and low-energy-dispersion high-quality electron beam. The high-quality electron beam enters the first-stage electron beam accelerator (21) for acceleration and is compressed in the longitudinal length by a beam-focusing device (3). An electron beam cutting device (4) is located in the middle of the beam-focusing device (3). Before the electron beam enters the beam-focusing device (4), the microwave phase in the first-stage electron beam accelerator (21) is adjusted to make the electron beam located on the microwave off-peak phase, resulting in a low-energy head and high-energy tail. Electron beam; When the electron beam enters the focusing device (3), under the dispersion effect of the first two diode magnets (31), electrons of different energies in the electron beam will be distributed at different horizontal positions. The electron beam cutting device (4) cuts off the part of the electron beam that does not meet the energy requirements in the horizontal direction, thereby obtaining a 100-femtosecond electron beam; After being cut, the 100-femtosecond electron beam is accelerated to 300MeV by the second-stage electron beam acceleration device (22) and enters the free electron laser generating device (5) to radiate a free electron laser with a 100-femtosecond pulse length.

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