Apparatus and method for boosting repetition rate of an accelerator coherent light source

Abstract

The application relates to a device and method for improving the repetition frequency of an accelerator coherent light source, which comprises a resonance device, a modulation device and a radiation undulator, the modulation device and the radiation undulator are arranged in sequence along the electron beam transmission direction and located in the same vertical plane, and the modulation device and the resonance device form a closed loop to make the modulation light circulate in the resonance device and the modulation device. The device and method for improving the repetition frequency of the accelerator coherent light source can make the modulation light circulate in the resonance device and the modulation device, repeatedly act on the electron beam, and adjust the repetition frequency of the modulation light, so that the repetition frequency is no longer limited by the repetition frequency of the external seed laser.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of accelerator coherent light source, and more particularly to a device and method for improving the repetition frequency of accelerator coherent light source. BACKGROUND

[0002] In the past few decades, light sources based on electron accelerators have become large scientific platforms to support multidisciplinary researches in physics, chemistry, biology, material science, etc.

[0003] The storage ring based synchrotron light source has high repetition frequency and supports multi-user operation. However, since the storage ring synchrotron light source is based on the spontaneous radiation of the electron beam, the peak current of the electron beam is low and the energy dispersion is large, so the brightness is not high and there is no longitudinal coherence.

[0004] The free electron laser based on the linear accelerator is a new generation of advanced light source, which pushes the peak brightness to a new level. The peak brightness of the free electron laser is several orders of magnitude higher than that of the storage ring light source, and the transverse and longitudinal full coherence of the extreme ultraviolet and soft x wave band can be obtained based on the external seed mode in the free electron laser. This unprecedented full coherence and high energy light source can be used to detect the ultrafast dynamics of microscopic material structure. However, the electron beam in the free electron laser cannot be reused in the ring like the synchrotron light source, which directly limits the repetition frequency of the radiation pulse. The repetition frequency can only be improved by using an expensive high repetition frequency electron gun and a superconducting linear accelerator. In addition, it cannot meet the use of multiple users. The energy recovery type light source based on the linear accelerator can push the electron beam repetition frequency to the GHz level. However, due to the low average current of the electron beam, it is not possible to generate high average power coherent radiation light.

[0005] Currently, generating high repetition frequency coherent extreme ultraviolet and x-ray radiation light is the goal pursued by most new advanced light sources in the world. In order to generate such light source based on electron accelerator, the most common technology is to modulate the electron beam based on external seed laser. However, in order to generate laser wavelength scale micro clusters in the electron beam, a large seed laser power is often needed for modulation, thereby generating full coherent extreme ultraviolet and x-ray radiation, which greatly limits the repetition frequency of the seed laser. Through the way of laser multi-dimensional manipulation of the electron beam, the synchrotron based on the role dispersion mechanism can introduce a small power seed laser to form a very strong pre-bunching before radiation, thereby generating full coherent soft x wave band radiation. However, the average power of the external seed laser is still difficult to meet the demand, thereby limiting the repetition frequency of the final radiation pulse, and it is difficult to meet some scientific experiments and industrial applications such as extreme ultraviolet lithography that require high average power coherent radiation light. SUMMARY

[0006] The present application aims to provide a device and method for improving the repetition frequency of an accelerator coherent light source to generate fully coherent radiation light with high repetition frequency.

[0007] To achieve the above object, the present application provides a device for improving the repetition frequency of an accelerator coherent light source, comprising a resonance device, a modulation device and a radiation undulator, the modulation device and the radiation undulator are arranged in sequence along the electron beam transmission direction and located in the same vertical plane, the modulation device and the resonance device form a closed loop to make the modulation light circulate in the resonance device and the modulation device.

[0008] Further, the modulation device comprises a transverse dispersion section, a modulation undulator and a bunching section arranged in sequence along the electron beam transmission direction.

[0009] Further, the transverse dispersion section is composed of two dipole magnets.

[0010] Further, the resonance device comprises a first mirror, a second mirror, a third mirror and a fourth mirror, the first mirror is located downstream of the modulation undulator, the fourth mirror is located upstream of the modulation device, after the modulation light passes through the modulation undulator, it is reflected by the first mirror, the second mirror, the third mirror and the fourth mirror in sequence and then reenters the modulation undulator to realize circulation.

[0011] Further, the bunching section is composed of two vertically opposite dipole magnets and a drift section between the two dipole magnets.

[0012] Further, the reflectivity of the first mirror, the second mirror, the third mirror and the fourth mirror is adjustable, so as to change the energy of the modulation light by adjusting the reflectivity of the first mirror, the second mirror, the third mirror and the fourth mirror.

[0013] Further, the spacing between the first mirror, the second mirror, the third mirror and the fourth mirror is adjustable, so as to change the repetition frequency of the modulation light by adjusting the sum of the spacing between the first mirror, the second mirror, the third mirror and the fourth mirror.

[0014] Further, a fifth mirror is provided, which is located upstream of the fourth mirror and is arranged to reflect external seed laser into the modulation device.

[0015] The present application also provides a method for improving the repetition frequency of an accelerator coherent light source, comprising the following steps:

[0016] The application provides a modulation device and a resonance device forming a closed loop; the modulation device comprises a transverse dispersion section, a modulation undulator and a bunching section arranged in sequence along the transmission direction of an electron beam; the resonance device comprises a first mirror, a second mirror, a third mirror and a fourth mirror; the first mirror is located downstream of the modulation undulator of the modulation device; and the fourth mirror is located upstream of the modulation device.

[0017] The distance between the first mirror, the second mirror, the third mirror and the fourth mirror is adjusted so that the sum of the distances between the first mirror, the second mirror, the third mirror and the fourth mirror is a first preset value.

[0018] An electron beam accelerated by an accelerator is continuously injected into the modulation device.

[0019] An external seed laser is introduced into the modulation device so that the seed laser is used as modulation light to modulate the energy of the electron beam in the modulation undulator; meanwhile, the radiation light generated by the modulation undulator reenters the modulation undulator after sequentially passing through the first mirror, the second mirror, the third mirror and the fourth mirror, so as to realize circulation, so that the electron beam generates radiation gain on the modulation light.

[0020] The reflectivity of the first mirror, the second mirror, the third mirror and the fourth mirror is adjusted so that the energy of the modulation light remains unchanged in the closed loop.

[0021] The modulation light with unchanged energy modulates the energy of the electron beam in the modulation undulator; the electron beam subjected to energy modulation generates micro-bunching after passing through the bunching section; and the electron beam subjected to micro-bunching emits coherent radiation light after passing through the radiation undulator.

[0022] The application also provides a method for improving the repetition frequency of an accelerator-based coherent light source, which comprises the following steps:

[0023] The application provides a modulation device and a resonance device forming a closed loop; the modulation device comprises a transverse dispersion section, a modulation undulator and a bunching section arranged in sequence along the transmission direction of an electron beam; the resonance device comprises a first mirror, a second mirror, a third mirror and a fourth mirror; the first mirror is located downstream of the modulation undulator of the modulation device; and the fourth mirror is located upstream of the modulation device.

[0024] The distance between the first mirror, the second mirror, the third mirror and the fourth mirror is adjusted so that the sum of the distances between the first mirror, the second mirror, the third mirror and the fourth mirror is a second preset value.

[0025] The electron beam accelerated by the accelerator is continuously injected into the modulation device, so that the electron beam generates radiation light by noise oscillation in the modulation wave undulator, the radiation light modulates the energy of the subsequent electron beam as the modulation light, and the radiation light reenters the modulation wave undulator after sequentially passing through the first mirror, the second mirror, the third mirror and the fourth mirror, so that the subsequent electron beam generates radiation gain of the modulation light;

[0026] The reflectivity of the first mirror, the second mirror, the third mirror and the fourth mirror is adjusted, so that the energy of the modulation light is enhanced in the closed loop with each round;

[0027] After the preset condition is met, the reflectivity of the first mirror, the second mirror, the third mirror and the fourth mirror is adjusted, so that the energy of the modulation light remains unchanged in the closed loop with each round;

[0028] The modulation light with unchanged energy modulates the energy of the electron beam in the modulation wave undulator, the electron beam after energy modulation generates micro-bunching after passing through the bunching section, and the electron beam generating micro-bunching emits coherent radiation light after passing through the radiation wave undulator.

[0029] The device and method for improving the repetition frequency of the accelerator coherent light source adopt seed laser input from outside or radiation light generated by noise oscillation of the electron beam as the modulation light, the modulation light can circulate in the resonant device and the modulation device, so that the modulation light repeatedly acts on the electron beam, the repetition frequency of the modulation light can be adjusted, and is no longer limited by the repetition frequency of the external seed laser; through the chromatic dispersion system, the electron beam forms a strong coherent cluster to realize the generation of high-repetition-frequency coherent extreme ultraviolet and X-ray. The device of the embodiment adopts elements such as diode, mirror and undulator, has low cost, small technical difficulty and low operation cost, and can meet the needs of extreme ultraviolet / X-ray lithography research and industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a structural block diagram of the device for improving the repetition frequency of the accelerator coherent light source according to the embodiment of the application;

[0031] Figure 2 It is a structural schematic diagram of the device for improving the repetition frequency of the accelerator coherent light source according to the first embodiment of the application;

[0032] Figure 3 It is a structural schematic diagram of the device for improving the repetition frequency of the accelerator coherent light source according to the second embodiment of the application;

[0033] Figure 4 It is a flowchart of the method for improving the repetition frequency of the accelerator coherent light source according to an embodiment of the application;

[0034] Figures 5A-5CFig. 2 is a schematic diagram of simulation results of the device for improving the repetition frequency of an accelerator coherent light source according to the first embodiment of the present application, wherein Figure 5A Fig. 2 shows the relationship between the number of turns and the pulse energy of the modulated light; Figure 5B Fig. 3 shows the radiation pulse power generated by the electron beams from the 50th to the 100th after passing through the radiation undulator, Figure 5B wherein s is the longitudinal position coordinate of the electrons in the electron beam; Figure 5C Fig. 4 shows the radiation spectrum generated by the electron beams from the 50th to the 100th after passing through the radiation undulator, Figure 5C wherein the horizontal axis λ is the wavelength and the vertical axis P(λ) is the normalized light intensity;

[0035] Figure 6 Fig. 5 is a flow chart of the method for improving the repetition frequency of an accelerator coherent light source according to another embodiment of the present application;

[0036] Figures 7A-7C Fig. 6 is a schematic diagram of simulation results of the device for improving the repetition frequency of an accelerator coherent light source according to the second embodiment of the present application, wherein Figure 7A Fig. 6 shows the relationship between the number of turns and the pulse energy of the modulated light; Figure 7B Fig. 7 shows the radiation pulse power generated by the electron beams from the 180th to the 250th after passing through the radiation undulator, Figure 7B wherein s is the longitudinal position coordinate of the electrons in the electron beam; Figure 7C Fig. 8 shows the radiation spectrum generated by the electron beams from the 180th to the 250th after passing through the radiation undulator, Figure 7C wherein the horizontal axis λ is the wavelength and the vertical axis P(λ) is the normalized light intensity. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0038] As Figure 1As shown, this embodiment of the invention provides an apparatus for increasing the repetition frequency of a coherent light source in an accelerator. The apparatus includes a resonant device 100, a modulation device 200, and a radiation undulator 300. The modulation device 200 and the radiation undulator 300 are arranged sequentially along the electron beam transmission direction and located in the same vertical plane. The resonant device 100 and the modulation device 200 form a closed loop, allowing the modulated light to circulate within them. In use, electron beams accelerated by the accelerator are sequentially input into the modulation device 200. In the modulation device 200, a seed laser interacts with each electron beam, generating a micro-focused electron beam in the extreme ultraviolet to X-ray band based on a divergence mechanism. The focused electron beam is then sent to the radiation undulator 300, thereby generating high-brightness extreme ultraviolet or X-ray radiation. Because the seed laser can circulate within the resonant device 100 and the modulation device 200, it can be reused to interact with the electron beam, no longer limited by the repetition frequency of the seed laser.

[0039] like Figure 2 As shown, in the first embodiment, the modulation device 200 includes a lateral dispersion section 210, a modulation undulator 220, and a focusing section 230 arranged sequentially along the electron beam transmission direction. The lateral dispersion section 210 may be composed of a single dipole, while the modulation undulator 220 and the radiation undulator 300 may each be composed of multiple quadrupoles. The focusing section 230 may be composed of two perpendicularly opposite dipoles 231 and 232, and a drift section 233 between them. The lateral dispersion section 210 primarily provides modulation of the electron beam angular dispersion, while the focusing section 230 primarily serves to coherently cluster the electron beam. The resonant device 100 includes a first reflector 110, a second reflector 120, a third reflector 130, and a fourth reflector 140. The four reflectors are located at the four corners of the closed loop formed by the resonant device 100 and the modulation device 200. The first reflector 110 is located downstream of the modulation device 200, and the fourth reflector 140 is located upstream of the modulation device 200. After passing through the modulation device 200, the modulated light reaches the first reflector 110 and is reflected by the first reflector 110 to the second reflector 120, then reflected by the second reflector 120 to the third reflector 130, then reflected by the third reflector 130 to the fourth reflector 140, and then reflected by the fourth reflector 140 back into the modulation device 200, and so on in a continuous cycle.

[0040] In some embodiments, the device can further comprise a fifth mirror 400, which is located upstream of the fourth mirror 140, for introducing the seed laser from outside into the closed loop composed of the resonant device 100 and the modulation device 200. Specifically, first pull open the fourth mirror 140, the external laser (not shown in the figure) sends a seed laser to the fifth mirror 400, which is reflected by the fifth mirror 400, enters the modulation device 200, and restores the position of the fourth mirror 140, so that the laser moves in the closed loop.

[0041] In an exemplary embodiment, the seed laser can be emitted by an ultrafast laser (i.e. a laser with a pulse width of less than 100 femtoseconds), the wavelength of the seed laser is 266 nm, the pulse width is 400 fs, and the peak power is 15 MW.

[0042] In use, the accelerated electron beam (for example, a high-energy electron beam generated by a synchrotron ring) can be continuously input into the modulation device 200 first, and then the seed laser is introduced into the modulation device 200 as the modulation light. After passing through the transverse dispersion section 210, the electron beam enters the modulation undulator 220, in which the modulation light modulates the energy of the electron beam, while the electron beam generates radiation gain (i.e. radiation light) of the modulation light in the modulation undulator 220, which can enhance the energy of the modulation light. The gain of the modulation light passes through the first mirror 110, the second mirror 120, the third mirror 130 and the fourth mirror 140 in turn and reenters the modulation undulator 220 to modulate the energy of the subsequent electron beam, and the subsequent electron beam generates radiation gain of the modulation light, which is repeated in a cycle. Since the modulation light will be lost during transmission in the optical path (i.e. closed loop), if the radiation gain of the electron beam to the modulation light is greater than the loss of the modulation light during transmission in the optical path, the energy of the modulation light will be enhanced a little bit every cycle, that is, the energy of the modulation light will be continuously enhanced. If the radiation gain of the electron beam to the modulation light is less than the loss of the modulation light during transmission in the optical path, the energy of the modulation light will be continuously weakened. If the radiation gain of the electron beam to the modulation light is equal to the loss of the modulation light during transmission in the optical path, the energy of the modulation light will remain unchanged. Therefore, in this embodiment, the energy of the modulation light can be changed by adjusting the loss of the modulation light during transmission in the optical path, so that the loss of the modulation light during transmission in the optical path is equal to the radiation gain of the electron beam to the modulation light, so that the pulse energy of the modulation light remains unchanged, so that the subsequent electron beam is repeatedly modulated by the modulation light with the same energy modulation depth.

[0043] In some embodiments, the loss of the modulated light during the transmission in the optical path can be changed by mechanically disturbing the reflecting surface of the mirror, or a filter can be added in the optical path to increase the loss of the modulated light during the transmission in the optical path, or the reflectivity of each mirror can be changed to change the loss of the modulated light during the transmission in the optical path.

[0044] After the energy-modulated electron beam passes through the bunching section 230, a strong micro-bunch is generated, and the interval of the micro-bunch is the wavelength of the seed laser (for example, 266 nm). After the micro-bunch electron beam passes through the radiation undulator 300, high-harmonic radiation of the wavelength of the seed laser can be emitted, and the radiation flux and brightness are proportional to the square of the number of electrons in the micro-bunch.

[0045] In some embodiments, the repetition frequency of the modulated light can be changed by adjusting the interval between the mirrors 110, 120, 130 and 140. Specifically, by adjusting the interval between the mirrors 110, 120, 130 and 140, the time required for the modulated light to make one revolution can be changed, thereby changing the repetition frequency of the modulated light. For example, in an exemplary embodiment, the repetition frequency of the modulated light is 10 MHz, which requires 10e7 revolutions in one second, and the distance traveled by the light in one second is 3*10e8 meters, so the distance traveled by the light for one revolution is 30 meters. That is, if the sum of the intervals of the four mirrors 110, 120, 130 and 140 is 30 meters, then the repetition frequency of the modulated light can reach 10 MHz. Based on this, the device of the first embodiment of the present application is no longer limited to the repetition frequency of the initially injected seed laser, and only needs to inject a seed laser with a repetition frequency of 1 Hz, and by adjusting the interval between the mirrors 110, 120, 130 and 140, a modulated light with a high repetition frequency can be obtained, thereby easily matching the repetition frequency of the electron beam in the electron accelerator.

[0046] The device for increasing the repetition frequency of the accelerator coherent light source of the present embodiment uses an externally input seed laser as the modulated light, which can circulate in the resonant device 100 and the modulation device 200, thereby repeatedly acting on the electron beam, so that the repetition frequency of the modulated light can be adjusted and is no longer limited by the repetition frequency of the external seed laser. Through the chromatic dispersion system, the electron beam forms a strong coherent cluster to achieve the generation of high-repetition-frequency coherent extreme ultraviolet and X-ray. The device of the present embodiment is composed of elements such as dipole magnets, mirrors and undulators, has low cost, small technical difficulty and low operating cost, and can meet the needs of extreme ultraviolet / X-ray lithography research and industrial applications.

[0047] As Figure 3As shown, the second embodiment of the present application provides a device for improving the repetition frequency of an accelerator coherent light source. The structure of the second embodiment is basically the same as that of the first embodiment, and the only difference is that the device of the second embodiment does not need an external seed laser, and therefore does not include the fifth mirror 400 and the external laser.

[0048] In use, the electron beam accelerated by the accelerator (e.g. a high-energy electron beam generated by a synchrotron ring) is continuously input into the modulation device 200. After passing through the transverse dispersion section 210, the electron beam enters the modulation undulator 230. In the modulation undulator 230, the electron beam generates radiation light by noise excitation. The radiation light reenters the modulation undulator 230 after passing through the first mirror 110, the second mirror 120, the third mirror 130, and the fourth mirror 140, and serves as modulation light to modulate the energy of the subsequent electron beam. In the modulation process, the electron beam generates radiation gain on the modulation light, thereby increasing the energy of the modulation light. Since the initial radiation power is very low, the radiation gain generated by the electron beam in the modulation undulator 230 can be greater than the loss of the modulation light in the transmission process in the optical path, so that the energy of the modulation light increases from one cycle to another. When the preset conditions are met (e.g. the transverse size of the modulation light reaches a stable state and the longitudinal light field of the modulation light conforms to a Gaussian distribution), the loss of the modulation light in the transmission process in the optical path is increased to balance the gain and the loss, so that the energy of the modulation light remains unchanged (i.e. reaches a stable state). Then, the stable modulation light repeatedly modulates the energy of the subsequent electron beam by the same amount. As in the first embodiment, by adjusting the spacing between the mirrors 110, 120, 130, and 140, the desired repetition frequency of the modulation light can be obtained, which can easily match the repetition frequency of the electron beam in the electron accelerator.

[0049] After the electron beam modulated by the stable modulation light passes through the bunching section 230, strong micro-bunches are generated in the electron beam, with a spacing of 266 nm. The electron beam generating micro-bunches can emit high-harmonic radiation after passing through the radiation undulator 300. The radiation flux and brightness are proportional to the square of the number of electrons in the micro-bunches.

[0050] Since the radiation light in the second embodiment is generated by noise excitation of the electron beam, the length of the modulation undulator 230 in the second embodiment needs to be long enough to generate radiation light with high enough power.

[0051] The device for improving the repetition frequency of the accelerator coherent light source of the embodiment adopts the radiation light generated by the noise start of the electron beam as the modulation light, the modulation light can circulate in the resonant device 100 and the modulation device 200, thereby repeatedly acting on the electron beam, so that the repetition frequency of the modulation light can be adjusted, and is no longer limited by the repetition frequency of the external seed laser; through the chromatic dispersion system, the electron beam forms a strong coherent cluster to realize the generation of high-repetition-frequency coherent extreme ultraviolet and X-ray. The device of the embodiment is composed of elements such as dipole magnets, mirrors, undulators, etc., has low cost, small technical difficulty and low operation cost, and can meet the needs of extreme ultraviolet / X-ray lithography research and industrial application.

[0052] As shown in Figure 4 An embodiment of the present application provides a method for improving the repetition frequency of the accelerator coherent light source, which adopts the device for improving the repetition frequency of the accelerator coherent light source of the first embodiment and comprises the following steps:

[0053] S510: providing the modulation device 200 and the resonant device 100 forming a closed loop; the modulation device 200 comprises a transverse dispersion section 210, a modulation undulator 220 and a bunching section 230 arranged in sequence along the transmission direction of the electron beam, and the resonant device 100 comprises a first mirror 110, a second mirror 120, a third mirror 130 and a fourth mirror 140, the first mirror 110 is located downstream of the modulation undulator 220 of the modulation device 200, and the fourth mirror 140 is located upstream of the modulation device 200.

[0054] S520: adjusting the spacing between the first mirror 110, the second mirror 120, the third mirror 130 and the fourth mirror 140 so that the sum of their spacings is a first preset value.

[0055] The first preset value is related to the repetition frequency of the electron beam after being accelerated by the accelerator, and when the sum of the spacings is the first preset value, the repetition frequency of the modulation light is the same as the repetition frequency of the electron beam.

[0056] S530: continuously injecting the electron beam accelerated by the accelerator into the modulation device 200.

[0057] S540: introducing the external seed laser into the modulation device 200 to make the seed laser act as the modulation light to modulate the energy of the electron beam in the modulation undulator 220, and the radiation light generated by the modulation undulator 220 reenters the modulation undulator after sequentially passing through the first mirror 110, the second mirror 120, the third mirror 130 and the fourth mirror 140 to realize circulation, so that the electron beam generates radiation gain to the modulation light.

[0058] S550: Adjust the reflectivity of the first reflector 110, the second reflector 120, the third reflector 130 and the fourth reflector 140 so that the energy of the modulated light remains constant in the closed loop.

[0059] As described in the first embodiment, the reflectivity of each mirror can be adjusted so that the radiation gain generated by the electron beam is equal to the loss of the modulated light during its transmission in the closed loop, thereby ensuring that the energy of the modulated light remains constant throughout the closed loop. Figure 5A As shown, due to the three-dimensional effect of the light field, the energy of the modulated light will gradually increase first, then gradually decrease and tend to stabilize. After several cycles, it will automatically reach equilibrium and remain unchanged.

[0060] S560: The modulated light with constant energy modulates the electron beam in the modulation undulator. The modulated electron beam generates a micro-beam after passing through the focusing section. The micro-beamed electron beam emits coherent radiation light after passing through the radiation undulator 300.

[0061] like Figure 5B and Figure 5C As shown, the radiation pulse power and radiation spectrum of the 50th to 100th electron beams have a high degree of overlap, indicating that after the 50th electron beam, the energy of the modulated light tends to stabilize, and therefore the radiation pulse power and radiation spectrum generated by the electron beam also tend to stabilize.

[0062] like Figure 6 As shown, one embodiment of the present invention provides a method for increasing the repetition frequency of a coherent light source in an accelerator, which employs the apparatus for increasing the repetition frequency of a coherent light source in an accelerator according to the second embodiment and includes the following steps:

[0063] S610: Provides a modulation device 200 and a resonant device 100 forming a closed loop; the modulation device 200 includes a transverse dispersion section 210, a modulation undulator 220 and a beam convergence section 230 arranged sequentially along the electron beam transmission direction; the resonant device 100 includes a first reflector 110, a second reflector 120, a third reflector 130 and a fourth reflector 140, the first reflector 110 being located downstream of the modulation undulator 220 of the modulation device 200, and the fourth reflector 140 being located upstream of the modulation device 200.

[0064] S620: Adjust the distance between the first reflector 110, the second reflector 120, the third reflector 130 and the fourth reflector 140 so that the sum of their distances is a second preset value.

[0065] The second preset value is related to the repetition frequency of the electron beam after acceleration by the accelerator. When the sum of the spacing is the second preset value, the repetition frequency of the modulated light is the same as the repetition frequency of the electron beam.

[0066] S630: continuously inject the electron beam accelerated by the accelerator into the modulation device 200, so that the electron beam generates radiation light by noise excitation in the modulation undulator 220, the radiation light modulates the subsequent electron beam as modulation light, and the radiation light reenters the modulation undulator 220 after sequentially passing through the first mirror 110, the second mirror 120, the third mirror 130, and the fourth mirror 140, to realize a cycle, so that the subsequent electron beam generates radiation gain of the modulation light.

[0067] S640: adjust the reflectivity of the first mirror 110, the second mirror 120, the third mirror 130, and the fourth mirror 140, so that the energy of the modulation light is enhanced in the closed loop.

[0068] As described in the second embodiment, by adjusting the reflectivity of each mirror, the radiation gain generated by the electron beam is greater than the loss of the modulation light in the transmission process in the closed loop, so that the energy of the modulation light is enhanced in the cycle.

[0069] S650: after meeting the preset requirements, adjust the reflectivity of the first mirror 110, the second mirror 120, the third mirror 130, and the fourth mirror 140, so that the energy of the modulation light remains unchanged in the closed loop.

[0070] When the modulation light meets the preset requirements, for example, the transverse size of the modulation light remains stable, and the longitudinal light field of the modulation light conforms to the Gaussian distribution, the reflectivity of each mirror can be adjusted to balance the radiation gain and the loss through each mirror, so that the energy of the modulation light remains unchanged in the cycle. Figure 7A As shown in the figure, with the increase of the number of cycles of the modulation light in the closed loop, the energy of the modulation light first gradually increases, then gradually decreases and tends to be stable.

[0071] S660: the modulation light with unchanged energy modulates the electron beam in the modulation undulator, and the electron beam modulated by the energy passes through the bunching section to generate micro-bunching, and the electron beam generating micro-bunching emits coherent radiation light after passing through the radiation undulator 300.

[0072] As shown in the figures, Figure 7B and Figure 7C The radiation pulse power and the radiation spectrum coincidence degree of the 180th to 250th electron beams are high, which indicates that after the 180th electron beam, the energy of the modulation light tends to be stable, and therefore the radiation pulse power and the radiation spectrum generated by the electron beam also tend to be stable.

[0073] From the device simulation results of the first embodiment and the second embodiment, it can be known that the devices of the first embodiment and the second embodiment can both generate stable coherent radiation light, the difference is that the radiation pulse power and the radiation spectrum generated by the electron beam after the 50th in the device of the first embodiment tend to be stable, while the radiation pulse power and the radiation spectrum generated by the electron beam after the 180th in the device of the second embodiment tend to be stable, and the main reason for the above difference is that the device of the first embodiment introduces a seed laser as a modulation light, so the energy of the modulation light can reach a stable state faster, while the device of the second embodiment generates radiation light as a modulation light by the noise of the electron beam, the initial energy of the modulation light is small, and it needs to be enhanced by the radiation gain of more electron beams, so it needs to spend more time to reach a stable state.

[0074] The above is only a preferred embodiment of the present application, not to limit the scope of the present application, the above embodiment of the present application can also be various changes. That is, the simple, equivalent changes and modifications made according to the content of the claims and the description of the present application, all fall within the scope of the claims of the present application. The present application is not described in detail, all are conventional technical content.

Claims

1. A device for increasing the repetition frequency of a coherent light source in an accelerator, characterized in that, The application relates to a resonant device, a modulation device and a radiation undulator, wherein the modulation device and the radiation undulator are arranged in sequence along the electron beam transmission direction and located in the same vertical plane, the modulation device and the resonant device form a closed loop to make the modulation light circulate in the resonant device and the modulation device; the modulation light is seed laser or radiation light generated by the electron beam in the modulation device by noise starting; The modulation device comprises a transverse dispersion section, a modulation undulator and a bunching section arranged in sequence along the electron beam transmission direction, the resonant device comprises a first mirror, a second mirror, a third mirror and a fourth mirror, the first mirror is located downstream of the modulation undulator, the fourth mirror is located upstream of the modulation device, after the modulation light passes through the modulation undulator, the modulation light is reflected by the first mirror, the second mirror, the third mirror and the fourth mirror in sequence and then reenters the modulation undulator to realize circulation; The reflectivity of the first mirror, the second mirror, the third mirror and the fourth mirror is adjustable, so that the energy of the modulation light can be changed by adjusting the reflectivity of the first mirror, the second mirror, the third mirror and the fourth mirror; The spacing between the first mirror, the second mirror, the third mirror and the fourth mirror is adjustable, so that the repetition frequency of the modulation light can be changed by adjusting the sum of the spacing between the first mirror, the second mirror, the third mirror and the fourth mirror.

2. The device for increasing the repetition rate of a coherent light source of a booster accelerator according to claim 1, characterized in that, The transverse dispersion section is composed of two dipole magnets.

3. The device for increasing the repetition rate of a coherent light source of a booster accelerator according to claim 1, characterized in that, The bunching section is composed of two vertically opposite dipole magnets and a drift section between the two dipole magnets.

4. The apparatus for repetition rate multiplication of a booster accelerator coherent light source of claim 1, wherein, A fifth mirror is further arranged upstream of the fourth mirror, and the fifth mirror is arranged to reflect external seed laser into the modulation device.

5. A method of increasing the repetition rate of an accelerator-based coherent light source, the method comprising: The application further discloses a method for generating radiation light by using the resonant device, the modulation device and the radiation undulator. The method comprises the following steps: providing a modulation device and a resonant device forming a closed loop; the modulation device comprises a transverse dispersion section, a modulation undulator and a bunching section arranged in sequence along the electron beam transmission direction, the resonant device comprises a first mirror, a second mirror, a third mirror and a fourth mirror, the first mirror is located downstream of the modulation undulator of the modulation device, and the fourth mirror is located upstream of the modulation device; adjusting the spacing between the first mirror, the second mirror, the third mirror and the fourth mirror so that the sum of the spacing between the first mirror, the second mirror, the third mirror and the fourth mirror is a first preset value; continuously injecting the electron beam accelerated by the accelerator into the modulation device; introducing external seed laser into the modulation device to make the seed laser as the modulation light to modulate the energy of the electron beam in the modulation undulator, and the radiation light generated by the modulation undulator reenters the modulation undulator in sequence after passing through the first mirror, the second mirror, the third mirror and the fourth mirror to realize circulation, so that the electron beam generates radiation gain to the modulation light; The reflectivity of the first mirror, the second mirror, the third mirror and the fourth mirror is adjusted so that the energy of the modulated light remains unchanged in the closed loop with each round; The modulated light with unchanged energy produces energy modulation on the electron beam in the modulation undulator, and the electron beam after energy modulation generates micro-bunching after passing through the bunching section, and the electron beam generating micro-bunching emits coherent radiation light after passing through the radiation undulator.

6. A method of increasing the repetition rate of an accelerator-based coherent light source, the method comprising: The method comprises the following steps: A modulation device and a resonance device forming a closed loop are provided; the modulation device comprises a transverse dispersion section, a modulation undulator and a bunching section arranged in sequence along the transmission direction of the electron beam, and the resonance device comprises a first mirror, a second mirror, a third mirror and a fourth mirror, the first mirror is located downstream of the modulation undulator of the modulation device, and the fourth mirror is located upstream of the modulation device; The spacing between the first mirror, the second mirror, the third mirror and the fourth mirror is adjusted so that the sum of the spacings between the first mirror, the second mirror, the third mirror and the fourth mirror is a second preset value; The electron beam accelerated by the accelerator is continuously injected into the modulation device so that the electron beam generates radiation light by noise excitation in the modulation undulator, the radiation light serves as modulated light to modulate the energy of the subsequent electron beam, and at the same time, the radiation light reenters the modulation undulator after sequentially passing through the first mirror, the second mirror, the third mirror and the fourth mirror to realize circulation, so that the subsequent electron beam generates radiation gain on the modulated light; The reflectivity of the first mirror, the second mirror, the third mirror and the fourth mirror is adjusted so that the energy of the modulated light is enhanced in the closed loop with each round; After the preset condition is met, the reflectivity of the first mirror, the second mirror, the third mirror and the fourth mirror is adjusted so that the energy of the modulated light remains unchanged in the closed loop with each round; The modulated light with unchanged energy produces energy modulation on the electron beam in the modulation undulator, and the electron beam after energy modulation generates micro-bunching after passing through the bunching section, and the electron beam generating micro-bunching emits coherent radiation light after passing through the radiation undulator.

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