Easy-to-adjust X-ray source enhancement system based on cascaded high-density structure

Abstract

An easy-to-adjust X-ray source enhancement system based on a cascaded high-density structure comprises a linear gas nozzle, a metal target, a fixed sleeve, a fixed rod and a three-dimensional mobile platform, and can effectively generate a two-stage high-density structure to enhance radiation of a betatron X-ray source. The device has the advantages of simplicity in operation, compact structure, generation of two-stage high-density structure distribution and good stability. The invention relates to the field of interaction of ultra-short and ultra-strong laser plasmas, in particular to a process of accelerating and driving high-brightness X-rays by laser tail field electrons, in the first stage, generated density falling edges are used for generating electron injection, and stable generation of large-charge electrons is promoted. And the second stage utilizes the characteristics of the high-density platform region to enhance the lateral oscillation of electrons, thereby improving the X-ray radiation energy and photon yield.

Description

Technical Field

[0001] The present invention relates to a radiation source generated by laser wakefield electron acceleration, in particular to an enhancement system of an X-ray source based on a cascaded high-density structure that is easy to adjust. The present invention uses the jet flow generated by a linear gas nozzle and the density drop edge generated by the first metal target to cause electron injection, promoting the stable generation of electrons with a large charge amount. At the same time, the jet flow generated by the linear gas nozzle and the second metal target generate a high-density platform region, enhancing the transverse oscillation of the electrons generated in the first stage, thereby increasing the X-ray radiation energy and photon yield. Background Art

[0002] Through the plasma wake wave driven by an ultra-intense and ultra-short pulse laser, the accelerating electric field that can be maintained can reach the order of 100 GV / m, which is more than three orders of magnitude higher than the accelerating field strength of traditional electron accelerators. Such a technology can achieve the output of GeV-level high-energy electron beams within an acceleration length of only a few centimeters. At the same time, under the mechanism of laser wakefield accelerating electrons, the plasma ion cavity can serve as both a longitudinal accelerator and a transverse undulator. The electron beam injected into the bubble will not only obtain longitudinal acceleration but also undergo transverse motion, and thus radiate rays. This keV-level X-ray radiation generated by a plasma undulator based on the millimeter scale is called Betatron radiation. For the current means of generating Betatron radiation, they often only focus on the enhancement of radiation while ignoring the optimization of the pre-stage acceleration. The current means of generating Betatron radiation usually focus on the enhancement of radiation while ignoring the optimization of the pre-stage acceleration process. Therefore, a cascaded means needs to be adopted to increase the yield and energy of Betatron radiation.

[0003] For the density drop edge, the decrease in plasma density will cause a decrease in the phase velocity of the wake wave. The decrease in the phase velocity of the plasma wave will reduce the critical value for capturing background electrons. When the electrons at the tail of the wake wave have a speed greater than the phase velocity of the tail of the wake wave, the electrons will be captured, thus enabling local self-injection to occur. This way of causing local self-injection can generate stable and high-quality electron beams, and the injection can be controlled by adjusting the density gradient. The number of photons generated by Betatron radiation depends on The critical energy is Therefore, the photon yield and energy of Betatron radiation are mainly related to the charge amount of electrons, the amplitude of electron oscillation, and the energy of electrons. And the density distribution of the plasma directly determines the above parameters.

[0004] There are many traditional methods for constructing plasma density distributions. The most typical ones are four ways. One is to have only a single gas nozzle, another is the interaction between a gas nozzle and a target, yet another is the combination of multiple gas nozzles, and the last one is the interaction between a gas nozzle and multiple target materials. In the above schemes, the first one only utilizes the mechanism of electron self-injection and it is difficult to generate a stable radiation source. The second one can either only optimize the electrons or only optimize the generation of the radiation source. And the last two are extremely difficult to implement experimentally. The complex gas structure makes it difficult to generate high-quality electron beams and radiation sources, greatly increasing the complexity of adjustment. Therefore, a plasma density distribution device that optimizes the electron acceleration stage and the generation of the radiation source separately is needed. Summary of the Invention

[0005] The object of the present invention is to provide a cascaded and easily adjustable plasma density distribution generation system in view of the defects existing in the traditional plasma density distribution construction system. By adjusting the first vertical optical path translation stage and the second vertical optical path translation stage, the two-stage plasma density regions to be generated are adjusted to the center of the optical path. By adjusting the first parallel optical path translation stage, the position of the first metal target is adjusted to further adjust the position of the generated density falling edge to optimize the electron acceleration process. By adjusting the second parallel optical path translation stage, the position of the second metal target is adjusted to further adjust the position of the generated high-density platform region to optimize the radiation process. It can effectively optimize the electron acceleration process and the generation process of the radiation source respectively, and the operation is simple.

[0006] The technical solution of the present invention is as follows:

[0007] An enhanced system of an X-ray source based on a cascaded high-density structure that is easy to adjust, comprising: A linear gas nozzle, a first metal target module, a first fixing rod, a first fixing sleeve, a first high-low translation stage, a first vertical optical path translation stage, a first parallel optical path translation stage, a second metal target module, a fixing connecting rod, a second fixing rod, a second fixing sleeve, a second high-low translation stage, a second vertical optical path translation stage, a second parallel optical path translation stage, a first high-low translation stage knob, a first vertical optical path translation stage knob, a first parallel optical path translation stage knob, a second high-low translation stage knob, a second vertical optical path translation stage knob, and a second parallel optical path translation stage knob.

[0008] The inner diameter of the linear gas nozzle is 5 mm, the outer diameter is 8 mm, and the length is 70 mm. The lower edge of the linear gas nozzle is 3 mm away from the upper edge position of the first metal target module, and the lower edge of the linear gas nozzle is 5 mm away from the upper edge position of the second metal target module.

[0009] The first metal target module is 10 mm long, 2 mm wide, and 30 mm high. There is a light-transmitting hole with a radius of 0.5 mm at the center 28 mm from the bottom for the laser to pass through. The lower end is equipped with a screw that can be screwed into the threaded round hole of the first fixing rod.

[0010] The second metal target module is 10 mm long, 20 mm wide, and 30 mm high. The lower end is equipped with a screw that can be screwed into the threaded round hole of the fixed connecting rod.

[0011] The first fixing rod is 100 mm long and 20 mm in diameter. The first fixing sleeve is 1000 mm long and 25 mm in inner diameter. There is a threaded round hole with an inner diameter of 6 mm on one side of the first fixing sleeve for screwing in a screw to clamp the first fixing rod tightly.

[0012] The fixed connecting rod is 200 mm long and 20 mm in diameter. It is placed at an angle of 45 degrees to the side of the laser propagation direction. The fixed connecting rod is equipped with screws. The second fixing rod is 100 mm long and 20 mm in diameter. There is a threaded round hole with an inner diameter of 6 mm on one side of the second fixing rod, which can be screwed into the fixed connecting rod. The second fixing sleeve is 1000 mm long and 25 mm in inner diameter. There is a threaded round hole with an inner diameter of 6 mm on one side of the second fixing sleeve, which can be screwed into a screw to clamp the second fixing rod tightly.

[0013] The adjustment precision of the first vertical translation stage, the first vertical optical path translation stage, the first parallel optical path translation stage, the second vertical translation stage, the second vertical optical path translation stage, and the second parallel optical path translation stage reaches 0.1 μm. Adjust the first parallel optical path translation stage to control the position of the falling edge of the first-stage gas density shock wave, and adjust the second parallel optical path translation stage to control the position of the high-density platform area of the second-stage gas.

[0014] Compared with the prior art, the present invention has the following remarkable features:

[0015] 1. It can generate a two-stage gas density distribution, and optimize the electron acceleration stage and the radiation generation stage respectively.

[0016] 2. The first-stage and second-stage gas density distributions can be adjusted separately. For the requirements of radiation sources with different energies and yields, the electron acceleration stage and the radiation generation stage are relatively adjusted, which has the advantages of simple, convenient, and efficient operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the enhanced system of the X-ray source based on the cascade high-density structure that is easy to adjust in the present invention

[0018] Figure 2 is a typical plasma density distribution generated by the enhanced system of the X-ray source based on the cascade high-density structure that is easy to adjust

[0019] Figure 3It is a typical energy spectrum distribution of a radiation source generated by an enhanced system of an easily adjustable X-ray source based on a cascaded high-density structure Specific implementation

[0020] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention should not be limited thereby.

[0021] In the embodiment of the present invention, it relates to the process of laser wakefield electron acceleration. In order to avoid high-power laser from breaking through air and air interfering with the formation of target plasma, it needs to be placed in a vacuum chamber.

[0022] Please first refer to Figure 1 , Figure 1 which is a schematic structural diagram of an enhanced system of an easily adjustable X-ray source based on a cascaded high-density structure of the present invention. After the laser enters the vacuum chamber, it is focused by a parabolic mirror to increase the energy density of the laser. As shown in the figure, a first metal target module 2 and its three-dimensional translation stage for fixation, a second metal target module 8 and its three-dimensional translation stage for fixation are successively arranged in the advancing direction of the laser; a linear gas nozzle 1 is located above the first metal target module 2 and the second metal target module 8; the first metal target module 2 can be screwed into the threaded round hole of the first fixing rod 3 through the lower-end screw. The first fixing sleeve 4 is provided with a round hole with threads for screwing in an internal hexagonal screw to clamp the first fixing rod 3; the first fixing sleeve 4 is fixed on the first high-low translation stage 5; the first high-low translation stage 5 is fixed on the first vertical optical path translation stage 6 by screwing an internal hexagonal screw into the threaded round hole; the first vertical optical path translation stage 6 is fixed on the first parallel optical path translation stage 7 by screwing an internal hexagonal screw into the threaded round holes on both sides thereof; the three-dimensional translation stage on which the second metal target module 8 is fixed is placed at a 45-degree angle to the side rear of the three-dimensional translation stage on which the first metal target module 2 is fixed to prevent blocking the optical path; similarly, the second metal target module 8 can be screwed into the fixed connecting rod 9 through the side screw; the fixed connecting rod 9 is fixed on the second fixing rod 10 through its threaded round hole in cooperation with an internal hexagonal screw; the second fixing rod 10 is provided with a threaded round hole and can be fixed on the second fixing sleeve 11 through an internal hexagonal screw; the second fixing sleeve 11 is fixed on the second high-low translation stage 12; the second high-low translation stage 12 is fixed on the second vertical optical path translation stage 13 by cooperating with the threaded round holes on both sides and an internal hexagonal screw; the second vertical optical path translation stage 13 is fixed on the second parallel optical path translation stage 14 through the threaded round holes on both sides.

[0023] The specific operations are as follows: Fix the linear gas nozzle 1 in the vacuum chamber to ensure it is perpendicular to the horizontal plane. Adjust the first vertical translation stage knob 15 and the first vertical optical path translation stage knob 16 to ensure that the laser passes through the center of the light passing hole of the first metal target module 2. Adjust the second vertical translation stage knob 18 and the second vertical optical path translation stage knob 19 to ensure that the laser passes through the center of the upper surface of the second metal target. Combining the actual laser parameters and the indicators of the energy and yield of the target radiation source, adjust the first parallel optical path translation stage knob 17 to change the position of the first-stage density decreasing edge to control the charge amount of electron injection, and adjust the second parallel optical path translation stage knob 20 to change the position of the second-stage high-density density plateau region to control the energy and yield of the radiation source.

[0024] Refer to Figure 2 , in an embodiment of the present invention, the possible gas density structure expected to be generated by the present invention is shown in the figure. A laser beam with a power of 100 TW, a pulse width of 30 fs, and a central wavelength of 800 nm interacts with the gas density structure; refer to Figure 3 , it is expected to generate a critical energy of 40 keV and the number of photons reaches 1×10 11 per shot; significantly improving the X-ray radiation energy and photon yield.

[0025] The above embodiment adopts a two-stage cascaded structure. Among them, the first stage interacts with the first metal target module through a linear gas nozzle to form a density decreasing edge, triggering the electron self-injection mechanism and stably generating a large-charge electron beam. The second stage forms a high-density plateau region through the cooperation of the second metal target module and the nozzle, enhancing the transverse oscillation amplitude of the electrons and improving the X-ray radiation energy and photon yield. By optimizing the electron acceleration and radiation processes in stages, the problem of performance compromise in the prior art is solved, and the synergistic improvement of the two goals of "acceleration" and "radiation" is achieved. The first metal target module and the second metal target module are independently controlled by three-dimensional translation stages (translation accuracy 0.1 μm) respectively. The first parallel optical path translation stage adjusts the position of the density decreasing edge, and the second parallel optical path translation stage adjusts the position of the high-density plateau region to independently optimize the parameters of the two stages. Through the micron-level adjustment ability, it can be flexibly adjusted according to different laser parameters (such as power, pulse width) and target radiation indicators (such as photon energy, yield), significantly improving the applicability and experimental efficiency of the system. Compared with the traditional multi-target or multi-nozzle scheme, the structure of this system is simple, the volume is small, it is suitable for limited space scenarios such as vacuum chambers, and reduces the difficulty of experimental setup and adjustment.

[0026] It should be understood that the purpose of the above embodiments is only to illustrate the technical concept of the present invention for the understanding of those skilled in the art, rather than to limit the protection scope of the present invention. Within the scope of the claims of the present invention, any improvement and equivalent replacement of the parts, structures or method steps involved in the above embodiments, especially the combination of different embodiments without structural or principle conflicts, fall within the protection scope of the present invention.

Claims

1. An enhanced system for an easily adjustable X-ray source based on a cascaded high-density structure, characterized in that, Comprising: A linear gas nozzle (1), the lower edge of which is spaced from the upper edges of the first metal target module (2) and the second metal target module (8) by a preset distance; The first metal target module (2) is provided with a light passing hole for the laser to pass through and is fixed in the first fixed sleeve (4) by the first fixing rod (3); the first fixed sleeve (4) is connected to the first vertical translation stage (5), and the first vertical translation stage (5) is fixed on the first vertical optical path translation stage (6), and the first vertical optical path translation stage (6) is fixed on the first parallel optical path translation stage (7); The second metal target module (8) is connected to the second fixing rod (10) through the fixing link (9), and the second fixing rod (10) is fixed in the second fixed sleeve (11); the second fixed sleeve (11) is connected to the second vertical translation stage (12), and the second vertical translation stage (12) is fixed on the second vertical optical path translation stage (13), and the second vertical optical path translation stage (13) is fixed on the second parallel optical path translation stage (14); The first vertical translation stage knob (15), the first vertical optical path translation stage knob (16), the first parallel optical path translation stage knob (17), the second vertical translation stage knob (18), the second vertical optical path translation stage knob (19), and the second parallel optical path translation stage knob (20) are used to adjust the displacement of the translation stage respectively.

2. The enhanced system of an X-ray source based on a cascaded high-density structure that is easily adjustable according to claim 1, wherein The inner diameter of the linear gas nozzle (1) is 5 mm, the outer diameter is 8 mm, and the length is 70 mm. The distance between the lower edge of the linear gas nozzle (1) and the upper edge of the first metal target module (2) is 3 mm, and the distance from the upper edge of the second metal target module (8) is 5 mm.

3. The enhanced system of the X-ray source based on a cascaded high-density structure that is easily adjustable according to claim 1, characterized in that, The first metal target module (2) has a length of 10 mm, a width of 2 mm, and a height of 30 mm; the radius of the light passing hole is 0.5 mm and is located at the center 28 mm from the bottom; the lower end of the first metal target module (2) is provided with a threaded round hole with a screw that can be screwed into the first fixing rod (3).

4. An enhanced system for an X-ray source based on a cascaded high-density structure that is easily adjustable according to claim 1, wherein the second metal target module (8) has a length of 10 mm, a width of 20 mm, and a height of 30 mm, and the lower end is provided with a threaded round hole with a screw that can be screwed into the fixing link (9).

5. An enhanced system for an easily adjustable X-ray source based on a cascaded high-density structure according to claim 1, characterized in that The length of the first fixing rod (3) is 100 mm and the diameter is 20 mm. The first fixed sleeve (4) has a length of 1000 mm and an inner diameter of 25 mm. There is a threaded round hole with an inner diameter of 6 mm on one side of the first fixed sleeve (4) to screw in a screw to clamp the first fixing rod (3).

6. An enhanced system for an easily adjustable X-ray source based on a cascaded high-density structure according to claim 1, characterized in that The length of the fixing link (9) is 200 mm and the diameter is 20 mm. It is placed at an angle of 45 degrees to the side of the laser propagation direction. The fixing link (9) is provided with screws. The second fixing rod (10) has a length of 100 mm and a diameter of 20 mm. There is a threaded round hole with an inner diameter of 6 mm on one side of the second fixing rod (10), which can be screwed into the fixing link (9). The second fixed sleeve (11) has a length of 1000 mm and an inner diameter of 25 mm. There is a threaded round hole with an inner diameter of 6 mm on one side of the second fixed sleeve (11), which can be screwed into a screw to clamp the second fixing rod (10).

7. An enhanced system for an easily adjustable X-ray source based on a cascaded high-density structure according to claim 1, characterized in that The adjustment precision of the first vertical and horizontal translation stage (5), the first vertical optical path translation stage (6), the first parallel optical path translation stage (7), the second vertical and horizontal translation stage (12), the second vertical optical path translation stage (13), and the second parallel optical path translation stage (14) reaches 0.1 μm. The first parallel optical path translation stage (7) is adjusted to control the position of the falling edge of the first-stage gas density shock wave, and the second parallel optical path translation stage (14) is adjusted to control the position of the second-stage gas high-density platform area.

8. The enhancement system of the X-ray source according to claim 1, characterized in that, The three-dimensional translation stages of the first metal target module (2) and the second metal target module (8) are modularly fixed through threaded round holes and hexagon socket head cap screws, and the translation stage of the second metal target module (8) is located 45 degrees behind and to the side of the translation stage of the first metal target module (2) to avoid blocking the optical path.

9. The enhancement system of the X-ray source according to claim 1, characterized in that, By adjusting the first parallel optical path translation stage (7) to control the position of the falling edge of the first-stage gas density shock wave and adjusting the second parallel optical path translation stage (14) to control the position of the second-stage gas high-density platform area, the independent optimization of the electron acceleration process and the X-ray radiation process can be achieved.

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