Method for generating spirally-distributed high-energy electron beam

Abstract

The invention relates to a method for generating a spirally-distributed high-energy electron beam, and the method comprises the steps: preparing an axial line focusing spiral pinhole plate which is provided with a plurality of rows of pinhole groups which are regularly arranged in the circumferential direction of a plate body of the axial line focusing spiral pinhole plate, and each pinhole group comprises a plurality of pinholes which are arranged in a spiral manner; a filamentous plasma target is coaxially arranged with the axial line focusing spiral pinhole plate, and the length of the filamentous plasma target is greater than or equal to the focal length range of the pinhole; a beam of Gaussian laser with relativistic intensity is adopted to irradiate an axial line focusing spiral pinhole plate, and based on pinholes in the axial line focusing spiral pinhole plate, laser transmitted by different pinholes reaches different optical paths of an optical axis, and angular phase difference is introduced for the transmitted Gaussian laser, so that vortex laser is formed on a filamentous plasma target in a focusing manner; the vortex laser propagates along the surface of the filamentous plasma target and extracts and accelerates electrons from the surface of the filamentous plasma target to generate spirally-distributed high-energy electron beams.

Description

Technical Field

[0001] The invention relates to the field of laser and plasma technology, and in particular to a method for generating a spirally distributed high-energy electron beam. Background Art

[0002] The interaction between relativistic vortex laser and plasma is one of the research hotspots in the field of laser-plasma interaction. Since relativistic vortex laser has the characteristics of carrying orbital angular momentum, having phase singularities and hollow intensity distribution, it has a wide range of applications in the generation of high angular momentum relativistic particle beams, the generation of vortex terahertz / high-order harmonics, and the generation of ultra-strong axial magnetic fields. The relativistic electron beam vortex generated by the interaction between vortex laser and plasma has potential application value in the generation of high angular momentum X-ray / gamma-ray beams and as a probe of nuclear reactions. However, due to the limited material damage threshold of current optical materials, it is impossible to produce intensities exceeding 100 nm in the laboratory. In addition, the existing methods of generating relativistic vortex lasers in laboratories face the problem of low main mode ratio when generating high-order mode relativistic vortex lasers. Furthermore, the current scheme of using high-intensity vortex lasers to generate high-energy electron beams still has great difficulties and shortcomings. Therefore, it is urgent to propose a new high-energy electron beam scheme to solve the current problems. Summary of the invention

[0003] The object of the present invention is to provide a method for generating a high-energy electron beam with a spiral distribution.

[0004] To achieve the above object, the present invention provides a method for generating a spirally distributed high-energy electron beam, comprising the following steps: S1. preparing an axial line focusing spiral pinhole plate, wherein the axial line focusing spiral pinhole plate is provided with a plurality of rows of pinhole groups regularly arranged along the circumference of the plate body, and each pinhole group includes a plurality of pinholes arranged along a spiral; S2. A filamentary plasma target is arranged coaxially with the axial line focusing spiral pinhole plate, wherein the length of the filamentary plasma target is greater than or equal to the focal length range of the pinhole; S3. A beam of Gaussian laser of relativistic intensity is used to irradiate the axial line focusing spiral pinhole plate, and based on the pinholes on the axial line focusing spiral pinhole plate, the optical path lengths of lasers transmitted through different pinholes to reach the optical axis are different, and an angular phase difference is introduced into the transmitted Gaussian laser to focus on the filamentary plasma target to form a vortex laser, and the vortex laser propagates along the surface of the filamentary plasma target and extracts and accelerates electrons from the surface of the filamentary plasma target to generate a spirally distributed high-energy electron beam.

[0005] According to one aspect of the present invention, in step S1, in the step of preparing an axial line focusing spiral pinhole plate, the angular position and radial position of each pinhole on the axial line focusing spiral pinhole plate are expressed as:

[0006] in, For the The angular position of the pinholes, For the The radial position of the pinholes, For the The focal length of a pinhole is expressed as: , and the focal length range of the pinhole is the minimum focal length To maximum focal length , the focal depth is ; is the number of pinholes; is the distance from the first pinhole in each column of pinhole groups to the center of the axial line focusing spiral pinhole plate, is the topological charge of the axial line focusing spiral pinhole plate, and its value is a positive integer, is the wavelength of the incident laser.

[0007] According to one aspect of the present invention, the minimum focal length of the pinhole on the axial line focusing spiral pinhole plate is It is expressed as: ; The maximum focal length of the pinhole on the axial line focusing spiral pinhole plate It is expressed as: .

[0008] According to one aspect of the present invention, on the axial line focusing spiral pinhole plate, each row of pinhole groups is arranged in a right-hand spiral manner; The pinhole closest to the center of the axial line focusing spiral pinhole plate in each column of pinhole groups is the first pinhole, and the distance from the first pinhole to the center of the axial line focusing spiral pinhole plate is The value range of is: ; The radius of the pinhole on the axial line focusing helical pinhole plate satisfy: .

[0009] According to one aspect of the present invention, the axial line focusing spiral pinhole plate is made of fully ionized carbon ion and hydrogen ion target materials, and the density ratio of carbon ions to hydrogen ions is 1:4.

[0010] According to one aspect of the present invention, the thickness of the axial line focusing spiral pinhole plate is satisfy: .

[0011] According to one aspect of the present invention, in step S2, the used Gaussian laser beam of relativistic intensity has a Gaussian intensity distribution, and its peak intensity is located at the optical axis; The intensity of the relativistic Gaussian laser beam used is .

[0012] According to one aspect of the present invention, the axial line focusing spiral pinhole plate is manufactured by electron beam etching.

[0013] According to one aspect of the present invention, in step S2, the filamentary plasma target is made of fully ionized hydrogen ion and electron target materials, and the density ratio of hydrogen ions to electrons is 1:1.

[0014] According to one aspect of the present invention, in step S2, in the step of arranging the filamentary plasma target coaxially with the axial line focusing spiral pinhole plate, the axial line focusing spiral pinhole plate and the filamentary plasma target are spaced apart; The interval between the first end of the filamentary plasma target and the axial line focusing spiral pinhole plate is The interval between the second end of the filamentary plasma target and the axial line focusing spiral pinhole plate is ; The radius of the filamentary plasma target is .

[0015] According to one scheme of the present invention, the present invention realizes that an ultra-strong Gaussian laser drives an axial line focusing spiral pinhole plate to generate an ultra-strong vortex laser, which then interacts with a wire target to generate a spirally distributed high-energy electron beam, making the generation of a high-energy electron beam more convenient and stable, greatly reducing the overall complexity, and reducing the corresponding application cost.

[0016] According to one solution of the present invention, a beam of light is used to illuminate the axial line focusing spiral pinhole plate, and the transmitted laser forms a vortex laser in the focusing area and interacts with the filamentary plasma target. Due to the spiral electromagnetic field of the vortex laser, the electron beam in the filament target is pulled out so that the electron beam is distributed in a spiral shape in space. Thereafter, the electron beam is accelerated to high energy under the action of the laser.

[0017] According to one solution of the present invention, by adjusting the arrangement of the pinholes on the target, the axial line focusing pinhole plate can generate the main mode The vortex laser interacts with the filamentary plasma target to produce a vortex-distributed high-energy electron beam. The electron beam energy can reach 350 MeV, and the divergence angle is about This electron beam has potential application value in the generation of vortex terahertz, high-order harmonics, and high angular momentum X / γ-ray beams. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a block diagram schematically showing the steps of a method for generating a spirally distributed high-energy electron beam according to an embodiment of the present invention; Figure 2 is a principle diagram schematically showing a method for generating a spirally distributed high-energy electron beam according to an embodiment of the present invention; Figure 3 is a structural diagram schematically showing an axial line focusing spiral pinhole plate according to an embodiment of the present invention; Figure 4 is a diagram schematically showing the simulation results of the simulation box in Example 1; Figure 5 The diagram schematically shows the result of the high-energy electron beam generated in Example 1, wherein (a) shows the energy result of the high-energy electron beam, (b) shows the divergence angle result of the high-energy electron beam, and (c) shows the orbital angular momentum result of the high-energy electron beam. DETAILED DESCRIPTION

[0019] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not therefore limited to the following embodiments.

[0020] Combination Figure 1 , Figure 2 and Figure 3 As shown, according to one embodiment of the present invention, a method for generating a spirally distributed high-energy electron beam of the present invention comprises the following steps: S1. preparing an axial line focusing spiral pinhole plate, wherein the axial line focusing spiral pinhole plate is provided with a plurality of rows of pinhole groups regularly arranged along the circumference of the plate body, and each pinhole group includes a plurality of pinholes arranged along a spiral; S2. A filamentary plasma target is arranged coaxially with the axial line focusing spiral pinhole plate, wherein the length of the filamentary plasma target is greater than or equal to the focal length range of the pinhole; S3. A beam of Gaussian laser of relativistic intensity is used to irradiate the axial line focusing spiral pinhole plate, and based on the pinholes on the axial line focusing spiral pinhole plate, the optical path lengths of the lasers transmitted by different pinholes to reach the optical axis are different, and an angular phase difference is introduced into the transmitted Gaussian laser to focus on the filamentary plasma target to form a vortex laser, and the vortex laser propagates along the surface of the filamentary plasma target and extracts and accelerates electrons from the surface of the filamentary plasma target to generate a spirally distributed high-energy electron beam.

[0021] like Figure 2 As shown, according to one embodiment of the present invention, in step S1, in the step of preparing an axial line focusing spiral pinhole plate, on the axial line focusing spiral pinhole plate, multiple rows of hole groups are arranged at equal intervals along the circumference of the plate body to achieve a regular arrangement of the pinhole groups. In this embodiment, each pinhole group includes a plurality of pinholes arranged along a spiral, wherein the hand direction of the pinholes of each pinhole group along the spiral arrangement is consistent, thereby, on the axial line focusing spiral pinhole plate, the pinholes are arranged in a spiral radiating form from the center to the surroundings. In this embodiment, the pinholes penetrate the body of the axial focusing spiral pinhole plate along the axial direction of the axial line focusing spiral pinhole plate.

[0022] In this embodiment, the axial line focusing spiral pinhole plate can be made of a regular plate, for example, a square plate, a circular plate, etc.

[0023] Through the above-mentioned arrangement, the present invention arranges spirally arranged pinholes on the axial line focusing spiral pinhole plate, so that when a beam of Gaussian laser of relativistic intensity is irradiated onto the axial line focusing spiral pinhole plate, the optical path lengths of lasers transmitted by different pinholes to reach the optical axis are different, thereby introducing an angular phase difference for the transmitted laser, thereby forming a vortex laser in the focusing area, that is, realizing the modulation of the seed laser into the vortex laser in the focusing volume.

[0024] like Figure 3 As shown, according to one embodiment of the present invention, in step S1, in the step of preparing the axial line focusing spiral pinhole plate, the angular position and radial position of each pinhole on the axial line focusing spiral pinhole plate are expressed as:

[0025] in, For the The angular position of the pinholes, For the The radial position of the pinholes, For the The focal length of a pinhole is expressed as: , and the focal length range of the pinhole is the minimum focal length To maximum focal length , the focal depth is ; is the number of pinholes; is the distance from the first pinhole in each column of pinhole groups to the center of the axial line focusing spiral pinhole plate, is the topological charge of the axial line focusing spiral pinhole plate, and its value is a positive integer, is the wavelength of the incident laser.

[0026] like Figure 3 As shown, according to one embodiment of the present invention, the minimum focal length of the pinhole on the axial line focusing spiral pinhole plate is It is expressed as: ; The maximum focal length of the pinhole on the axial line focusing spiral pinhole plate It is expressed as: .

[0027] Through the above arrangement, it is effectively ensured that the vortex laser generated by the present invention has a wide focusing range, making it more widely applicable and further ensuring its convenience of use.

[0028] like Figure 3 As shown, according to an embodiment of the present invention, on the axial line focusing spiral pinhole plate, each column of pinhole groups is arranged in a right-hand spiral manner; wherein the pinhole closest to the center of the axial line focusing spiral pinhole plate in each column of pinhole groups is the first pinhole, and the distance from the first pinhole to the center of the axial line focusing spiral pinhole plate is The value range of is: ; Through the above arrangement, the present scheme can more advantageously generate a high-order mode vortex laser in the corresponding focusing area by arranging the first pinhole in each column of pinhole groups with a spacing from the center of the axial focusing spiral pinhole plate, thereby making the generated vortex laser more stable.

[0029] In this embodiment, the radius of the pinhole on the axial line focusing helical pinhole plate is satisfy: .

[0030] Through the above settings, this solution sets the radius of the pinhole within the above range, so that the arranged pinhole can better match the input Gaussian laser, which is more advantageous for the solution to generate a high-order mode vortex laser in the corresponding focusing area, making the generated vortex laser more stable and accurate.

[0031] According to one embodiment of the present invention, the axial line focusing spiral pinhole plate is made of fully ionized carbon ion and hydrogen ion target materials, and the density ratio of carbon ions to hydrogen ions is 1:4.

[0032] Through the above arrangement, the present invention adopts an axial focusing spiral pinhole plate made of fully ionized carbon ion and hydrogen ion target materials with a density ratio of 1:4, which can enhance the interaction between laser and plasma, optimize the laser acceleration process, promote the generation of high-order mode vortex laser, and improve the propagation characteristics of the laser beam; wherein, through the above-mentioned axial focusing spiral pinhole plate, it can form a Gaussian laser that better matches the input, which can significantly enhance the nonlinear effect of the laser. And the focusing ability can be significantly improved by the set density ratio.

[0033] According to one embodiment of the present invention, the thickness of the axial line focusing spiral pinhole plate is satisfy: .

[0034] Through the above arrangement, the present solution sets the thickness of the axially focusing spiral pinhole plate within the above range, which is more advantageous for the present solution to generate a high-order mode of vortex laser in the corresponding focusing area, making the generated vortex laser more stable and effective.

[0035] According to an embodiment of the present invention, in step S2, a beam of relativistic intensity Gaussian laser light used has a Gaussian intensity distribution, and its peak intensity is located at the optical axis.

[0036] According to one embodiment of the present invention, the intensity of a Gaussian laser beam of relativistic intensity is .

[0037] Through the above arrangement, the present invention can more effectively adapt to the input of high-intensity laser and can also provide more favorable conditions for realizing high-intensity vortex laser.

[0038] According to one embodiment of the present invention, the axial line focusing spiral pinhole plate is manufactured by electron beam etching.

[0039] According to an embodiment of the present invention, in step S2, the filamentary plasma target is made of fully ionized hydrogen ion and electron target materials, and the density ratio of hydrogen ions to electrons is 1:1.

[0040] like Figure 2 As shown, according to one embodiment of the present invention, in step S2, in the step of arranging the filamentary plasma target coaxially with the axial line focusing spiral pinhole plate, the axial line focusing spiral pinhole plate and the filamentary plasma target are spaced apart; In this embodiment, the interval between the first end of the filamentary plasma target and the axial line focusing spiral pinhole plate is , the distance between the second end of the filamentary plasma target and the axial line focusing spiral pinhole plate is .

[0041] In this embodiment, the radius of the filamentary plasma target is .

[0042] Through the above arrangement, the present solution can conveniently achieve full coverage of the vortex laser focusing area through the arranged filamentary plasma target, thereby achieving more reliable and beneficial full formation of the high-energy electron beam.

[0043] To further illustrate this scheme, further examples are given to illustrate this scheme.

[0044] Example 1 Specifically, the 3D-PIC simulation using the relativistic electromagnetic code EPOCH was demonstrated. In this embodiment, the grid size of the simulation box is ,Therefore, the grid is set to 2000×800×800, and there are 9 macro particles in each grid.

[0045] Furthermore, the dimensionless laser electric field amplitude of the linearly polarized Gaussian laser pulse is , which is incident from the left side of the simulation box; where, and are the peak amplitude of the laser electric field and the laser focus spot size, respectively; is the laser wavelength, where is the laser period, is the laser frequency; , and are the unit charge, the mass of the electron and the speed of light in vacuum, for The unit vector of the direction, is the radial coordinate in the cylindrical coordinate system.

[0046] Furthermore, the initial position of the axial line focusing spiral pinhole plate is in the simulation box The thickness of the axial line focusing spiral pinhole plate is ; Among them, the focal length range of the pinhole on the axial line focusing spiral pinhole plate can be set to arrive Thus, the initial position of the pinhole in the simulation box is set based on the axial line focusing spiral pinhole plate so that its focal length ranges from Start to Finish.

[0047] In this embodiment, in the axial line focusing spiral pinhole plate, the distance from the first pinhole in each column of pinhole groups to the center of the axial line focusing spiral pinhole plate is , the radius of each pinhole is , the number of pinholes is , topological charge of the axial line focusing helical pinhole plate .

[0048] Furthermore, on the axial line focusing spiral pinhole plate, the pinholes in each column of the pinhole group are arranged in a right-handed spiral.

[0049] Furthermore, the axial line focusing spiral pinhole plate is made of fully ionized carbon ion and hydrogen ion target materials, and its composition is composed of fully ionized carbon ions and hydrogen ions with a density ratio of 1:4; wherein, electrons, protons ( ) and carbon ions ( ) has a corresponding density of , and .

[0050] Furthermore, the axial line focusing spiral pinhole plate is manufactured by electron beam etching.

[0051] Through the above-mentioned axial line focusing spiral pinhole plate, when the incident seed laser (i.e., a beam of Gaussian laser of relativistic intensity) irradiates the axial line focusing spiral pinhole plate, only a part of the laser can pass through the pinhole area. Since the optical path difference of the laser passing through the pinholes at different positions when reaching the focal volume is different, the axial line focusing spiral pinhole plate can modulate the seed laser into a vortex laser in the focal volume.

[0052] In this embodiment, in the simulation box, the radius of the filamentary plasma target is , initially located at arrive Among them, the filamentary plasma target is made of fully ionized hydrogen ion and electron target materials, and the density ratio of hydrogen ions and electrons is 1:1; specifically, the density of hydrogen ions and electrons is , is the critical density, is the vacuum dielectric constant, is the frequency of the laser.

[0053] Combination Figure 4 and Figure 5 As shown, it shows The transverse electric field of the vortex laser output The output vortex laser propagates along the target surface, and its super strong transverse electric field Electrons are extracted and accelerated from the surface of the filamentary plasma target. Due to the electric field distribution of the output vortex laser, the high-energy electron beam pulled out and accelerated from the filamentary plasma target presents a spiral topological structure in space. Figure 5 (a) and Figure 5 (b) shows that the maximum energy of the electron beam is It can reach 350MeV and the divergence angle is about 16°. In addition, as the electrons are accelerated by the vortex laser, the electron beam also acquires the orbital angular momentum carried by the vortex laser. Figure 5 As shown in (c), the orbital angular momentum of the electron beam gradually increases and finally achieve This high-energy and high-orbital angular momentum electron beam has potential applications in generating vortex terahertz waves and high-angular momentum X / γ-ray beams.

[0054] The above contents are merely examples of specific solutions of the present invention. For devices and structures not described in detail therein, it should be understood that they can be implemented by adopting general devices and general methods available in the art.

[0055] The above is only one solution of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for generating a spirally distributed high-energy electron beam, characterized in that: The following steps are involved: S1. preparing an axial line focusing spiral pinhole plate, wherein the axial line focusing spiral pinhole plate is provided with a plurality of rows of pinhole groups regularly arranged along the circumference of the plate body, and each pinhole group includes a plurality of pinholes arranged along a spiral; S2. A filamentary plasma target is arranged coaxially with the axial line focusing spiral pinhole plate, wherein the length of the filamentary plasma target is greater than or equal to the focal length range of the pinhole; S3. A beam of Gaussian laser of relativistic intensity is used to irradiate the axial line focusing spiral pinhole plate, and based on the pinholes on the axial line focusing spiral pinhole plate, the optical path lengths of lasers transmitted through different pinholes to reach the optical axis are different, and an angular phase difference is introduced into the transmitted Gaussian laser to focus on the filamentary plasma target to form a vortex laser, and the vortex laser propagates along the surface of the filamentary plasma target and extracts and accelerates electrons from the surface of the filamentary plasma target to generate a spirally distributed high-energy electron beam.

2. The method for generating a spirally distributed high-energy electron beam according to claim 1, characterized in that: In step S1, in the step of preparing the axial line focusing spiral pinhole plate, the angular position and radial position of each pinhole on the axial line focusing spiral pinhole plate are expressed as: in, For the The angular position of the pinholes, For the The radial position of the pinholes, For the The focal length of a pinhole is expressed as: , and the focal length range of the pinhole is the minimum focal length To maximum focal length , the focal depth is ; is the number of pinholes; is the distance from the first pinhole in each column of pinhole groups to the center of the axial line focusing spiral pinhole plate, is the topological charge of the axial line focusing spiral pinhole plate, and its value is a positive integer, is the wavelength of the incident laser.

3. The method for generating a spirally distributed high-energy electron beam according to claim 2, characterized in that: The minimum focal length of the pinhole on the axial line focusing spiral pinhole plate It is expressed as: ； The maximum focal length of the pinhole on the axial line focusing spiral pinhole plate It is expressed as: 。 4. The method for generating a spirally distributed high-energy electron beam according to claim 3, characterized in that: On the axial line focusing spiral pinhole plate, each row of pinhole groups is arranged in a right-hand spiral manner; The pinhole closest to the center of the axial line focusing spiral pinhole plate in each column of pinhole groups is the first pinhole, and the distance from the first pinhole to the center of the axial line focusing spiral pinhole plate is The value range of is: ； The radius of the pinhole on the axial line focusing helical pinhole plate satisfy: 。 5. The method for generating a spirally distributed high-energy electron beam according to claim 4, characterized in that: The axial line focusing spiral pinhole plate is made of fully ionized carbon ion and hydrogen ion target materials, and the density ratio of carbon ions to hydrogen ions is 1:

4.

6. The method for generating a spirally distributed high-energy electron beam according to claim 5, characterized in that: The thickness of the axial line focusing spiral pinhole plate satisfy: 。 7. The method for generating a spirally distributed high-energy electron beam according to claim 6, characterized in that: In step S2, a beam of relativistic intensity Gaussian laser light is used which has a Gaussian intensity distribution, and its peak intensity is located at the optical axis; The intensity of the relativistic Gaussian laser beam used is .

8. The method for generating a spirally distributed high-energy electron beam according to claim 7, characterized in that: The axial line focusing spiral pinhole plate is manufactured by electron beam etching.

9. The method for generating a spirally distributed high-energy electron beam according to claim 8, characterized in that: In step S2, the filamentary plasma target is made of fully ionized hydrogen ion and electron target materials, and the density ratio of hydrogen ions to electrons is 1:

1.

10. The method for generating a spirally distributed high-energy electron beam according to claim 9, characterized in that: In step S2, in the step of arranging the filamentary plasma target coaxially with the axial line focusing spiral pinhole plate, the spacing between the axial line focusing spiral pinhole plate and the filamentary plasma target is set; The interval between the first end of the filamentary plasma target and the axial line focusing spiral pinhole plate is The interval between the second end of the filamentary plasma target and the axial line focusing spiral pinhole plate is ; The radius of the filamentary plasma target is .

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