A method of generating a helically distributed high energy electron beam

Abstract

The application relates to a method for generating a spiral-distributed high-energy electron beam, comprising the following steps: preparing an axial line focusing spiral pinhole plate, wherein the axial line focusing spiral pinhole plate is provided with multiple pinhole groups arranged along the circumferential direction of the plate body in a regular manner, and each pinhole group comprises multiple pinholes arranged in a spiral manner; arranging a filamentous plasma target coaxially with the axial line focusing spiral pinhole plate, wherein the length of the filamentous plasma target is greater than or equal to the focal length range of the pinholes; irradiating a high-intensity Gaussian laser on the axial line focusing spiral pinhole plate, and introducing an angular phase difference into the transmitted Gaussian laser based on the pinholes on the axial line focusing spiral pinhole plate, so that the optical path of the transmitted Gaussian laser reaching the optical axis is different, and the vortex laser is focused on the filamentous plasma target, the vortex laser propagates along the surface of the filamentous plasma target, extracts and accelerates electrons from the surface of the filamentous plasma target, and generates a spiral-distributed high-energy electron beam.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser and plasma technology, and particularly relates to a method for generating a spiral-distributed high-energy electron beam. BACKGROUND

[0002] The interaction of relativistic vortex laser and plasma is one of the research hotspots in the field of laser plasma interaction. Due to the characteristics of carrying orbital angular momentum, having phase singularity and hollow intensity distribution, the relativistic vortex laser has wide applications in the generation of high angular momentum relativistic particle beams, vortex terahertz / high harmonic generation and super strong axial magnetic field generation. The relativistic electron beam vortex generated by the interaction of vortex laser and plasma has potential application value in the generation of high angular momentum X / gamma ray beams and as a probe for nuclear reactions. However, due to the limited material damage threshold of current optical materials, it is impossible to generate a vortex laser with an intensity exceeding in the laboratory. In addition, the existing method for generating relativistic vortex laser in the laboratory has the problem of low proportion of main modes when generating high-order mode relativistic vortex laser. Furthermore, there are still great difficulties and deficiencies in the current scheme for generating high-energy electron beams by using high-intensity vortex laser. Therefore, it is urgent to propose a new scheme for generating high-energy electron beams to solve the problems faced at present. SUMMARY

[0003] The purpose of the present application is to provide a method for generating a spiral-distributed high-energy electron beam.

[0004] To achieve the above-mentioned purpose of the application, the present application provides a method for generating a spiral-distributed high-energy electron beam, comprising the following steps:

[0005] S1. Preparing an axial line focusing spiral pinhole plate, wherein the axial line focusing spiral pinhole plate is provided with a plurality of pinhole groups arranged regularly along the circumferential direction of the plate body, and each pinhole group includes a plurality of pinholes arranged in a spiral;

[0006] S2. Arranging a filamentous plasma target coaxially with the axial line focusing spiral pinhole plate, wherein the length of the filamentous plasma target is greater than or equal to the focal length range of the pinholes;

[0007] S3. Using a beam of relativistic intensity Gaussian laser to irradiate the axial line focusing spiral pinhole plate, and based on the pinholes on the axial line focusing spiral pinhole plate, introducing an angular phase difference for the transmitted Gaussian laser so as to focus to form a vortex laser on the filamentous plasma target, and 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 a spiral-distributed high-energy electron beam.

[0008] According to one aspect of the present invention, in step S1, 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 represented as follows:

[0009]

[0010] in, For the first The angular position of each pinhole For the first The radial position of each pinhole For the first The focal length of a pinhole is expressed as: Furthermore, the focal length range of the pinhole is the minimum focal length. to maximum focal length , focus is ; This refers to the number of pinholes. It is the distance from the first pin in each pin group to the center of the axial-line focusing spiral pin plate. Let be the topological charge of the axially focused spiral pinhole plate, and let its value be a positive integer. It is the wavelength of the incident laser.

[0011] According to one aspect of the invention, the minimum focal length of the pinhole on the axial focusing spiral pinhole plate is... Represented as:

[0012] ;

[0013] The maximum focal length of the pinholes on the axial focusing spiral pinhole plate Represented as:

[0014] .

[0015] According to one aspect of the present invention, in the axial line focusing spiral pinhole plate, each column of pinholes is arranged in a right-hand spiral configuration;

[0016] In each group of pinholes, the pinhole closest to the center of the axial focusing spiral pinhole plate is the first pinhole, and the distance from the first pinhole to the center of the axial focusing spiral pinhole plate is... The range of values ​​for:

[0017] ;

[0018] The radius of the pinholes on the axially focused spiral pinhole plate satisfy:

[0019] .

[0020] According to an aspect of the present application, the axial line focusing spiral pinhole plate is made of a fully ionized carbon ion and hydrogen ion target, and the density ratio of the carbon ion and the hydrogen ion is 1:4.

[0021] According to an aspect of the present application, the thickness of the axial line focusing spiral pinhole plate satisfies:

[0022] .

[0023] According to an aspect of the present application, in step S2, a beam of relativistic intensity Gaussian laser with a Gaussian intensity distribution is used, and the peak intensity is located at the optical axis.

[0024] The intensity of the beam of relativistic intensity Gaussian laser is .

[0025] According to an aspect of the present application, the axial line focusing spiral pinhole plate is made by electron beam etching.

[0026] According to an aspect of the present application, in step S2, the filamentous plasma target is made of a fully ionized hydrogen ion and electron target, and the density ratio of the hydrogen ion and the electron is 1:1.

[0027] According to an aspect of the present application, in step S2, the axial line focusing spiral pinhole plate is arranged coaxially with the filamentous plasma target.

[0028] The interval between the first end of the filamentous plasma target and the axial line focusing spiral pinhole plate is , and the interval between the second end of the filamentous plasma target and the axial line focusing spiral pinhole plate is .

[0029] The radius of the filamentous plasma target is .

[0030] According to a scheme of the present application, the present application realizes the generation of super-strong vortex laser driven by super-strong Gaussian laser and the interaction of the super-strong vortex laser with the filament target to generate a spiral distributed high-energy electron beam, so that the generation of the high-energy electron beam is more convenient and stable, and the overall complexity is greatly reduced, and the corresponding application cost is reduced.

[0031] According to one of the schemes of the present application, the present application irradiates an axial line focusing spiral pinhole plate with a light beam, and transmits laser to form a vortex laser in a focusing area and interact with a filament plasma target. Since the vortex laser has a spiral electromagnetic field, it will make the electron beam in the filament target spiral when the electron beam is pulled out. Then the electron beam is accelerated to high energy under the action of the laser.

[0032] According to one of the schemes of the present application, the present application can generate a vortex laser with a main mode of by adjusting the arrangement of pinholes on the target, and interact with a filament plasma target to generate a high-energy electron beam with a vortex distribution. 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 harmonic and high angular momentum X / γ ray beam. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a schematic block diagram showing the steps of a method for generating a spiral-distributed high-energy electron beam according to one embodiment of the present application;

[0034] Figure 2 is a schematic diagram showing the principle of a method for generating a spiral-distributed high-energy electron beam according to one embodiment of the present application;

[0035] Figure 3 is a schematic diagram showing the structure of an axial line focusing spiral pinhole plate according to one embodiment of the present application;

[0036] Figure 4 is a simulation result diagram of a simulation box in Example 1;

[0037] Figure 5 is a result diagram of the high-energy electron beam generated in Example 1, wherein (a) shows the energy result diagram of the high-energy electron beam, (b) shows the divergence angle result diagram of the high-energy electron beam, and (c) shows the orbital angular momentum result diagram of the high-energy electron beam. DETAILED DESCRIPTION

[0038] The present application will be described in detail below in conjunction with the drawings and specific embodiments, but the embodiments of the present application are not limited to the following embodiments.

[0039] According to one embodiment of the present application, a method for generating a spiral-distributed high-energy electron beam according to the present application includes the following steps: Figure 1 , Figure 2 and Figure 3

[0040] ​S1. preparing an axial line focusing spiral pinhole plate, wherein the axial line focusing spiral pinhole plate is provided with a plurality of pinhole groups arranged regularly along the circumferential direction of the plate body, and each pinhole group comprises a plurality of pinholes arranged in a spiral;

[0041] S2. arranging a filamentous plasma target coaxially with the axial line focusing spiral pinhole plate, wherein the length of the filamentous plasma target is greater than or equal to the focal length range of the pinholes;

[0042] S3. irradiating a beam of relativistic intensity Gaussian laser onto the axial line focusing spiral pinhole plate, and based on the pinholes on the axial line focusing spiral pinhole plate, the laser transmitted by different pinholes has different optical paths to the optical axis, thereby introducing an angular phase difference for the transmitted Gaussian laser, so as to focus to form a vortex laser on the filamentous plasma target, and 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 a spiral distributed high-energy electron beam.

[0043] As shown in Figure 2 According to an embodiment of the present application, in step S1, in the step of preparing the axial line focusing spiral pinhole plate, a plurality of pinhole groups are arranged at equal intervals along the circumferential direction of the plate body on the axial line focusing spiral pinhole plate to achieve regular arrangement of the pinhole groups. In this embodiment, each pinhole group comprises a plurality of pinholes arranged in a spiral, and the rotational direction of the pinholes arranged in a spiral in each pinhole group is consistent, so that the pinholes on the axial line focusing spiral pinhole plate are arranged in a spiral radiating from the center to the periphery. In this embodiment, the pinholes penetrate the body of the axial line focusing spiral pinhole plate along the axial direction of the axial line focusing spiral pinhole plate.

[0044] In this embodiment, the axial line focusing spiral pinhole plate as a whole can be made of a regular plate body, such as a square plate, a circular plate, etc.

[0045] Through the above arrangement, the present application, by arranging the pinholes in a spiral on the axial line focusing spiral pinhole plate, causes the laser transmitted by different pinholes to have different optical paths to the optical axis when a beam of relativistic intensity Gaussian laser is irradiated onto the axial line focusing spiral pinhole plate, thereby introducing an angular phase difference for the transmitted laser, so as to form a vortex laser in the focusing region, i.e. to achieve modulation of the seed laser into a vortex laser in the focusing volume.

[0046] As shown in Figure 3 According to an embodiment of the present application, 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 represented as:

[0047]

[0048] wherein, For the first The angular position of each pinhole For the first The radial position of each pinhole For the first The focal length of a pinhole is expressed as: Furthermore, the focal length range of the pinhole is the minimum focal length. to maximum focal length , focus is ; This refers to the number of pinholes. It is the distance from the first pin in each pin group to the center of the axial-line focusing spiral pin plate. Let be the topological charge of the axially focused spiral pinhole plate, and let its value be a positive integer. It is the wavelength of the incident laser.

[0049] like Figure 3 As shown, according to one embodiment of the present invention, the minimum focal length of the pinhole on the axial focusing spiral pinhole plate is... Represented as:

[0050] ;

[0051] Maximum focal length of the pinhole on the axial focusing spiral pinhole plate Represented as:

[0052] .

[0053] The above settings effectively ensure that the vortex laser generated by this invention has a wide focusing range, making it more widely applicable and further guaranteeing its ease of use.

[0054] like Figure 3 As shown, according to one embodiment of the present invention, in the axial line focusing spiral pinhole plate, each column of pinholes is spirally arranged in a right-handed manner; wherein, in each column of pinholes, the pinhole closest to the center of the axial line focusing spiral pinhole plate is the first pinhole, and the distance from the first pinhole to the center of the axial line focusing spiral pinhole plate is... The range of values ​​for:

[0055] ;

[0056] By setting the first pinhole in each pinhole group at a distance from the center of the axial focusing spiral pinhole plate, this scheme can more effectively generate a higher-order vortex laser in the corresponding focusing area, making the generated vortex laser more stable.

[0057] In this embodiment, the radius of the pinhole on the axially focused spiral pinhole plate is... satisfy:

[0058] .

[0059] Through the above arrangement, the radius of the pinhole is arranged in the above range, so that the arranged pinhole is more matched with the input Gaussian laser, and more advantageously, the high-order mode vortex laser is generated in the corresponding focusing area, so that the generated vortex laser is more stable and accurate.

[0060] According to an embodiment of the present application, the axial line focusing spiral pinhole plate is made of fully ionized carbon ions and hydrogen ions target material, and the density ratio of carbon ions and hydrogen ions is 1:4.

[0061] Through the above arrangement, the axial focusing spiral pinhole plate made of fully ionized carbon ions and hydrogen ions target material with a density ratio of 1:4 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 laser beam; wherein the axial focusing spiral pinhole plate arranged above can form a more matched Gaussian laser input, which can significantly enhance the nonlinear effect of laser. Moreover, the focusing ability can be significantly improved by the density ratio arranged above.

[0062] According to an embodiment of the present application, the thickness of the axial line focusing spiral pinhole plate is satisfies:

[0063] .

[0064] Through the above arrangement, the thickness of the axial focusing spiral pinhole plate is arranged in the above range, and more advantageously, the high-order mode vortex laser is generated in the corresponding focusing area, so that the generated vortex laser is more stable and effective.

[0065] According to an embodiment of the present application, in step S2, a beam of Gaussian laser with relativistic intensity is used, which has a Gaussian intensity distribution, and the peak intensity is located at the optical axis.

[0066] According to an embodiment of the present application, the intensity of the beam of Gaussian laser with relativistic intensity is .

[0067] Through the above arrangement, the present application can more effectively adapt to the input of high-intensity laser, and also provides more advantageous conditions for realizing high-intensity vortex laser.

[0068] According to an embodiment of the present application, the axial line focusing spiral pinhole plate is made by electron beam etching.

[0069] According to an embodiment of the present application, in step S2, the filamentary plasma target is made of fully ionized hydrogen ions and electrons, and the density ratio of the hydrogen ions to the electrons is 1:1.

[0070] As shown in FIG. 2, according to an embodiment of the present application, in step S2, the filamentary plasma target is arranged coaxially with the axial line focusing spiral pinhole plate. Figure 2

[0071] In the present embodiment, the interval between the first end of the filamentary plasma target and the axial line focusing spiral pinhole plate is , and the interval between the second end of the filamentary plasma target and the axial line focusing spiral pinhole plate is .

[0072] In the present embodiment, the radius of the filamentary plasma target is .

[0073] Through the above arrangement, the filamentary plasma target provided by the present application can conveniently achieve full coverage of the vortex laser focusing area, thereby achieving more reliable and beneficial formation of high-energy electron beams.

[0074] To further illustrate the present application, the present application is further exemplified.

[0075] Example 1

[0076] Specifically, the 3D-PIC simulation using the relativistic electromagnetic code EPOCH proves it. In the present embodiment, the grid size of the simulation box is , and thus the grid is set to 2000x800x800, and there are 9 macro-particles in each grid.

[0077] Further, 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; wherein and are the peak amplitude and the laser focusing spot size of the laser electric field, respectively; is the laser wavelength, wherein is the laser period, is the laser frequency; , and are the unit charge, electron mass and light speed in vacuum, respectively, is the unit vector in the direction, is the radial coordinate in the cylindrical coordinate system.

[0078] ​Further, the initial position of the axial line focusing spiral pinhole plate is in the position of the simulation box , and the thickness of the axial line focusing spiral pinhole plate is ; wherein the focal length range of the pinholes on the axial line focusing spiral pinhole plate can be set to to , and then the initial position of the pinholes in the simulation box based on the axial line focusing spiral pinhole plate is set to start from to end at .

[0079] In the embodiment, the distance from the first pinhole in each pinhole group on the axial line focusing spiral pinhole plate to the center of the axial line focusing spiral pinhole plate is , the radius of each pinhole is , the number of pinholes is , and the topological charge of the axial line focusing spiral pinhole plate is .

[0080] Further, the pinholes in each pinhole group on the axial line focusing spiral pinhole plate are spirally arranged in a right-handed manner.

[0081] Further, the axial line focusing spiral pinhole plate is made of fully ionized carbon ions and hydrogen ions target material, and the composition is composed of fully ionized carbon ions and hydrogen ions at a density ratio of 1:4; wherein the corresponding densities of electrons, protons and carbon ions are , and .

[0082] Further, the axial line focusing spiral pinhole plate is made by electron beam etching.

[0083] Through the axial line focusing spiral pinhole plate set as above, when the incident seed laser (i.e. a beam of relativistic intensity Gaussian laser) irradiates the axial line focusing spiral pinhole plate, only a part of the laser can pass through the pinhole area. Because the optical path difference of the laser passing through different position pinholes is different when reaching the focusing volume, the axial line focusing spiral pinhole plate can modulate the seed laser into vortex laser in the focusing volume.

[0084] In the embodiment, in the simulation box, the radius of the filament plasma target is , and the initial position is between and . Wherein the filament plasma target is made of fully ionized hydrogen ions and electron target material, 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, It is the vacuum permittivity. It is the frequency of the laser.

[0085] Combination Figure 4 and Figure 5 As shown, it demonstrates in Transverse electric field of the vortex laser output Distribution and energy density distribution of electrons in the filamentary plasma target. The output vortex laser propagates along the surface of the target, with its extremely strong transverse electric field. Electrons are extracted and accelerated from the surface of a 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 exhibits a helical topology in space. Figure 5 (a) and Figure 5 (b) shows that the maximum energy of the electron beam is at It can reach 350 MeV with a divergence angle of approximately 16°. Furthermore, as electrons are accelerated by the vortex laser, the electron beam also acquires orbital angular momentum carried by the vortex laser. Just as... Figure 5 As shown in (c), the orbital angular momentum of the electron beam gradually increases, eventually reaching... achieve This type of high-energy, high-orbital-angular-momentum electron beam has potential applications in generating vortex terahertz waves and high-angular-momentum X / γ-ray beams.

[0086] The above description is merely an example of a specific solution of the present invention. For any devices and structures not described in detail herein, it should be understood that they are implemented using common devices and methods already available in the art.

[0087] The above description is merely one embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of generating a helically distributed high energy electron beam, characterized by, The method 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 pinhole groups arranged along the circumferential direction of the plate body in a regular manner, and each pinhole group comprises a plurality of pinholes arranged in a spiral manner; S2. Arranging a filamentous plasma target coaxially with the axial line focusing spiral pinhole plate, wherein the length of the filamentous plasma target is greater than or equal to the focal length range of the pinholes; S3. Using a beam of relativistic intensity Gaussian laser 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 of the laser transmitted by different pinholes to the optical axis is different, an angular phase difference is introduced for the transmitted Gaussian laser, so as to focus to form a vortex laser on the filamentous plasma target, and 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 a spiral distributed high-energy electron beam.

2. The method of claim 1, wherein the helical distribution of high energy electron beam is generated by, 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 represented as: wherein, is the angular position of the th pinhole, is the radial position of the th pinhole, is the focal length of the th pinhole, denoted as: , and the focal length range of the pinhole is from the minimum focal length to the maximum focal length , and the depth of focus is ; is the number of pinholes; is the distance from the first pinhole in each column of pinholes 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 of claim 2, wherein the helical distribution of high energy electron beams is generated by, The axial line focusing spiral pinhole plate has a minimum focal length of the pinhole is represented as: ； The axial line focusing spiral pinhole plate has a maximum focal length of the pinhole is represented as: 。 4. The method of claim 3, wherein the helical distribution of high energy electron beams is generated by, Each pinhole group on the axial line focusing spiral pinhole plate is arranged in a right-handed spiral manner; The first pinhole in each pinhole group is closest to the center of the axial line focusing helical pinhole plate, and the distance from the first pinhole to the center of the axial line focusing helical pinhole plate is The value range of the distance from the first pinhole to the center of the axial line focusing helical pinhole plate is: ； The radius of the pinholes on the axial line focusing pinhole plate satisfies: 。 5. The method of claim 4, wherein the helical distribution of the high energy electron beam is generated by, The axial line focusing spiral pinhole plate is made of fully ionized carbon ions and hydrogen ions, and the density ratio of carbon ions to hydrogen ions is 1:

4.

6. The method of claim 5, wherein the helical distribution of high energy electron beams is generated by, The thickness of the axial line focusing spiral pinhole plate satisfies: 。 7. The method of claim 6, wherein the helical distribution of high energy electron beams is generated by, In step S2, the beam of relativistic intensity Gaussian laser has a Gaussian intensity distribution, and the peak intensity is located at the optical axis; The intensity of the employed beam of a relativistic intensity Gaussian laser is .

8. The method of claim 7, wherein the helical distribution of high energy electron beams is generated by, The axial line focusing spiral pinhole plate is made by electron beam etching.

9. The method of claim 8, wherein the helical distribution of high energy electron beams is generated by, In step S2, the filamentous plasma target is made of fully ionized hydrogen ions and electrons, and the density ratio of hydrogen ions to electrons is 1:

1.

10. The method of claim 9, wherein the helical distribution of high energy electron beams is generated by, In step S2, the filamentous plasma target is arranged coaxially with the axial line focusing spiral pinhole plate in a spaced manner. a spacing between a first end of the filamentary plasma target and the axial line focusing spiral pinhole plate is a spacing between a second end of the filamentary plasma target and the axial line focusing spiral pinhole plate is ; The radius of the filamentary plasma target is .

Images