A monoenergetic attosecond positron train generation system and generation method thereof

Abstract

The invention discloses a monoenergetic attosecond positron train generation system and a generation method thereof. The generation system comprises a Laguerre-Gaussian laser source for generating a Laguerre-Gaussian laser which enters a near-critical density target via a first optical system, a near-critical density target having a columnar band with a radial density gradient, and a Gaussian laser source for generating an ordinary Gaussian laser which enters the near-critical density target via a second optical system, wherein the Laguerre-Gaussian laser and the ordinary Gaussian laser in the near-critical density target are opposite to each other. The generation method generates a monoenergetic attosecond positron train by using the monoenergetic attosecond electron train generation system through the interaction of a vortex laser (Laguerre-Gaussian laser and ordinary Gaussian laser) with a near-critical density gradient target.

Description

Technical Field

[0001] The invention relates to the field of laser and plasma technology, and in particular to a monoenergetic attosecond positron train generation system and a generation method thereof. Background Art

[0002] Since the existence of positrons was proven in the 1930s, people have conducted a lot of research on their generation and application, covering many fields. For example, materials science, nuclear physics, laboratory astrophysics, plasma physics, medical imaging and treatment, etc. High-intensity lasers can achieve spontaneous electron-positron pair generation in a vacuum, but the intensity of the laser is extremely high. 29 W / cm 2 , the corresponding electric field strength is as high as 1.32×10 18 V / m, this field strength is also called the Schwinger critical field strength. Spontaneous electron-positron avalanche is difficult to achieve experimentally.

[0003] In order to achieve high-energy-density positron excitation, most current technical routes utilize the Trident process and the BH process. The former is the interaction between high-energy electrons and the nuclides of high-Z metal targets to produce positron-electron pairs, while the latter is the interaction between γ photons and nuclides to produce positron-electron pairs. Both of these schemes involve the interaction between high-energy particles and high-Z solid targets. Another more commonly used scheme is the use of the BW process. The difference from the previous two is that the multi-photon BW process is an all-optical process in which high-energy photons interact with multiple laser photons to produce positron-electron pairs. The high-energy photons required for the multi-photon BW process can be generated by the oscillation of electrons in the laser field, or provided by a nonlinear Compton scattering process.

[0004] In the research fields of material vacancy detection, gamma-ray bursts and black holes, there is a high demand for the monoenergeticity of positrons. Although high energy density positron excitation can be provided by the above process, it is still difficult to control the energy dispersion and divergence angle of positrons. In addition to momentum and direction, the angular momentum of positrons provides another degree of freedom that can carry more information. Summary of the invention

[0005] The object of the present invention is to provide a monoenergetic attosecond positron train generation system and a generation method thereof, wherein the monoenergetic attosecond electron train generation system is used to generate a monoenergetic attosecond electron train; and the generation method generates a monoenergetic attosecond electron train based on the monoenergetic attosecond electron train generation system.

[0006] The present invention is achieved through the following technical scheme: a monoenergetic attosecond positron train generation system comprises a Laguerre-Gaussian laser source, a columnar near-critical density target with a radial density gradient, and a Gaussian laser source, wherein the Laguerre-Gaussian laser generated by the Laguerre-Gaussian laser enters the near-critical density target through a first optical system, and the Gaussian laser source generates an ordinary Gaussian laser which enters the near-critical density target through a second optical system, and the Laguerre-Gaussian laser and the ordinary Gaussian laser which enter the near-critical density target are opposite to each other.

[0007] The intensity of a single beam generated by a Laguerre-Gaussian laser source is 1.3 to 9.5×10 22 W / cm 2 The left-handed circularly polarized Laguerre-Gaussian laser is focused and emitted by the first optical system and then incident from one end of a cylindrical near-critical density target (columnar near-critical plasma) with a radial density gradient. The Laguerre-Gaussian laser forms a Gaussian laser field composed of a transverse electromagnetic field and a longitudinal electromagnetic field in the near-critical density target. The transverse electromagnetic field causes the electrons in the near-critical density target to form a string structure. The electrons in the string structure are accelerated under the action of the longitudinal electromagnetic field. After acceleration, when the electrons in the string structure (i.e., high-energy electrons) collide with ordinary Gaussian laser (generated by an ordinary Gaussian laser source) incident from the other end of the near-critical density target, a large number of high-energy gamma photons will be excited due to nonlinear Compton scattering.

[0008] When high-energy gamma photons collide with ordinary Gaussian laser (generated by ordinary Gaussian laser source) incident from the other end of the near-critical density target, they will excite a large number of positron-electron pairs due to the multi-photon BW effect.

[0009] Most of the positrons in the positron-electron pairs will be transmitted to the second optical system side along with the Laguerre-Gaussian laser. During the transmission process, an attosecond string structure will be formed and accelerated to a higher energy. The energy dispersion of a single positron string is as low as 6%, forming a monoenergetic attosecond positron string.

[0010] Due to the lateral pinching effect of Laguerre-Gaussian laser on charged particles, the energy angular distribution of various particles obtained is relatively concentrated. The more secondary the particles produced, the closer their angular distribution will be to the axis and the smaller the divergence angle will be.

[0011] The present invention uses a double-beam collision structure and adopts a strength of 1.3 to 9.5×10 22 W / cm 2The Laguerre-Gaussian laser makes it possible to conduct experimental research under existing laser technology conditions, and the energy and angular momentum of gamma photons and positrons can be adjusted by adjusting the length of the columnar near-critical density target (near-critical density plasma) with radial density gradient, the collision position, and the intensity of the driving vortex laser. The monoenergetic attosecond positron train with orbital angular momentum provides a new direction for scientific researchers to understand and manipulate microscopic particles, which has important practical and scientific significance.

[0012] Furthermore, in order to better realize the monoenergetic attosecond positron train generation system, the first optical system includes a concave mirror for focusing the Laguerre-Gaussian laser generated by the Laguerre-Gaussian laser source, and a first reflector for reflecting the Laguerre-Gaussian laser focused by the concave mirror into a near-critical density target; the second optical system uses a second reflector that can reflect ordinary Gaussian laser into the near-critical density target.

[0013] Furthermore, in order to better realize the monoenergetic attosecond positron train generation system, the Laguerre-Gaussian laser source generates Laguerre-Gaussian laser which enters the near-critical density target along the axis of the near-critical density target through the first optical system.

[0014] Furthermore, in order to better realize the monoenergetic attosecond positron train generation system, the near-critical density target is generated by nozzle A and nozzle B relatively arranged on both sides of the optical axis between the first optical system and the second optical system, and the density distribution of the near-critical density target along the axial direction is low in the middle and high on both sides.

[0015] Among them, nozzle A and nozzle B are used to eject near-critical density plasma, and the ejected near-critical density plasma forms a near-critical density target with a low middle and high sides under the effect of diffusion.

[0016] Furthermore, in order to better realize the monoenergetic attosecond positron train generation system, a second magnet system composed of two second magnets and a second detection system composed of a second positron detector and a second negative electron detector are respectively arranged on both sides of the optical axis between the second optical system and the near-critical density target.

[0017] Furthermore, in order to better realize the monoenergetic attosecond positron train generation system, a first magnet system composed of two first magnets and a first detection system composed of a first positron detector and a first negative electron detector are respectively arranged on both sides of the optical axis between the first optical system and the near-critical density target.

[0018] Furthermore, in order to better realize the monoenergetic attosecond positron train generation system, the laser intensity of the Laguerre-Gaussian laser is 1.3-9.5×10 22 W / cm2 , can be focused to a focal spot radius of 3μm, a wavelength of λ=1μm, a Gaussian time configuration, and a pulse width of 12T0, where T0=c / λ is the laser period and c is the speed of light in a vacuum.

[0019] Furthermore, in order to better realize the monoenergetic attosecond positron train generation system, the ordinary Gaussian laser has an intensity of 3.2×10 22 W / cm 2 , the focal spot radius is 5μm, the wavelength is λ=1μm, the time configuration is Gaussian, and the pulse width is 10T0; where T0=c / λ is the laser period, and c is the speed of light in vacuum.

[0020] A method for generating a monoenergetic attosecond positron train is implemented based on a monoenergetic attosecond positron train generation system, comprising the following steps:

[0021] 1) The Laguerre-Gaussian source generates a Laguerre-Gaussian laser and injects it into the near-critical density target to form a Gaussian laser field composed of a transverse electromagnetic field and a longitudinal electromagnetic field. The transverse electromagnetic field causes the electrons in the near-critical density target to form a string structure, and the longitudinal electromagnetic field accelerates the electrons in the string structure.

[0022] 2) The Gaussian laser source generates a Gaussian laser that enters the near-critical density target from the opposite direction and collides with the electrons in the accelerated string structure, generating a large number of high-energy gamma photons, which are then scattered nonlinearly by the near-critical density target to obtain a high-energy gamma photon string;

[0023] 3) The high-energy gamma photon train interacts with the Gaussian laser field in a near-critical density target, generating attosecond positron trains through a multiphoton Breit-Wheeler process;

[0024] 4) As the attosecond positron train continues to propagate along with the Laguerre-Gaussian laser, it is accelerated by the longitudinal electromagnetic field and acquires orbital angular momentum from the Gaussian laser field, eventually forming a monoenergetic attosecond electron train.

[0025] Furthermore, in order to better implement the method for generating a monoenergetic attosecond positron train, the monoenergetic attosecond electron train is an attosecond positron train with orbital angular momentum.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] (1) The present invention uses Laguerre-Gaussian laser as the driving light and utilizes its unique electromagnetic field structure to effectively accelerate and spatially separate electrons and generated positrons, thereby forming a special attosecond string structure.

[0028] (2) The present invention uses vortex light to efficiently transfer angular momentum to gamma photons and positrons. The orbital angular momentum conversion efficiency from laser to positron is as high as 2%, which is much higher than the conversion rate of ordinary Gaussian laser.

[0029] (3) The near-critical density target with radial density gradient used in the present invention maintains the focusing effect of the Laguerre-Gaussian laser, so that the Laguerre-Gaussian laser fully interacts with the target while also ensuring the energy intensity during collision. This ensures the conversion efficiency of the Laguerre-Gaussian laser to positrons, and the conversion efficiency of the total energy of the two laser beams to the positron energy can reach 0.3% in the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structure of a monoenergetic attosecond positron train generation system described in the present invention.

[0031] In the accompanying drawings, the numbers are explained as follows: 101-concave mirror, 102-first reflecting mirror, 103-first positron detector, 104-first negative electron detector, 105-first magnet, 106-nozzle A, 107-nozzle B, 108-second magnet, 109-second positron detector, 110-second negative electron detector, 111-second reflecting mirror. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0038] Embodiment 1:

[0039] The present invention designs a monoenergetic attosecond positron train generation system, comprising a Laguerre-Gaussian laser source, a columnar near-critical density target with a radial density gradient, and a Gaussian laser source. The Laguerre-Gaussian laser generated by the Laguerre-Gaussian laser enters the near-critical density target through a first optical system, and the Gaussian laser source generates an ordinary Gaussian laser that enters the near-critical density target through a second optical system, and the Laguerre-Gaussian laser and the ordinary Gaussian laser that enter the near-critical density target are opposite to each other.

[0040] As a preferred setting scheme, the monoenergetic attosecond electron string generation system is mainly composed of three parts: the first is a Laguerre-Gaussian laser source for generating Laguerre-Gaussian laser, the second is a Gaussian laser source for generating ordinary Gaussian laser, and the third is a near-critical density target with a columnar radial density gradient.

[0041] The intensity of a single beam generated by a Laguerre-Gaussian laser source is 1.3 to 9.5×10 22 W / cm 2 The left-handed circularly polarized Laguerre-Gaussian laser is focused and emitted by the first optical system and then incident from one end of a cylindrical near-critical density target (columnar near-critical plasma) with a radial density gradient. The Laguerre-Gaussian laser forms a Gaussian laser field composed of a transverse electromagnetic field and a longitudinal electromagnetic field in the near-critical density target. The transverse electromagnetic field causes the electrons in the near-critical density target to form a string structure. The electrons in the string structure are accelerated under the action of the longitudinal electromagnetic field. After acceleration, when the electrons in the string structure (i.e., high-energy electrons) collide with ordinary Gaussian laser (generated by an ordinary Gaussian laser source) incident from the other end of the near-critical density target, a large number of high-energy gamma photons will be excited due to nonlinear Compton scattering.

[0042] When high-energy gamma photons collide with ordinary Gaussian laser (generated by ordinary Gaussian laser source) incident from the other end of the near-critical density target, they will excite a large number of positron-electron pairs due to the multi-photon BW effect.

[0043] Most of the positrons in the positron-electron pairs will be transmitted to the second optical system side along with the Laguerre-Gaussian laser. During the transmission process, an attosecond string structure will be formed and accelerated to a higher energy. The energy dispersion of a single positron string is as low as 6%, forming a monoenergetic attosecond positron string.

[0044] Due to the lateral pinching effect of Laguerre-Gaussian laser on charged particles, the energy angular distribution of various particles obtained is relatively concentrated. The more secondary the particles produced, the closer their angular distribution will be to the axis and the smaller the divergence angle will be.

[0045] The present invention uses a double-beam collision structure and adopts a strength of 1.3 to 9.5×10 22 W / cm 2The Laguerre-Gaussian laser makes it possible to conduct experimental research under existing laser technology conditions, and the energy and angular momentum of gamma photons and positrons can be adjusted by adjusting the length of the columnar near-critical density target (near-critical density plasma) with radial density gradient, the collision position, and the intensity of the driving vortex laser. The monoenergetic attosecond positron train with orbital angular momentum provides a new direction for scientific researchers to understand and manipulate microscopic particles, which has important practical and scientific significance.

[0046] Embodiment 2:

[0047] This embodiment is further optimized on the basis of the above embodiment, and the same parts as the above technical solution will not be repeated here. Figure 1 As shown, further, in order to better realize the monoenergetic attosecond positron train generation system, the first optical system includes a concave mirror 101 for focusing the Laguerre-Gaussian laser generated by the Laguerre-Gaussian laser source, and a first reflector 102 for reflecting the Laguerre-Gaussian laser focused by the concave mirror 101 into the near-critical density target; the second optical system adopts a second reflector 111 capable of reflecting ordinary Gaussian laser into the near-critical density target; the Laguerre-Gaussian laser generated by the Laguerre-Gaussian laser source is focused by the concave mirror 101 and then reflected by the first reflector 102 into the near-critical density target through one end thereof; the ordinary Gaussian laser generated by the Gaussian laser source can enter the near-critical density target through the second reflector 111 through the other end thereof, and the two lasers are opposite to each other in the near-critical density target.

[0048] Preferably, the Laguerre-Gaussian laser source generates a Laguerre-Gaussian laser which enters the near-critical density target along the axis of the near-critical density target through the first optical system.

[0049] Embodiment 3:

[0050] This embodiment is further optimized on the basis of any of the above embodiments, and the same parts as the above technical solutions will not be repeated here. Figure 1 As shown, further, in order to better realize the monoenergetic attosecond positron train generation system, the near-critical density target is generated by nozzle A106 and nozzle B107 relatively arranged on both sides of the optical axis between the first optical system and the second optical system, and the density distribution of the near-critical density target along the axial direction is low in the middle and high on both sides.

[0051] During setting, nozzle A106 and nozzle B107 are arranged relative to each other, which can generate a near-critical density target with a radial density gradient of a columnar band (preferably a cylindrical band), and make the optical axis formed by the laser passing through the near-critical density target and the relative position connection line between nozzle A106 and nozzle B107 reach a state of orthogonal intersection.

[0052] Among them, nozzle A and nozzle B are used to eject near-critical density plasma, and the ejected near-critical density plasma forms a near-critical density target with a low middle and high sides under the effect of diffusion.

[0053] Embodiment 4:

[0054] This embodiment is further optimized on the basis of any of the above embodiments, and the same parts as the above technical solutions will not be repeated here. Figure 1 As shown, further, in order to better realize the monoenergetic attosecond positron train generation system, a second magnet system composed of two second magnets 108 and a second detection system composed of a second positron detector 109 and a second negative electron detector 110 are respectively arranged on both sides of the optical axis between the second optical system and the near-critical density target.

[0055] As a preferred setting scheme, a second magnet system and a second detection system are arranged between the second optical system and the near-critical density target, the second magnet system includes two second magnets 108, and the second detection system includes a second positron detector 109 and a second negative electron detector 110. When the two lasers enter the near-critical density target from their respective directions, they both enter along the optical axis. At the optical axis between the second optical system and the near-critical density target, the two second magnets 108 are respectively located on both sides of the optical axis, and the two second magnets 108 are arranged opposite to each other. The second positron detector 109 and the second negative electron detector 110 are also respectively located on both sides of the optical axis, and the second positron detector 109 and the second negative electron detector 110 are arranged opposite to each other. The second magnet system is arranged far from the second optical system, and the second detection system is arranged close to the second optical system.

[0056] A first magnet system consisting of two first magnets 105 and a first detection system consisting of a first positron detector 103 and a first negative electron detector 104 are respectively arranged on both sides of the optical axis between the first optical system and the near-critical density target; preferably, the first magnet system and the first detection system are arranged between the first optical system and the near-critical density target, the first magnet system includes two first magnets 105, and the first detection system includes a first positron detector 103 and a first negative electron detector 104. When the two lasers enter the near-critical density target from their respective directions, they both enter along the optical axis. At the optical axis between the second optical system and the near-critical density target, the two first magnets 105 are respectively located on both sides of the optical axis, and the two first magnets 105 are arranged opposite to each other. The first positron detector 103 and the first negative electron detector 104 are also respectively located on both sides of the optical axis, and the first positron detector 103 and the first negative electron detector 104 are arranged opposite to each other; and the first magnet system is arranged far from the first optical system, and the first detection system is arranged close to the first optical system.

[0057] Embodiment 5:

[0058] This embodiment is further optimized on the basis of any of the above embodiments, and the same parts as the above technical solutions will not be repeated here. Figure 1 As shown, further, in order to better realize the monoenergetic attosecond positron train generation system, the laser intensity of the Laguerre-Gaussian laser is 1.3-9.5×10 22 W / cm 2 , can be focused to a focal spot radius of 3μm, a wavelength of λ=1μm, a Gaussian time configuration, and a pulse width of 12T0, where T0=c / λ is the laser period and c is the speed of light in a vacuum.

[0059] The ordinary Gaussian laser has an intensity of 3.2×10 22 W / cm 2 , the focal spot radius is 5μm, the wavelength is λ=1μm, the time configuration is Gaussian, and the pulse width is 10T0; where T0=c / λ is the laser period, and c is the speed of light in vacuum.

[0060] Embodiment 6:

[0061] This embodiment is further optimized on the basis of any of the above embodiments, and the same parts as the above technical solutions will not be repeated here. Figure 1 As shown, a method for generating a monoenergetic attosecond positron train is implemented based on a monoenergetic attosecond positron train generation system, comprising the following steps:

[0062] 1) The Laguerre-Gaussian source generates a Laguerre-Gaussian laser and injects it into the near-critical density target to form a Gaussian laser field composed of a transverse electromagnetic field and a longitudinal electromagnetic field. The transverse electromagnetic field causes the electrons in the near-critical density target to form a string structure, and the longitudinal electromagnetic field accelerates the electrons in the string structure.

[0063] 2) The Gaussian laser source generates a Gaussian laser that enters the near-critical density target from the opposite direction and collides with the electrons in the accelerated string structure, generating a large number of high-energy gamma photons, which are then scattered nonlinearly by the near-critical density target to obtain a high-energy gamma photon string;

[0064] 3) The high-energy gamma photon train interacts with the Gaussian laser field in a near-critical density target, generating attosecond positron trains through a multiphoton Breit-Wheeler process;

[0065] 4) As the attosecond positron train continues to propagate along with the Laguerre-Gaussian laser, it is accelerated by the longitudinal electromagnetic field and acquires orbital angular momentum from the Gaussian laser field, eventually forming a monoenergetic attosecond electron train with orbital angular momentum.

[0066] Embodiment 7:

[0067] A monoenergetic attosecond positron train generation system, such as Figure 1 As shown, it includes a Laguerre-Gaussian laser source, a first optical system composed of a concave mirror 101 and a first reflecting mirror 102, a first magnet system composed of two oppositely arranged first magnets 105, a first detection system composed of an oppositely arranged first positron detector 103 and a first negative electron detector 104, a near-critical density target with a columnar radial density gradient generated by an oppositely arranged nozzle A and a nozzle B, a second detection system composed of two oppositely arranged second magnets 108, a oppositely arranged second positron detector 109 and a second negative electron detector 110, a second optical system composed of a second reflecting mirror 111, and a Gaussian laser source.

[0068] like Figure 1 As shown, a beam of circularly polarized Laguerre-Gaussian laser generated by a Laguerre-Gaussian laser source is focused by a concave mirror 101, reflected by a first reflector 102, and incident from the left along the axis of a columnar near-critical plasma (a columnar near-critical density target with a radial density gradient).

[0069] Plasma is ejected from nozzles (nozzle A106, nozzle B107) to form a near-critical density plasma (near-critical density target) with a radial density gradient (low in the middle and high on both sides). The Laguerre-Gaussian laser forms a Gaussian laser field composed of a transverse electromagnetic field and a longitudinal electromagnetic field in the near-critical density target. The transverse electromagnetic field will cause the electrons in the near-critical density target to form a string structure, while the longitudinal electromagnetic field will accelerate the electrons in the string structure. Figure 1 As shown, when the electrons (i.e., high-energy electrons) in the accelerated post-series structure collide with ordinary Gaussian lasers (generated by ordinary Gaussian laser sources) incident from the other end (right side) of the near-critical density target, a large number of high-energy gamma photons will be excited due to nonlinear Compton scattering.

[0070] When high-energy gamma photons collide with ordinary Gaussian laser (generated by ordinary Gaussian laser source) incident from the other end of the near-critical density target (right side), they will excite a large number of positron-electron pairs due to the multi-photon BW effect.

[0071] Most of the positrons in the positron-electron pairs will be transmitted to the second optical system side (right side) along with the Laguerre-Gaussian laser. During the transmission process, an attosecond string structure will be formed and accelerated to a higher energy. The energy dispersion of a single positron string is as low as 6%, forming a monoenergetic attosecond positron string.

[0072] Due to the lateral pinching effect of Laguerre-Gaussian laser on charged particles, the energy angular distribution of various particles obtained is relatively concentrated. The more secondary the particles produced, the closer their angular distribution will be to the axis and the smaller the divergence angle will be.

[0073] For ease of application, after the generated attosecond positron train is deflected by the second magnet system (composed of a pair of second magnets 108), the positrons can be detected by the second positron detector 109, or the entire deflected attosecond positron train can be injected into an accelerator that can be used in conjunction with it to carry out other high-energy physics experiments; and the electrons will be detected by the second negative electron detector 110.

[0074] Since another part of the positron-electron pairs (i.e., part of the large number of positron-electron pairs excited by the multi-photon BW effect) will propagate toward the first optical system side (left side) along with the ordinary Gaussian light, a first magnet system (composed of a pair of first magnets 105) and a first detection system (composed of a first positron detector 103 and a first negative electron detector 104) are set in this direction. The divergence angle of the attosecond positron train finally propagating toward the second optical system side (right side) is controlled within 10°. In the process of the interaction between the laser (Laguerre Gaussian laser, ordinary laser) and the plasma to produce gamma photons and positrons, in addition to the energy transfer and evolution, the orbital angular momentum of the Laguerre Gaussian laser as a vortex light will also be transferred to these particles. The angular momentum conversion efficiency of the laser to gamma photons and positrons can reach 30% and 2%, respectively. By adjusting the plasma length and the position where the two laser beams (Laguerre Gaussian laser, ordinary laser) collide, the energy and angular momentum of the obtained gamma light and positron train can be changed.

[0075] In this embodiment, the driving light used is a circularly polarized Laguerre-Gaussian laser, and the parameters are set as follows: the laser intensity is 9.5×10 22 W / cm 2 The focal spot radius is 3 μm, the wavelength is λ=1 μm, the time configuration is Gaussian, the pulse width is 12T0, T0=c / λ is the laser period, and c is the speed of light in vacuum. The scattered light used is a linearly polarized ordinary Gaussian laser, and the parameters are set as follows: the intensity is 3.2×10 22 W / cm 2 , the focal spot radius is 5 μm, the wavelength is λ=1 μm, the time configuration is Gaussian, and the pulse width is 10T0. The near-critical density plasma is composed of hydrogen ions (H + ) and electronic (e - ) with a length of about 100 μm and maintains electrical neutrality as a whole.

[0076] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A monoenergetic attosecond positron train generation system, characterized by: The invention comprises a Laguerre-Gaussian laser source, a columnar near-critical density target with a radial density gradient, and a Gaussian laser source. The Laguerre-Gaussian laser generated by the Laguerre-Gaussian laser enters the near-critical density target through a first optical system. The Gaussian laser source generates an ordinary Gaussian laser which enters the near-critical density target through a second optical system. The Laguerre-Gaussian laser and the ordinary Gaussian laser which enter the near-critical density target are opposite to each other.

2. A monoenergetic attosecond positron train generation system according to claim 1, characterized in that: The first optical system comprises a concave mirror (101) for focusing Laguerre-Gaussian laser light generated by a Laguerre-Gaussian laser source, and a first reflecting mirror (102) for reflecting the Laguerre-Gaussian laser light focused by the concave mirror (101) into a near-critical density target; the second optical system uses a second reflecting mirror (111) capable of reflecting ordinary Gaussian laser light into the near-critical density target.

3. The monoenergetic attosecond positron train generation system according to claim 1, characterized in that: The Laguerre-Gaussian laser source generates a Laguerre-Gaussian laser which enters the near-critical density target along the axis of the near-critical density target through the first optical system.

4. A monoenergetic attosecond positron train generation system according to any one of claims 1 to 3, characterized in that: The near-critical density target is generated by nozzle A (106) and nozzle B (107) which are relatively arranged on both sides of the optical axis between the first optical system and the second optical system, and the density distribution of the near-critical density target along the axial direction is low in the middle and high on both sides.

5. A monoenergetic attosecond positron train generation system according to any one of claims 1 to 3, characterized in that: A second magnet system consisting of two second magnets (108) and a second detection system consisting of a second positron detector (109) and a second negative electron detector (110) are respectively arranged on both sides of the optical axis between the second optical system and the near-critical density target.

6. A monoenergetic attosecond positron train generation system according to any one of claims 1 to 3, characterized in that: A first magnet system consisting of two first magnets (105) and a first detection system consisting of a first positron detector (103) and a first negative electron detector (104) are respectively arranged on both sides of the optical axis between the first optical system and the near-critical density target.

7. A monoenergetic attosecond positron train generation system according to any one of claims 1 to 3, characterized in that: The laser intensity of the Laguerre-Gaussian laser is 1.3 to 9.5×10 22 W / cm 2 , can be focused to a focal spot radius of 3μm, a wavelength of λ=1μm, a Gaussian time configuration, and a pulse width of 12T0, where T0=c / λ is the laser period and c is the speed of light in a vacuum.

8. A monoenergetic attosecond positron train generation system according to any one of claims 1 to 3, characterized in that: The ordinary Gaussian laser has an intensity of 3.2×10 22 W / cm 2 , the focal spot radius is 5μm, the wavelength is λ=1μm, the time configuration is Gaussian, and the pulse width is 10T0; where T0=c / λ is the laser period, and c is the speed of light in vacuum.

9. A method for generating a monoenergetic attosecond positron train, implemented based on a monoenergetic attosecond positron train generation system as claimed in any one of claims 1 to 8, characterized in that: The steps include: 1) The Laguerre-Gaussian source generates a Laguerre-Gaussian laser and injects it into the near-critical density target to form a Gaussian laser field composed of a transverse electromagnetic field and a longitudinal electromagnetic field. The transverse electromagnetic field causes the electrons in the near-critical density target to form a string structure, and the longitudinal electromagnetic field accelerates the electrons in the string structure. 2) The Gaussian laser source generates a Gaussian laser that enters the near-critical density target from the opposite direction and collides with the electrons in the accelerated string structure, generating a large number of high-energy gamma photons, which are then scattered nonlinearly by the near-critical density target to obtain a high-energy gamma photon string; 3) The high-energy gamma photon train interacts with the Gaussian laser field in a near-critical density target, generating attosecond positron trains through a multiphoton Breit-Wheeler process; 4) As the attosecond positron train continues to propagate along with the Laguerre-Gaussian laser, it is accelerated by the longitudinal electromagnetic field and obtains orbital angular momentum from the Gaussian laser field, eventually forming a monoenergetic attosecond electron train.

10. A method for generating a monoenergetic attosecond positron train according to claim 9, characterized in that: The monoenergetic attosecond electron train is an attosecond positron train with orbital angular momentum.

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