Laser plasma electron accelerator based on density gradient

Abstract

The utility model discloses a laser plasma electron accelerator based on density gradient, which comprises a laser component, the laser component generates a high-intensity tightly-focused femtosecond laser pulse beam, and a sleeve is arranged on the path of the femtosecond laser pulse beam; a gas nozzle and a vacuum pump are arranged at the upper end and the lower end of the sleeve respectively, and an outlet of the gas nozzle is perpendicular to the femtosecond laser pulse beam; and a blade-shaped barrier parallel to the femtosecond laser pulse beam is also arranged in the sleeve close to one side of the gas nozzle. The sleeve is arranged at the outlet of the gas nozzle, so that a gas circulation area can be limited, continuous and stable density gradient distribution gas can be generated, the laser accelerator can always accelerate the same density distribution gas target, and a high-energy electron beam group in a stable state can be stably generated for a long time; the charge quantity of the electron beam bunch in single acceleration is improved, and the operation stability of the laser wake field electron accelerator is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of laser particle acceleration, in particular to a laser plasma electron accelerator based on density gradient. Background Art

[0002] Laser particle acceleration technology is a major breakthrough in the field of particle accelerators in recent years. It has successfully broken through the limitations of materials on acceleration gradients that traditional accelerators rely on, and can accelerate high-energy particles with the same energy in a smaller volume. The development of this technology provides new possibilities for the miniaturization and affordability of accelerators. Its core technology is based on laser chirped pulse amplification (CPA), which is a technology that first stretches ultrashort laser pulses in time, amplifies their energy, and then compresses them again to obtain ultra-intense laser pulses. By using this ultra-intense laser pulse to interact with plasma, an accelerating electric field of more than 100 gigavolts per meter (GV / m) can be generated, thereby achieving efficient acceleration of particles.

[0003] In mainstream laser electron acceleration technology, most of the laser energy is converted into plasma field potential energy, which limits the amount of charge of the electron bunch finally produced. Utility Model Content

[0004] In view of the above-mentioned deficiencies in the prior art, the utility model provides a density gradient-based laser plasma electron accelerator which can capture more electrons for acceleration during laser particle acceleration and increase the charge of electron bunches accelerated by a laser wakefield accelerator in a single time.

[0005] A density gradient-based laser plasma electron accelerator comprises a laser component, which generates a high-intensity tightly focused femtosecond laser pulse beam. A sleeve is arranged on the path of the femtosecond laser pulse beam. A gas nozzle and a vacuum pump are arranged at the upper and lower ends of the sleeve respectively, and the outlet of the gas nozzle is perpendicular to the femtosecond laser pulse beam. A blade-shaped barrier parallel to the femtosecond laser pulse beam is also arranged in the sleeve on the side close to the gas nozzle.

[0006] Furthermore, the laser component includes a laser and a focusing assembly; the laser generates a laser beam, and the focusing assembly is located on the path of the laser beam and focuses the laser beam to generate a high-intensity, tightly focused femtosecond laser pulse beam.

[0007] Furthermore, the gas nozzle is a curved rotating body structure.

[0008] Furthermore, one side of the blade-shaped barrier is thin-edged, and the thin-edged side is parallel to the femtosecond laser pulse beam.

[0009] Furthermore, one side of the thin blade of the blade-shaped barrier is smooth or toothed.

[0010] Furthermore, the blade-shaped barrier is made of high-strength metal material.

[0011] Furthermore, the sleeve is a curved rotating body cavity structure.

[0012] Furthermore, the sleeve is provided with an entrance hole and an exit hole along the direction of the femtosecond laser pulse beam.

[0013] Furthermore, the sleeve is provided with a gas inlet, the gas inlet is communicated with the outlet of the gas nozzle, and the gas inlet and the outlet of the gas nozzle are sealed.

[0014] Furthermore, the laser component, the gas nozzle, the sleeve and the blade-shaped barrier are all arranged in the vacuum chamber.

[0015] Compared with the prior art, the laser plasma electron accelerator based on density gradient provided by the utility model has the following beneficial technical effects:

[0016] 1. By installing a sleeve at the outlet of the gas nozzle, the gas flow area can be limited, and the gas used in the previous round of acceleration can be extracted in time through a vacuum pump to generate a continuous and stable density gradient distribution gas, ensuring that the laser accelerator can always accelerate the gas target with the same density distribution and stably generate a stable high-energy electron bunch for a long time;

[0017] 2. A blade-shaped barrier parallel to the femtosecond laser pulse beam is set in the sleeve, that is, the blade-shaped barrier is perpendicular to the outlet of the gas nozzle, which can generate a gas target with a density gradient in the sleeve, increase the charge of the electron bunch accelerated in a single time, and improve the operating stability of the laser wakefield electron accelerator. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0019] Figure 1 This is a schematic diagram of the structure of a laser plasma electron accelerator based on density gradient in an embodiment of the utility model;

[0020] Figure 2 It is a schematic diagram of the structure of the gas nozzle and the front-type barrier in the embodiment of the utility model.

[0021] Reference numerals: laser 1 , femtosecond laser pulse beam 11 , electron bunch 12 , focusing assembly 2 , sleeve 3 , gas nozzle 4 , vacuum pump 5 , knife-edge barrier 6 , first vacuum chamber 71 , second vacuum chamber 72 .

[0022] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0024] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0025] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0026] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] See also Figure 1 and Figure 2 , a density gradient-based laser plasma electron accelerator provided by the utility model, includes a laser component, the laser component generates a high-intensity tightly focused femtosecond laser pulse beam 11, a sleeve 3 is arranged on the path of the femtosecond laser pulse beam 11; a gas nozzle 4 and a vacuum pump 5 are arranged at the upper and lower ends of the sleeve 3, respectively, and the outlet of the gas nozzle 4 is perpendicular to the femtosecond laser pulse beam 11; on the side close to the gas nozzle 4, a blade-shaped barrier 6 parallel to the femtosecond laser pulse beam 11 is also arranged in the sleeve 3.

[0029] Specifically, the laser component includes a laser 1 and a focusing component 2; the laser 1 generates a laser beam, and the focusing component 2 is located on the path of the laser beam and focuses the laser beam to generate a high-intensity tightly focused femtosecond laser pulse beam 11. The laser 1 is preferably a titanium sapphire laser device, and the wavelength of the generated laser is 0.8 or 1 micron, and the laser power is TW-100 TW.

[0030] The focusing component 2 can use high-quality optical elements, such as using mirrors and gratings to tightly focus laser pulses, or a chirped pulse amplification system can be used to generate tightly focused laser pulses. In the utility model, the focusing component 2 preferably uses a chirped pulse amplification system to achieve high-intensity focusing of the laser beam.

[0031] On the path of the femtosecond laser pulse beam 11, a sleeve 3 is provided. The sleeve 3 is mainly used to limit the flow area of ​​the gas ejected from the outlet of the gas nozzle 4. The gas nozzle 4 and the vacuum pump 5 are respectively provided at the upper and lower ends of the sleeve 3. Figure 1 A gas inlet is provided at the lower end of the sleeve 3, and a gas outlet is provided at the upper end of the sleeve 3, wherein the gas inlet is connected to the outlet of the gas nozzle 4, and the gas outlet is connected to the vacuum pump 5 through a pipeline. It is worth noting that in order to ensure the sealing of the connection, a sealing ring or a sealant or a sealing gasket or welding is used to seal the connection. The sleeve 3 is a curved rotating body cavity structure, preferably a cylindrical cavity structure. The cylindrical structure can minimize the flow resistance of the gas and increase the flow speed of the gas, thereby ensuring a continuous and stable supply of the gas. In addition, the cylindrical structure can also reduce gas leakage and improve the sealing of the gas, thereby ensuring the normal operation of the laser accelerator.

[0032] The sleeve 3 is also provided with an entrance hole and an exit hole along the path of the femtosecond laser pulse beam 11, so that the femtosecond laser pulse beam 11 can be injected into the sleeve 3 from the entrance hole, and after reacting with the gas target, an accelerated electron bunch 12 is formed, and the accelerated electron bunch 12 is emitted from the exit hole.

[0033] The gas nozzle 4 is mainly used to provide gas, and its lower end is connected to the gas cylinder, and a gas source is provided through the gas cylinder. The gas in the gas cylinder includes but is not limited to hydrogen, oxygen or nitrogen. The gas nozzle 4 is a curved rotating body structure, including but not limited to a conical structure, a cylindrical structure, a gradual curve structure, a waist tightening structure or a big belly structure, which can be selected according to the specific situation. For example, when a gradual flow rate needs to be formed, a gradual curve structure, a waist tightening structure or a big belly structure can be selected. In this embodiment, a conical structure is preferred so that the gas forms a uniform flow velocity distribution at the outlet, thereby improving the uniformity of the gas flow rate and flow rate. Furthermore, a porous structure can be used at the outlet of the gas nozzle 4 to further improve the uniformity of the gas flow rate and flow rate.

[0034] The sleeve 3 is connected to the gas nozzle 4 and the vacuum pump 5 respectively. The gas nozzle 4 sprays gas to form a certain gas area in the sleeve 3, and the vacuum pump 5 promptly extracts the gas used in the previous round of acceleration, and cooperates with the blade-shaped barrier 6 to produce a continuous and stable density gradient distribution gas, ensuring that the femtosecond laser pulse beam 11 can always accelerate the same density distribution gas target and stably generate a stable high-energy electron beam cluster for a long time.

[0035] The blade-shaped barrier 6 is arranged in the sleeve 3, and its setting direction is parallel to the direction of the femtosecond laser pulse beam 11, and is mainly used to create a gas density gradient perpendicular to the laser propagation direction. It can be understood that according to the fluid properties, when the barrier is maintained for a period of time and does not move, the gas density distribution in the air duct reaches a steady state and no longer changes with time. Perpendicular to the laser incident direction, the edge of the blade-shaped barrier is projected relative to the gas nozzle on the plane where the laser movement position is located as a boundary, forming a gas density gradient with a higher and uniform density on the side away from the barrier and a lower and gradually decreasing density on the side close to the barrier. In this way, more electrons can be captured for acceleration during the laser plasma acceleration process, thereby increasing the charge of the electron bunch accelerated by the laser wakefield accelerator in a single time. Therefore, the insertion depth and insertion angle of the blade-shaped barrier 6 relative to the laser focal spot can be adjusted.

[0036] See also Figure 2 , one side of the blade-shaped barrier 6 is a thin blade-shaped structure, and the thin blade-shaped side is parallel to the femtosecond laser pulse beam 11. The thin blade-shaped barrier 6 is inserted into the sleeve 3, and a gas density gradient is formed in the sleeve 3, with a higher and uniform density on the side away from the blade-shaped barrier 6 and a lower and gradually decreasing density on the side close to the blade-shaped barrier 6. Furthermore, one side of the thin blade of the blade-shaped barrier 6 can be smooth or toothed, which is specifically determined according to the gas density gradient to be formed. In order to ensure that the blade-shaped barrier 6 works normally in a high-energy laser plasma environment, it is made of high-strength metal materials, such as tungsten, molybdenum, tantalum, etc.

[0037] The laser components, the gas nozzle 4, the sleeve 3 and the blade-shaped barrier 6 are all placed in a vacuum environment. Figure 1 As shown, the laser component is placed in a first vacuum chamber 71 , and the gas nozzle 4 , the sleeve 3 and other devices are placed in a second vacuum chamber 72 .

[0038] During operation, the gas cylinder is connected to the lower end of the gas nozzle 4, the gas nozzle 4 is connected to the sleeve 3 through the gas inlet, the true gas pump 5 is connected to the sleeve through the gas outlet, a gas target is generated through the gas nozzle 4, and the gas is continuously extracted through the true gas pump 5 to generate continuous and stable gas.

[0039] Along the gas propagation direction, a knife-edge barrier 6 is inserted between the laser incident point and the gas nozzle to create a gas density gradient perpendicular to the propagation direction of the femtosecond laser pulse beam 11 .

[0040] Start the laser 1, the laser beam passes through the focusing assembly 2 to form a high-intensity, tightly focused femtosecond laser pulse beam 11, and is injected into the sleeve 3 through the entrance hole to react with the gas target. During the reaction, the femtosecond laser pulse beam 11 ionizes the gas and generates accelerated cavitation through its own light pressure. Some electrons are captured in the accelerated cavitation, move forward with the laser and gradually gain energy, forming a high-energy electron bunch 12.

[0041] The accelerated electron bunch 12 is emitted from the exit hole of the sleeve 3 along the coaxial direction of the incident femtosecond laser pulse beam 11, completing the laser plasma electron acceleration.

[0042] Specifically, the femtosecond laser pulse beam 11 is injected into the gas target, and the process of accelerating electrons using the wake field is as follows:

[0043] The high-intensity, tightly focused femtosecond laser pulse beam 11 is incident on the gas target, instantly ionizing the gas molecules that the front edge of the femtosecond laser pulse beam 11 contacts, forming plasma. In this process, due to the addition of the blade-shaped barrier 6, the density of the plasma after ionization is positively correlated with the gas density before ionization, so a plasma similar to the gas density distribution is formed, which is uniform and dense on one side and sparse and gradually decreasing on the other side.

[0044] Under the action of light pressure, the femtosecond laser pulse beam 11 pushes away the electrons in the plasma, forming a positively charged area. As the femtosecond laser pulse beam 11 continues to move forward, the positively charged area continues to expand, and the ability to attract electrons increases. At the same time, the femtosecond laser pulse beam 11 continues to move forward, and the light pressure decreases. Eventually, the electrons return to close, and the positively charged area in the plasma closes, forming a bubble.

[0045] The stable existence of cavitation is the product of the balance between the light pressure of the femtosecond laser pulse beam11 and the attraction between positive and negative charges, and is also the prerequisite for the acceleration of the laser wake field. Figure 2, the plasma on the dense side will ensure the stable existence of the cavitation bubble.

[0046] The electrons at the front of the cavitation bubble on the sparse side are pushed away by the electron clusters gathered in the front of the cavitation bubble, and then fall back into the cavitation bubble due to the electric field force. Some of them will fall into the acceleration zone, get focused and continue to accelerate. Through this process, the amount of electron charge that can be accelerated will be greatly increased, and a high-energy electron bunch with higher quality and larger charge can be obtained.

[0047] The above description is only a preferred embodiment of the utility model, and does not limit the patent scope of the utility model. All equivalent structural changes made by using the contents of the utility model specification and drawings under the utility model concept, or directly

[0048] / Indirect application in other related technical fields is included in the patent protection scope of this utility model.

Claims

1. A density gradient-based laser plasma electron accelerator, comprising a laser component, the laser component generates a high-intensity tightly focused femtosecond laser pulse beam, characterized in that: placing a sleeve in a path of a femtosecond laser pulse beam; A gas nozzle and a vacuum pump are respectively arranged at the upper and lower ends of the sleeve, and the outlet of the gas nozzle is perpendicular to the femtosecond laser pulse beam; On the side close to the gas nozzle, a blade-shaped barrier parallel to the femtosecond laser pulse beam is also arranged in the sleeve.

2. The density gradient based laser plasma electron accelerator according to claim 1, characterized in that: The laser component includes a laser and a focusing assembly; The laser generates a laser beam, and the focusing component is located on the path of the laser beam and focuses the laser beam to generate a high-intensity and tightly focused femtosecond laser pulse beam.

3. The density gradient based laser plasma electron accelerator according to claim 1 or 2, characterized in that: The gas nozzle is a curved surface rotating body structure.

4. The density gradient based laser plasma electron accelerator according to claim 1 or 2, characterized in that: One side of the blade-shaped barrier is thin-edged, and the thin-edged side is parallel to the femtosecond laser pulse beam.

5. The density gradient based laser plasma electron accelerator according to claim 4, characterized in that: One side of the thin blade of the blade-shaped barrier is smooth or toothed.

6. The density gradient-based laser plasma electron accelerator according to claim 5, characterized in that: The blade-shaped barrier is made of high-strength metal material.

7. The density gradient based laser plasma electron accelerator according to claim 1 or 2, characterized in that: The sleeve is a curved rotating body cavity structure.

8. The density gradient based laser plasma electron accelerator according to claim 7, characterized in that: The sleeve is provided with an incident hole and an exit hole along the direction of the femtosecond laser pulse beam.

9. The density gradient based laser plasma electron accelerator according to claim 1 or 2, characterized in that: The sleeve is provided with a gas inlet, the gas inlet is communicated with the outlet of the gas nozzle, and the gas inlet and the outlet of the gas nozzle are sealed.

10. The density gradient based laser plasma electron accelerator according to claim 1 or 2, characterized in that: The laser component, the gas nozzle, the sleeve and the blade-shaped barrier are all arranged in the vacuum chamber.

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