Modularized multi-nozzle gas target system

Abstract

The invention provides a modular multi-nozzle gas target system. The modular multi-nozzle gas target system comprises a main body, a plurality of replaceable accessories and a control part arranged outside a vacuum cavity. The main body can be connected with a plurality of replaceable accessories, a proper gas environment is provided for laser tail field electron accelerators with different electron energy requirements, and electron beams of hundred MeV to 10 GeV magnitude can be generated. The gas target is an open type gas target, so that the problem that elements are damaged by strong laser is avoided; and the expandability is good, accessories can be developed on the basis, and support is provided for potential laser tail field electron acceleration experiment requirements.

Description

Technical Field

[0001] The present invention relates to the technical fields of high-energy laser physics and electron accelerators, and particularly relates to a modular multi-nozzle gas target system applicable to laser wakefield electron accelerators. Background Art

[0002] Using the laser wakefield acceleration principle, electrons can obtain high energy within an extremely short distance. The generated high-energy electron beam has relatively rich application possibilities: such as being applied in fields like cancer treatment (requiring electron beams of dozens to hundreds of MeV); using the wakefield to drive electrons to generate secondary radiation sources such as Betatron radiation for imaging and other work; and electrons generated based on the wakefield with GeV or even TeV magnitudes are expected to be used in high-energy physics experiments, such as verifying the properties of the Higgs boson. The gas environments required by these needs are different, so a gas generating device that can provide different gas environments is necessary.

[0003] The energy obtained by electrons in an accelerator can be simply characterized by the acceleration gradient × acceleration distance. Therefore, for different electron beam energy requirements, different acceleration distances are needed, and the acceleration distance is related to the gas target length. Thus, the gas target structure can be regulated to adapt to different electron beam energy requirements.

[0004] To meet different requirements, there are various gas targets applied in wakefield acceleration experiments so far, including open nozzles, gas cells, and capillaries. Each of these three gas targets has its own advantages and disadvantages; the open nozzle has advantages such as a large design space, the ability to use structures with different geometries to achieve the goal, no physical structure constraints, and no damage when interacting with intense lasers, making it the current mainstream solution.

[0005] Application No. 202010635881.X, with the title of a multi-stage gas target system for 10 GeV electron acceleration, discloses a gas target system based on a multi-stage gas cell and capillary scheme, which can generate a low-density gas environment from centimeters to dozens of centimeters. However, the specific length of its gas target unit with a fixed length is in the range of 1 cm to 20 cm, unable to cover the millimeter range, and the uniform density distribution inside a single box limits the diversity of experimental designs.

[0006] Therefore, it is necessary to have a multi-nozzle system with modular design, open structure, and applicable to laser wakefield electron acceleration experiments with different energy requirements. Summary of the Invention

[0007] In order to utilize the device combination for laser wakefield acceleration experiments with different electron beam requirements, the present invention provides a modular multi-nozzle gas target system, which can flexibly control the gas environment in the range of several millimeters to dozens of centimeters through replacing accessories and solenoid valve control, and adapt to the requirements for generating high-energy electron beams from hundreds of MeV to 10 GeV.

[0008] The solution of the present invention is as follows:

[0009] A modular multi-nozzle gas target system, characterized in that it includes a device main body, a duckbill fitting, a straight nozzle fitting, a long gas groove fitting, and a control part E placed outside the vacuum chamber.

[0010] The device main body includes at least 11 air outlets, 1 air inlet, a gas storage tank, a position and interface for accommodating a gas pressure detection device. Among them, each air outlet is controlled by a solenoid valve to open and close at its lower part or middle part. The solenoid valve is connected to a jet controller, and the control method can be to control the opening and closing simultaneously using a signal synchronizer, or to set switch delays and gate widths for different air outlets; a connecting lower plate is connected above the air outlet, which can be tightly combined with the connecting upper plate of the fitting, and different gas density distributions under different conditions are formed through different fitting structures.

[0011] The internal dimensions of the gas storage tank are 30 cm in length, >2 cm in width, and >2.5 cm in height. The width and height dimensions need to meet the size requirements for accommodating the solenoid valve and the gas pressure detection device. Its material can be metal or other materials that do not deform significantly under one atmosphere pressure. The thickness is also set according to the condition of not deforming significantly, and interfaces for fixing on a 5D (three-dimensional translation + pitch, yaw) moving platform can be left outside.

[0012] The duckbill fitting includes a duckbill part, a connecting upper plate, and a straight nozzle part. The size of the internal transverse cross-section of the duckbill part of the fitting is described by the formula where r 0 is the inner diameter of the circle on the lower surface of the duckbill part, r is the half-width of any cross-section, and w is the length of any cross-section. A line perpendicular to the lower surface is established with an intersection point, and this line passes through the plane of any cross-section with an intersection point. The length of the line segment formed by connecting these two intersection points is y. r 1 is the half-width of the upper surface, and d is the length of the upper surface. By specifying the dimensions of the upper and lower surfaces, a definite duckbill shape can be obtained.

[0013] Its function is to cooperate with the device main body and can generate relatively uniform gas with a length of 0.8 - 2 cm on the upper surface.

[0014] The described straight nozzle fitting includes a straight nozzle part and a connecting upper disk. The straight nozzle part is a hollow straight pipe with a length of about 3 cm and an inner diameter consistent with that of the gas outlet. The gas is directly ejected after passing through a straight pipe with a length of about 3 cm, creating a short gas environment with a length of the gas environment < 1 cm. The outer part of the straight injection pipe is sleeved with a connecting upper disk that can be fitted and connected with the connecting lower disk of the gas outlet in Claim 2. The upper disk and the lower disk have the same shape, and a sealing rubber ring can be attached in the middle.

[0015] Its function is to cooperate with the main body of the device and can generate a relatively uniform gas with a length of 0.45 cm on the upper surface.

[0016] The described long gas groove fitting of the device main body includes a gas groove part and a connecting upper disk. The gas groove part is designed as a strip-shaped device that is wider at the bottom and narrower at the top and hollowed out in the middle, with a number of air inlets. The number of air inlets is the same as the number of gas outlets of the device, and their sizes and spacings are also the same as those of the gas outlets in the device. Each air inlet is fixed to the connecting upper disk.

[0017] Its function is to cooperate with the main body of the device and generate a low-density gas environment with a length of 30 cm in the laser wakefield electron acceleration experiment.

[0018] The described control part is characterized in that a gas cylinder is placed outside the vacuum cavity. The gas cylinder can be filled with different types of gases, including but not limited to hydrogen, helium, nitrogen, argon, and various gas mixtures. The gas cylinder is equipped with a back pressure detection device that can monitor the back pressure, and it is connected through a pipeline. Its main purpose is to control the gate width of the jet gas, the delay with the laser, and provide a pressure reference.

[0019] The technical effects of the present invention are as follows:

[0020] The present invention has the characteristics of good scalability, no physical structure constraint in the gas environment and will not be damaged by intense laser, flexible and practical, etc.

[0021] The present invention can provide a gas environment for laser wakefield electron acceleration experiments in the range of hundreds of MeV to 10 GeV. Different gas target structures can be given through different fittings. By combining with the fittings, a long and uniform gas environment and a short gas environment can be realized, and the versatility is relatively strong.

[0022] The present invention also has the potential to provide a gas environment for electron acceleration experiments above 10 GeV, and is not limited to the capillary and gas cell schemes to achieve it. It is expected to achieve high repetition rate and no need for an externally applied electric field. And it can use a pure optical scheme to realize high-energy laser wakefield electron acceleration. Description of the Drawings Figure 1 It is a schematic structural diagram of an embodiment of the main body A in the modular multi-nozzle gas target system of the present invention. Figure 2 It is a schematic structural diagram of a replaceable accessory in the modular multi-nozzle gas target system of the present invention. Among them, B is a duckbill and a schematic diagram of the connection between the duckbill and the device main body, C is a straight nozzle and a schematic diagram of the connection between the straight nozzle and the device main body, and D is a long air groove and a schematic diagram of the connection between the long air groove and the device main body. Figure 3 It is a schematic diagram of the control part placed outside the vacuum chamber. Specific embodiments

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention should not be limited thereby.

[0024] First, according to the phenomenological theory proposed by Lu Wei et al. from Tsinghua University, under specific laser parameters, the electron beam energy gain can be calculated through the formula By combining different accessories with the device main body, high-energy electron beams of several hundred MeV - 10 GeV can be obtained in the laser wakefield electron acceleration experiment. The following will take the combination of several accessories and the device main body A as an example for illustration.

[0025] Please refer to Figure 1 , Figure 1 It is a schematic structural diagram of an embodiment of the modular multi-nozzle gas target system of the present invention. As shown in the figure, the main body A includes a gas storage tank A-1, an air inlet A-2, at least 11 air outlets A-4, a pressure detection interface A-3 and a solenoid valve A-5. One side of the gas storage tank A-1 is opened with a hole as the air inlet A-2, which is connected to the external gas cylinder E-1 through a sealed pipeline. The other side is processed into a pressure detection interface A-3 for real-time monitoring of the air pressure in the gas storage tank. At least 11 round holes are opened at the top, which are connected to the straight pipes of the air outlets A-4, and the ends of the straight pipes are fixedly connected to the lower plate. The lower plate is connected, and the upper plate for connecting with the accessory is fixed by screws or welding, and a sealing rubber ring is combined to prevent gas leakage. An electromagnetic valve A-5 is installed below or in the middle of each air outlet A-4, and the switch timing, delay and gate width (jet duration) are controlled by a jet controller E-2 outside the vacuum chamber. In this embodiment, the internal dimensions of the gas storage tank A-1 of the gas storage tank A-1 are 30 cm in length, > 2 cm in width, and > 2.5 cm in height. The width and height dimensions need to meet the size requirements for accommodating the solenoid valve and the pressure detection device. Its material can be made of metal or other materials that do not deform significantly under one atmosphere pressure. The thickness is also set according to the condition of not being significantly deformed, and an interface that can be fixed on a 5-dimensional (three-dimensional translation + pitch, yaw) moving platform can be left outside.

[0026] The size of the internal transverse section of the duckbill part B-1 of the accessory is described by the formula where r 0Let \(d_0\) be the inner diameter of the circle on the lower surface of the duckbill part, \(r\) be the half-width of any cross-section, and \(w\) be the length of any cross-section. A line perpendicular to the lower surface is established with an intersection point. This line passes through the plane of any cross-section with an intersection point, and the length of the line segment formed by connecting these two intersection points is \(y\). \(r\) 1 Let \(r_1\) be the half-width of the upper surface and \(d_1\) be the length of the upper surface. By specifying the dimensions of the upper and lower surfaces, a definite duckbill shape can be obtained. Its function is to be used in conjunction with the device main body A to generate a relatively uniform gas layer with a length of 0.8 - 2 cm on the upper surface. The connecting upper disk B-2 matches the connecting lower disk of the device main body to ensure airtightness.

[0027] The straight nozzle fitting C includes a straight nozzle part C-1 and a connecting upper disk C-2. The straight nozzle part C-1 is a hollow straight pipe with a length of about 3 cm and an inner diameter consistent with that of the gas outlet A-4. The gas is ejected directly after passing through a straight pipe with a length of about 3 cm, creating a short gas environment with a gas environment length of < 1 cm. The outer part of the straight nozzle part is sleeved with a connecting upper disk C-2 that can be connected and matched with the connecting lower disk of the gas outlet A-4 in Claim 2. The upper disk and the lower disk have the same shape, and a sealing rubber ring can be attached in the middle. Its function is to be used in conjunction with the device main body A to generate a relatively uniform gas layer with a length of 0.45 cm on the upper surface. The connecting upper disk C-2 is connected to the main body A through a sealing rubber ring.

[0028] The long gas groove fitting D includes a gas groove part D-1 and a connecting upper disk D-2. The gas groove part D-1 is designed as a strip-shaped device that is wider at the bottom and narrower at the top with a hollowed-out middle, with a number of air inlets. The number of air inlets is the same as the number of gas outlets of the device A, and their sizes and spacings are also the same as those of the gas outlets in the device A. Each air inlet is fixed to the connecting upper disk D-2. Its function is to be used in conjunction with the device main body A to generate a low-density gas environment with a length of 30 cm in the laser wakefield electron acceleration experiment. The connecting upper disk D-2 is docked one by one with the main body gas outlet.

[0029] The control part E is characterized by a gas cylinder E-1 placed outside the vacuum chamber. The gas cylinder E-1 can be filled with different types of gases, including but not limited to hydrogen, helium, nitrogen, argon, and various gas mixtures. The gas cylinder E-1 is equipped with a backpressure detection device that can monitor the backpressure, and it is connected to A-2 through a pipeline. Its main purpose is to control the gate width of the gas jet, the delay with the laser, and provide a pressure reference.

[0030] By replacing the fittings, the system can generate gas environments with different lengths and shapes. For example: The A + B combination: generates a 1 GeV electron beam (gas target length 1 cm). The A + C combination: generates a hundred MeV electron beam (gas target length 0.45 cm). The A + D combination: generates a 10 GeV electron beam (gas target length 30 cm). Select the fitting (B, C, or D) according to the experimental requirements and fix it to the device main body through the connecting disk.

[0031] The air inlet A-2 of the main body A is connected to Figure 2 the gas cylinder E-1 in

[0032] Taking the combination use of the accessory B and the device main body A as an example, Figure 1 Figure B-Ⅱ in is a schematic diagram of the combined use of one such duckbill accessory B and the device main body A. Multiple duckbill accessories B can be used and connected to the device main body A. The connection method is to use the connection lower plate on the air outlet A-4 of the device main body and the connection upper plate B- of the duckbill accessory to be connected by means of screws and hex nuts, or directly connected by a buckle. A rubber ring is attached to the connection plate to prevent gas leakage or prevent the generation of an unwanted gas distribution. After connecting the accessory B and the device main body A, place the combined device on a five-dimensional moving platform. The connection method with the moving platform can be to weld the device main body to a breadboard, and then fix the breadboard and the five-dimensional moving platform with M6 screws. When conducting experiments, the entire device needs to be moved into a vacuum chamber.

[0033] Taking the combination of A-B and the number of nozzles N being 1 as an example, first, make the laser propagation path parallel to the long side of the duckbill part B-1 and then conduct the experiment. A laser beam with an energy in the joule level, a wavelength of 800 nm, and a pulse width of 25 - 30 fs is incident above the duckbill part B-1; before this beam arrives, the solenoid valve A-5 is opened, and the advance amount T and the gate width τ of its arrival time relative to the laser can be determined by the jet controller and the timing system. The pressure at the jet port is approximately equal to the reading of the pressure sensor accommodated in A-5. After interacting with the laser, it is expected to generate a relatively uniform plasma environment in the order of 1e17 - 1e18 cm^(-3). According to the formula calculation, a high-energy electron beam of about 1 GeV can be generated. Secondly, taking the combination use of the accessory C and the device with the device main body A as an example, Figure 1C-II in it is a schematic diagram of the straight nozzle fitting used in combination with the device main body A. Among them, the connecting upper plate that connects the lower plate and the straight nozzle fitting C-2 in the air outlet A-4 of the device main body is connected by the cooperation of through-hole screws and hex nuts or by using fasteners. The rubber ring attached to the upper plate or the lower plate can prevent gas leakage or prevent the generation of gas distribution that does not meet the requirements. The whole can be regarded as a hollow straight injection pipe. The combination of this fitting and the device main body can generate a gas environment with a length of 0.45 cm. The combination of multiple nozzles can generate a gas environment with a length of N * 0.45, and the intermediate interval is the distance between the air outlets of the device main body A (L - 0.45 cm). There is no gas or only gas with a very low density in the intermediate interval. A cascade experiment of laser wakefield acceleration can be carried out using a larger interval.

[0034] Taking the A-C combination, the number of nozzles is 1, and the experiment is carried out in the same way as the A-B combination. According to the formula calculation, it is expected to generate high-energy electron beams in the order of hundreds of MeV.

[0035] Finally, taking the combination of fitting D and device main body A as an example, Figure 1 D-II in it is a schematic diagram of the gas groove fitting used in combination with the device main body A. Among them, the connecting upper plate D-2 that connects the lower plate and the long gas groove fitting D in the air outlet A-4 of the device main body is connected by the cooperation of through-hole screws and hex nuts or by using fasteners. The rubber ring attached to the upper plate or the lower plate can prevent gas leakage or prevent the generation of gas distribution that does not meet the requirements. The connected part can be regarded as a hollow straight injection pipe.

[0036] After connecting the fitting D and the device main body A, the combined device is placed on a five-dimensional moving platform. The connection method with the moving platform can be to weld the device main body to a breadboard, and then fix the breadboard and the five-dimensional moving platform with M6 screws. Different from B-II and C-II, when the gas groove is connected to the device main body, an equal number of connecting plates need to be connected in sequence.

[0037] Taking the A-D combination for the experiment, first make the laser propagation direction parallel to the long side of the rectangular cross-section of the gas groove part D-1 and then conduct the experiment. A laser with an energy of dozens of joules, a wavelength of 800 nm, and a pulse width of 25 - 30 fs is injected above the gas groove D-1; before this beam arrives, the solenoid valve is opened, and the advance amount T and the gate width τ of its arrival time relative to the laser can be determined by the gas injection controller and the timing system. The pressure at the gas injection port is approximately equal to the reading of the pressure sensor accommodated in A-5. After interacting with the laser, it is expected to generate a relatively uniform plasma environment with a length of 30 cm and a density in the order of 1e17 cm^(-3). According to the formula calculation, high-energy electron beams of about 5 - 10 GeV can be generated.

Claims

1. A modular multi-nozzle gas target system, characterized in that: It includes a main body placed in the vacuum chamber, a plurality of replaceable accessories, and a control part placed outside the vacuum chamber; The main body includes a gas storage tank, an air inlet, an air pressure measurement interface, at least 11 air outlets and a solenoid valve; an air inlet is provided on one side of the gas storage tank, and the other side is processed into a pressure measurement interface. At least 11 round holes are provided on the top, which are connected to the straight pipe of the air outlet. The end of the straight pipe is fixedly connected to the lower plate, and the connecting lower plate is used to be fixed to the connecting upper plate of the accessories by screws or welding, and is attached with a sealing rubber ring to prevent gas leakage; each air outlet is equipped with a solenoid valve, and the switch timing, delay and jet gate width are controlled by the jet controller outside the vacuum chamber; The replaceable accessories include duckbill accessories, straight nozzle accessories and long gas slot accessories, which are fixed to the connecting lower plate of the main body through their respective connecting upper plates to form different gas distributions; The control part includes a gas cylinder and a jet controller; the gas cylinder is filled with a variety of gases or a mixed gas and is connected to the air inlet through a pipeline, and the jet controller is connected to the solenoid valve for adjusting the jet parameters; The system generates a gas environment of 0.45 cm to 30 cm by replacing accessories, which is adapted to the laser tailfield acceleration requirements of electron beams from 100 MeV to 10 GeV.

2. The modular multi-nozzle gas target system according to claim 1, characterized in that: The duckbill accessory includes a duckbill part, a duckbill connecting upper plate and a straight nozzle part. The straight nozzle is a hollow pipe, and the duckbill part is a hollow nozzle with a round bottom and an oblong top. The duckbill and the straight nozzle part are welded together, and the straight nozzle and the duckbill connecting upper plate are connected together. The duckbill connecting upper plate is consistent with the connecting lower plate of the air outlet, and a rubber ring can be attached to the lower part for sealing.

3. The modular multi-nozzle gas target system according to claim 1, characterized in that: The straight nozzle accessory includes a straight nozzle part and a straight nozzle connecting upper plate. The straight nozzle part is a hollow straight tube whose inner diameter is consistent with the air outlet. The straight nozzle part and the straight nozzle connecting upper plate are fixed together. A rubber ring can be attached to the lower part of the straight nozzle connecting upper plate for sealing.

4. The modular multi-nozzle gas target system according to claim 1, characterized in that: The long air trough accessory includes an air trough portion and an air trough connecting upper plate. The air trough portion is a strip-shaped groove that is wide at the bottom and narrow at the top, and has a plurality of air inlets. The number of the air inlets is consistent with the number of the air outlets of the main body, and the size and spacing of the air inlets are also consistent with the size and spacing of the air outlets in the device. Each air inlet is fixed to the air trough connecting upper plate.

5. The modular multi-nozzle gas target system according to claim 1, characterized in that: The gas storage tank has a size of 30 cm in length, width>2 cm, and height>2.5 cm. It is made of plexiglass, metal, or other materials that can maintain no obvious gas leakage in a short time scale (<100ms). The wall thickness can be set according to the actual air pressure requirements.

6. The modular multi-nozzle gas target system according to claim 5, characterized in that: The distance between the centers of two adjacent circular holes on the top of the gas storage tank is ≤2.5 cm.

7. The modular multi-nozzle gas target system according to claim 1, characterized in that: The jet controller supports independent or synchronous control of solenoid valves, and can set the switch delay and door width of different air outlets.

8. The modular multi-nozzle gas target system according to claim 1, characterized in that: The gas cylinders are filled with different types of gases, including but not limited to hydrogen, helium, nitrogen, argon and a mixture of multiple gases.

9. The modular multi-nozzle gas target system according to claim 1, characterized in that: The gas cylinder is equipped with a back pressure detection device, which can monitor the back pressure and is connected to the gas cylinder through a pipeline.

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