Desk-top femtosecond hard x-ray pulse source device and pulse generation method

Abstract

The tabletop femtosecond hard X-ray pulse source device and pulse generation method, comprising a laser light source, a laser focusing assembly, a metal micro-liquid droplet target generating assembly and a vacuum cavity, the metal micro-liquid droplet target generating assembly is arranged in the vacuum cavity, the vacuum cavity is provided with an incident window and an emission window, and the laser focusing assembly is used for receiving laser and guiding the laser to the metal micro-liquid droplet target generated by the metal micro-liquid droplet target generating assembly through the incident window. In the application, the metal micro-liquid droplet target replaces the solid target, and when the metal micro-liquid droplet target is subjected to laser action, due to its natural falling characteristics in the vacuum, the jitter generated by the solid target during mechanical movement is eliminated, the stability of the X-ray pulse is improved, and the metal micro-liquid droplet target can be used to replace the solid target, and the stable operation time is longer. Due to the tabletop characteristics of the device, the cost performance is higher, the maintainability is stronger, and it is more suitable for the use requirements of scientific research institutions such as colleges and universities.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of femtosecond hard X-ray pulse generation device, in particular to a desktop femtosecond hard X-ray pulse source device and a pulse generation method. BACKGROUND

[0002] At present, one of the dreams of human beings to understand the material world is to take "molecular movies" on the atomic space-time scale, and to promote the development of many directions such as the design and development of new optoelectronic materials, the functional simulation of biological macromolecules, and the efficiency improvement of photocatalytic reactions. In order to meet this demand, new technologies with atomic time (better than picoseconds) and spatial (better than angstroms) resolution are needed. One of the related technical paths is to combine the high time resolution of ultrashort pulses with the high spatial resolution of X-rays to study the transient structure and ultrafast dynamics of matter. Therefore, a kind of ultra-short femtosecond hard X-ray pulse with time resolution in the order of femtosecond and spatial resolution meeting certain scientific research needs is needed.

[0003] The generation of short X-ray pulses mainly falls into two categories: one is the X-ray pulse source based on synchrotron radiation, such as X-ray free electron laser device; however, the X-ray free electron laser is expensive and has limited machine time. The other is the desktop X-ray pulse source based on laser system; this kind of desktop radiation source can generate ultra-short X-ray probe pulses with a width comparable to femtosecond laser pulses, which has natural synchronization due to the homology with the pump pulse, and can obtain ultra-high time resolution (hundred femtosecond level); the whole set of device occupies less than 20 square meters, which brings great flexibility and high economy to practical application, and is suitable for universities and research institutes to carry out work. At present, the stability, working persistence and photon yield of the desktop X-ray radiation source still have room for improvement, and the present application proposes new technical methods for the above aspects. SUMMARY

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a more stable desktop femtosecond hard X-ray pulse source device and pulse generation method with stable photon yield, which is used to solve the problems of limited machine time and small number of femtosecond hard X-ray free electron laser devices in the prior art, and to optimize the stability, photon yield and other technical problems of the existing desktop femtosecond hard X-ray pulse source.

[0005] In order to achieve the above object and other related objects, the application provides a tabletop femtosecond hard X-ray pulse source device, which comprises a laser light source, a laser focusing assembly, a metal micro-droplet target generating assembly, a metal micro-droplet target regulating assembly, and a vacuum cavity, the metal micro-droplet target generating assembly is arranged in the vacuum cavity, the vacuum cavity is provided with an incident window and an emission window, the laser focusing assembly is used for receiving ultrafast laser and guiding the ultrafast laser into the vacuum cavity through the incident window, the metal micro-droplet target generating assembly generates a metal micro-droplet target, the metal micro-droplet target is bombarded by the ultrafast laser through the metal micro-droplet target regulating assembly to generate a femtosecond hard X-ray pulse, and the emission window guides the generated femtosecond hard X-ray pulse out.

[0006] Preferably, an optical flatness window piece is arranged in the incident window, an X-ray transparent film is arranged in the emission window, and an observation window is further arranged on one side of the emission window.

[0007] Preferably, the tabletop femtosecond hard X-ray pulse source device further comprises a reaction chamber, the reaction chamber is arranged in the vacuum cavity, the reaction chamber comprises a reaction chamber partition plate and a reaction chamber top plate, the reaction chamber partition plate divides the vacuum cavity into two spaces, the reaction chamber is arranged in the space with the intersection point of the incident window and the emission window extension line, and a top plate through hole is further arranged on the reaction chamber top plate.

[0008] Preferably, the metal micro-droplet target regulating assembly comprises a parallel-plate capacitor, an energized solenoid, a control console, and an electrically controlled delay device, a clock source is further arranged in the laser light source, the control console is connected with the clock source through the electrically controlled delay device, the control console is respectively connected with the parallel-plate capacitor and the energized solenoid in communication, the parallel-plate capacitor and the energized solenoid are arranged in the reaction chamber, pole plate holes are arranged on two pole plates of the parallel-plate capacitor, the centers of the pole plate holes are on the same vertical line with the center of the top plate through hole, and a connecting line of the centers of the two pole plate holes penetrates the intersection point of the incident window and the emission window extension line, the axis of the energized solenoid is opposite to the connecting line of the centers of the two pole plate holes, and a liquid collecting tank is further arranged on the lower side of the parallel-plate capacitor.

[0009] Preferably, a light-transmitting shielding tape disc, a plurality of shielding tape guide columns, and a shielding tape driving assembly are arranged in the other space of the vacuum cavity, the plurality of shielding tape guide columns are arranged on the inner sides of the incident window and the emission window, and the light-transmitting shielding tape on the light-transmitting shielding tape disc is connected with the shielding tape driving assembly through the shielding tape guide columns.

[0010] Preferably, the metal micro-droplet target generating assembly comprises a liquid storage tank, a gas valve, a heating assembly, and a droplet nozzle, the liquid storage tank is arranged above the vacuum chamber and communicates with the vacuum chamber; the gas valve is arranged on the upper side of the liquid storage tank, the heating assembly is arranged on the circumferential periphery of the liquid storage tank, and the droplet nozzle is arranged at the outlet of the liquid storage tank and is connected with a positive or negative electrode circuit.

[0011] Preferably, the metal micro-droplet target generating assembly further comprises a bellows, the bellows is arranged between the liquid storage tank and the vacuum chamber, and the liquid storage tank communicates with the reaction chamber through the bellows and the top plate through hole; a displacement driving assembly is arranged on the outer peripheral side of the bellows.

[0012] Preferably, the laser focusing assembly comprises a beam splitter and a mirror, the ultrafast laser emitted by the laser light source is guided onto the metal micro-droplet target through the beam splitter and the mirror and then through the incident window; the metal micro-droplet target regulating assembly further comprises an observation assembly, and the observation assembly is arranged on the outer side of the observation window.

[0013] Preferably, the desktop femtosecond hard X-ray pulse source device further comprises an X-ray photodetector, a source light photodetector, and an oscilloscope, the X-ray photodetector is arranged on the outer side of the exit window, the source light photodetector is arranged on the outer side of the beam splitter, and the X-ray photodetector and the source light photodetector are both in communication connection with the oscilloscope.

[0014] The application also provides a femtosecond hard X-ray pulse generation method, and the specific steps are as follows:

[0015] S1: installing the metal micro-droplet target generating assembly in the vacuum chamber;

[0016] S2: operating the metal micro-droplet target generating assembly, and the metal micro-droplet target generating assembly generates a metal micro-droplet target during operation;

[0017] S3: the laser light source emits ultrafast laser, and the position of the laser focusing assembly is adjusted so that the ultrafast laser enters the incident window through the laser focusing assembly;

[0018] S4: adjusting the metal micro-droplet target generating assembly to make the falling track of the metal micro-droplet target coincide with the ultrafast laser in space; and adjusting the metal micro-droplet target regulating assembly to make the falling track of the metal micro-droplet target coincide with the ultrafast laser in time and synchronously;

[0019] S5: the ultrafast laser focused by the laser focusing assembly synchronously hits the generated metal micro-droplet target through the incident window, the ultrafast laser interacts with the metal micro-droplet target, and a femtosecond hard X-ray pulse is generated;

[0020] S6: The generated femtosecond hard X-ray pulse is guided out through the exit window.

[0021] As described above, the tabletop femtosecond hard X-ray pulse source device and the pulse generation method have the following beneficial effects:

[0022] 1. The tabletop femtosecond hard X-ray pulse source device and the pulse generation method, which are provided with a metal micro-droplet target generating assembly, replace the solid target with the metal micro-droplet target generated by the metal micro-droplet target generating assembly. When the laser irradiates the solid target, the solid target needs to be stored in the form of a solid belt or a solid wire, and the solid target is transported into the target chamber by the conveying belt to interact with the laser. Thus, when the solid target interacts with the laser, it is not easy to control the surface flatness and the jitter during the movement of the solid target. In addition, the storage capacity of the solid target is limited, and the solid target belt or the solid target wire can be exhausted within a few hours, which cannot be operated stably for a long time. However, the metal micro-droplet target has the characteristics of natural falling in the vacuum, which eliminates the jitter of the solid target during mechanical movement. In addition, the tabletop femtosecond hard X-ray pulse source device has a metal micro-droplet target generating assembly that can continuously generate new target sources, and can continuously obtain femtosecond hard X-ray pulses, which can be operated stably for a long time.

[0023] 2. The tabletop femtosecond hard X-ray pulse source device and the pulse generation method, which are provided with a metal micro-droplet target generating assembly, adjust the falling trajectory of the metal micro-droplet target to coincide with the light path of the ultrafast laser in space; and are provided with a metal micro-droplet target regulating assembly, which synchronizes and coincides the falling trajectory of the metal micro-droplet target with the ultrafast laser in time. The running trajectory of the metal micro-droplet target is adjusted in space and time at the same time, so that the intensity, pulse width and repetition frequency of the femtosecond hard X-ray pulse generated by the ultrafast laser bombarding the metal micro-droplet target are stable.

[0024] 3. The tabletop femtosecond hard X-ray pulse source device has high cost performance, wide application range and strong maintainability, and is more suitable for the use requirements of scientific research institutions such as colleges and universities. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a spatial structure diagram of the tabletop femtosecond hard X-ray pulse source device of the present application;

[0026] Figure 2 It is an internal plan view of the vacuum cavity of the tabletop femtosecond hard X-ray pulse source device of the present application;

[0027] Figure 3 It is Figure 1 A sectional view along A-A;

[0028] Figure 4 It is a spatial structure diagram of the displacement driving assembly of the tabletop femtosecond hard X-ray pulse source device of the present application;

[0029] Figure 5 Figure 1 is a schematic diagram of a desktop femtosecond hard X-ray pulse source device according to the present application.

[0030] Reference signs:

[0031] 1, vacuum chamber; 101, vacuum chamber top cover; 102, entrance window; 103, exit window; 104, observation window; 105, reaction chamber; 106, energized solenoid; 107, parallel-plate capacitor; 108, pole plate hole; 109, reaction chamber partition; 110, reaction chamber bottom plate; 111, reaction chamber top plate; 112, top plate through hole; 113, bottom plate through hole; 114, control console; 115, electrically controlled delay device; 2, bellows; 3, displacement driving assembly; 301, displacement assembly base; 302, displacement assembly connecting platform; 303, left and right driving plate; 304, front and rear driven plate; 305, left and right driven plate; 306, front and rear driving plate; 307, left and right driving shaft; 308, front and rear driving shaft; 309, up and down driving shaft; 310, front and rear translation guide rail; 311, left and right translation guide rail; 312, up and down translation guide rail; 313, up and down fixed plate; 4, liquid storage tank; 5, heating assembly; 501, liquid droplet filtering cavity; 6, gas valve; 7, liquid receiving cavity; 701, receiving cavity flange; 702, liquid collection tank; 703, quick opening handle; 704, quick opening door; 705, collection tank handle; 8, light-transmitting shielding tape reel; 801, shielding tape driving assembly; 802, shielding tape guide column; 9, vacuum pump; 10, laser light source; 1001, clock source; 11, beam splitter; 12, source light ray photodetector; 13, reflecting mirror; 14, X-ray photodetector; 15, observation assembly; 16, oscilloscope. DETAILED DESCRIPTION

[0032] The embodiments of the present application will be described in detail by the following specific examples, and other advantages and effects of the present application can be easily understood by those skilled in the art from the contents disclosed in the specification.

[0033] It should be noted that the structures, proportions, sizes, etc. shown in the drawings attached to the specification are only used to understand and read the contents disclosed in the specification by those skilled in the art, and are not used to limit the defined conditions under which the present application can be implemented, and therefore do not have technical significance. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that can be produced by the present application and the purposes that can be achieved, should still fall within the scope of the technical content disclosed by the present application. At the same time, the terms such as "upper", "lower", "left", "right", "middle", and "one" used in the specification are only for the purpose of clear understanding of the description, and are not used to limit the scope in which the present application can be implemented, and the change or adjustment of the relative relationship, without substantially changing the technical content, is also considered as the scope in which the present application can be implemented.

[0034] As Figure 5 indicated, the present application provides a desktop femtosecond hard X-ray pulse source device, comprising a laser light source 10, a laser focusing assembly, a metal micro-droplet target generating assembly, a metal micro-droplet target regulating assembly, and a vacuum cavity 1, the metal micro-droplet target generating assembly is arranged in the vacuum cavity 1, two side walls of the vacuum cavity 1 are respectively provided with an incident window 102 and an exit window 103, the laser focusing assembly is used for receiving ultrafast laser and guiding the ultrafast laser into the vacuum cavity 1 through the incident window 102, the metal micro-droplet target generating assembly generates a metal micro-droplet target, the metal micro-droplet target is bombarded by the ultrafast laser through the metal micro-droplet target regulating assembly to generate a femtosecond hard X-ray pulse, and the exit window 103 guides the generated femtosecond hard X-ray pulse out.

[0035] The desktop femtosecond hard X-ray pulse source device provided by the present application adopts a metal micro-droplet target instead of a solid target, overcomes the defects that the surface flatness of the solid target is not easy to control when the solid target acts on the ultrafast laser and the solid target shakes during operation, and meanwhile, the storage amount of the solid target is limited and the solid target cannot be operated stably for a long time after being used for several hours. In the present application, the metal micro-droplet target generating assembly can generate metal micro-droplets stably and continuously, so that the femtosecond hard X-ray pulse can be generated continuously. The present application has high cost performance, is widely applicable, and has strong maintainability.

[0036] Preferably, as Figure 1 indicated, an optical flatness window piece is fixed in the incident window 102 through a clamping groove, an X-ray transparent film is fixed or glued in the exit window 103 through a clamping groove, and an observation window 104 is further arranged on one side of the exit window 103, and a transparent observation window piece is fixed or glued in the observation window 104. In the present embodiment, the optical flatness window piece is used for sealing the incident window 102 on one hand to ensure the vacuum environment in the vacuum cavity 1, and on the other hand to make the incident ultrafast laser enter the vacuum cavity 1 and interact with the metal micro-droplet target. The X-ray transparent film is used for sealing the exit window 103 on one hand to ensure the vacuum environment in the vacuum cavity 1, and on the other hand to guide the generated femtosecond hard X-ray pulse out. The observation window 104 is used for the operator to observe whether the incident ultrafast laser irradiates on the metal micro-droplet target and the size and shape of the metal micro-droplet target through the metal micro-droplet target morphology monitoring assembly. Further, in the present embodiment, the exit window 103 and the observation window 104 are at the same height, and the interval therebetween is 2-10 mm. The constituent parts of the metal micro-droplet target morphology monitoring assembly are prior art, and optical CCD and the like can be used.

[0037] Preferably, as Figure 2 , Figure 3As shown, in order to ensure continuous generation of femtosecond hard X-ray pulse. The desktop femtosecond hard X-ray pulse source device further comprises a reaction chamber 105, the reaction chamber 105 is arranged in the vacuum cavity 1, the reaction chamber 105 comprises a reaction chamber partition plate 109 and a reaction chamber top plate 111, the reaction chamber top plate 111 is detachably connected with the reaction chamber partition plate 109 through screws, the reaction chamber partition plate 109 divides the vacuum cavity 1 into two spaces, the reaction chamber 105 is arranged in the space having the intersection point of the extension lines of the incident window 102 and the exit window 103; The reaction chamber top plate 111 is further provided with a top plate through hole 112. Further, as shown in Figure 2 As shown, in this embodiment, the incident ultrafast laser irradiates on the metal microdroplet target, the metal microdroplet target is excited into a plasma with a lifetime of femtosecond order, and the femtosecond hard X-ray pulse is generated by the acceleration electron bombarding the shell layer electron in the metal microdroplet target. The angle between the extension line of the femtosecond hard X-ray pulse and the extension line of the incident ultrafast laser is an acute angle, so in this embodiment, the shape of the vacuum cavity 1 is similar to a combination of a rectangle and an isosceles triangle with the length of the rectangle as the base side, and the incident window 102 and the exit window 103 are arranged on the two waists of the isosceles triangle. Further, the reaction chamber 105 further comprises a reaction chamber bottom plate 110, the reaction chamber partition plate 109 is fastened between the reaction chamber bottom plate 110 and the reaction chamber top plate 111 through screws, the reaction chamber partition plate 109 is a circular arc, and the reaction chamber partition plate 109, the reaction chamber top plate 111 and the reaction chamber bottom plate 110 can effectively block the splashing of the metal microdroplet target under the bombardment of the ultrafast laser. Further, the reaction chamber bottom plate 110 is further provided with a bottom plate through hole 113, the position and specification of the bottom plate through hole 113 correspond one-to-one with the position and specification of the top plate through hole 112. The laser light source 10 in this embodiment adopts an ultrafast pulse laser light source.

[0038] Preferably, as shown in Figure 2 , Figure 3 , Figure 5As shown, to ensure that the position of the metal micro-droplet target can be irradiated by the incident ultrafast laser, and to ensure that the irradiated metal micro-droplet target contact surface is flat and stable. The metal micro-droplet target regulating assembly includes a parallel plate capacitor 107, an energized solenoid 106, a control console 114, and an electrically controlled delay 115, and the laser light source 10 is also provided with a clock source 1001; the control console 114 is connected with the clock source 1001 through the electrically controlled delay 115, and the control console 114 is respectively in communication connection with the parallel plate capacitor 107 and the energized solenoid 106; the parallel plate capacitor 107 and the energized solenoid 106 are both arranged in the reaction chamber 105. The parallel plate capacitor 107 and the energized solenoid 106 are both arranged in the reaction chamber 105. The two polar plate holes 108 are vertically arranged on the two polar plates of the parallel plate capacitor 107, the center of the polar plate hole 108 is on the same vertical line with the center of the top plate through hole 112, and the midpoint of the center distance of the two polar plate holes 108 coincides with the intersection point of the extension lines of the incident window 102 and the exit window 103; the axis of the energized solenoid 106 is opposite to the midpoint of the center distance of the two polar plate holes 108; the lower side of the parallel plate capacitor 107 is also provided with a liquid collection tank 702. Further, as shown in Figure 3 The parallel plate capacitor 107 is circular, and the parallel plate capacitor 107 includes an upper polar plate and a lower polar plate. The upper polar plate is fixed on the bottom surface of the reaction chamber top plate 111 by screws, and the center of the polar plate hole 108 of the upper polar plate is vertically coincided with the center of the top plate through hole 112; the lower polar plate is fixed on the top surface of the reaction chamber bottom plate 110 by screws, and the center of the polar plate hole 108 of the lower polar plate is vertically coincided with the center of the bottom plate through hole 113. In this embodiment, the metal micro-droplet target regulating assembly is used to ensure that the drop speed of the metal micro-droplet and the irradiation time of the laser light source 10 have coincidence. The control console 114 is used to control the generation of voltage by the parallel plate capacitor 107, and the generation of current in the energized solenoid 106, and also controls the size of the voltage and current. Further, the control console 114 is connected with the clock source 1001 through the electrically controlled delay 115, to ensure the time coincidence between the incident ultrafast laser and the metal micro-droplet target, and the oscilloscope 16 is also directly connected with the clock source 1001, to play a role in displaying the communication signal.

[0039] Further, the parallel plate capacitor 107 is used to correct the height position of the charged metal microdroplet target, so that the metal microdroplet target can pass through the position of the laser focal spot when the incident ultrafast laser pulse arrives, thereby completing the time coincidence of the metal microdroplet target with the incident ultrafast laser pulse. On the other hand, the drop speed of the metal microdroplet target is controlled by controlling the voltage between the parallel plates, and the morphology of the metal microdroplet is controlled. The solenoid 106 generates a magnetic field in the energized state, which is used to fine-tune the morphology of the metal microdroplet target and assist the parallel plate in controlling the drop trajectory of the metal microdroplet target. The parallel plate capacitor 107 and the solenoid 106 are controlled by the control console 114, and together complete the time coincidence of the metal microdroplet target with the incident ultrafast laser pulse. The liquid collection tank 702 is used to collect the droplets after interaction with the incident ultrafast laser. In this embodiment, the diameter of the plate hole 108 is 5-20mm, and the plate hole 108 is opened at the center of the two parallel plates.

[0040] Further, as shown in Figure 3 the lower part of the vacuum chamber 1 is also provided with a liquid receiving cavity 7, and the liquid collection tank 702 is detachably fixed in the liquid receiving cavity 7 through a clamping groove. The top end of the liquid receiving cavity 7 is communicated with the vacuum chamber 1 through a receiving cavity flange 701, and the bottom end of the liquid receiving cavity 7 is also provided with a quick opening door 704 and a quick opening handle 703, which is used to open the quick opening door 704. Further, the bottom end of the liquid collection tank 702 is also provided with a collection tank handle 705, and the sidewall of the liquid collection tank 702 is provided with a protruding part, and the inner wall of the liquid receiving cavity 7 is provided with an L-shaped groove; the liquid collection tank 702 is pushed into the liquid receiving cavity 7 from the quick opening door 704, at this time the protruding part enters the groove, when the protruding part reaches the corner of the L-shaped groove, the collection tank handle 705 is rotated, so that the protruding part is clamped into the L-shaped groove to realize the fixation of the liquid collection tank 702; when it is needed to take out the liquid collection tank 702, the collection tank handle 705 is rotated in the opposite direction, so that the protruding part is separated from the groove. In this embodiment, the distance between the liquid collection tank 702 and the liquid receiving cavity 7 is 5mm, and the 5mm distance forms a vacuum layer, which achieves the effect of isolating temperature and avoids scalding by touching the quick opening door 704. The volume of the liquid collection tank 702 is between 20-90ml.

[0041] Preferably, as shown in Figure 2As shown in the figure, in order to avoid the metal micro-droplet target from blocking the exit window 103 after being bombarded by the incident ultrafast laser, a light-transmitting shielding belt disc 8 and a plurality of shielding belt guide columns 802 are arranged in the space of the vacuum chamber 1 away from the reaction chamber 105, the shielding belt guide columns 802 are arranged on the inner side of the incident window 102 and the exit window 103, and the light-transmitting shielding belt on the light-transmitting shielding belt disc 8 is connected with the shielding belt drive assembly 801 through the shielding belt guide columns 802. Further, in the embodiment, the light-transmitting shielding belt adopts Mylar film, which has good light-transmitting property. The light-transmitting shielding belt disc 8, the shielding belt guide columns 802 and the shielding belt drive assembly 801 are all fastened on the reaction chamber bottom plate 110 by screws. Further, the inner side of the two side walls of the vacuum chamber 1 with the incident window 102, the exit window 103 and the observation window 104 must be covered with the light-transmitting shielding belt to avoid the metal micro-droplet target from splashing onto the window pieces of the incident window 102, the exit window 103 and the observation window 104 after being bombarded; the other side walls of the vacuum chamber 1 can not be covered with the light-transmitting shielding belt. When the metal micro-droplets splashed on the light-transmitting shielding belt affect the generation of the femtosecond hard X-ray pulse, the light-transmitting shielding belt disc 8 is rotated by the shielding belt drive assembly 801 to replace the new light-transmitting shielding belt. The shielding belt drive assembly 801 in the embodiment adopts a motor.

[0042] Preferably, as shown in the figure, Figure 1 , Figure 3 in order to ensure that the femtosecond hard X-ray pulse can be continuously generated, the metal micro-droplet target generating assembly includes a liquid storage tank 4, a gas valve 6, a heating assembly 5 and a droplet nozzle, the liquid storage tank 4 is arranged above the vacuum chamber 1 and communicates with the vacuum chamber 1; the gas valve 6 is communicated at the top end of the liquid storage tank 4, the heating assembly 5 is arranged on the circumferential periphery of the liquid storage tank 4, and the droplet nozzle is arranged at the outlet of the liquid storage tank 4 and is connected with a positive or negative electrode circuit, preferably a positive electrode circuit. As shown in the figure, Figure 3 in the embodiment, the liquid storage tank 4 is used to contain liquid metal, preferably tin; the heating assembly 5 surrounds the outer periphery of the liquid storage tank 4 for one turn, the heating assembly 5 adopts an electric heating wire, the temperature of the heating assembly 5 is 300±20℃ and can keep constant, and the melting point of tin is 231.89℃, so the tin can be melted.

[0043] Further, the gas valve 6 can be filled with inert gas, preferably argon. The inert gas can adjust the pressure in the liquid storage tank 4, so as to adjust the droplet speed of the metal micro-droplets, and in the embodiment, the falling speed of the metal micro-droplets is not less than 1000 droplets / s.

[0044] Further, the liquid storage tank 4 and the vacuum cavity 1 are further connected by flanges with a liquid droplet filtering cavity 501, which is used to filter impurities possibly existing in the metal microdroplets. A liquid droplet nozzle is arranged in the liquid droplet filtering cavity 501, which is used to control the diameter of the metal microdroplets to be in the order of sub-millimeter and is connected with a positive electrode circuit to make the metal microdroplets carry positive electricity, so that the metal microdroplets are subjected to the force of the parallel-plate capacitor 107 to adjust the speed and shape. In the embodiment, the air valve 6, the liquid storage tank 4, the liquid droplet filtering cavity 501, the bellows 2, the vacuum cavity 1 and the liquid receiving cavity 7 are sequentially connected by flanges from top to bottom.

[0045] Preferably, as shown in Figure 1 、 Figure 3 、 Figure 4 To ensure that the metal microdroplets can accurately enter the parallel-plate capacitor 107 and ensure the spatial coincidence of the metal microdroplet target and the incident ultrafast laser, the liquid storage tank 4 and the vacuum cavity 1 are further provided with the bellows 2. The liquid storage tank 4 is communicated with the reaction chamber 105 through the bellows 2 and the top plate through hole 112. The outer circumferential side of the bellows 2 is provided with the displacement driving assembly 3. Further, the top end and the bottom end of the bellows 2 are provided with connecting flanges. The top end of the bellows 2 is connected with the liquid droplet filtering cavity 501 through the flange, and the bottom end of the bellows 2 is fastened with the vacuum cavity top cover 101 at the top of the vacuum cavity 1 through the flange. In the embodiment, the bellows 2 is made of metal material, which can only be finely adjusted in the radial direction and can be stretched in the axial direction. In the embodiment, the vacuum cavity top cover 101 and the reaction chamber top plate 111 are both made of transparent material, which is convenient for observing the running state of the mechanical mechanism in the vacuum cavity 1.

[0046] Further, as shown in Figure 4As shown, the displacement driving assembly 3 comprises a displacement assembly base 301, a displacement assembly connecting platform 302, left and right driving plates 303, left and right driven plates 305, front and rear driving plates 306, front and rear driven plates 304, left and right driving shafts 307, front and rear driving shafts 308, and up and down driving shafts 309, and the up and down fixed plates 313 are further arranged above the left and right driven plates 305, wherein the displacement assembly base 301 is sleeved on the outer periphery of the flange at the bottom end of the bellows 2, the displacement assembly connecting platform 302 is sleeved on the outer periphery of the flange at the top end of the bellows 2, the front and rear driving plates 306 and the front and rear driven plates 304 are connected through the front and rear translation rails 310 penetrating the displacement assembly connecting platform 302, the front and rear driving shafts 308 penetrate the front and rear driving plates 306 and are threaded in the displacement assembly connecting platform 302. The left and right driving plates 303 and the left and right driven plates 305 are connected through the left and right translation rails 311, the number of the left and right translation rails 311 is two, the two left and right translation rails 311 penetrate the front and rear driving plates 306 and the front and rear driven plates 304 respectively, the left and right driving shafts 307 penetrate the left and right driving plates 303 and are integrally connected with any one of the left and right translation rails 311 (in this embodiment, the left and right driving shafts 307 are connected with the left and right translation rails 311 penetrating the front and rear driven plates 304), the left and right translation rails 311 connected with the left and right driving shafts 307 are provided with external threads, and the front and rear driven plates 304 are provided with internal threads.

[0047] When the left and right driving shafts 307 rotate, the front and rear driven plates 304 move on the left and right translation rails 311. The up and down translation rails 312 are arranged between the up and down fixed plates 313 and the displacement assembly base 301, the number of the up and down translation rails 312 is two, the left and right driven plates 305 are sleeved on the up and down translation rails 312 and are connected through threaded cooperation. The up and down driving shafts 309 are integrally connected with any one of the up and down translation rails 312 (in this embodiment, the up and down driving shafts 309 are integrally connected with the up and down translation rails 312 on the front side), when the up and down driving shafts 309 rotate, the left and right driven plates 305 move on the up and down translation rails 312.

[0048] Further, the flange at the top end of the bellows 2 can also be replaced by a differential extraction rotation platform to realize the micro-rotation of the displacement assembly connecting platform 302 around the central axis of the bellows 2, and the differential extraction rotation platform is a prior art.

[0049] Preferably, as Figure 5As shown, to ensure that the incident ultrafast laser meets the bombardment requirements of the metal microdroplet target, the laser focusing assembly includes a beam splitter 11 and a reflector 13. The ultrafast laser pulse emitted by the laser source 10 is guided to the metal microdroplet target through the incident window 102 via the beam splitter 11 and the reflector 13. An observation assembly 15 is also provided on the outside of the observation window 104. Further, in this embodiment, the beam splitter 11 splits the ultrafast laser emitted by the laser source 10 into an excitation beam and a detection beam. The excitation beam, after being reflected by the reflector 13, enters the reaction chamber 105. The reflector 13 is an off-axis parabolic reflector. The observation assembly 15 uses an optical CCD and is connected to the metal microdroplet target morphology monitoring assembly to observe whether the incident ultrafast laser can bombard the metal microdroplet target and monitor the morphology of the metal microdroplet in real time. Further, in this embodiment, the detection beam can also be simultaneously connected to a pump probe beam path (not shown in the figure) to conduct ultrafast scientific experiments together with the generated X-rays.

[0050] Preferred, such as Figure 5 As shown, to further ensure the overlap between the droplet velocity of the metal microdroplets and the irradiation time of the laser source 10, the desktop femtosecond hard X-ray pulse source device also includes an X-ray photodetector 14, a source beam photodetector 12, and an oscilloscope 16. The X-ray photodetector 14 is located outside the exit window 103, and the source beam photodetector 12 is located outside the beam splitter 11. Both the X-ray photodetector 14 and the source beam photodetector 12 are communicatively connected to the oscilloscope 16. In this embodiment, the X-ray photodetector 14 is used to detect hard X-ray light, and the source beam photodetector 12 is used to detect the detection light generated by the beam splitter 11. Both the X-ray photodetector 14 and the source beam photodetector 12 are communicatively connected to the oscilloscope 16.

[0051] Furthermore, the metal microdroplet target control component works in conjunction with the X-ray photodetector 14, the source beam photodetector 12, and the oscilloscope 16 to ensure the timing of the metal microdroplet droplet's droplet velocity and the irradiation time of the laser source 10. Specifically, using the clock source 1001 of the laser source 10 as a reference signal, the timing of the voltage application of the parallel plate capacitor 107 is controlled after passing through the electronically controlled delay unit 115, and the voltage magnitude and the current magnitude of the energized solenoid 106 are adjusted until plasma generated by the interaction between the metal microdroplet and the ultrafast laser pulse can be observed through the observation component 15, indicating that the timing coincidence is initially completed. When the pulse signal frequencies of the two channels detecting X-rays and the source beam on the oscilloscope 16 are consistent, and the pulse width and intensity of the X-ray channel pulse signal are stable (i.e., a pulse signal appears on the X-ray photodetector 14 at the same time as a pulse signal appears on the source beam photodetector 12, and the peak time interval between each pair of signals is the same), at this time, the metal microdroplet and the laser source 10 have coincidence. The photon energy of the femtosecond hard X-ray pulse is several thousand electron volts.

[0052] Preferred, such as Figure 5 As shown, a vacuum pump 9 is connected to the rear end of the vacuum chamber 1 to ensure the vacuum environment of the vacuum chamber 1; a sealing strip is provided on the top cover 101 of the vacuum chamber to keep the entire vacuum chamber 1 in a closed state. The sealing strip can be removed to replace the light-transmitting shielding tape 8 and to clean the inside of the vacuum chamber 1.

[0053] This invention also provides a method for generating femtosecond hard X-ray pulses, the specific steps of which are as follows:

[0054] A1: Generate metal microdroplets. Turn on the vacuum pump 9 to create a vacuum inside the vacuum chamber 1; place the molten metal in the liquid storage tank 4 and keep the molten metal in a molten state using the heating component 5;

[0055] A2: Adjusting the dripping rate of metal microdroplets. Inert gas is introduced or released into the liquid storage tank 4 through the gas valve 6 to change the pressure in the liquid storage tank 4, thereby controlling the rate of metal microdroplet generation. After being filtered by the droplet filter chamber 501, the metal microdroplets are positively charged after passing through the droplet nozzle and drip from the droplet nozzle. The diameter of the metal microdroplets is on the sub-millimeter scale.

[0056] A3: The falling metal micro-droplets enter the space between the two plates of the parallel plate capacitor 107 through the bellows 2 → vacuum chamber top cover 101 → vacuum chamber 1 → top plate through hole 112 → plate hole 108, and the morphology and falling trajectory of the metal micro-droplets are monitored in real time through the observation window 104 via the observation component 15.

[0057] A4: Spatial overlap of the metal microdroplet and the ultrafast laser pulse. The laser source 10 emits an ultrafast laser pulse, which, guided by the beam splitter 11 and the reflector 13, enters the parallel plate capacitor 107 through the incident window 102. The falling trajectory of the metal microdroplet is observed by the observation component 15, and the displacement driving component 3 is adjusted in the left-right, front-back, and up-down directions to make the falling trajectory of the metal microdroplet coincide with the focal spot of the focused ultrafast laser pulse, thus achieving spatial overlap between the metal microdroplet and the ultrafast laser pulse. The adjustment steps of the displacement driving component 3 are as follows:

[0058] A4.1: As Figure 4 As shown, the front and rear drive shaft 308 rotates, and the displacement component connecting platform 302 is subjected to the frictional force generated by the threaded engagement of the front and rear drive shaft 308. The displacement component connecting platform 302 moves back and forth along the front and rear translation guide rail 310, thereby causing the liquid storage tank 4 to shift in front and rear position by ±10mm.

[0059] A4.2: Rotate the left and right driving shafts 307, and the left and right translation rails 311 connected to the left and right driving shafts 307 rotate. The front and rear driven plates 304 are subjected to the friction force generated by the threaded cooperation of the left and right translation rails 311, and the front and rear driven plates 304 move left and right along the left and right translation rails 311, thereby driving the displacement assembly connecting platform 302, the front and rear driving plates 306 to move together, and further driving the liquid storage tank 4 to shift left and right, with a shift distance of ±10 mm.

[0060] A4.3: Rotate the upper and lower driving shafts 309, and the upper and lower fixed plates 313 are stationary. The left and right driven plates 305 are subjected to the friction force of the threaded connection of the upper and lower driving shafts 309, and move in the direction away from or close to the displacement assembly base 301 along the upper and lower translation rails 312. The left and right driven plates 305 drive the displacement assembly connecting platform 302 to shift in the axial direction of the bellows 2 through the left and right translation rails 311 and the front and rear translation rails 310, thereby driving the liquid storage tank 4 to shift, with a shift distance of 10-30 mm.

[0061] Further, in this embodiment, the front and rear driving shafts 308, the left and right driving shafts 307, and the upper and lower driving shafts 309 all include two-stage adjustment mechanisms, which can accurately adjust the shift distance (the two-stage adjustment mechanism is similar to a screw micrometer).

[0062] A5: The time coincidence of the metal micro-droplet and the ultrafast laser pulse can produce femtosecond hard X-ray pulses. The specific steps of time coincidence are as follows:

[0063] A5.1: Take the clock source 1001 of the laser light source 10 as the reference signal, and after passing through the electrically controlled delay device 115, control the pressurization time of the parallel plate capacitor 107, and adjust the voltage size and the current size of the energized solenoid 106. Under the influence of the force between the parallel plate capacitor 107 and the energized solenoid 106, the shape of the metal micro-droplet is ellipsoidal. When the interaction between the metal micro-droplet and the ultrafast laser pulse is observed by the observation assembly 15 to produce plasma, it indicates that the time coincidence is initially completed.

[0064] A5.2: The metal micro-droplet between the two plates of the parallel plate capacitor 107 is bombarded by the incident ultrafast laser to produce femtosecond hard X-ray pulses with photon energy of several thousand electron volts, and the femtosecond hard X-ray pulses are guided out from the exit window 103;

[0065] A6: Further precise time coincidence of the metal micro-droplet and the ultrafast laser pulse can stably produce high-flux femtosecond hard X-ray pulses. The specific steps of further time coincidence are as follows:

[0066] A6.1: Adjust the position of the X-ray photodetector 14, the source light photodetector 12, so that the X-ray photodetector 14 receives the femtosecond hard X-ray pulse, and the source light photodetector 12 receives the detection light pulse signal split by the beam splitter 11; further adjust the pressurization time and voltage of the air valve 6 and the parallel plate capacitor 107, and the current of the energized solenoid 106, when the pulse signal pulse width and intensity of the X-ray photodetector 14 on the oscilloscope 16 are stable, and each pair of pulse signals on the oscilloscope 16 of the X-ray photodetector 14 and the source light photodetector 12 always appears together and the center peak time difference of each pair is constant, that is, the time accurate overlap of the metal microdroplet and the ultrafast laser pulse emitted by the laser light source 10 is completed;

[0067] A7: The metal microdroplet bombarded by the incident ultrafast laser falls into the liquid collection tank 702 from the pole hole 108, and the liquid collection tank 702 collects and cools the metal microdroplet; when the metal microdroplet in the liquid collection tank 702 is collected and cooled, the quick-opening door 704 is opened by the quick-opening handle 703, and the liquid collection tank handle 705 is held to rotate the liquid collection tank 702 out of the clamping groove to take out the liquid collection tank 702;

[0068] A8: The device is running with light transmission shielding belt transmission, and the contaminated light transmission shielding belt is replaced with a new one at any time to ensure the normal generation of the femtosecond hard X-ray pulse.

[0069] The tabletop femtosecond hard X-ray pulse source device and pulse generation method of the present application heat the liquid metal into a molten state through the liquid storage tank 4 and the heating assembly 5, control the droplet speed of the metal microdroplet through the air valve 6, and control the falling direction of the metal microdroplet through the displacement driving assembly 3, so that the metal microdroplet is continuously bombarded by the incident ultrafast laser, thereby generating a femtosecond hard X-ray pulse.

[0070] The tabletop femtosecond hard X-ray pulse source device and pulse generation method of the present application use a metal microdroplet target instead of a solid target, which overcomes the shortcomings of short running time and difficult control of the solid target, and has the advantages of long running time, stable photon yield, high time resolution, high photon energy, and can generate photon pulses with energy of thousands of electron volts and repetition frequency of thousands of hertz; at the same time, the structure is simple, the size is small, the cost performance is high, and the application range is wide.

[0071] Therefore, the present application effectively overcomes the shortcomings of the prior art and has high industrial utilization value.

[0072] The above embodiments are only illustrative of the principles of the present application and its efficacy, and are not intended to limit the present application. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present application shall be covered by the claims of the present application.

Claims

1. A tabletop femtosecond hard X-ray pulse source apparatus, characterized by: The application relates to a laser source (10), a laser focusing assembly, a metal micro-droplet target generating assembly, a metal micro-droplet target regulating assembly and a vacuum cavity (1), the metal micro-droplet target generating assembly is arranged in the vacuum cavity (1), the vacuum cavity (1) is provided with an incident window (102) and an emission window (103), the laser focusing assembly is used for receiving ultrafast laser and guiding the ultrafast laser into the vacuum cavity (1) through the incident window (102), the metal micro-droplet target generating assembly generates a metal micro-droplet target, the metal micro-droplet target is bombarded by the ultrafast laser through the metal micro-droplet target regulating assembly to generate a femtosecond hard X-ray pulse, and the emission window (103) guides out the generated femtosecond hard X-ray pulse; the vacuum cavity (1) is provided with a light-transmitting shielding belt disc (8), a plurality of shielding belt guide columns (802) and a shielding belt driving assembly (801), the plurality of shielding belt guide columns (802) are arranged on the inner side of the incident window (102) and the emission window (103), and the light-transmitting shielding belt on the light-transmitting shielding belt disc (8) is connected with the shielding belt driving assembly (801) through the shielding belt guide columns (802). The incident window (102) and the emission window (103) are both covered with the light-transmitting shielding belt, the shielding belt driving assembly (801) continuously transports the light-transmitting shielding belt, the residues splashed or deposited on the light-transmitting shielding belt after the metal micro-droplet target is bombarded by the ultrafast laser are discharged, the window sheets of the incident window (102) and the emission window (103) are prevented from being polluted, and then the ultrafast laser generated by the laser source (10) is prevented from entering the vacuum cavity (1) and the generated femtosecond hard X-ray pulse is prevented from being guided out of the vacuum cavity (1).

2. The tabletop femtosecond hard X-ray pulse source apparatus according to claim 1, characterized by: The incident window (102) is provided with an optical flatness window sheet, the emission window (103) is provided with an X-ray transparent film, and one side of the emission window (103) is further provided with an observation window (104).

3. The tabletop femtosecond hard X-ray pulse source apparatus according to claim 2, characterized by: The application further relates to a reaction chamber (105), the reaction chamber (105) is arranged in the vacuum cavity (1), the reaction chamber (105) comprises a reaction chamber partition plate (109) and a reaction chamber top plate (111), the reaction chamber partition plate (109) divides the vacuum cavity (1) into two spaces, the reaction chamber (105) is arranged in the space with the intersection point of the extension lines of the incident window (102) and the emission window (103), and the reaction chamber top plate (111) is further provided with a top plate through hole (112).

4. The tabletop femtosecond hard X-ray pulse source apparatus according to claim 3, characterized by: The metal micro-droplet target regulation assembly includes a parallel-plate capacitor (107), an energized solenoid (106), a control console (114), and an electrically controlled delay device (115), and the laser light source (10) is further provided with a clock source (1001); the control console (114) is connected with the clock source (1001) through the electrically controlled delay device (115), and the control console (114) is respectively in communication connection with the parallel-plate capacitor (107) and the energized solenoid (106); the parallel-plate capacitor (107) and the energized solenoid (106) are both arranged in the reaction chamber (105), and the two polar plate holes (108) are both arranged on the two polar plates of the parallel-plate capacitor (107), the centers of the polar plate holes (108) are on the same vertical line with the center of the top plate through hole (112), and the center connecting line of the two polar plate holes (108) penetrates the intersection of the incident window (102) and the extended line of the exit window (103); the axis of the energized solenoid (106) is opposite to the center connecting line of the two polar plate holes (108); and the lower side of the parallel-plate capacitor (107) is further provided with a liquid collecting tank (702).

5. The tabletop femtosecond hard X-ray pulse source apparatus according to claim 1, wherein: The metal micro-droplet target generation assembly includes a liquid storage tank (4), a gas valve (6), a heating assembly (5), and a droplet nozzle, the liquid storage tank (4) is arranged above the vacuum cavity (1) and is in communication with the vacuum cavity (1); the gas valve (6) is arranged on the upper side of the liquid storage tank (4), the heating assembly (5) is arranged on the circumferential periphery of the liquid storage tank (4), and the droplet nozzle is arranged at the outlet of the liquid storage tank (4) and is connected with a positive or negative electrode circuit.

6. The tabletop femtosecond hard X-ray pulse source apparatus according to claim 5, characterized by: The metal micro-droplet target generation assembly further includes a bellows (2), the bellows (2) is arranged between the liquid storage tank (4) and the vacuum cavity (1), the liquid storage tank (4) is in communication with the reaction chamber (105) through the bellows (2) and the top plate through hole (112); the outer peripheral side of the bellows (2) is provided with a displacement driving assembly (3), the displacement driving assembly (3) can adjust the bellows (2) in the radial direction and the axial direction, so as to ensure that the metal micro-droplet target and the incident ultrafast laser coincide in space and time.

7. The desktop femtosecond hard X-ray pulse source apparatus according to claim 2, wherein: The laser focusing assembly includes a beam splitter (11) and a reflector (13), and the ultrafast laser emitted by the laser light source (10) is transmitted through the incident window (102) to the metal micro-droplet target through the beam splitter (11) and the reflector (13); the metal micro-droplet target regulation assembly further includes an observation assembly (15), and the observation assembly (15) is arranged outside the observation window (104).

8. The tabletop femtosecond hard X-ray pulse source apparatus according to claim 7, characterized by: Further including an X-ray photodetector (14), a source light photodetector (12), and an oscilloscope (16), the X-ray photodetector (14) is arranged outside the exit window (103), the source light photodetector (12) is arranged outside the beam splitter (11), and the X-ray photodetector (14) and the source light photodetector (12) are both in communication connection with the oscilloscope (16).

9. A method for generating femtosecond hard X-ray pulses, using the tabletop femtosecond hard X-ray pulse source device according to any one of claims 1-8, characterized in that, The following steps are adopted: S1: install the metal micro-droplet target generating assembly on the vacuum chamber (1); S2: operate the metal micro-droplet target generating assembly, and the metal micro-droplet target generating assembly generates the metal micro-droplet target; S3: the laser light source (10) emits ultrafast laser, and the position of the laser focusing assembly is adjusted so that the ultrafast laser enters the incident window (102) through the laser focusing assembly; S4: adjust the metal micro-droplet target generating assembly, and make the falling track of the metal micro-droplet target coincide with the light path of the ultrafast laser in space; adjust the metal micro-droplet target regulating assembly, and make the falling track of the metal micro-droplet target coincide with the ultrafast laser in time; S5: the focused ultrafast laser through the laser focusing assembly synchronously hits the generated metal micro-droplet target through the incident window (102), the ultrafast laser and the metal micro-droplet target interact, and femtosecond hard X-ray pulses are generated; S6: the generated femtosecond hard X-ray pulses are guided out through the exit window (103).

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