A positive group velocity dispersion crystal pulse compressor

Abstract

The present application discloses a positive group velocity dispersion crystal pulse compressor, which relates to the field of free electron laser technology. The positive group velocity dispersion crystal pulse compressor comprises a first asymmetric cut crystal, a first concave reflector, a second concave reflector and a second asymmetric cut crystal arranged in sequence along an optical path. The present application provides a new scheme for generating hard X-ray attosecond free electron laser pulses, which can have higher stability.

Description

Technical Field

[0001] The present application relates to the field of free electron laser technology, and in particular to a positive group velocity dispersion crystal pulse compressor. Background Art

[0002] In the process of studying ultrafast physical chemistry and dynamics, especially the exploration of ultrafast dynamics at the atomic scale, it is necessary to explore ultrafast dynamics at the atomic scale, which requires the use of attosecond pulses. Currently, attosecond pulses are mainly generated by high-order harmonic generation, which can cover the soft X-ray band, but the generated pulse energy is relatively low.

[0003] Generating attosecond pulses based on free electron lasers is also a current research hotspot. With the construction and stable operation of free electron laser devices, it has become possible to generate stable, high pulse energy, isolated hard X-ray attosecond pulses on user devices.

[0004] The existing hard X-ray attosecond free electron laser pulse generation is mainly based on the technology route of electron bunch manipulation, such as controlling the local emittance destruction of the electron bunch, the local orbital mismatch of the electron bunch, laser modulation of the electron bunch, etc. However, this technology only utilizes part of the electron beam and may cause instability and other problems due to beam manipulation. Summary of the invention

[0005] The present application provides a positive group velocity dispersion crystal pulse compressor for generating hard X-ray attosecond free electron laser pulses with higher stability.

[0006] This application provides:

[0007] A positive group velocity dispersion crystal pulse compressor is used for compressing down-chirped hard X-ray free electron laser pulses to generate hard X-ray attosecond free electron laser pulses, the positive group velocity dispersion crystal pulse compressor comprising a first asymmetric cut crystal, a first concave reflector, a second concave reflector and a second asymmetric cut crystal which are sequentially arranged along an optical path;

[0008] The first asymmetric cut crystal is used to disperse the down-chirped hard X-ray free electron laser pulse to form a multi-path pulse. The multi-path pulse is reflected by the first concave reflector and the second concave reflector in sequence and then projected to the second asymmetric cut crystal. The multi-path pulse converges at the second asymmetric cut crystal to form the hard X-ray attosecond free electron laser pulse.

[0009] In some possible implementations, the distance between the first asymmetric cut crystal and the first concave reflector is f 1 , the distance between the first concave reflecting mirror and the second concave reflecting mirror is (f1 +f 2 ), the distance between the second concave reflecting mirror and the second asymmetric cut crystal is f 2 ′;

[0010] Among them, f 1 represents the focal length of the first concave reflector, f 2 represents the focal length of the second concave reflector, f 2 ′≤f 2 .

[0011] In some possible implementations, the first asymmetric cut crystal and the second asymmetric cut crystal both include a crystal face and a physical surface;

[0012] In the same asymmetric cut crystal, the angle η between the crystal plane and the physical surface is smaller than the Bragg angle.

[0013] In some possible implementations, the positive group velocity dispersion crystal pulse compressor further includes two sets of first posture adjustment mechanisms, and the first asymmetric cut crystal and the second asymmetric cut crystal are mounted on the two first posture adjustment mechanisms in a one-to-one correspondence;

[0014] The first posture adjustment mechanism is used to adjust the posture of the asymmetric cut crystal to which it is connected.

[0015] In some possible implementations, the first posture adjustment mechanism includes a first swing unit, and the first swing unit is used to adjust the angle between the asymmetrically cut crystal and the optical axis of the down-chirped hard X-ray free electron laser pulse;

[0016] The first swing table unit includes a base, a first driving member and an adapter plate, one side of the base is provided with an arc-shaped guide rail, the adapter plate is slidably matched with the arc-shaped guide rail, the first driving member is transmission-connected with the adapter plate, and the asymmetric cut crystal is installed on a side of the adapter plate away from the base;

[0017] The first driving member is used to drive the adapter plate to move along the arc-shaped guide rail to drive the asymmetric cut crystal to rotate relative to the optical axis of the down-chirped hard X-ray free electron laser pulse.

[0018] In some possible implementations, the first posture adjustment mechanism further includes a first leveling unit, and the first leveling unit is used to drive the asymmetric cut crystal to move in five dimensions to adjust the asymmetric cut crystal to a level.

[0019] In some possible implementations, the positive group velocity dispersion crystal pulse compressor further includes two second posture adjustment mechanisms, the first concave reflecting mirror and the second concave reflecting mirror are mounted on the two second posture adjustment mechanisms in a one-to-one correspondence, and the second posture adjustment mechanism is used to adjust the posture of the concave reflecting mirror connected to itself;

[0020] The second posture adjustment mechanism includes a second leveling unit, a second swing unit and a slide unit, the slide unit is connected between the second leveling unit and the second swing unit, and the concave reflector is installed on the second swing unit;

[0021] The second leveling unit is used to level the concave reflecting mirror, the second swing unit is used to adjust the angle between the concave reflecting mirror and the optical axis of the down-chirped hard X-ray free electron laser pulse, and the sliding unit is used to drive the concave reflecting mirror to approach or move away from the asymmetric cut crystal to adjust the distance between the concave reflecting mirror and the asymmetric cut crystal.

[0022] In some possible implementations, the slide unit includes a second driving member, a mounting seat, a transmission rod and a slider;

[0023] The mounting seat and the second driving member are both fixedly mounted relative to the second leveling unit, the slider is slidably mounted on a side of the mounting seat away from the second leveling unit, the transmission rod is transmission-connected between the second driving member and the slider, and the second swing unit is mounted on the slider via a movable frame;

[0024] The second driving member is used to drive the slider to slide relative to the mounting seat, so as to drive the concave reflecting mirror to approach or move away from the asymmetric cut crystal.

[0025] In some possible embodiments, the positive group velocity dispersion crystal pulse compressor also includes a connected cold source and a plurality of refrigerant transmission tubes, and the plurality of refrigerant transmission tubes are thermally connected one-to-one with the first asymmetric cut crystal, the first concave reflector, the second concave reflector and the second asymmetric cut crystal.

[0026] In some possible implementations, the positive group velocity dispersion crystal pulse compressor further includes two vacuum boxes, and an optical channel is connected between the two vacuum boxes;

[0027] The first asymmetric cut crystal and the first concave reflector are installed in a vacuum box, and the first concave reflector is arranged close to one end of the light channel;

[0028] The second concave reflecting mirror and the second asymmetric cut crystal are installed in another of the vacuum boxes, and the second concave reflecting mirror is arranged close to one end of the light channel.

[0029] The beneficial effects of the present application are as follows: the present application proposes a positive group velocity dispersion crystal pulse compressor, comprising a first asymmetric cut crystal, a first concave reflector, a second concave reflector and a second asymmetric cut crystal arranged in sequence along the optical path, and using the asymmetric cut crystal to disperse the down-chirped hard X-ray free electron laser pulse, so as to perform pulse compression to generate hard X-ray attosecond free electron laser pulses. That is, the present application provides a new scheme for generating hard X-ray attosecond free electron laser pulses, and in the process of generating hard X-ray attosecond free electron laser pulses, the photons generated by the entire electron beam can also be utilized, and it has higher stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A partial structural schematic diagram of a positive group velocity dispersion crystal pulse compressor in some embodiments is shown;

[0032] Figure 2 A schematic diagram of dimensioning of a positive group velocity dispersion crystal pulse compressor in some embodiments is shown;

[0033] Figure 3 A schematic diagram of the main structure of a positive group velocity dispersion crystal pulse compressor in some embodiments is shown;

[0034] Figure 4 A schematic diagram of the internal structure of a positive group velocity dispersion crystal pulse compressor in some embodiments is shown;

[0035] Figure 5 A schematic diagram of a top view of the structure of a first leveling unit in some embodiments is shown;

[0036] Figure 6 A schematic diagram of the side structure of the first leveling unit in some embodiments is shown;

[0037] Figure 7 A schematic diagram of the three-dimensional structure of the first posture adjustment mechanism in some embodiments is shown;

[0038] Figure 8 A schematic diagram of the three-dimensional structure of the first posture adjustment mechanism and the second posture adjustment mechanism in some embodiments is shown;

[0039] Fig. 9Shows a schematic diagram of the structure of the slide unit in some embodiments;

[0040] Fig.10 A partial structural schematic diagram of a light plate detection mechanism in some embodiments is shown.

[0041] Description of main component symbols:

[0042] 1000-positive group velocity dispersion crystal pulse compressor;

[0043] 110-asymmetric cut crystal; 110a-crystal plane; 110b-physical surface; 111-first asymmetric cut crystal; 112-second asymmetric cut crystal; 120-concave reflector; 121-first concave reflector; 122-second concave reflector; 210-vacuum box; 211-light inlet channel; 212-light outlet channel; 213-observation window; 220-ion pump; 230-light channel; 240-gate valve; 250-vacuum gauge; 260-support; 300-first posture adjustment mechanism; 310-first leveling unit; 311-first support plate; 312-second support plate; 313-adjusting bolt; 314-fixing bolt; 315-mounting block; 316-limiting bolt; 317-nut; 320-first swing table Unit; 321-base; 3211-arc guide rail; 322-first drive member; 323-adapter plate; 324-fixture; 400-second posture adjustment mechanism; 410-second leveling unit; 420-slide unit; 421-mounting base; 4211-first slide rail; 422-second drive member; 423-transmission rod; 424-first slider; 430-movable frame; 440-second swing unit; 500-spot detection mechanism; 510-scintillating crystal; 520-reflector; 530-spot detector; 540-lifting assembly; 541-third drive member; 542-mounting frame; 543-second slide rail; 544-second slider; 545-connecting rod; 546-mounting seat; 600-cooling mechanism; 610-refrigerant transmission pipe;

[0044] 2000-Chirped hard X-ray free electron laser pulses;

[0045] 3000-hard X-ray attosecond free-electron laser pulses. DETAILED DESCRIPTION

[0046] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0047] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0048] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0049] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0050] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0051] Chirped pulses refer to light whose pulse frequency changes over time, that is, the frequencies of the pulse head and pulse tail are different. A chirped pulse compressor can make different wavelengths of light pass through different optical paths through dispersion. When the optical path difference is at a certain value, the pulse tail can catch up with the pulse head, thereby achieving pulse compression. However, in the hard X-ray band, chirped pulse compressors have not yet been used.

[0052] In an embodiment, a positive group velocity dispersion crystal pulse compressor 1000 is provided, which can be used to compress down-chirped hard X-ray free electron laser pulses 2000 to generate hard X-ray attosecond free electron laser pulses 3000.

[0053] like Figure 1 As shown, the positive group dispersion crystal pulse compressor may include two asymmetric cut crystals 110 (i.e., a first asymmetric cut crystal 111 and a second asymmetric cut crystal 112) and two concave reflectors 120 (i.e., a first concave reflector 121 and a second concave reflector 122). The first asymmetric cut crystal 111, the first concave reflector 121, the second concave reflector 122 and the second asymmetric cut crystal 112 may be arranged in sequence along the transmission direction of the light path. Among them, the first asymmetric cut crystal 111 is symmetrical with the second asymmetric cut crystal 112, and the first concave reflector 121 is symmetrical with the second concave reflector 122. The concave surface of the first concave reflector 121 is the light incident side, and is located on the side close to the first asymmetric cut crystal 111. The concave surface of the second concave reflector 122 is the light incident side, and is located on the side close to the second asymmetric cut crystal 112.

[0054] During use, after the down-chirped hard X-ray free electron laser pulse 2000 is incident on the positive group dispersion crystal pulse compressor, the first asymmetric cut crystal 111 can produce a dispersion effect on it and separate it into multiple pulses. The multiple pulses can be reflected by the first concave reflector 121 and the second concave reflector 122 in sequence and reach the second asymmetric cut crystal 112. The multiple pulses can be merged at the second asymmetric cut crystal 112 and output the hard X-ray attosecond free electron laser pulse 3000. In this process, the light with different frequencies in the longitudinal direction of the down-chirped hard X-ray free electron laser pulse 2000 can pass through different optical paths, so that the tail of the pulse catches up with the head of the pulse, and the longitudinal compression of the pulse is achieved to generate the hard X-ray attosecond free electron laser pulse 3000.

[0055] The positive group dispersion crystal pulse compressor provided in the embodiment utilizes the chirped pulse compression principle and uses the asymmetric cut crystal 110 as a dispersion device for the down-chirped hard X-ray free electron laser pulse 2000. The down-chirped hard X-ray free electron laser pulse 2000 is compressed to obtain a hard X-ray attosecond free electron laser pulse 3000. The photons generated by the entire electron beam can be utilized and have higher stability.

[0056] like Figure 1 As shown, the asymmetrically cut crystal 110 may include a crystal face 110a and a physical surface 110b. The angle η between the crystal face 110a and the physical surface 110b is smaller than the Bragg angle. In an embodiment, the concave reflector 120 may be an elliptical cylindrical mirror.

[0057] like Figure 1 and Figure 2 As shown, the distance between the first asymmetric cut crystal 111 and the first concave reflecting mirror 121 is f 1 The distance between the first concave reflecting mirror 121 and the second concave reflecting mirror 122 is (f 1 +f 2 ). The distance between the second concave reflecting mirror 122 and the second asymmetric cut crystal 112 is f 2 ′. Among them, f 1 represents the focal length of the first concave reflecting mirror 121, f 2 represents the focal length of the second concave reflecting mirror 122, f 2 ′≤f 2 In the embodiment, the distance between the first asymmetric cut crystal 111 and the first concave reflector 121 may refer to the distance between the center of the incident surface of the first asymmetric cut crystal 111 and the center of the incident surface of the first concave reflector 121. The distance between the first concave reflector 121 and the second concave reflector 122 may refer to the distance between the center of the incident surface of the first concave reflector 121 and the center of the incident surface of the second concave reflector 122. The distance between the second concave reflector 122 and the second asymmetric cut crystal 112 may refer to the distance between the center of the incident surface of the second concave reflector 122 and the center of the incident surface of the second asymmetric cut crystal 112.

[0058] Exemplarily, in some embodiments, the distance between the first asymmetric cut crystal 111 and the first concave reflector 121 is set to 1 m. The distance between the second concave reflector 122 and the second asymmetric cut crystal 112 is set to 1 m. The focal length f of the first concave reflector 121 is 1 is 1 m, and the focal length f of the second concave reflecting mirror 122 is 2 is 1m.

[0059] It can be understood that both the first asymmetric cut crystal 111 and the first concave reflector 121 can be tilted relative to the optical axis of the incident down-chirped hard X-ray free electron laser pulse 2000. In the embodiment, the tilt angles of the first asymmetric cut crystal 111 and the first concave reflector 121 can be set according to the length of the incident down-chirped hard X-ray free electron laser pulse 2000.

[0060] Combined with Figure 3The positive group velocity dispersion crystal pulse compressor 1000 further includes a support 260, two vacuum boxes 210, a plurality of ion pumps 220 and a molecular pump (not shown). It can be understood that the vacuum box 210 can be used to provide an ultra-high vacuum clean environment. The two vacuum boxes 210 and the ion pump 220 can be installed on the support 260. Each vacuum box 210 can be connected to a molecular pump and an ion pump 220, and the vacuum box 210 can be evacuated by the molecular pump and the ion pump 220. For example, the vacuum in the vacuum box 210 can be set to 10 -8 In some embodiments, a vacuum gauge 250 is further disposed on the vacuum box 210 , which can be used to detect the vacuum degree in the vacuum box 210 .

[0061] The first asymmetric cut crystal 111 and the first concave reflector 121 may be installed in one vacuum box 210. The second concave reflector 122 and the second asymmetric cut crystal 112 may be installed in another vacuum box 210. An optical channel 230 may be provided between the two vacuum boxes 210 for optical transmission between the first concave reflector 121 and the second concave reflector 122. In the embodiment, a gate valve 240 may be provided on the optical channel 230. When the device in one vacuum box 210 needs to be repaired, the gate valve 240 may be used to disconnect the connection between the two vacuum boxes 210 to ensure the vacuum degree in the other vacuum box 210.

[0062] In some embodiments, a light input channel 211 is further provided on the vacuum box 210 for mounting the first asymmetric cut crystal 111 and the first concave reflector 121, which can be used for input of the down-chirped hard X-ray free electron laser pulse 2000, and the light input channel 211 can be opposite to the light channel 230. In contrast, a light output channel 212 can be further provided on the other vacuum box 210, which can be used for output of the hard X-ray attosecond free electron laser pulse 3000, and the light output channel 212 can also be opposite to the light channel 230.

[0063] like Figure 3 As shown, in some embodiments, the vacuum box 210 may also be provided with an observation window 213 , which can be used by the user to view the postures of the asymmetrically cut crystal 110 and the concave reflector 120 .

[0064] like Figure 1 , Figure 3 and Figure 4 As shown, the positive group velocity dispersion crystal pulse compressor 1000 further includes two sets of first attitude adjustment mechanisms 300 and two sets of second attitude adjustment mechanisms 400. Two asymmetric cut crystals 110 are mounted on the two first attitude adjustment mechanisms 300 in a one-to-one correspondence, and the attitude of the asymmetric cut crystals 110 can be adjusted by the first attitude adjustment mechanisms 300. Two concave reflectors 120 are mounted on the two second attitude adjustment mechanisms 400 in a one-to-one correspondence, and the attitude of the concave reflectors 120 can be adjusted by the second attitude adjustment mechanisms 400.

[0065] It can be understood that the first posture adjustment mechanism 300 for installing the first asymmetric cut crystal 111 can be closer to the light entrance channel 211 relative to the second posture adjustment mechanism 400 for installing the first concave reflector 121. The first posture adjustment mechanism 300 for installing the second asymmetric cut crystal 112 can be closer to the light exit channel 212 relative to the second posture adjustment mechanism 400 for installing the second concave reflector 122.

[0066] In the embodiment, the structures of the two first posture adjustment mechanisms 300 may be set to be the same.

[0067] Combined with Figures 5 to 7 The first posture adjustment mechanism 300 may include a first leveling unit 310 and a first swing unit 320. The first swing unit 320 is mounted on the first leveling unit 310, and the asymmetric cut crystal 110 may be mounted on the first swing unit 320. The first leveling unit 310 may be used to level the asymmetric cut crystal 110 before the positive group velocity dispersion crystal pulse compressor 1000 is used, so that the asymmetric cut crystal 110 is horizontal in the initial state with its central axis parallel to the optical axis. The first swing unit 320 may be used to drive the asymmetric cut crystal 110 to rotate, so as to adjust the inclination angle of the asymmetric cut crystal 110 relative to the optical axis of the down-chirped hard X-ray free electron laser pulse 2000.

[0068] In some embodiments, the first leveling unit 310 includes a first support plate 311 and a second support plate 312. The first support plate 311 is a rectangular plate structure or a square plate structure. During normal use of the positive group velocity dispersion crystal pulse compressor 1000, the first support plate 311 can be roughly parallel to the horizontal direction. In an embodiment, two sides of the first support plate 311 can be parallel to the x-axis, and the other two sides of the first support plate 311 can be parallel to the y-axis.

[0069] The first support plate 311 may be connected to three adjusting bolts 313. The three adjusting bolts 313 may be distributed in a triangular shape, wherein two adjusting bolts 313 are located at two adjacent angular positions of the first support plate 311, and another adjusting bolt 313 is located at the middle of the opposite side of the first support plate 311. A nut 317 may be fixedly connected to the corresponding position of the first support plate 311, and the adjusting bolt 313 may be screwed to the nut 317 at the corresponding position and protrude relative to the side of the first support plate 311 close to the bottom plate of the vacuum box 210. It can be understood that the adjusting bolt 313 may abut against the bottom plate of the vacuum box 210. By adjusting the length of the adjusting bolt 313 extending relative to the side of the first support plate 311 close to the bottom plate of the vacuum box 210, the distance between the corresponding position of the first support plate 311 and the bottom plate of the vacuum box 210 can be adjusted. By adjusting the three adjusting bolts 313 at the same time, the overall height of the first support plate 311 can be adjusted. When an adjusting bolt 313 is adjusted, the first support plate 311 can be swung around the x-axis or y-axis. Thus, the position of the asymmetrically cut crystal 110 in the z-axis direction, as well as the position around the x-axis and around the y-axis can be adjusted.

[0070] In addition, the first support plate 311 may also be connected to the bottom plate of the vacuum box 210 via three fixing bolts 314 , and the three fixing bolts 314 and the three adjusting bolts 313 are alternately arranged.

[0071] The second support plate 312 can be placed flat on the first support plate 311. The second support plate 312 can also be a rectangular plate structure or a square plate structure. Each side of the second support plate 312 can be parallel to the side of the first support plate 311 at a relative position. The first leveling unit 310 also includes at least four mounting blocks 315. Exemplarily, the first leveling unit 310 may include four mounting blocks 315, and the four mounting blocks 315 are respectively arranged at four positions in the circumferential direction of the second support plate 312, and are respectively opposite to the middle of the corresponding side of the second support plate 312. The four mounting blocks 315 can be fixed to the first support plate 311 by screw connection, welding, clamping, etc.

[0072] In the embodiment, at least one limiting bolt 316 is screwed to each of the four mounting blocks 315. For example, two limiting bolts 316 are screwed to each of the mounting blocks 315, and the head of the limiting bolt 316 is located on the side of the mounting block 315 away from the second support plate 312. The side of the limiting bolt 316 close to the second support plate 312 can abut against the side wall of the second support plate 312. In use, the position of the second support plate 312 on the x-axis or y-axis can be adjusted by rotating the limiting bolt 316 on the corresponding side of the second support plate 312. In this way, the position of the asymmetrically cut crystal 110 on the x-axis and y-axis can be adjusted.

[0073] Thus, the asymmetric cut crystal 110 can be driven to move in five dimensions through the first leveling unit 310 to achieve five-dimensional adjustment.

[0074] In other embodiments, the first leveling unit 310 may further include six, eight, or other number of mounting blocks 315 .

[0075] Combined with Figure 7 The first swing table unit 320 may include a base 321, a first driving member 322, an adapter plate 323 and a gear transmission assembly (not shown). The base 321 is fixedly mounted on the second support plate 312. The adapter plate 323 is slidably mounted on the side of the base 321 away from the second support plate 312, and the asymmetric cut crystal 110 may be fixedly mounted on the side of the adapter plate 323 away from the base 321 through a fixture 324. It can be understood that the asymmetric cut crystal 110 may be exposed relative to the side of the fixture 324 away from the adapter plate 323.

[0076] In some embodiments, a curved guide rail 3211 extending along the x-axis direction is provided on one side of the base 321 close to the adapter plate 323, and the middle portion of the curved guide rail 3211 is recessed toward the second support plate 312. The adapter plate 323 can be slidably matched with the curved guide rail 3211, and the adapter plate 323 can move along the curved guide rail 3211, thereby driving the asymmetric cut crystal 110 to rotate around the y-axis to adjust the angle between the asymmetric cut crystal 110 and the optical axis of the down-chirped hard X-ray free electron laser pulse 2000. In an embodiment, the shape of the adapter plate 323 close to the base 321 can be adapted to the curved guide rail 3211.

[0077] In some embodiments, a motor can be used for the first driving member 322. The first driving member 322 can be fixedly mounted on one end of the base 321. The output shaft of the first driving member 322 can extend between the base 321 and the adapter plate 323, and the output shaft of the first driving member 322 can be rotatably connected to the adapter plate 323 through a gear transmission assembly, so that the first driving member 322 can drive the adapter plate 323 to move along the guide rail.

[0078] In some embodiments, the gear transmission assembly may include a bevel gear set, a flat gear and a rack. Among them, a bevel gear in the bevel gear set is fixedly connected to the output shaft of the first driving member 322, and the bevel gear set can realize the steering of the power output direction of the first driving member 322. The flat gear can be fixedly connected to another bevel gear of the bevel gear set to realize power transmission. The rack can be fixedly arranged on the side of the adapter plate 323 close to the base 321 along the sliding direction of the adapter plate 323, and the rack is meshed with the flat gear. In this way, power transmission between the first driving member 322 and the adapter plate 323 can be realized, and the first driving member 322 drives the adapter plate 323 to move, thereby driving the asymmetric cut crystal 110 to rotate around the y-axis, so as to realize the adjustment of the angle between the asymmetric cut crystal 110 and the optical axis of the down-chirped hard X-ray free electron laser pulse 2000.

[0079] In other embodiments, the output shaft of the first driving member 322 may be parallel to the y-axis direction, and the output shaft of the first driving member 322 may be meshed and connected with the rack on the adapter plate 323 via a flat gear.

[0080] In the embodiment, the first swing unit 320 can be used to drive the asymmetrically cut crystal 110 to rotate 0° to 90°, with a rotation accuracy of 0.05 arc seconds.

[0081] like Figure 4 and Figure 8 As shown, in some embodiments, the structures of the two second posture adjustment mechanisms 400 may also be set to be the same.

[0082] The second posture adjustment mechanism 400 may include a second leveling unit 410, a slide unit 420, a movable frame 430, and a second swing unit 440. The second leveling unit 410 is mounted on the bottom plate of the vacuum box 210, the movable frame 430 is slidably mounted on the second leveling unit 410 through the slide unit 420, the second swing unit 440 is mounted on one end of the movable frame 430 away from the slide unit 420, and the concave reflector 120 may be mounted on the second swing unit 440.

[0083] Combined with Figure 5 In the embodiment, the second leveling unit 410 can be used to level the concave reflecting mirror 120 before the positive group velocity dispersion crystal pulse compressor 1000 is used, so that the concave reflecting mirror 120 is horizontally parallel to the central axis of the optical axis in the initial state. In some embodiments, the specific structure of the second leveling unit 410 can be the same as the specific structure of the first leveling unit 310, which will not be repeated here.

[0084] like Figure 8 and Fig. 9As shown, the slide unit 420 can be used to drive the concave reflecting mirror 120 to approach or move away from the adjacent asymmetric cut crystal 110 to adjust the distance between the concave reflecting mirror 120 and the adjacent asymmetric cut crystal 110 .

[0085] The slide unit 420 may include a mounting base 421, a second driving member 422, a transmission rod 423 and a slider (i.e., a first slider 424). The transmission rod 423 is transmission-connected between the first slider 424 and the second driving member 422, and the first slider 424 may be fixedly connected to an end of the movable frame 430 away from the second swing unit 440. Thus, the movable frame 430 may be driven to move by the second driving member 422.

[0086] In some embodiments, the second driving member 422 may be a motor, and the transmission rod 423 may be a lead screw. In the embodiment, the mounting base 421 is fixedly mounted on the second support plate 312 in the second leveling unit 410. The second driving member 422 may be fixedly mounted on one end of the mounting base 421. The transmission rod 423 is rotatably mounted on the mounting base 421, and the transmission rod 423 is transmission-connected to the output shaft of the second driving member 422, and the transmission rod 423 is driven to rotate by the second driving member 422. In the embodiment, the transmission rod 423 may extend along the x-axis direction. The first slider 424 may be connected to the transmission rod 423 through a lead screw nut.

[0087] In the embodiment, two first slide rails 4211 are protrudingly provided on one side of the mounting base 421 close to the transmission rod 423. The two first slide rails 4211 are respectively provided on both sides of the transmission rod 423, and the two first slide rails 4211 are parallel to the transmission rod 423. Both ends of the first slider 424 can be slidably matched with the first slide rails 4211 on the corresponding side.

[0088] During use, the second driving member 422 can drive the transmission rod 423 to rotate, thereby driving the first slider 424 to move along the transmission rod 423, and the first slider 424 drives the movable frame 430, the second swing unit 440 and the concave reflector 120 to approach or move away from the asymmetrically cut crystal 110.

[0089] In other embodiments, the second driving member 422 may also be a cylinder, an electric push rod or other structural members.

[0090] like Figures 7 to 9 As shown, the movable frame 430 may be a rectangular frame structure. The middle of the movable frame 430 is a hollow structure, and the side of the movable frame 430 close to the asymmetric cut crystal 110 and the side away from the asymmetric cut crystal 110 are both open structures, so that the light path can pass smoothly.

[0091] The second swing unit 440 can be used to drive the concave reflector 120 to rotate to adjust the inclination angle of the concave reflector 120 relative to the optical axis of the down-chirped hard X-ray free electron laser pulse 2000. In the embodiment, the specific structure of the second swing unit 440 can be the same as that of the first swing unit 320, which will not be repeated here.

[0092] The second swing unit 440 is installed at one end of the movable frame 430 away from the slide unit 420 and is located on the inner side of the movable frame 430. The adapter plate 323 in the second swing unit 440 can be arranged close to one side of the slide unit 420, and correspondingly, the concave reflector 120 can also be fixedly installed on one side of the adapter plate 323 close to the slide unit 420 through a fixture 324. In the embodiment, the second swing unit 440 can be used to drive the concave reflector 120 to rotate around the y-axis to adjust the angle between the concave reflector 120 and the optical axis of the down-chirped hard X-ray free electron laser pulse 2000.

[0093] In the embodiment, the positive group velocity dispersion crystal pulse compressor 1000 also includes a controller (not shown), which is electrically connected to the electrical components in the positive group velocity dispersion crystal pulse compressor 1000, respectively, and the operation of each electrical component in the positive group velocity dispersion crystal pulse compressor 1000 can be controlled by the controller.

[0094] like Figure 3 , Figure 4 and Fig.10 As shown, the positive group velocity dispersion crystal pulse compressor 1000 also includes one or two sets of spot detection mechanisms 500. Before using the positive group velocity dispersion crystal pulse compressor 1000, it is usually necessary to adjust the posture of the asymmetric cut crystal 110 and the concave reflector 120. In the process of adjusting the posture of the asymmetric cut crystal 110 and the concave reflector 120, a coarse adjustment can be performed with the help of an X-ray tube or a synchrotron radiation light source. After the coarse adjustment is completed, a working down-chirped hard X-ray free electron laser pulse 2000 is used for fine adjustment. The spot detection mechanism 500 can be used to feedback the position information of the spot during the coarse adjustment and fine adjustment process, so that the controller controls the first posture adjustment mechanism 300 and the second posture adjustment mechanism 400 to operate according to the feedback spot position information, so as to adjust the posture of the asymmetric cut crystal 110 and the posture of the concave reflector 120 respectively.

[0095] In some embodiments, the positive group velocity dispersion crystal pulse compressor 1000 includes two sets of light spot detection mechanisms 500 , and the two sets of light spot detection mechanisms 500 are respectively installed on two vacuum boxes 210 .

[0096] In other embodiments, the positive group velocity dispersion crystal pulse compressor 1000 may include a set of spot detection mechanisms 500, and the spot detection mechanisms 500 may be detachably connected to the vacuum box 210. The user may install the spot detection mechanisms 500 on the corresponding vacuum box 210 as needed to adjust the postures of the asymmetric cut crystal 110 and the concave reflector 120 in the vacuum box 210.

[0097] In an embodiment, the structures of the two sets of light spot detection mechanisms 500 may be set to be the same.

[0098] The spot detection mechanism 500 may include a scintillation crystal 510, a reflector 520, a spot detector 530 and a lifting assembly 540. The lifting assembly 540 includes a third driving member 541, a mounting frame 542, a second slide rail 543, a second slider 544, a connecting rod 545 and a mounting seat 546. The second slide rail 543 is fixedly mounted on the top of the vacuum box 210 through the mounting frame 542 and is located outside the vacuum box 210. In an embodiment, the extension direction of the second slide rail 543 may be parallel to the z-axis. The third driving member 541 may be mounted on one end of the second slide rail 543 away from the vacuum box 210. One end of the connecting rod 545 may be transmission-connected to the output shaft of the third driving member 541 through the second slider 544, and the second slider 544 is slidably mounted on the second slide rail 543. The other end of the connecting rod 545 extends into the vacuum box 210 and can be telescopic relative to the vacuum box 210. In some embodiments, the third driving member 541 may be a motor. The output shaft of the third driving member 541 can be connected to the second sliding block 544 via a screw nut pair.

[0099] In other embodiments, the third driving member 541 may also be a cylinder, an electric push rod or other structures.

[0100] In the embodiment, the third driving member 541 can drive the second slider 544 to slide along the second slide rail 543, so as to drive the connecting rod 545 to extend and retract along the z-axis relative to the vacuum box 210. The mounting seat 546 can be fixedly connected to the end of the connecting rod 545 away from the second slider 544, that is, the mounting seat 546 is located in the vacuum box 210. Along the x-axis direction, the mounting seat 546 can be located between the concave reflector 120 and the light channel 230.

[0101] In an embodiment, the scintillation crystal 510 may be fixedly mounted on a side of the mounting base 546 close to the concave reflector 120, and the reflector 520 may be mounted on a side of the mounting base 546 away from the concave reflector 120. In some embodiments, the scintillation crystal 510 may be perpendicular to the x-axis. The reflector 520 may be tilted 45° relative to the optical axis of the down-chirped hard X-ray free electron laser pulse 2000. The reflector 520 may be opposite to the light emitting side of the scintillation crystal 510.

[0102] The light spot detector 530 may be installed at one end of the vacuum box 210 close to the light channel 230. The signal input axis of the light spot detector 530 may be perpendicular to the outgoing light path of the concave reflector 120 and located at the same height.

[0103] When the asymmetric cut crystal 110 and the concave reflector 120 need to be adjusted in posture, the scintillation crystal 510 can be positioned on the outgoing light path of the concave reflector 120 by the lifting assembly 540, and the spot detector 530 is opposite to the reflector 520. The pulse emitted from the concave reflector 120 can be projected onto the scintillation crystal 510 and generate fluorescence, which can be projected onto the reflector 520 and projected onto the lens of the spot detector 530 after being reflected by the reflector 520. Subsequently, the lens in the spot detector 530 can transmit the light beam to the CCD photosensitive element to obtain the position information of the light spot. Subsequently, the controller can control the first posture adjustment mechanism 300 and the second posture adjustment mechanism 400 to move according to the position information of the light spot to achieve the posture adjustment of the asymmetric cut crystal 110 and the concave reflector 120. When the adjustment is completed, the lifting assembly 540 can drive the scintillation crystal 510 and the reflector 520 to move upward to avoid the light path between the concave reflector 120 and the optical channel 230.

[0104] like Figure 4 , Figure 7 and Figure 8 As shown, the positive group velocity dispersion crystal pulse compressor 1000 further includes a cooling mechanism 600, which can be used to reduce the deformation of the asymmetric cut crystal 110 and the concave reflector 120 under high heat load, and make the center displacement of the crystal rocking curve caused by the deformation of the asymmetric cut crystal 110 not exceed half the Darwin width. Before using the positive group velocity dispersion crystal pulse compressor 1000, the temperature of the asymmetric cut crystal 110 can also be brought to a thermal equilibrium state by the cooling mechanism 600.

[0105] In some embodiments, the cooling mechanism 600 may include a cold source (not shown) and a plurality of cold medium transmission tubes 610. One end of the plurality of cold medium transmission tubes 610 may be connected to the asymmetric cut crystal 110 and the concave reflector 120 in a one-to-one correspondence by thermal conduction to absorb the heat of the asymmetric cut crystal 110 and the concave reflector 120. The other end of the cold medium transmission tube 610 may be connected to the cold source by thermal conduction to dissipate the heat through the cold source. The cold source may be a device such as liquid nitrogen or water cooling.

[0106] In the embodiment, a flow channel (not shown) connected to the refrigerant transmission pipe 610 may be provided inside the fixture 324 for the refrigerant to pass through. It is understandable that the refrigerant transmission pipe 610 may form a circulation loop with the flow channel in the fixture 324. The refrigerant with a lower temperature is transported to the flow channel of the fixture 324 through the refrigerant transmission pipe 610, and absorbs the heat generated by the asymmetric cut crystal 110 or the concave reflector 120. The refrigerant after absorbing the heat can be transported back to the cold source through the refrigerant transmission pipe 610 to release the heat for cooling.

[0107] The present application provides a positive group velocity dispersion crystal pulse compressor 1000, which can be used to compress down-chirped hard X-ray free electron laser pulses 2000 and output hard X-ray attosecond free electron laser pulses 3000. The positive group velocity dispersion crystal pulse compressor 1000 provided by the present application only needs to be installed on the beam line of the hard X-ray free electron laser device, and will not cause disruptive changes to the front-end equipment (such as accelerators, electron bunch compressors, etc.), and is simpler and more convenient to use.

[0108] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0109] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A positive group velocity dispersion crystal pulse compressor, characterized in that: Used to compress down-chirped hard X-ray free electron laser pulses to generate hard X-ray attosecond free electron laser pulses, the positive group velocity dispersion crystal pulse compressor comprises a first asymmetric cut crystal, a first concave reflector, a second concave reflector and a second asymmetric cut crystal arranged in sequence along an optical path; The first asymmetric cut crystal is used to disperse the down-chirped hard X-ray free electron laser pulse to form a multi-path pulse, and the multi-path pulse is reflected by the first concave reflector and the second concave reflector in sequence and then projected to the second asymmetric cut crystal, and the multi-path pulse is merged at the second asymmetric cut crystal to form the hard X-ray attosecond free electron laser pulse; The distance between the first asymmetric cut crystal and the first concave reflecting mirror is f1, the distance between the first concave reflecting mirror and the second concave reflecting mirror is (f1+f2), and the distance between the second concave reflecting mirror and the second asymmetric cut crystal is f2′; Wherein, f1 represents the focal length of the first concave reflecting mirror, f2 represents the focal length of the second concave reflecting mirror, and f2′≤f2; The first asymmetric cut crystal and the second asymmetric cut crystal both include crystal faces and physical surfaces; In the same asymmetric cut crystal, the angle η between the crystal plane and the physical surface is smaller than the Bragg angle.

2. The positive group velocity dispersion crystal pulse compressor according to claim 1, characterized in that: The positive group velocity dispersion crystal pulse compressor further includes two sets of first posture adjustment mechanisms, and the first asymmetric cut crystal and the second asymmetric cut crystal are mounted on the two first posture adjustment mechanisms in a one-to-one correspondence; The first posture adjustment mechanism is used to adjust the posture of the asymmetric cut crystal to which it is connected.

3. The positive group velocity dispersion crystal pulse compressor according to claim 2, characterized in that: The first posture adjustment mechanism comprises a first swing unit, and the first swing unit is used to adjust the angle between the asymmetrically cut crystal and the optical axis of the down-chirped hard X-ray free electron laser pulse; The first swing table unit includes a base, a first driving member and an adapter plate, one side of the base is provided with an arc-shaped guide rail, the adapter plate is slidably matched with the arc-shaped guide rail, the first driving member is transmission-connected with the adapter plate, and the asymmetric cut crystal is installed on a side of the adapter plate away from the base; The first driving member is used to drive the adapter plate to move along the arc-shaped guide rail to drive the asymmetric cut crystal to rotate relative to the optical axis of the down-chirped hard X-ray free electron laser pulse.

4. The positive group velocity dispersion crystal pulse compressor according to claim 3, characterized in that: The first posture adjustment mechanism further includes a first leveling unit, which is used to drive the asymmetric cut crystal to move in five dimensions to adjust the asymmetric cut crystal to a level.

5. The positive group velocity dispersion crystal pulse compressor according to claim 1, characterized in that: The positive group velocity dispersion crystal pulse compressor further includes two second posture adjustment mechanisms, the first concave reflecting mirror and the second concave reflecting mirror are mounted on the two second posture adjustment mechanisms in a one-to-one correspondence, and the second posture adjustment mechanism is used to adjust the posture of the concave reflecting mirror connected to itself; The second posture adjustment mechanism includes a second leveling unit, a second swing unit and a slide unit, the slide unit is connected between the second leveling unit and the second swing unit, and the concave reflector is installed on the second swing unit; The second leveling unit is used to level the concave reflecting mirror, the second swing unit is used to adjust the angle between the concave reflecting mirror and the optical axis of the down-chirped hard X-ray free electron laser pulse, and the sliding unit is used to drive the concave reflecting mirror to approach or move away from the asymmetric cut crystal to adjust the distance between the concave reflecting mirror and the asymmetric cut crystal.

6. The positive group velocity dispersion crystal pulse compressor according to claim 5, characterized in that: The slide unit includes a second driving member, a mounting seat, a transmission rod and a slide block; The mounting seat and the second driving member are both fixedly mounted relative to the second leveling unit, the slider is slidably mounted on a side of the mounting seat away from the second leveling unit, the transmission rod is transmission-connected between the second driving member and the slider, and the second swing unit is mounted on the slider via a movable frame; The second driving member is used to drive the slider to slide relative to the mounting seat, so as to drive the concave reflecting mirror to approach or move away from the asymmetric cut crystal.

7. The positive group velocity dispersion crystal pulse compressor according to claim 1, characterized in that: The positive group velocity dispersion crystal pulse compressor also includes a connected cold source and a plurality of refrigerant transmission tubes, wherein the plurality of refrigerant transmission tubes are thermally connected to the first asymmetric cut crystal, the first concave reflector, the second concave reflector and the second asymmetric cut crystal in a one-to-one correspondence.

8. The positive group velocity dispersion crystal pulse compressor according to claim 1, characterized in that: The positive group velocity dispersion crystal pulse compressor further comprises two vacuum boxes, and an optical channel is connected between the two vacuum boxes; The first asymmetric cut crystal and the first concave reflector are installed in a vacuum box, and the first concave reflector is arranged close to one end of the light channel; The second concave reflecting mirror and the second asymmetric cut crystal are installed in another of the vacuum boxes, and the second concave reflecting mirror is arranged close to one end of the light channel.

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