A Negative Group Velocity Dispersion Crystal Pulse Compressor

Abstract

The present application discloses a negative group velocity dispersion crystal pulse compressor, which relates to the field of free electron laser technology. The negative group velocity dispersion crystal pulse compressor includes at least one pair of asymmetric cut crystals, and the two asymmetric cut crystals of the same pair are opposite and parallel; the at least one pair of asymmetric cut crystals is used to make the up-chirped hard X-ray free electron laser pulse generate dispersion to achieve longitudinal compression and output of the hard X-ray attosecond free electron laser pulse. The negative group velocity dispersion crystal pulse compressor provided by the present application can provide a new hard X-ray attosecond free electron laser pulse generation method with higher stability.

Description

Technical Field

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

[0002] Attosecond pulses are an important tool for studying electron dynamics at the atomic scale. With the development of free electron lasers, it has become possible to generate stable, high pulse energy, isolated hard X-ray attosecond pulses.

[0003] In recent years, the generation of hard X-ray attosecond pulses is mainly based on the manipulation of electron bunches, such as local emittance destruction of electron bunches, local orbital mismatch of electron bunches, laser modulation of electron bunches, etc. However, these technologies can only use part of the electron beam, or require synchronous control, resulting in instability when generating hard X-ray attosecond pulses. Summary of the invention

[0004] The present application provides a negative group velocity dispersion crystal pulse compressor, which generates hard X-ray attosecond free electron laser pulses in different ways.

[0005] This application provides:

[0006] A negative group velocity dispersion crystal pulse compressor for compressing up-chirped hard X-ray free electron laser pulses to generate hard X-ray attosecond free electron laser pulses;

[0007] The negative group velocity dispersion crystal pulse compressor comprises at least one pair of asymmetric cut crystals, wherein the two asymmetric cut crystals of the same pair are opposite and parallel;

[0008] The at least one pair of asymmetrically cut crystals is used to disperse the up-chirped hard X-ray free electron laser pulses to achieve longitudinal compression and output of the hard X-ray attosecond free electron laser pulses.

[0009] In some possible implementations, the negative group velocity dispersion crystal pulse compressor includes two pairs of asymmetric cut crystals, and the two pairs of asymmetric cut crystals are symmetrically arranged.

[0010] In some possible implementations, the asymmetrically cut crystal includes a crystal plane and a physical surface, and an angle η between the crystal plane and the physical surface is smaller than a Bragg angle.

[0011] In some possible implementations, the negative group velocity dispersion crystal pulse compressor further includes at least one position adjustment mechanism, on which a pair of the asymmetric cut crystals are mounted;

[0012] The adjustment mechanism is used to adjust the vertical distance d, the dislocation distance m and the tilt angle relative to the optical axis of the up-chirped hard X-ray free electron laser pulse between the two asymmetrically cut crystals in the same pair.

[0013] In some possible implementations, the position adjustment mechanism includes two first driving units, and the two asymmetric cut crystals in the same pair are mounted on the two first driving units in a one-to-one correspondence;

[0014] The first driving unit comprises a first driving member, a first transmission rod and a first adapter plate, the first transmission rod is transmission-connected between the first driving member and the first adapter plate, and the asymmetrically cut crystal is mounted on the first adapter plate;

[0015] The first driving member is used to drive the asymmetric cut crystal connected to it to move so as to adjust the vertical distance d between the two asymmetric cut crystals in the same pair.

[0016] In some possible implementations, the position adjustment mechanism further includes two second driving units;

[0017] The second driving unit comprises a second driving member, a second transmission rod and a second adapter plate, the two first driving units are mounted on the second adapter plates of the two second driving units in a one-to-one correspondence, the second transmission rod is transmission-connected between the second driving member and the second adapter plate, and the second transmission rod is perpendicular to the first transmission rod;

[0018] The second driving member is used to drive the asymmetric cut crystal connected to it to move, so as to adjust the misalignment distance m between the two asymmetric cut crystals of the same pair.

[0019] In some possible implementations, the first driving unit further includes a sliding plate and a plurality of guide wheels, the sliding plate is transmission-connected between the first transmission rod and the first adapter plate, both sides of the sliding plate relative to the first transmission rod are provided with mounting edges, the mounting edges are protruding relative to the second adapter plate, and the plurality of guide wheels are respectively provided on the two mounting edges;

[0020] The second adapter plate is provided with guide flanges on both sides relative to the first transmission rod. The guide flanges are parallel to the first transmission rod. The guide wheel is in rolling engagement with the guide flanges opposite to itself.

[0021] In some possible implementations, the position adjustment mechanism further includes a third driving unit;

[0022] The third driving unit comprises a third driving member, a gear transmission assembly and a third adapter plate, the gear transmission assembly is transmission-connected between the third driving member and the third adapter plate, and both of the second driving units are mounted on the third adapter plate;

[0023] The third driving member is used to drive the third adapter plate to rotate, and drive the two asymmetric cut crystals connected to it to rotate, so as to adjust the inclination angle of the two asymmetric cut crystals relative to the optical axis of the up-chirped hard X-ray free electron laser pulse.

[0024] In some possible implementations, the negative group velocity dispersion crystal pulse compressor further includes a light spot detection mechanism, which includes a scintillation crystal, a reflector, a detector, and a lifting assembly;

[0025] The scintillation crystal and the reflector are connected to the lifting assembly, and the lifting assembly is used to drive the scintillation crystal and the reflector to extend and retract relative to the optical path between the at least one pair of asymmetrically cut crystals;

[0026] When the scintillation crystal and the reflector are located in the optical path between the at least one pair of asymmetric cut crystals, the scintillation crystal is opposite to the output ends of a pair of asymmetric cut crystals close to the input side of the up-chirped hard X-ray free electron laser pulse, and the reflector is used to reflect the fluorescence at the scintillation crystal to the detector.

[0027] In some possible implementations, the negative group velocity dispersion crystal pulse compressor further includes a plurality of heat conducting plates, and the plurality of heat conducting plates are thermally conductively connected to the plurality of asymmetric cut crystals in a one-to-one correspondence.

[0028] The beneficial effects of the present application are as follows: the present application proposes a negative group velocity dispersion crystal pulse compressor, comprising at least one pair of asymmetric cut crystals, which can make up-chirped hard X-ray free electron laser pulses generate dispersion to achieve longitudinal compression and output of hard X-ray attosecond free electron laser pulses. That is, the present application starts from the manipulation of up-chirped hard X-ray free electron laser pulses, uses asymmetric cut crystals as dispersion devices, and provides a new hard X-ray attosecond free electron laser pulse generation method with higher stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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.

[0030] Figure 1 A partial structural schematic diagram of a negative group velocity dispersion crystal pulse compressor in some embodiments is shown;

[0031] Figure 2 A schematic diagram of the main structure of a negative group velocity dispersion crystal pulse compressor in some embodiments is shown;

[0032] Figure 3 A schematic diagram of the three-dimensional structure of a negative group velocity dispersion crystal pulse compressor in some embodiments is shown;

[0033] Figure 4 A schematic diagram of the internal structure of a negative group velocity dispersion crystal pulse compressor in some embodiments is shown;

[0034] Figure 5 A three-dimensional structural schematic diagram of a position adjustment mechanism in some embodiments is shown;

[0035] Figure 6 Another schematic diagram of the three-dimensional structure of the position adjustment structure in some embodiments is shown;

[0036] Figure 7 shows a schematic structural diagram of a second driving unit in some embodiments;

[0037] Figure 8 shows a schematic structural diagram of a first driving unit in some embodiments;

[0038] Fig. 9 A partial structural schematic diagram of a light spot detection mechanism in some embodiments is shown.

[0039] Description of main component symbols:

[0040] 1000-negative group velocity dispersion crystal pulse compressor; 100-vacuum chamber; 110-light inlet channel; 120-light outlet channel; 130-visible window; 210-first asymmetric cut crystal pair; 211-asymmetric cut crystal; 211a-first asymmetric cut crystal; 211b-second asymmetric cut crystal; 2111-crystal surface; 2112-physical surface; 220-second asymmetric cut crystal pair; 300-position adjustment mechanism; 310-first drive unit; 311-first drive member; 312-first transmission rod; 313-first adapter plate; 314-sliding plate; 3141-mounting edge; 315-guide wheel; 320-second drive unit; 321-second drive member; 322-second transmission rod; 323-second adapter plate; 3231-guide flange; 324- The first slider; 325-the first slide rail; 330-the third driving unit; 331-the third driving member; 332-the mounting table; 333-the third adapter plate; 334-the rotating table; 340-the fixed seat; 350-the clamp; 410-the first mounting frame; 420-the base; 430-the ion pump; 440-the vacuum detector; 450-the angle valve; 500-the light spot detection mechanism; 510-the scintillating crystal; 520-the reflector; 530-the detector; 540-the lifting assembly; 541-the fourth driving member; 542-the second mounting frame; 543-the second slide rail; 544-the second slider; 545-the connecting rod; 546-the mounting seat; 600-the cooling mechanism; 610-the heat conducting plate; 2000-the up-chirped hard X-ray free electron laser pulse; 3000-the hard X-ray attosecond free electron laser pulse. DETAILED DESCRIPTION

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] like Figure 3 As shown, a Cartesian coordinate system is established, and it is defined that the length direction of the negative group velocity dispersion crystal pulse compressor 1000 is parallel to the direction shown by the x-axis, the width direction of the negative group velocity dispersion crystal pulse compressor 1000 is parallel to the direction shown by the y-axis, and the height direction of the negative group velocity dispersion crystal pulse compressor 1000 is parallel to the direction shown by the z-axis.

[0047] 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.

[0048] In an embodiment, a negative group velocity dispersion crystal pulse compressor 1000 is provided, which can be used to compress up-chirped hard X-ray free electron laser pulses 2000 to generate hard X-ray attosecond free electron laser pulses 3000.

[0049] like Figure 1As shown, the negative group velocity dispersion crystal pulse compressor 1000 may include at least one pair of asymmetric cut crystals 211. The two asymmetric cut crystals 211 of the same pair are opposite and parallel. The asymmetric cut crystals 211 may be used as dispersion devices.

[0050] In use, at least one pair of asymmetrically cut crystals 211 can cause the up-chirped hard X-ray free electron laser pulses 2000 to produce dispersion and achieve longitudinal compression to generate hard X-ray attosecond free electron laser pulses 3000 .

[0051] In this embodiment, starting from the manipulation of the up-chirped hard X-ray free electron laser pulse 2000, and using the asymmetrically cut crystal 211 as a dispersion device, a pulse compressor applicable to hard X-ray free electron laser is formed. The up-chirped hard X-ray free electron laser pulse 2000 is compressed by the negative group velocity dispersion crystal pulse compressor 1000 to generate a hard X-ray attosecond free electron laser pulse 3000. Compared with the prior art, the scheme for generating the hard X-ray attosecond free electron laser pulse 3000 provided in this embodiment can utilize the photons in the entire electron beam and has higher stability.

[0052] like Figures 1 to 3 As shown, the negative group velocity dispersion crystal pulse compressor 1000 also includes a vacuum chamber 100, a U-shaped base 420, an ion pump 430 and a molecular pump (not shown). Among them, the ion pump 430 can be fixedly installed in the U-shaped groove of the base 420. The vacuum chamber 100 can be fixedly installed on the base 420 and connected to the ion pump 430 and the molecular pump. The ion pump 430 can cooperate with the molecular pump to evacuate the vacuum chamber 100. Exemplarily, before using the negative group velocity dispersion crystal pulse compressor 1000, the vacuum chamber 100 can be evacuated to 10 by the molecular pump and the ion pump 430. -8 Pa.

[0053] In some embodiments, the vacuum chamber 100 may also be connected to a vacuum detector 440 and an angle valve 450. The vacuum detector 440 may be used to detect the vacuum degree in the vacuum chamber 100. The angle valve 450 may be used to control the connection between the vacuum chamber 100 and the external environment. It is understood that the angle valve 450 may be a solenoid valve.

[0054] In the embodiment, the asymmetrically cut crystal 211 is installed in the vacuum chamber 100. The vacuum chamber 100 can be used to provide an ultra-high vacuum clean environment and improve the working accuracy of the negative group velocity dispersion crystal pulse compressor 1000.

[0055] In some embodiments, the vacuum chamber 100 includes a relative and coaxial light input channel 110 and a light output channel 120, and the light input channel 110 and the light output channel 120 are respectively arranged at two opposite ends of the vacuum chamber 100. Among them, the light input channel 110 can be used to connect the emission source of the chirped hard X-ray free electron laser pulse 2000, and the light output channel 120 can be used to output the hard X-ray attosecond free electron laser pulse 3000. In the embodiment, the light input channel 110 and the light output channel 120 can be parallel to the length direction of the negative group velocity dispersion crystal pulse compressor 1000.

[0056] In some embodiments, a visual window 130 is further provided on the vacuum chamber 100 , allowing staff to view the posture of the asymmetrically cut crystal 211 .

[0057] like Figure 1 As shown, the asymmetrically cut crystal 211 may include a crystal plane 2111 and a physical surface 2112. The crystal plane 2111 may be inclined relative to the physical surface 2112 and form an angle η. In an embodiment, the angle η between the crystal plane 2111 and the physical surface 2112 is smaller than the Bragg angle.

[0058] like Figures 1 to 4 As shown, in some embodiments, the negative group velocity dispersion crystal pulse compressor 1000 may include two pairs of asymmetric cut crystals 211, namely a first asymmetric cut crystal pair 210 and a second asymmetric cut crystal pair 220. The first asymmetric cut crystal pair 210 and the second asymmetric cut crystal pair 220 are sequentially arranged between the light input channel 110 and the light output channel 120, and are symmetrical. Among them, the first asymmetric cut crystal 211a is arranged close to the light input channel 110.

[0059] In the embodiment, the first asymmetrically cut crystal pair 210 is taken as an example for detailed description.

[0060] The first asymmetric cut crystal pair 210 may include a first asymmetric cut crystal 211a and a second asymmetric cut crystal 211b that are opposite and parallel to each other. In some embodiments, the first asymmetric cut crystal 211a may be opposite to the light input channel 110 for receiving the up-chirped hard X-ray free electron laser pulse 2000 .

[0061] The two asymmetric cut crystals 211 are both tilted relative to the optical axis of the upper chirped hard X-ray free electron laser pulse 2000, and form an angle α, wherein the angle α can be set between 0° and 90°. It can be understood that the two asymmetric cut crystals 211 are spaced apart, and the vertical distance d between the two asymmetric cut crystals 211 can be set to 5 mm to 30 mm. In addition, the two asymmetric cut crystals 211 can be misaligned with each other. In the embodiment, the tilt angle of the asymmetric cut crystal 211 relative to the optical axis of the upper chirped hard X-ray free electron laser pulse 2000, the vertical distance d between the two asymmetric cut crystals 211, and the two misalignment distances m can be specifically set as needed.

[0062] During operation, the up-chirped hard X-ray free electron laser pulse 2000 with a tilted wavefront is input through the light input channel 110. After passing through the first asymmetric cut crystal pair 210, the up-chirped hard X-ray free electron laser pulse 2000 may be dispersed and longitudinally compressed. It can be understood that the light with different frequencies in the lateral direction of the compressed pulse is still in a separated state, that is, there is lateral dispersion. Subsequently, the wavefront tilt can be compensated by the second asymmetric cut crystal pair 220, and the laterally separated light beams are mixed together to output the hard X-ray attosecond free electron laser pulse 3000. Accordingly, the hard X-ray attosecond free electron laser pulse 3000 does not have lateral dispersion.

[0063] Combined with Figures 4 to 8 The negative group velocity dispersion crystal pulse compressor 1000 further includes two position adjustment mechanisms 300, which are arranged in the vacuum chamber 100 at intervals. The two asymmetric cut crystal pairs are mounted on the two position adjustment mechanisms 300 in a one-to-one correspondence. The position adjustment mechanisms 300 can be used to adjust the vertical distance d between the two asymmetric cut crystals 211 in the same pair, the misalignment distance m between the two asymmetric cut crystals 211, and the angle α between the two asymmetric cut crystals 211 and the optical axis of the up-chirped hard X-ray free electron laser pulse 2000.

[0064] In the embodiment, the structures of the two position adjustment mechanisms 300 may be set to be symmetrical, and a detailed description will be given by taking the position adjustment mechanism 300 close to the light incident channel 110 as an example.

[0065] The position adjustment mechanism 300 may include two first drive units 310, two second drive units 320 and a third drive unit 330. The two asymmetric cut crystals 211 in the first asymmetric cut crystal pair 210 are mounted on the two first drive units 310 in a one-to-one correspondence, the two first drive units 310 are mounted on the two second drive units 320 in a one-to-one correspondence, and the two second drive units 320 are both mounted on the third drive unit 330.

[0066] In the embodiment, the third driving unit 330 is used to drive the first asymmetric cut crystal pair 210 to rotate so as to adjust the angle α between the two asymmetric cut crystals 211 and the optical axis of the up-chirped hard X-ray free electron laser pulse 2000. In the embodiment, the rotation axis of the two asymmetric cut crystals 211 is parallel to the width direction of the negative group velocity dispersion crystal pulse compressor 1000. The two second driving units 320 can be used to drive the two asymmetric cut crystals 211 to move respectively so as to adjust the misalignment distance m between the two asymmetric cut crystals 211. The two first driving units 310 can be used to drive the two asymmetric cut crystals 211 to move closer to or farther from each other so as to adjust the vertical distance d between the two asymmetric cut crystals 211.

[0067] In the embodiment, the direction in which the asymmetric cut crystal 211 is driven to move by the first driving unit 310 may be perpendicular to the physical surface 2112. The direction in which the asymmetric cut crystal 211 is driven to move by the second driving unit 320 may be parallel to the physical surface 2112 and perpendicular to the direction in which the asymmetric cut crystal 211 is driven to move by the first driving unit 310. In addition, the direction in which the asymmetric cut crystal 211 is driven to move by the first driving unit 310 and the direction in which the asymmetric cut crystal 211 is driven to move by the second driving unit 320 are both perpendicular to the width direction of the negative group velocity dispersion crystal pulse compressor 1000.

[0068] like Figure 1 , Figures 4 to 6 As shown, the third driving unit 330 may include a third driving member 331, a gear transmission assembly (not shown), a third adapter plate 333 and a mounting platform 332. The mounting platform 332 is fixedly mounted on the bottom plate of the vacuum chamber 100 through an L-shaped first mounting frame 410, and the mounting platform 332 may be located at an end of the first mounting frame 410 away from the bottom plate of the vacuum chamber 100. The third driving member 331 is fixedly mounted on a side of the mounting platform 332 close to the first mounting frame 410.

[0069] The gear transmission assembly may include two meshingly connected gears, both of which are rotatably mounted on the mounting platform 332. One of the gears may be fixedly connected to the output shaft of the third driving member 331. The other gear may be fixedly connected to the rotating platform 334. The third adapter plate 333 may be fixedly connected to the rotating platform 334. In an embodiment, the third adapter plate 333 is perpendicular to the width direction of the negative group velocity dispersion crystal pulse compressor 1000. The two second driving units 320 may be mounted on a side of the third adapter plate 333 away from the first mounting bracket 410. In some embodiments, the third driving member 331 may be a motor.

[0070] During use, the third driving member 331 can drive the gear transmission assembly to drive the rotating table 334 and the third adapter plate 333 to rotate, and then drive the two asymmetric cut crystals 211 in the first asymmetric cut crystal pair 210 to rotate synchronously, so as to synchronously adjust the angle α between the two asymmetric cut crystals 211 and the optical axis of the chirped hard X-ray free electron laser pulse 2000 to satisfy the Bragg formula.

[0071] In the embodiment, the rotation range of the two asymmetric cut crystals 211 driven by the third driving unit 330 can be set to 0° to 90°, and the adjustment accuracy is 0.05 arc seconds. It can be understood that in the process of the third driving unit 330 driving the two asymmetric cut crystals 211 to rotate synchronously, the light incident side of the first asymmetric cut crystal 211a can face the side of the light incident channel 110.

[0072] Combined with Figure 7 The two second drive units 320 may be arranged along the radial direction of the third adapter plate 333 and disposed on a side of the third adapter plate 333 away from the first mounting bracket 410, and may be symmetrical about the rotation axis of the third adapter plate 333. In some embodiments, the structures of the two second drive units 320 may be arranged to be symmetrical.

[0073] The second drive unit 320 may include a second drive member 321, a second transmission rod 322, a second adapter plate 323, a first slider 324, and a first slide rail 325. In some embodiments, the second drive member 321 may be a motor, and the second transmission rod 322 may be a lead screw. The second drive member 321 is fixedly mounted on the third adapter plate 333. One end of the second transmission rod 322 is fixedly connected to the output shaft of the second drive member 321. One end of the first slider 324 may be connected to the second transmission rod 322 via a lead screw nut. In some embodiments, the extension direction of the second transmission rod 322 may be parallel to the third adapter plate 333 and the physical surface 2112 at the same time, and the two second transmission rods 322 in the two second drive units 320 are coaxial.

[0074] The first slide rail 325 can also be fixedly mounted on the third adapter plate 333, and the first slide rail 325 is arranged in parallel on one side of the second transmission rod 322, that is, the first slide rail 325 is parallel to the second transmission rod 322. The end of the first slider 324 away from the second transmission rod 322 can be slidably matched with the first slide rail 325. The second adapter plate 323 is fixedly connected to the side of the first slider 324 away from the first slide rail 325. The first driving unit 310 can be installed on the side of the second adapter plate 323 away from the first slider 324.

[0075] During operation, the second driving member 321 can drive the second transmission rod 322 to rotate, thereby driving the first slider 324 to drive the second adapter plate 323 to move along the second transmission rod 322, and the second adapter plate 323 can drive the first driving unit 310 and the corresponding asymmetric cut crystal 211 to move synchronously. When the two second driving units 320 drive the two asymmetric cut crystals 211 to move, the two asymmetric cut crystals 211 can move toward or away from each other, and the offset distance m between the two asymmetric cut crystals 211 can be adjusted.

[0076] In other embodiments, the second driving member 321 does not exclude the use of structures such as a cylinder and an electric push rod.

[0077] Combined with Figure 8 The two first drive units 310 are mounted on the two second adapter plates 323 in a one-to-one correspondence and are arranged opposite to each other. In the embodiment, the structures of the two first drive units 310 can be arranged to be the same.

[0078] The first drive unit 310 may include a first drive member 311, a first transmission rod 312, a first adapter plate 313 and a sliding plate 314. In some embodiments, the first drive member 311 may be a motor, and the first transmission rod 312 may be a lead screw. The first drive member 311 is fixedly mounted on the second adapter plate 323. One end of the first transmission rod 312 is fixedly connected to the output shaft of the first drive member 311. The extension direction of the first transmission rod 312 may be parallel to the third adapter plate 333, and the extension direction of the first transmission rod 312 is perpendicular to the extension direction of the second transmission rod 322. In the embodiment, the first transmission rods 312 in the two first drive units 310 may be arranged in parallel.

[0079] The sliding plate 314 can also be connected to the first transmission rod 312 through a lead screw nut, and the sliding plate 314 can move along the first transmission rod 312. The first adapter plate 313 is fixedly connected to the side of the sliding plate 314 away from the second adapter plate 323. The asymmetric cut crystal 211 can be embedded in a fixture 350. It can be understood that the light incident side of the asymmetric cut crystal 211 is exposed relative to the fixture 350. The fixture 350 is installed on the side of the first adapter plate 313 away from the sliding plate 314 through a fixing seat 340.

[0080] In the embodiment, the first adapter plate 313 may be an L-shaped plate. The first adapter plates 313 in the two first driving units 310 are arranged opposite to each other. The asymmetric cut crystal 211 may be installed on a side of the first adapter plate 313 opposite to the other first adapter plate 313. Accordingly, the two asymmetric cut crystals 211 in the first asymmetric cut crystal pair 210 may be arranged opposite to each other.

[0081] like Figure 7 and Figure 8As shown, further, the sliding plate 314 is provided with a mounting edge 3141 protruding on both sides relative to the first transmission rod 312. In the embodiment, the mounting edge 3141 may protrude relative to the side of the second adapter plate 323. The first drive unit 310 also includes a plurality of guide wheels 315. Exemplarily, the first drive unit 310 may include four guide wheels 315. The four guide wheels 315 may be evenly distributed on both sides of the sliding plate 314 relative to the first transmission rod 312. The guide wheels 315 may be rotatably connected to the mounting edge 3141 on the corresponding side, and are located on the side of the mounting edge 3141 close to the second adapter plate 323.

[0082] In other embodiments, the guide wheels 315 may also be provided in a number of two, three, five, six, etc.

[0083] Correspondingly, a guide flange 3231 is protruded on both sides of the second adapter plate 323 relative to the first transmission rod 312, and the guide flange 3231 is parallel to the first transmission rod 312. The guide wheels 315 located on both sides of the sliding plate 314 can roll with the guide flange 3231 opposite to the guide wheel 315. When the first driving member 311 drives the sliding plate 314 to move, the guide flange 3231 and the guide wheel 315 can cooperate to guide it, and the stability of the movement can also be improved.

[0084] During operation, the first driving member 311 can drive the first transmission rod 312 to rotate, so as to drive the sliding plate 314 to drive the first adapter plate 313 to move along the first transmission rod 312 , thereby driving the asymmetric cut crystal 211 to move.

[0085] When the two first driving units 310 drive the two asymmetric cut crystals 211 to move, the two asymmetric cut crystals 211 can move closer to or farther from each other to adjust the vertical distance d between the two asymmetric cut crystals 211. In some embodiments, the adjustment accuracy of the two first driving units 310 when driving the two asymmetric cut crystals 211 to move is 50nm.

[0086] It can be understood that the negative group velocity dispersion crystal pulse compressor 1000 may also include a control mechanism (not shown), which may be electrically connected to the electrical components in the negative group velocity dispersion crystal pulse compressor 1000. Thus, the control mechanism may uniformly control the operation of each electrical component in the negative group velocity dispersion crystal pulse compressor 1000.

[0087] like Figure 4 and Fig. 9As shown, the negative group velocity dispersion crystal pulse compressor 1000 also includes a spot detection mechanism 500. Before using the negative group velocity dispersion crystal pulse compressor 1000, it is usually necessary to adjust the posture of the asymmetric cut crystal 211. During the adjustment process of the asymmetric cut crystal 211, 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, fine adjustment is performed using the working up-chirped hard X-ray free electron laser pulse 2000. 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 action of the position adjustment mechanism 300 according to the feedback spot position information to adjust the posture of the asymmetric cut crystal 211.

[0088] In some embodiments, the light spot detection mechanism 500 may include a scintillation crystal 510 , a reflector 520 , a detector 530 , and a lifting assembly 540 .

[0089] The lifting assembly 540 includes a fourth driving member 541, a second 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 chamber 100 through the second mounting frame 542 and is located outside the vacuum chamber 100. In an embodiment, the extension direction of the second slide rail 543 can be parallel to the height direction of the negative group velocity dispersion crystal pulse compressor 1000. The fourth driving member 541 can be mounted on an end of the second slide rail 543 away from the vacuum chamber 100. One end of the connecting rod 545 can be connected to the output shaft of the fourth 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 chamber 100 and can be retracted relative to the vacuum chamber 100. In some embodiments, the fourth driving member 541 can be a motor. The output shaft of the fourth driving member 541 can be connected to the second slider 544 through a screw nut pair.

[0090] In other embodiments, the fourth driving member 541 may also be a cylinder, an electric push rod or other structures.

[0091] In the embodiment, the fourth 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 height direction of the negative group velocity dispersion crystal pulse compressor 1000 relative to the vacuum chamber 100. 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 chamber 100. The mounting seat 546 can be located between the two position adjustment mechanisms 300, that is, the mounting seat 546 is located between the two asymmetric cut crystal pairs. In the embodiment, the scintillation crystal 510 can be fixedly mounted on the side of the mounting seat 546 close to the first asymmetric cut crystal pair 210, and the reflector 520 can be mounted on the side of the mounting seat 546 close to the second asymmetric cut crystal pair 220. In some embodiments, the scintillation crystal 510 can be perpendicular to the length direction of the negative group velocity dispersion crystal pulse compressor 1000. The reflector 520 can be tilted 45° relative to the optical axis of the up-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 .

[0092] When the negative group velocity dispersion crystal pulse compressor 1000 needs to be debugged, the scintillation crystal 510 and the reflector 520 can be moved between the two asymmetric cut crystal pairs through the lifting assembly 540, and the scintillation crystal 510 can be opposite to the output end of the first asymmetric cut crystal pair 210, and the detector 530 can be opposite to the reflector 520.

[0093] The pulse output from the first asymmetric cut crystal 211a 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 detector 530 after being reflected by the reflector 520. Subsequently, the lens in the detector 530 can transmit the light beam to the CCD photosensitive element to obtain the position information of the light spot. Subsequently, the position adjustment mechanism 300 can fine-tune the vertical distance d between the two opposite asymmetric cut crystals 211 according to the light spot position information detected by the light spot detection mechanism 500.

[0094] It is understandable that after debugging is completed, the lifting assembly 540 can drive the scintillation crystal 510 and the reflector 520 to move upward to avoid the optical path between the first asymmetric cut crystal pair 210 and the second asymmetric cut crystal pair 220 .

[0095] like Figures 6 to 8 As shown, in some embodiments, the negative 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 211 under high heat load, and make the center displacement of the crystal rocking curve caused by the deformation of the asymmetric cut crystal 211 not exceed half the Darwin width. Before using the negative group velocity dispersion crystal pulse compressor 1000, the temperature of the asymmetric cut crystal 211 can also be brought to a thermal equilibrium state by the cooling mechanism 600.

[0096] In some embodiments, the cooling mechanism 600 may include a cold end (not shown) and four heat conducting sheets 610. The four heat conducting sheets 610 are connected to the four asymmetric cut crystals 211 in a one-to-one correspondence to absorb the heat of the asymmetric cut crystals 211. The other end of the heat conducting sheet 610 may be connected to the cold end in a heat conducting manner to dissipate the heat through the cold end. The cold end may be a device such as liquid nitrogen or water cooling.

[0097] In some embodiments, one end of the heat conductive sheet 610 may be fixedly disposed between the clamp 350 and the fixing seat 340. Thus, the heat in the asymmetric cut crystal 211 may be transferred to the heat conductive sheet 610 through the clamp 350, and then transferred out through the heat conductive sheet 610. In some embodiments, the heat conductive sheet 610 may be a copper braid.

[0098] In other embodiments, the heat conductive sheet 610 may also be made of a copper sheet or other structure.

[0099] In other embodiments, the negative group velocity dispersion crystal pulse compressor 1000 may further include a pair of asymmetric cut crystals 211, and accordingly, the position adjustment mechanism 300 may also be set as a group. The up-chirped hard X-ray free electron laser pulse 2000 may be longitudinally compressed by a pair of asymmetric cut crystals 211 to generate a hard X-ray attosecond free electron laser pulse 3000, and the hard X-ray attosecond free electron laser pulse 3000 has transverse dispersion, that is, light of different frequencies is separated from each other in the transverse direction.

[0100] In summary, the present application provides a negative group velocity dispersion crystal pulse compressor 1000, which can be used to compress the up-chirped hard X-ray free electron laser pulse 2000 and output the hard X-ray attosecond free electron laser pulse 3000. The negative 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.

[0101] 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.

[0102] 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 negative group velocity dispersion crystal pulse compressor, characterized in that: Used to compress up-chirped hard X-ray free electron laser pulses to generate hard X-ray attosecond free electron laser pulses; The negative group velocity dispersion crystal pulse compressor comprises at least one pair of asymmetric cut crystals, wherein the two asymmetric cut crystals of the same pair are opposite and parallel; The at least one pair of asymmetrically cut crystals is used to disperse the up-chirped hard X-ray free electron laser pulses to achieve longitudinal compression and output of the hard X-ray attosecond free electron laser pulses; The asymmetrically cut crystal comprises a crystal plane and a physical surface, and an angle η between the crystal plane and the physical surface is smaller than a Bragg angle.

2. The negative group velocity dispersion crystal pulse compressor according to claim 1, characterized in that: The negative group velocity dispersion crystal pulse compressor comprises two pairs of asymmetric cut crystals, and the two pairs of asymmetric cut crystals are symmetrically arranged.

3. The negative group velocity dispersion crystal pulse compressor according to claim 1, characterized in that: The negative group velocity dispersion crystal pulse compressor further comprises at least one position adjustment mechanism, on which a pair of the asymmetric cut crystals are mounted; The adjustment mechanism is used to adjust the vertical distance d, the dislocation distance m and the tilt angle relative to the optical axis of the up-chirped hard X-ray free electron laser pulse between the two asymmetrically cut crystals in the same pair.

4. The negative group velocity dispersion crystal pulse compressor according to claim 3, characterized in that: The position adjustment mechanism comprises two first driving units, and the two asymmetrically cut crystals in the same pair are mounted on the two first driving units in a one-to-one correspondence; The first driving unit comprises a first driving member, a first transmission rod and a first adapter plate, the first transmission rod is transmission-connected between the first driving member and the first adapter plate, and the asymmetrically cut crystal is mounted on the first adapter plate; The first driving member is used to drive the asymmetric cut crystal connected to it to move so as to adjust the vertical distance d between the two asymmetric cut crystals in the same pair.

5. The negative group velocity dispersion crystal pulse compressor according to claim 4, characterized in that: The position adjustment mechanism also includes two second driving units; The second driving unit comprises a second driving member, a second transmission rod and a second adapter plate, the two first driving units are mounted on the second adapter plates of the two second driving units in a one-to-one correspondence, the second transmission rod is transmission-connected between the second driving member and the second adapter plate, and the second transmission rod is perpendicular to the first transmission rod; The second driving member is used to drive the asymmetric cut crystal connected to it to move, so as to adjust the misalignment distance m between the two asymmetric cut crystals of the same pair.

6. The negative group velocity dispersion crystal pulse compressor according to claim 5, characterized in that: The first driving unit further comprises a sliding plate and a plurality of guide wheels, the sliding plate being transmission-connected between the first transmission rod and the first adapter plate, the sliding plate being provided with mounting edges protruding on both sides relative to the first transmission rod, the mounting edges protruding relative to the second adapter plate, and the plurality of guide wheels being provided on the two mounting edges; The second adapter plate is provided with guide flanges on both sides relative to the first transmission rod. The guide flanges are parallel to the first transmission rod. The guide wheel is in rolling engagement with the guide flanges opposite to itself.

7. The negative group velocity dispersion crystal pulse compressor according to claim 5 or 6, characterized in that: The position adjustment mechanism further includes a third driving unit; The third driving unit comprises a third driving member, a gear transmission assembly and a third adapter plate, the gear transmission assembly is transmission-connected between the third driving member and the third adapter plate, and both of the second driving units are mounted on the third adapter plate; The third driving member is used to drive the third adapter plate to rotate, and drive the two asymmetric cut crystals connected to it to rotate, so as to adjust the inclination angle of the two asymmetric cut crystals relative to the optical axis of the up-chirped hard X-ray free electron laser pulse.

8. The negative group velocity dispersion crystal pulse compressor according to claim 3, characterized in that: The negative group velocity dispersion crystal pulse compressor further includes a light spot detection mechanism, which includes a scintillation crystal, a reflector, a detector and a lifting assembly; The scintillation crystal and the reflector are connected to the lifting assembly, and the lifting assembly is used to drive the scintillation crystal and the reflector to extend and retract relative to the optical path between the at least one pair of asymmetrically cut crystals; When the scintillation crystal and the reflector are located in the optical path between the at least one pair of asymmetric cut crystals, the scintillation crystal is opposite to the output ends of a pair of asymmetric cut crystals close to the input side of the up-chirped hard X-ray free electron laser pulse, and the reflector is used to reflect the fluorescence at the scintillation crystal to the detector.

9. The negative group velocity dispersion crystal pulse compressor according to claim 1, characterized in that: The negative group velocity dispersion crystal pulse compressor further comprises a plurality of heat conducting plates, which are thermally connected to the asymmetric cut crystals in a one-to-one correspondence.

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