1. An X-ray free electron laser single pulse online diagnosis energy spectrometer is characterized in that: the device comprises a vacuum cavity (1), a four-axis adjusting frame (2), a quick switching cavity (4), a refrigerating system (23), a detection mechanism and a bent crystal (8);

the four-axis adjusting frame (2) comprises an adjusting mechanism and a working rod (26), the working rod (26) is connected with the adjusting mechanism, and the adjusting mechanism has X-direction, Y-direction, Z-direction and rotation adjusting functions and is used for adjusting the working rod (26);

the working rod (26) extends into the vacuum cavity (1) through an interface on the vacuum cavity (1), the curved crystal (8) is arranged at the tail end of the working rod (26), an incident light interface (11) and an emergent light interface (12) are arranged on the vacuum cavity (1), and the position of the curved crystal (8) in the vacuum cavity (1) is adjusted through the adjusting mechanism, so that the center of the curved crystal (8) is positioned on the same straight line with the incident light interface (11) and the emergent light interface (12);

the fast switching cavity (4) is connected with the vacuum cavity (1) in a vacuum manner and used for replacing the bent crystal (8);

the refrigerating system (23) is connected with the bent crystal (8) for cooling;

the detection mechanism is arranged outside the vacuum cavity (1) and detects X-rays through a detection window (13) on the vacuum cavity (1).

2. The X-ray free electron laser single pulse online diagnostic energy spectrometer of claim 1, characterized in that: curved brilliant (8) including planoconcave base (81), planoconvex base (82), through-hole (83), screw (84), elasticity plunger (85), ultra-thin single crystal wafer (86) and holder (87), planoconcave base (81) and convex base (82) center set up through-hole (83), centre gripping ultra-thin single crystal wafer (86) in the middle of the concave surface of planoconcave base (81) and the convex surface of planoconcave base (82), holder (87) are established and are played the clamping action at the both ends of planoconcave base (81) and planoconcave base (82), holder (87) facial make-up has elasticity plunger (85), elasticity plunger (85) compress tightly respectively in the plane of concave surface base (81) and convex base (82), holder (87) both sides set up screw (84), through screwing up screw (84) fixed holder (87).

3. The X-ray free electron laser single pulse online diagnostic energy spectrometer of claim 1, characterized in that: the fast switching cavity (4) is connected with the vacuum cavity (1) through a valve (3).

4. The X-ray free electron laser single pulse online diagnostic energy spectrometer of claim 1, characterized in that: the vacuum cavity (1) is connected with a vacuum pump (14).

5. The X-ray free electron laser single pulse online diagnostic energy spectrometer of claim 1, characterized in that: the detection window (13) is horizontally vertical to the direction of the light path, and the detection window (13) is made of high-transmission X-ray materials.

6. The X-ray free electron laser single pulse online diagnostic energy spectrometer of claim 1, characterized in that: the detection mechanism comprises a surface detector (6) and a displacement table (5), the surface detector (6) is arranged on the displacement table (5) and is just opposite to a detection window (13), and the distance between the surface detector (6) and the detection window (13) is adjusted through the displacement table (5).

7. The X-ray free electron laser single pulse online diagnostic energy spectrometer of claim 1, characterized in that: four-axis alignment jig (2) include X to displacement platform (21), rotary displacement platform (22), Z to displacement platform (24) and Y to displacement platform (25), X is connected with work rod (26) respectively to displacement platform (21), rotary displacement platform (22), Z to displacement platform (24) and Y to displacement platform (25) and is used for adjusting work rod (26).

8. The X-ray free electron laser single pulse online diagnostic energy spectrometer of claim 1, characterized in that: the four-axis adjusting frame (2) is connected with the vacuum cavity (1) through a flange sleeved on the working rod (26).

9. The X-ray free electron laser single pulse online diagnostic energy spectrometer of claim 6, wherein: the vacuum device is characterized by further comprising a supporting table board (7), wherein the vacuum cavity (1) and the displacement table (5) are arranged on the supporting table board (7).

10. The X-ray free electron laser single pulse online diagnostic energy spectrometer of claim 2, characterized in that: the ultra-thin monocrystalline wafer (86) is monocrystalline silicon, monocrystalline germanium, or monocrystalline diamond.

Background

Hard X-Ray Free-Electron Laser (XFEL) is a new generation of X-Ray light source that can provide unprecedented brightness, high coherence, and ultra-short pulses. By combining the XFLL spectroscopy technology and the pumping-detecting technology, the ultrafast process of energy or charge transfer and transfer after the substance system is excited can be observed in real time, and the mechanism of the ultrafast process can be known from the atom and molecule level, so that the nature and course of the photoreaction of the complex system can be deeply known. In fact, XFEL-generated X-ray pulses of the self-amplified spontaneous emission (SASE) mechanism have random energy distributions and intensities with different spectral distributions for each pulse. This requires a high degree of accuracy in characterizing each pulse, enabling the experimenter to improve its data quality by using the incident spectrum for normalization. Therefore, developing an online energy spectrometer that can observe the energy distribution and incident intensity of single-pulse X-ray photons in real time is critical for developing XFEL-based experiments.

A single-pulse online energy spectrometer suitable for an XFEL device should have the following characteristics:

1. the energy resolution requirement of an XFEL laboratory station is typically 1 x 10 "4, which places higher energy resolution requirements on online diagnostics. Meanwhile, the light beam passes through an online energy spectrometer and then is subjected to subsequent experiments. In order to ensure sufficient luminous flux for subsequent experiments, it is required that the online spectrometer must have high transmittance.

2. The online spectrometer is mounted on the XFEL beam line. Due to the long beam line, an ultra-high vacuum tube is chosen in order to ensure a high efficiency transmission of the generated XFEL. Therefore, the online spectrometer needs to design an ultra-high vacuum cavity to be compatible with beam line transmission.

3. The optical element needs to be aligned when dimming on line, and a position adjusting device with high precision is required. In addition, higher peak brightness and repetition frequency of XFEL can result in higher thermal loads that can damage optical components. A refrigeration system is required to take away heat in time, thereby protecting the optical elements from long-term operation.

4. When the online energy spectrometer is operated, the optical elements need to be switched when the service life of the optical elements is reached due to the thermal load effect, or a plurality of optical elements need to be selected according to different energy resolution and transmissivity requirements, and the capacity of switching the optical elements without breaking vacuum is required.

Aiming at the requirement of the latest hard X-ray free electron laser device on a single-pulse online spectrometer, no corresponding solution exists at present.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the prior art does not have an online energy spectrometer capable of observing the energy distribution and the incident intensity of single-pulse X-ray photons in real time.

In order to solve the problems, the technical scheme of the invention is to provide an X-ray free electron laser single-pulse online diagnosis energy spectrometer, which is characterized in that: the device comprises a vacuum cavity, a four-axis adjusting frame, a quick switching cavity, a refrigerating system, a detection mechanism and a curved crystal;

the four-axis adjusting frame comprises an adjusting mechanism and a working rod, the working rod is connected with the adjusting mechanism, and the adjusting mechanism has X-direction, Y-direction, Z-direction and rotation adjusting functions and is used for adjusting the working rod;

the working rod extends into the vacuum cavity through an interface on the vacuum cavity, the bent crystal is arranged at the tail end of the working rod, an incident light interface and an emergent light interface are arranged on the vacuum cavity, and the position of the bent crystal in the vacuum cavity is adjusted through the adjusting mechanism, so that the center of the bent crystal, the incident light interface and the emergent light interface are positioned on the same straight line;

the fast switching cavity is connected with the vacuum cavity in a vacuum manner and used for replacing the bent crystal;

the refrigerating system is connected with the bent crystal and used for cooling;

the detection mechanism is arranged outside the vacuum cavity and detects the X-ray through a detection window on the vacuum cavity.

Preferably, the curved crystal comprises a planoconcave substrate, a planoconvex substrate, a through hole, a screw, an elastic plunger, an ultrathin single crystal wafer and a retainer, wherein the through hole is formed in the center of the planoconcave substrate and the center of the convex substrate, the ultrathin single crystal wafer is clamped between the concave surface of the planoconcave substrate and the convex surface of the planoconcave substrate, the retainer is arranged at two ends of the planoconcave substrate and the two ends of the convex substrate to play a clamping role, the elastic plunger is arranged on the retainer, the elastic plunger is respectively pressed on the planes of the planoconcave.

Preferably, the quick switching cavity is connected with the vacuum cavity through a valve.

Preferably, the vacuum chamber is connected with a vacuum pump.

Preferably, the detection window is horizontally vertical to the direction of the light path, and the detection window is made of a high-transmission X-ray material.

Preferably, the detection mechanism comprises a surface detector and a displacement table, the surface detector is arranged on the displacement table and is opposite to the detection window, and the distance between the surface detector and the detection window is adjusted through the displacement table.

Preferably, four-axis alignment jig includes X to displacement platform, rotary displacement platform, Z to displacement platform and Y to displacement platform, X to displacement platform, rotary displacement platform, Z to displacement platform and Y to displacement platform are connected with the working rod respectively and are used for adjusting the working rod.

Preferably, the four-axis adjusting frame is connected with the vacuum cavity through a flange sleeved on the working rod.

Preferably, the vacuum chamber further comprises a supporting table top, and the vacuum chamber and the displacement table are arranged on the supporting table top.

Preferably, the ultra-thin single crystal wafer is single crystal silicon, single crystal germanium, or single crystal diamond.

Compared with the prior art, the invention has the beneficial effects that:

1. high-performance crystal spectroscopy can be realized: the crystal can realize the diffraction and light splitting of X-rays due to the fact that the lattice spacing is close to the wavelength scale of the X-rays, and has high energy resolution. The plane crystal is bent and fixed to manufacture the bent crystal, so that photons with different energies are spread in space, and X-ray light splitting can be realized. Different positions of the surface detector correspond to photons with different energies, and online spectrum monitoring is achieved. The ultrathin transmission type curved crystal is designed, and high energy resolution and high transmissivity can be achieved at the same time.

2. The ultrahigh vacuum cavity is provided with: through the design of the multi-interface ultrahigh vacuum cavity, the online energy spectrometer can be compatible with beam line ultrahigh vacuum transmission. Meanwhile, the vacuum detection window is made of Be window or KAPTON and other X-ray high-transmission materials, and the ultrahigh vacuum window is compatible with ultrahigh vacuum and has higher X-ray transmittance.

3. Can realize high accuracy crystal four-axis and adjust: the four-axis adjusting device for the optical element is designed, comprises an X-axis displacement table, a rotary displacement table, a Z-axis displacement table and a Y-axis displacement table, is used for respectively adjusting X, Y, Z and theta-direction positions of the online optical element, and has higher precision and more flexible adaptive scenes. In addition, four-axis adjusting device has still designed refrigerating system, and refrigerating system and curved brilliant base pipe connection pack the liquid nitrogen in the pipeline and can take away the heat that curved brilliant produced, can reach 4K minimum, have higher heat load ability, can guarantee that optical element moves for a long time.

4. Can realize fast on-line crystal switching: the rapid sample introduction cavity is arranged, so that the optical element can be switched without breaking vacuum. Set up the valve between fast switch over chamber and the vacuum cavity, when changing curved brilliant, close the valve, isolated inside and outside vacuum, change curved brilliant at the fast sampling chamber, then carry out the evacuation in fast sampling chamber, when the vacuum of fast switch over chamber and vacuum cavity is less than two orders of magnitude, open the valve, will bend brilliant from fast switch over the chamber and convey the vacuum cavity in, reduced online spectrum appearance and maintained the degree of difficulty.

Drawings

FIG. 1 is a schematic structural diagram of an X-ray free electron laser single-pulse online diagnosis energy spectrometer according to the present invention;

FIG. 2 is a schematic view of a vacuum chamber;

FIG. 3 is a schematic structural view of a four-axis adjusting bracket;

FIG. 4 is a schematic view of a curved crystal structure;

FIG. 5 is a light path diagram of an X-ray free electron laser single-pulse online diagnosis energy spectrometer;

FIG. 6 is the main parameter diagram of the X-ray free electron laser single pulse online diagnosis energy spectrometer.

Detailed Description

In order to make the invention more comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.

The invention provides a high-performance multi-mode X-ray free electron laser single-pulse online diagnosis energy spectrometer, which aims at the requirements of a latest hard X-ray free electron laser device on single-pulse online spectrometer on high-energy resolution diffraction spectroscopy, high transmittance, high vacuum compatibility, high heat load capacity and the like. The design principle is based on X-ray diffraction, and the diffraction and light splitting of the X-ray are realized by utilizing the fact that the lattice spacing of silicon atoms is close to the wavelength scale of the X-ray. The ultrathin single crystal has low X-ray absorption and high transmissivity, so that the energy and incident intensity distribution of the X-ray free electron laser single pulse can be detected in real time.

As shown in fig. 1 to 4, the X-ray free electron laser single pulse online diagnosis energy spectrometer of the present invention includes a vacuum chamber 1, a four-axis adjusting frame 2, a valve 3, a fast switching chamber 4, a displacement stage 5, a surface detector 6, a supporting platform 7, a curved crystal 8, and a vacuum pump 14.

An incident light interface 11, an emergent light interface 12 and a detection window 13 are processed on the vacuum cavity 1, and the incident light interface 11 and the emergent light interface 12 are kept at 180 degrees. The detection window 13 is horizontally vertical to the direction of the light path and is made of high-transmission X-ray materials. The vacuum pump 14 is arranged outside the vacuum chamber 1 and connected with the vacuum chamber 1.

Vacuum chamber 1 and fast switch over chamber 4 and pass through valve 3 vacuum connection, valve 3 and fast switch over chamber 4 can realize not destroying vacuum of vacuum chamber 1 just can switch curved brilliant 8, have reduced the online spectrum appearance and have maintained the degree of difficulty.

The surface detector 6 is arranged on the displacement table 5 and is opposite to the detection window 13, and the surface detector 6 can be a counting surface detector or an integrating surface detector. The displacement table 5 is arranged outside the vacuum cavity 1 and used for adjusting the relative positions of the surface detector 6 and the detection window 13, and the stroke of the displacement table 5 can be 100mm, 300mm and 500 mm. The vacuum cavity 1 and the displacement table 5 are arranged on the supporting table surface 7 and are fixedly connected with the supporting table surface 7.

The curved crystal 8 comprises a planoconvex substrate 81, a planoconvex substrate 82, a through hole 83, a screw 84, an elastic plunger 85, an ultrathin single crystal wafer 86 and a holder 87, wherein the through hole 83 is arranged in the center of the planoconvex substrate 81 and the planoconvex substrate 82, and the through hole 83 can ensure the transmission light to be directly transmitted. The ultra-thin single crystal wafer 86 is held between the concave surface of the planoconcave substrate 81 and the convex surface of the planoconvex substrate 82, and the surface shape of the ultra-thin single crystal wafer 86 is in conformity with the concave surface of the planoconcave substrate 81 and the planoconvex substrate 82. The retainer 87 is arranged at two ends of the planoconcave substrate 81 and the planoconcave substrate 82 to play a role in clamping, the elastic plunger 85 is arranged above the retainer 87, and the elastic plunger 85 is respectively pressed on the planes of the planoconcave substrate 81 and the convex substrate 82 to uniformly apply pressure and reduce wafer damage. Screws 84 are provided on both sides of the holder 87, and the holder 87 is fixed by tightening the screws 84.

The ultra-thin monocrystalline wafer 86 may be a perfect crystal of monocrystalline silicon, monocrystalline germanium, monocrystalline diamond, or the like. The number of the bent crystals 8 may be one or more.

The four-axis adjusting frame 2 comprises an X-direction displacement table 21, a rotary displacement table 22, a Z-direction displacement table 24, a Y-direction displacement table 25 and a working rod 26, wherein the X-direction displacement table 21, the rotary displacement table 22, the Z-direction displacement table 24 and the Y-direction displacement table 25 form an adjusting mechanism for adjusting the position of the working rod 26, the adjusting mechanism is connected with the curved crystal 8 through the working rod 26, and the spatial position of the curved crystal 8 is adjusted through adjustment of the working rod 26. The working rod 26 extends into the vacuum cavity 1 through a port on the vacuum cavity 1, and the four-axis adjusting frame 2 is connected with the vacuum cavity 1 through a flange sleeved on the working rod 26. The bent crystal 8 is arranged in the center of the vacuum cavity 1, and the center of the bent crystal 8 is collinear with the centers of the incident light interface 11 and the emergent light interface 12. The refrigerating system 23 is arranged on the four-axis adjusting frame 2 and is connected with the curved crystal 8.

When a beam of X-rays of known divergence is directed through the incident light interface 11 of the vacuum chamber 1 onto the convex surface of the curved crystal 8, each wavelength satisfying the bragg condition is reflected and dispersed in a radial direction away from the center of the curved circle, as shown in fig. 5. According to the equation n λ i-2 dsin θ_B，iWhere d is the lattice spacing, θ_B，iIs the bragg angle and i denotes each different wavelength within the beam. The spectral dispersion position Δ x of the bragg diffracted pulse on the detector plane corresponding to the energy interval Δ E is given by:

l' represents the distance from the crystal to the detector and R is the radius of curvature.Is the spectral resolution of the spectrometer.

Maximum spectral range Δ E_maxDepending on the incident beam size H and the radius R of the curved crystal.

The main parameters of the X-ray free electron laser single pulse online diagnosis energy spectrometer can be obtained by the two formulas, and the main parameters comprise crystal face selection Bragg angle, transmissivity, energy range and energy resolution which respectively correspond to the graph in turn in the graph of 6a, b, c and d.

Selection of crystal face: as shown in fig. 6a, the intrinsic darwin widths of crystals of different crystallographic planes at a particular photon energy are different, which causes the bragg angles of the crystals to be different. For example, at 10keV photon incidence, the Bragg angle for Si (111) is 11.4, while the Bragg angle for Si (333) is 36.38. The bragg angle of the same crystal plane decreases as the incident energy becomes larger. The higher order facets have a small facet spacing and a large bragg angle.

Transmittance: as shown in fig. 6b, the transmission of a silicon crystal increases with decreasing thickness in the energy range of 10-25 keV. The transmittance of more than 80% can be maintained by using silicon crystals with the thickness of less than 20 um.

Energy range: the energy range of the spectrometer refers to the spectral range of the X-rays that the analyzing crystal can detect, as shown in fig. 6 c. The spectral width of a single excitation of a free electron laser device is typically 0.001-0.01. I.e. the incident light energy is 10keV, the spectrometer should have an energy range of 10-100 eV.

Energy resolution: energy resolution is the most important parameter of a spectrometer. The free electron laser single-emission spectrum is not the gaussian distribution of the conventional synchrotron radiation light source, but the random distribution of the SASE mode. The single-emission spectrum has dozens of peaks and the angular width can reach 2 mu rad. During experiments, the distance between the surface detector 6 and the curved crystal 8 can be adjusted according to crystal faces or the radius of the curved crystal 8, and parameters such as the surface detector 6 with higher resolution are selected to realize high-energy resolution. The radius of curvature is 300mm, the detector is 400mm away from the curved crystal, the pixel size is 50um, and the energy resolution of different crystal planes is shown in fig. 6 d.