Ultra-high vacuum four-blade slit suitable for soft x-ray free electron laser beam collimation

Abstract

The application discloses a kind of ultra-high vacuum four-knife slits suitable for soft X-ray free electron laser beam collimation, characterized in that, including ultra-high vacuum cavity and the four-knife slit completely located in ultra-high vacuum cavity, after soft X-ray free electron laser pulse enters ultra-high vacuum cavity from the front CF100 flange of ultra-high vacuum cavity, from the rear CF100 flange of ultra-high vacuum cavity, wherein: four-knife slit includes vertical direction double-knife slit and horizontal direction double-knife slit, respectively, to form constraint from horizontal and vertical direction to X-ray free electron laser beam.The application has the characteristics of high precision, high reliability, compact, simple structure, can work in ultra-high vacuum environment, etc.

Description

Ultra-high vacuum four-knife slit suitable for collimation of soft X-ray free-electron laser beams Technical Field

[0001] This invention relates to an ultra-high vacuum four-blade slit suitable for collimating soft X-ray free electron laser beams, belonging to the field of X-ray free electron laser instruments. Background Technology

[0002] As a new generation of X-ray sources, X-ray free-electron lasers can provide highly coherent, extremely short X-ray pulses with brightness approximately 9-10 orders of magnitude higher than synchrotron radiation. The Shanghai Soft X-ray Free-Electron Laser Facility, the first free-electron laser facility in China to cover the water window band, is based on a self-amplified spontaneous emission (SASE) emission mode and can provide extremely short X-ray pulses of up to 100 fs in the 200-620 eV energy range. It is a powerful tool for research in live-cell imaging, ultrafast chemical kinetics, and ultrafast physics. However, in SASE emission mode, the electron micro-beam clusters are affected by space charge effects and tail fields in the linear accelerator stage, increasing the instability of the electron micro-beam clusters and causing significant spatial jitter in each pulse. This phenomenon has a serious impact on end-user experiments. For example, the jitter reduces the energy resolution of the X-ray spectrometer, and the non-alignment of the pump and probe spots affects the temporal resolution of the spectrometer. Therefore, it is necessary to develop an ultra-high vacuum four-slit slit suitable for collimating soft X-ray free electron laser beams to constrain the beam in space and ensure that the position of the free electron laser incident on the sample remains stable.

[0003] Currently, the existing four-blade slits used in soft X-ray free electron lasers mainly use an external motor to drive the relative movement of the blades to form the slit. The motor is located outside the vacuum chamber and drives the blades inside the vacuum chamber to move through a magnetohydrodynamic sealing device. The structure is complex and the overall size of the equipment is relatively large, occupying a large space on the beamline. Summary of the Invention

[0004] The purpose of this invention is to provide a simple, highly precise, and compact ultra-high vacuum four-blade slit to meet the requirements of terminal experimental stations for collimation of soft X-ray free electron laser optical paths.

[0005] To achieve the above objectives, the technical solution of this invention provides an ultra-high vacuum four-slit slit suitable for collimating soft X-ray free-electron laser beams. Its characteristic is that it includes an ultra-high vacuum cavity and four slits completely located within the ultra-high vacuum cavity. The soft X-ray free-electron laser pulse enters the ultra-high vacuum cavity from the front CF100 flange and exits from the rear CF100 flange, wherein:

[0006] The four-blade slit includes a vertical double-blade slit and a horizontal double-blade slit, which respectively constrain the X-ray free electron laser beam in the vertical and horizontal directions; the vertical double-blade slit includes two vertical blades and two vertical linear displacement stages that drive the two vertical blades; the horizontal double-blade slit includes two horizontal blades and two horizontal linear displacement stages that drive the two horizontal blades.

[0007] Preferably, the four-blade slits partially overlap with the front CF100 flange in the axial direction.

[0008] Preferably, the four-blade slit is fixed on at least three stepped components located inside the ultra-high vacuum chamber, and the stepped structure set on the stepped components makes the four-blade slit partially overlap with the front CF100 flange in the axial direction.

[0009] Preferably, the vertical double-blade slit and the horizontal double-blade slit are respectively located on the front and rear sides of the mounting disc, and the mounting disc and the stepped component are connected and fixed by screws.

[0010] Preferably, the vertical double-blade slit and the horizontal double-blade slit are fixed to the mounting disc by screws; the vertical blade is fixed to the vertical linear displacement stage by screws; and the horizontal blade is fixed to the horizontal linear displacement stage by screws.

[0011] Preferably, an arc-shaped groove is formed on the edge of the mounting disc, corresponding one-to-one with the stepped component, providing 6° rotational freedom during the installation of the four-blade slit.

[0012] Preferably, both the horizontal blade and the vertical blade are made of high-purity tungsten material.

[0013] Preferably, the ultra-high vacuum chamber, the mounting disk, and the screws are all made of ultra-high vacuum material, capable of operating at a vacuum level of 10... -11 Working long-term in an mbar environment.

[0014] Preferably, one of the two horizontal blades has a stepped structure at its cutting edge. When the horizontal slit needs to be closed, the stepped structure causes the cutting edges of the two horizontal blades to be misaligned and partially overlapped, ensuring that the horizontal slit is completely closed.

[0015] One of the two vertical blades has a stepped structure at its cutting edge. When the vertical slit needs to be closed, the stepped structure causes the cutting edges of the two vertical blades to be misaligned and partially overlapped, ensuring that the vertical slit is completely closed.

[0016] Preferably, the movement of the vertical blade and the horizontal blade is controlled by a closed loop, and optical sensors with a resolution of 1 nm are integrated in the vertical linear displacement stage and the horizontal linear displacement stage to provide real-time feedback on the movement status information of the vertical blade and the horizontal blade.

[0017] This invention features high precision, high reliability, compact design, simple structure, and the ability to operate in ultra-high vacuum environments. Compared with existing technologies, this invention offers the following specific advantages:

[0018] 1. High-precision adjustment: The four-blade slit drive consists of four linear displacement stages integrated on both sides of the mounting disk, arranged in pairs, and paired with pure tungsten slit blades to form two double-blade slits in the horizontal and vertical directions. The ultra-high vacuum chamber is based on a cylindrical design, with three multi-functional interfaces on the top and sides for the entry and exit of the linear displacement stage control lines and other expansion components. The overall design structure is simple and clear.

[0019] 2. Compact Design: The linear displacement stages of the four-slit slit are all located inside the ultra-high vacuum chamber, which significantly reduces the overall radial dimension of the four-slit slit. In addition, the design of the stepped components inside the ultra-high vacuum chamber allows the installation position of the four-slit slit to partially coincide with the interface flange axially, making full use of the axial space occupied by the interface flange and further reducing the space occupied by the ultra-high vacuum chamber along the beamline axis.

[0020] 3. Capable of operating in ultra-high vacuum environments: The four-slit linear displacement stage has the capability to operate in 10... -11 The system is capable of operating in an ultra-high vacuum environment of mbar. Furthermore, the ultra-high vacuum chamber is compatible with the ultra-high vacuum environment of soft X-ray free-electron laser beamlines via a CF100 flange. Attached Figure Description

[0021] Figure 1 is a schematic diagram of an ultra-high vacuum four-blade slit structure suitable for collimation of soft X-ray free electron laser beams according to the present invention;

[0022] Figure 2 is a front view and a cross-sectional view of the present invention;

[0023] Figure 3 is a schematic diagram of the front structure of the four-blade slit of the present invention;

[0024] Figure 4 is a schematic diagram of the rear structure of the four-blade slit of the present invention;

[0025] Figure 5 is a schematic diagram of the side structure of the four-blade slit of the present invention;

[0026] Figure 6 is a schematic diagram of the structure of the present invention with a disc installed in a four-blade slit;

[0027] Figure 7 is a schematic diagram of the front structure of the ultra-high vacuum cavity of the present invention;

[0028] Figure 8 is a schematic diagram of the rear structure of the ultra-high vacuum cavity of the present invention. Detailed Implementation

[0029] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0030] As shown in Figure 1, this embodiment discloses an ultra-high vacuum four-slit slit suitable for collimating soft X-ray free electron laser beams, comprising a four-slit slit 1 and an ultra-high vacuum cavity 2. The four-slit slit 1 is fixed inside the ultra-high vacuum cavity 2 using screws. In the four-slit slit 1, a vertical double-slit is located on the front side, and a horizontal double-slit is located on the rear side.

[0031] As shown in Figure 2, the ultra-high vacuum chamber 2 includes a chamber shell 17. The front and rear ends of the chamber shell 17 are a front CF100 flange 21 and a rear CF100 flange 22, respectively. Three CF35 interfaces 23, 24, and 25 are respectively provided on the left, right, and top sides of the chamber shell 17, and a base 26 is located at the bottom. As can be seen from the front view of Figure 2, the radial dimension of the four-blade slit 1 is smaller than the inner diameter of the front CF100 flange 21, i.e., less than 100 mm, which reflects the compact design of the four-blade slit 1 of this invention. As can be seen from the AA-direction cross-sectional view of Figure 2, the four-blade slit 1 and the front CF100 flange 21 partially overlap in the axial direction. This design allows the overall axial dimension of this invention to be controlled within 100 mm, greatly reducing the space occupied by the beamline axial direction.

[0032] As shown in Figures 3 and 4, in this embodiment, the four-blade slit 1 mainly includes a mounting disk 3, four linear displacement stages 4, 5, 6, and 7, and four pure tungsten blades 8, 9, 10, and 11. The four linear displacement stages 4, 5, 6, and 7 are mounted on the mounting disk 3 and are all of the same model and specifications. In this embodiment, an ultra-high vacuum piezoelectric linear displacement stage is used to control the movement of the four pure tungsten blades 8, 9, 10, and 11. Linear displacement stages 4 and 5 are located on the front side of the mounting disk 3, and linear displacement stages 6 and 7 are located on the rear side of the mounting disk 3. The four pure tungsten blades 8, 9, 10, and 11 are made of high-purity tungsten material with a thickness of 2 mm, which can completely block soft X-rays. The four pure tungsten blades 8, 9, 10, and 11 are combined in pairs to form a horizontal double-blade slit and a vertical double-blade slit, respectively constraining the X-ray free electron laser beam in the horizontal and vertical directions. The pure tungsten blade 10 in the horizontal double-blade slit is identical to the pure tungsten blade 8 in the vertical double-blade slit, and the pure tungsten blade 11 in the horizontal double-blade slit is identical to the pure tungsten blade 9 in the vertical double-blade slit. The four linear displacement stages 4, 5, 6, and 7, the four pure tungsten blades 8, 9, 10, and 11, and the four linear displacement stages 4, 5, 6, and 7, and the mounting disk 3 are all fixed with screws. In this embodiment, the four linear displacement stages 4, 5, 6, and 7 integrate optical sensors with a resolution of 1 nm, namely incremental high-precision grating encoders, ensuring that the blade motion status information is fed back in real time, thereby guaranteeing the stability and reliability of the system operation. In this embodiment, the motion of the four pure tungsten blades 8, 9, 10, and 11 adopts closed-loop control, which can achieve a movement accuracy of 1 micrometer, with an actual motion accuracy higher than 1 μm and a stroke of 12 mm.

[0033] In this embodiment, the linear displacement stage 4 drives the pure tungsten blade 8 to perform linear reciprocating motion, and the linear displacement stage 5 drives the pure tungsten blade 9 to perform linear reciprocating motion. The pure tungsten blade 8 and the pure tungsten blade 9 form a vertical double-blade slit with a maximum opening of 12mm, which can be closed at any point within the opening range.

[0034] The linear displacement stage 6 drives the pure tungsten blade 10 to perform linear reciprocating motion, and the linear displacement stage 7 drives the pure tungsten blade 11 to perform linear reciprocating motion. The pure tungsten blade 10 and the pure tungsten blade 11 form a horizontal double-blade slit with a maximum opening of 12mm, which can be closed at any point within the opening range.

[0035] As shown in Figure 5, a 2mm step is designed at the cutting edge of the pure tungsten insert 9, primarily for its compatibility with the pure tungsten insert 8. When the slit needs to be closed, the two cutting edges are offset from each other, forming a partial overlap to ensure complete slit closure. The pure tungsten insert 10 and pure tungsten insert 11 have the same design.

[0036] As shown in Figure 6, the arc-shaped groove 15 located on the edge of the mounting disk 3 is used to connect the four-blade slit 1 to the ultra-high vacuum chamber 2. The arc-shaped groove design provides 6° of rotational freedom during the installation of the four-blade slit 1, which can be adjusted in conjunction with a high-precision robotic arm. The mounting disk 3 has threaded holes 13 and 14 for mounting four linear displacement stages 4, 5, 6, and 7.

[0037] As shown in Figures 7 and 8, the four-blade slit 1 is installed inside the ultra-high vacuum chamber 2 via four stepped components 18 within the cavity shell 17. Each stepped component 18 has a positioning groove 19 for positioning the four-blade slit 1 and a threaded hole 20 for mounting the four-blade slit 1. In this embodiment, the four-blade slit 1 is fixed inside the ultra-high vacuum chamber 2 with screws. The front CF100 flange 21 on the ultra-high vacuum chamber 2 is used to connect the beamline, the rear CF100 flange 22 is used to connect to the experimental station chamber, the CF35 interface 23 is used for the control line output of the linear displacement stages 4, 5, 6, and 7, and the CF35 interfaces 24 and 25 can be connected to expansion equipment as needed.

[0038] All modules of the above system are made of ultra-high vacuum materials and can operate at a vacuum level of 10. -11 Long-term operation in mbar environment will not cause contamination to other components inside the vacuum pipeline. The axial dimension of the vacuum chamber is only 100 mm, and it is connected to the beamline vacuum pipeline through standard CF100 flanges at both ends of the axis, making it suitable for the ultra-high vacuum environment of soft X-ray free electron laser beamlines.

[0039] During the experiment, the soft X-ray free-electron laser is transmitted to the terminal experimental station via a beamline, passing through the four-slit device of this invention. The soft X-ray free-electron laser pulse during focusing enters the ultra-high vacuum cavity 2 from the front CF100 flange 21, first passing through a vertical double-slit composed of pure tungsten blades 8 and 9, then through a horizontal double-slit composed of pure tungsten blades 10 and 11, and finally entering the terminal experimental station from the rear CF100 flange 22.

[0040] Because soft X-ray free-electron lasers exhibit pulse spatial jitter in SASE mode, the opening size and position of the four-slit 1 need to be adjusted before the experiment to ensure the stability of the spot size and position at the sample point. The following is a description of the specific implementation process:

[0041] First, the sample stage coated with phosphor is placed on the sample point, with the four-slit 1 fully open. The position of the sample point is adjusted so that the soft X-ray free electron laser pulse irradiates the sample point, causing the phosphor sample to emit visible light. At this time, the actual landing point of the pulse is observed with a camera, and it can be seen that it exhibits a certain random offset around the theoretical landing point.

[0042] Subsequently, the blades were adjusted one by one. Taking the pure tungsten blade 8 as an example, the linear displacement stage 4 was controlled by an automated program to slowly jog and fine-tune the pure tungsten blade 8 from the outside in until the light spot at the sample point was observed to be blocked. At this point, the pulse beam began to be constrained by the pure tungsten blade 8, and the blade edge of the pure tungsten blade 8 was located at the edge of the beam. The same operation was performed on the other blades. After completion, all four blade edges of the four-blade slit 1 were located at the edge of the pulse beam, thus defining the size and position of the pulse beam spot at the slit.

[0043] Subsequently, the slit size is reduced. Taking pure tungsten blades 8 and 9 as examples, the linear displacement stages 4 and 5 are controlled by the program to perform synchronous inward jogging fine adjustments. During this process, the center position of the slit remains unchanged, and the slit size gradually decreases. The process stops when the longitudinal dimension of the light spot at the sample point reaches the required value. The same operation is performed on pure tungsten blades 10 and 11, and the transverse dimension of the light spot at the sample point is specified.

[0044] After completing the above operations, the pulse spatial jitter caused by the SASE emission mode, and the pulses deviating from the theoretical landing point, are blocked and absorbed by the blades of the four-blade slit 1. Only pulses at the theoretical landing point can pass through the four-blade slit 1 and be incident on the sample point. The spot size at the sample point meets the experimental requirements, and the spot position is stable, thus achieving spatial coupling between the soft X-ray free electron laser beam and the sample point.

Claims

1. A high-vacuum four-blade slit suitable for collimating soft X-ray free-electron laser beams, characterized in that, The system includes an ultra-high vacuum chamber and a four-blade slit entirely within the chamber. A soft X-ray free-electron laser pulse enters the ultra-high vacuum chamber through the front CF100 flange and exits through the rear CF100 flange. The four-blade slit includes a vertical double-blade slit and a horizontal double-blade slit, respectively constraining the X-ray free-electron laser beam in the horizontal and vertical directions. The vertical double-blade slit includes two vertical blades and two vertical linear displacement stages that drive the blades. The horizontal double-blade slit includes two horizontal blades and two horizontal linear displacement stages that drive the blades. The four-blade slit is fixed to at least three stepped components located within the ultra-high vacuum chamber. The stepped structure on these components allows the four-blade slit to partially overlap with the front CF100 flange in the axial direction. The vertical double-blade slit and the horizontal double-blade slit... The directional double-blade slits are respectively located on the front and rear sides of the mounting disc, and the mounting disc is fixed to the stepped component by screws; the vertical double-blade slit and the horizontal double-blade slit are fixed to the mounting disc by screws; the vertical blade is fixed to the vertical linear displacement stage by screws; the horizontal blade is fixed to the horizontal linear displacement stage by screws; one of the two horizontal blades has a stepped structure at its cutting edge. When the horizontal slit needs to be closed, this stepped structure causes the cutting edges of the two horizontal blades to be misaligned, forming a partial overlap, ensuring that the horizontal slit is completely closed; one of the two vertical blades has a stepped structure at its cutting edge. When the vertical slit needs to be closed, this stepped structure causes the cutting edges of the two vertical blades to be misaligned, forming a partial overlap, ensuring that the vertical slit is completely closed.

2. The ultra-high vacuum four-blade slit for collimating soft X-ray free-electron laser beams as described in claim 1, characterized in that, An arc-shaped groove is formed on the edge of the mounting disc, corresponding to the stepped component, providing 6° rotational freedom during the installation of the four-blade slit.

3. The ultra-high vacuum four-blade slit for collimating soft X-ray free-electron laser beams as described in claim 1, characterized in that, Both the horizontal and vertical blades are made of high-purity tungsten material.

4. The ultra-high vacuum four-blade slit for collimating soft X-ray free-electron laser beams as described in claim 3, characterized in that, The ultra-high vacuum chamber, the mounting disk, and the screws are all made of ultra-high vacuum material, capable of operating at a vacuum level of 10... -11 Long-term operation under the mbar environment.

5. The ultra-high vacuum four-blade slit for collimating soft X-ray free-electron laser beams as described in claim 1, characterized in that, The movement of the vertical blade and the horizontal blade is controlled by a closed loop. An optical sensor with a resolution of 1 nm is integrated in the vertical linear displacement stage and the horizontal linear displacement stage to provide real-time feedback on the movement status information of the vertical blade and the horizontal blade.

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