A combined vacuum differential structure

Abstract

The present invention provides a combined vacuum differential structure, which includes a bellows and a differential tube, wherein the upstream end of the bellows is connected to a double-sided knife-edge flange, a through hole is provided at the center of the double-sided knife-edge flange, and the differential tube is provided in the cavity of the bellows and one end is fixed to the through hole of the double-sided knife-edge flange. The combined vacuum differential structure of the present invention saves space because the differential tube extends into the interior of the bellows, which is equivalent to increasing the differential distance and improving the differential ratio. It can maximize the use of the effective distance between devices, improve the differential efficiency, and then complete the working pressure transition between different devices in the synchrotron radiation beam line in an ultra-high vacuum environment in a limited space. The structure is compact and occupies a small space; at the same time, it can meet the relative movement requirements of the equipment to meet the switching requirements of different modes.

Description

Technical Field

[0001] The invention relates to the field of synchrotron radiation beam lines, and in particular to a vacuum differential structure. Background Art

[0002] The main function of the synchrotron radiation beamline is to further process the synchrotron light generated by the accelerator through various devices and finally transmit it to the experimental station to meet the needs of different experimental applications. Since the transmission environment of synchrotron light must be high vacuum or even ultra-high vacuum, the materials used and the processing and cleaning processes of all key equipment and components in the transmission area must be strictly controlled. However, due to the different complexity of functions and structures, the ultimate vacuum degree that each key equipment can achieve is different, and some even differ by more than one order of magnitude.

[0003] In order to ensure that the equipment does not interfere with each other during normal operation, that is, to maintain a relatively stable working pressure, two methods are usually used to achieve stable working pressure: direct isolation by beryllium window or vacuum differential. Since the use of beryllium window isolation for soft X-rays will cause the loss of low-energy photons, the transition of pressure gradient must be achieved through vacuum differential. The vacuum differential method is to use a differential structure (small hole or pipe) to limit the flow in the transition zone from high pressure to low pressure, and to obtain a vacuum device with a certain pumping speed in the low pressure area to meet different differential ratio requirements. If it is difficult to achieve the required differential ratio using a single-stage differential, it can also be achieved through a multi-stage differential method.

[0004] The main difficulties in designing vacuum differentials of beamlines are the aperture of the differential structure, the differential distance, and the limitations of the acquisition equipment. First, the differential structure must allow the light beam to pass smoothly, so the differential aperture cannot be reduced indefinitely. Secondly, the differential distance determines the effective length of the differential pipeline, but in some beamlines, the maximum distance that can be set between differential devices is very limited. The selection of acquisition equipment in the high vacuum and ultra-high vacuum differential areas is mainly molecular pumps, ion pumps, etc., and the appropriate pumping speed must be determined by comprehensively considering factors such as the appearance and cost of the acquisition equipment. Under the premise that the above difficulties exist at the same time, if there is relative motion between differential devices, higher requirements are placed on the vacuum differential design.

[0005] At present, the existing differential methods are all suitable for pressure transition between fixed devices. The differential structure usually adopts small holes or straight pipes. For the differential structure design that is difficult to ensure the beam collimation accuracy requirements (referring to the extremely small differential hole required in some occasions, which cannot retain sufficient collimation margin relative to the spot size), it is also necessary to add bellows upstream or downstream of each level of differential structure to meet the position adjustment requirements, which directly leads to an increase in the differential distance. Please refer to Figure 1 , Figure 1It is a typical structure of the existing vacuum differential structure. For example, the vacuum differential structure introduced in the literature [Liu Junnan, Wu Renzhi, Xue Song, et al. A multi-stage vacuum differential system with stable pressure [J]. Journal of Vacuum Science and Technology, 2017 (10)] adopts a multi-stage differential method, that is, a differential tube 3' and a bellows 1' of multiple circular cross-section pipes are connected in series and finally connected to the upstream device 100' and the downstream device 200', with a suitable pumping speed, so as to achieve the purpose of pressure gradient transition. It can be seen from the figure that the differential distance of this structure is very long and occupies a large space. The space between the devices determines the length of the differential distance. This space is determined by the physical design and cannot be changed at will. Therefore, the existing differential method is not suitable for differential occasions with extremely small space. In addition, there may be relative movement between the devices to meet the needs of switching between different modes, but the upstream and downstream devices 100' and 200' of the existing differential structure must be in a fixed state without relative movement.

[0006] In summary, how to achieve vacuum differential between devices in relative motion in a very limited space is a technical problem that urgently needs to be solved. Summary of the invention

[0007] The core of the present invention is to provide a combined vacuum differential structure to achieve the transition of working pressure gradients of different devices, save differential space, and meet the requirements of relative movement of devices.

[0008] In order to achieve the above-mentioned purpose, the present invention provides a combined vacuum differential structure, which includes a bellows and a differential tube, the upstream end of the bellows is connected to a double-sided knife-edge flange, a through hole is provided at the center of the double-sided knife-edge flange, and the differential tube is arranged in the cavity of the bellows and one end is fixed to the through hole of the double-sided knife-edge flange.

[0009] The bellows is a welded bellows, which comprises a hard pipe joint and two single-sided knife-edge flanges respectively arranged at the upstream end and the downstream end thereof.

[0010] The single-sided knife-edge flange arranged at the upstream end of the corrugated pipe is a loose flange, and its flange connection hole is a through hole.

[0011] The double-sided knife-edge flange includes a plate-shaped body and knife-edge sealing grooves respectively arranged on two side surfaces of the body. The flange connection holes of the double-sided knife-edge flange are threaded holes, one of which is fixed to the single-sided knife-edge flange at the upstream end of the bellows by bolts, and the other knife-edge sealing groove is used for sealing and connecting upstream equipment.

[0012] The cross-sectional dimensions of the through hole are consistent with the outer contour dimensions of the matching cross-sectional dimensions of the differential tube, and one end of the differential tube is welded and fixed to the through hole of the double-sided knife-edge flange.

[0013] The differential pipe has a circular cross section, and one end of the differential pipe is processed into a pipe with a flange. The flange is provided with a sealing edge, and the sealing edge is sealed and fixed to the edge of the double-sided knife flange through a copper gasket.

[0014] The cross section of the differential tube is circular or rectangular.

[0015] The length l of the differential tube is:

[0016] l≦2δ1+δ2+(Dd)L / 2Δ,

[0017] Among them, d is the outer diameter of the circular section of the differential pipe, in mm, δ1 is the flange thickness connecting the double-sided knife-edge flange and the bellows, in mm, δ2 is the length of the hard pipe joint of the bellows, in mm, L is the length of the bellows, in mm, D is the inner diameter of the bellows, in mm, and ±Δ is the lateral movement displacement of the bellows, in mm.

[0018] The length of the differential tube is at most the length of the bellows.

[0019] The bellows, double-sided knife-edge flange and differential pipe are all made of stainless steel.

[0020] The combined vacuum differential structure of the present invention has a compact structure and saves space because the differential tube extends into the interior of the bellows, which is equivalent to increasing the differential distance and improving the differential ratio. It can maximize the use of the effective distance between devices, improve the differential efficiency, and then complete the working pressure transition between different devices in the synchrotron radiation beam line in an ultra-high vacuum environment within a limited space; at the same time, the diameter of the differential tube extending into the present invention is not very small relative to the spot size, and sufficient collimation margin is retained, which can meet the relative movement requirements of the equipment and meet the requirements of switching between different modes. During processing, the verticality between the differential tube and the double-sided knife-edge flange can be ensured. In addition, the double-sided knife-edge flange of the present invention can be arbitrarily connected to standard flanges of other sizes, and the differential tube does not need to design an independent support structure. The combination of the two can be applied between any beam line differential devices, and different differential tube apertures, lengths, and corrugation lengths only need to be used according to different physical design requirements during design. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the installation working condition diagram of the differential structure of the prior art;

[0022] Figure 2 is a structural schematic diagram of a combined vacuum differential structure according to an embodiment of the present invention;

[0023] Figure 3 Yes Figure 2 The assembly diagram of the combined vacuum differential structure shown;

[0024] Figure 4 It is a curve diagram of vacuum degree variation of upstream and downstream equipment after the combined vacuum differential structure of the present invention is installed. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the structural diagram and specific examples. It should be understood that the following examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0026] like Figure 2-Figure 3 The figure shows a combined vacuum differential structure of the present invention, which includes a bellows 1, a double-sided knife-edge flange 2 connected to the upstream end of the bellows 1, and a differential tube 3 arranged in the cavity of the bellows 1. A through hole 211 is provided at the center of the double-sided knife-edge flange 2. One end of the differential tube 3 is fixed to the through hole 211 of the double-sided knife-edge flange 2, and the other end is suspended and extends into the cavity of the bellows 1.

[0027] In this embodiment, under the condition of satisfying the processing accuracy and ultra-high vacuum cleaning requirements of the special double-sided knife-edge flange 2 and the differential tube 3, the differential tube 3 should ensure the welding accuracy and the quality of the weld when it is welded to the double-sided knife-edge flange 2. The welding accuracy mainly ensures the verticality between the flange end face of the double-sided knife-edge flange 2 and the differential tube 3. Generally, the welding accuracy of the differential tube 3 and the double-sided knife-edge flange 2 is less than or equal to ±0.2mm. During welding, slag inclusion and pores are avoided, thereby affecting the ultimate vacuum degree of the equipment. In addition, the materials of the bellows 1, the double-sided knife-edge flange 2 and the differential tube 3 are all stainless steel.

[0028] like Figure 3 As shown, the structure of the bellows 1 is consistent with the existing bellows, and the bellows itself has two types of welding type and pressing type. The bellows 1 is a welded bellows, which can produce a larger displacement under the lateral and axial force action relative to the pressed bellows, and comprises a hard pipe joint 11 and two single-sided knife-edge flanges 12, 13 respectively arranged at its upstream end and downstream end, wherein the bellows 1 will be welded with the single-sided knife-edge flanges 12, 13, so a section of hard pipe joint 11 is needed to connect the corrugation and the flange two parts. The single-sided knife-edge flange 12 at the upstream end of the bellows 1 is a loose flange, so that the upstream end of the bellows 1 is connected to the double-sided knife-edge flange 2 through the loose flange, and the flange connection hole of the single-sided knife-edge flange 12 at the upstream end of the bellows 1 is a through hole, so as to facilitate installation. The single-sided knife-edge flange 13 at the downstream end of the bellows 1 is an internal welding flange, and the downstream end of the bellows 1 is connected to the downstream device 200 via the internal welding flange, thereby realizing the switching movement of the working position of the downstream device 200 through the lateral deformation of the bellows.

[0029] The double-sided knife-edge flange 2 can be modified from a standard blind flange by changing its single-sided knife edge into a double-sided knife edge. It includes a plate-shaped body 21 and knife-edge sealing grooves 22 and 23 respectively arranged on the two sides of the body 21. The flange connection hole of the double-sided knife-edge flange 2 must be a threaded hole. One of the knife-edge sealing grooves 22 is fixed to the single-sided knife-edge flange 12 at the upstream end of the bellows 1 by bolts, thereby realizing the connection between the double-sided knife-edge flange 2 and the bellows 1, and the other knife-edge sealing groove 23 is used for sealing and connecting the upstream equipment 100. The cross-sectional dimensions of the through hole 211 at the center of the double-sided knife-edge flange 2 are consistent with the outer contour dimensions of the matching cross section of the differential pipe 3 for easy welding. One end of the differential pipe 3 is welded and fixed to the through hole 211 of the double-sided knife-edge flange 2, thereby realizing the connection between the differential pipe 3 and the upstream equipment 100 through the through hole 211 of the double-sided knife-edge flange 2.

[0030] The differential tube 3 is a pipe, and its cross section is circular or rectangular.

[0031] The design of the aperture of the cross section of the differential tube 3 should leave sufficient margin on the premise of ensuring smooth passage of the light beam to avoid the light beam drifting and irradiating the tube wall, causing potential safety hazards to the equipment. When the above conditions are met, the aperture should be reduced as much as possible to achieve the best current limiting effect. Therefore, the aperture of the cross section of the differential tube 3 is preferably the minimum aperture that ensures smooth passage of the light beam when drifting.

[0032] The length of the differential tube 3 should be designed in consideration of the structural dimensions and motion parameter requirements of the bellows. Specifically, taking the cross section of the differential tube 3 as a circle as an example, the length l of the differential tube 3 must satisfy:

[0033] l≦2δ1+δ2+(Dd)L / 2Δ,

[0034] Among them, d is the outer diameter of the circular section of the differential pipe 3, δ1 is the thickness of the flange connecting the double-sided knife-edge flange 2 and the bellows 1, δ2 is the length of the hard pipe joint 11 of the bellows 1, L is the length of the bellows 1, D is the inner diameter of the bellows 1, ±Δ is the lateral movement displacement of the bellows 1, and the unit is mm. In this way, it is ensured that the differential pipe 3 and the bellows 1 will not interfere with each other when the connected equipment moves.

[0035] In addition, although the length of the differential tube 3 should be as long as possible to improve the differential efficiency, care must be taken not to interfere with the structures in the upstream and downstream devices. Therefore, the length l of the differential tube 3 is at most the length of the bellows 1.

[0036] When the length of the differential tube 3 is slightly longer, in order to ensure its rigidity, the wall thickness of the differential tube 3 needs to be increased. The selection of wall thickness is related to the processing method of the pipeline, the welding clamping and fixing method, and the welding process level. It needs to be determined based on various factors. When the wall thickness is sufficient, sufficient welding allowance can be left to ensure that the weld width does not affect the effective light aperture.

[0037] The following is a detailed description of the installation method of the combined vacuum differential structure described above. Taking the energy material research beamline as an example, the vacuum chambers of two key devices, the upstream device DCM (liquid nitrogen double crystal monochromator) and the downstream device PGM2 (grating monochromator), are directly connected. The working pressure of the upstream device DCM is 1×10 -6 Pa, the working pressure of the downstream equipment PGM2 is less than 1×10 -7 Pa. If the vacuum differential is not set, the working vacuum degree of the downstream device PGM2 will be directly affected by the upstream device DCM. However, the connection distance between the two is only 350mm, and the upstream device DCM also needs to realize the horizontal switching function between Si (111) crystal and Si (311) crystal, and the switching stroke is ±40mm. If the ordinary differential method is used, it is difficult to simultaneously achieve a differential ratio of more than one order of magnitude and the movement requirements of the upstream device DCM within a distance of 350mm. The structure of the present invention can easily achieve these two functions. It can be calculated that, under the premise of meeting the requirements of the spot size, the inner hole length of the differential square tube is set to 35mm × width 15mm, and the depth is 150mm. By placing this differential tube in a DN100 corrugated tube with a length of 350mm, the movement requirements of the upstream device DCM ±40mm can be simultaneously achieved. The combined vacuum differential structure of the present invention has a differential tube 3 disposed inside the bellows 1, rather than being directly connected to the outside of the bellows 1 as in conventional differential designs. Therefore, it is equivalent to directly adding a differential tube 3, and the conventional differential design can achieve a differential effect only with a connection distance of 350+150mm. Therefore, the ultimate vacuum degree of PGM2 can be controlled within 1×10 -7 Pa (PGM2 is equipped with a pump of 500L / s ion pump + 2000L / s NEG non-evaporable getter pump). Figure 4 shown.

[0038] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be changed in various ways. For example, when the cross section of the differential pipe is circular, the connection form between the double-sided knife-edge flange and the differential pipe can be changed, and the fixing method can be changed from welding to knife-edge sealing, that is, the differential pipe is directly processed from a bar material into a pipe with a flange at one end, and a sealing knife edge is provided on the flange, and the sealing knife edge and the knife edge processed on the double-sided knife-edge flange are sealed and fixed through a copper gasket. Even when the leakage rate has a small effect on the differential ratio, the flange of the differential pipe may not have a knife edge, and only be connected by plane contact. That is, all simple, equivalent changes and modifications made according to the claims and the contents of the specification of the present invention application fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A combined vacuum differential structure, comprising a bellows (1) and a differential tube (3), characterized in that: The upstream end of the bellows (1) is connected to a double-sided knife-edge flange (2), a through hole (211) is provided at the center of the double-sided knife-edge flange (2), and the differential pipe (3) is arranged in the cavity of the bellows (1) and one end is fixed to the through hole (211) of the double-sided knife-edge flange (2).

2. The combined vacuum differential structure according to claim 1, characterized in that: The bellows (1) is a welded bellows, comprising a hard pipe joint (11) and two single-sided knife-edge flanges (12, 13) respectively arranged at its upstream end and downstream end.

3. The combined vacuum differential structure according to claim 2, characterized in that: The single-sided knife-edge flange (12) arranged at the upstream end of the corrugated pipe (1) is a loose flange, and its flange connection hole is a through hole.

4. The combined vacuum differential structure according to claim 3, characterized in that: The double-sided knife-edge flange (2) comprises a plate-shaped body (21) and knife-edge sealing grooves (22, 23) respectively arranged on two side surfaces of the body (21); the flange connection holes of the double-sided knife-edge flange (2) are threaded holes, one of the knife-edge sealing grooves (22) is fixed to the single-sided knife-edge flange (12) at the upstream end of the bellows (1) by bolts, and the other knife-edge sealing groove (23) is used for sealing and connecting an upstream device (100).

5. The combined vacuum differential structure according to claim 1, characterized in that: The cross-sectional dimensions of the through hole (211) are consistent with the outer contour dimensions of the matching cross-sectional dimensions of the differential tube (3), and one end of the differential tube (3) is welded and fixed to the through hole (211) of the double-sided knife-edge flange (2).

6. The combined vacuum differential structure according to claim 1, characterized in that: The differential pipe has a circular cross section, and one end of the differential pipe is processed into a pipe with a flange. The flange is provided with a sealing edge, and the sealing edge is sealed and fixed to the edge of the double-sided knife flange through a copper gasket.

7. The combined vacuum differential structure according to claim 1, characterized in that: The cross section of the differential tube (3) is circular or rectangular.

8. The combined vacuum differential structure according to claim 1, characterized in that: The length l of the differential tube (3) is: l≦2δ1+δ2+(Dd)L / 2Δ, Wherein, d is the outer diameter of the circular cross section of the differential pipe (3), in mm, δ1 is the thickness of the flange connecting the double-sided knife-edge flange (2) and the bellows (1), in mm, δ2 is the length of the hard pipe joint (11) of the bellows (1), in mm, L is the length of the bellows (1), in mm, D is the inner diameter of the bellows (1), in mm, and ±Δ is the lateral movement displacement of the bellows (1), in mm.

9. The combined vacuum differential structure according to claim 1, characterized in that: The length of the differential tube (3) is at most the length of the bellows (1).

10. The combined vacuum differential structure according to claim 1, characterized in that: The materials of the bellows (1), the double-sided knife-edge flange (2) and the differential pipe (3) are all stainless steel.

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