Filtering differential tube, gas filtering pool and beam suppression method

Abstract

The invention discloses a filtering differential tube, a gas filtering pool and a beam suppression method, and belongs to the technical field of high-energy photon and particle beam regulation and control. Each filtering differential tube comprises a round tube, an end plate and a differential hole consisting of a front-end rectangular hole and a rear-end reducing hole, and the divergence of gas molecules is enhanced by the design of a reducing angle of 3 degrees; the gas filtering tank is connected in series through 12 stages of vacuum cavities and is configured with a graded pumping system, so that the higher harmonic absorption efficiency is optimized; and the beam effect is weakened by replacing the differential tube, so that the vacuum degree of the No.11 vacuum cavity is improved by 9.8%. The problem that a traditional gas filtering pool is remarkable in beam effect is solved, the vacuum degree of the 11 # vacuum cavity is improved, and the gas filtering pool can be widely applied to scenes such as synchrotron radiation light sources and particle accelerators.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-energy photon and particle beam control, and specifically relates to a filter differential tube, a multi-stage gas filter pool and a beam suppression method for synchrotron radiation vacuum ultraviolet beam lines. In particular, the invention enhances the divergence of gas molecules and optimizes the vacuum chamber pumping configuration by improving the differential hole structure to reduce the beam density and improve the system vacuum degree. Background Art

[0002] The vacuum ultraviolet light (wavelength 10-200nm) produced by synchrotron radiation sources has the characteristics of wide spectrum, high brightness and good collimation, making it an ideal light source for single photon ionization mass spectrometry, surface science, photochemistry and other fields. As the core connecting unit between the light source and the experimental station, the beamline needs to convert the polychromatic light into monochromatic light through a grating monochromator. However, the diffraction characteristics of the grating cause the output light to be mixed with high-order harmonics (such as 、 These harmonics can interfere with experimental signals and reduce data reliability. For example, in mass spectrometry experiments, the background noise generated by high-order harmonics can mask the target signal and lead to misjudgment.

[0003] At present, the main technologies for suppressing high-order harmonics include the following three categories:

[0004] (1) Solid filter

[0005] Material limitations: The absorption cutoff wavelength of materials such as quartz and magnesium fluoride is usually lower than 108nm, which cannot cover the high-energy vacuum ultraviolet band (such as 30-100nm).

[0006] Risk of thermal damage: The optical power of synchrotron radiation is as high as hundreds of watts. After the filter absorbs photons, it is easy to form color centers or thermal stress cracks, and its lifespan is short.

[0007] (2) Multiple mirror reflections

[0008] Large fundamental wave loss: The short-wavelength component is weakened through multiple reflections, but the fundamental wave intensity can be attenuated by more than 50%, affecting the experimental efficiency.

[0009] Narrow applicable wavelength band: Due to the lack of efficient mirror coating technology in the 50-110 nm range (e.g., B4C / Mg multilayer coating is only applicable to specific wavelengths), the vacuum ultraviolet beamline of the Swiss Light Source (SLS) adopts a hybrid filtering scheme, which results in high system complexity.

[0010] (3) Gas absorption filtering

[0011] Principle advantage: The ionization energy characteristics of rare gases (such as argon, neon, and helium) allow them to selectively absorb photons with higher ionization energies. For example, argon has an ionization energy of 15.76 eV (corresponding to a wavelength of 78.7 nm), which allows it to efficiently absorb shorter wavelength higher harmonics while having weaker absorption of the longer wavelength fundamental wave.

[0012] Technical bottlenecks:

[0013] Beam effect: The linear motion of gas molecules causes the pressure in the upstream vacuum chamber to increase, the vacuum degree to deteriorate, and the stability of the beam line optical elements (such as gratings and mirrors) to be affected.

[0014] Differential tube design defects: Traditional differential tubes use a single rectangular hole, the gas molecules are not divergent enough, and the proportion of particles with small angles of 0 to 1.8° at the outlet is too high (about 0.8%), exacerbating the beam focusing effect.

[0015] Low efficiency of the exhaust system: The molecular pump and dry pump are not configured properly, and it is difficult to balance the extraction of high-flow gas (such as argon 1300SCCM) and the maintenance of high vacuum.

[0016] In summary, existing technologies have failed to effectively resolve the contradiction between the beam effect and high vacuum in the gas filter cell. There is an urgent need for a comprehensive solution that takes into account gas absorption efficiency, enhanced molecular divergence, and optimized pumping system. Summary of the Invention

[0017] The present invention aims to solve the problems in the existing gas filter pool caused by the beam effect leading to vacuum deviation, insufficient divergence of the differential tube exacerbating particle aggregation, and low efficiency and high energy consumption of the pumping system.

[0018] In order to solve the above problems, the specific technical solutions of the present invention are as follows:

[0019] In a first aspect, the present invention provides a filter differential tube, comprising:

[0020] Round tube with an outer diameter of 16 mm;

[0021] an end plate fixed to one end of the circular tube;

[0022] A differential hole is opened along the axial center of the circular tube, the differential hole consisting of a front rectangular hole and a rear tapered hole;

[0023] The length of the front rectangular hole is the total length of the differential hole , the cross section is rectangular, and the size matches the incident spot to maintain the entrance particle number stable;

[0024] The length of the rear end tapered hole is the total length of the differential hole , tapering angle It is 3°, which is used to enhance the divergence of gas molecules by deflecting the wall normal and reduce the proportion of particles with small angles at the outlet.

[0025] In one embodiment, the cross-sectional size of the front rectangular hole matches the size of the incident light spot and is larger than the major axis and minor axis of the light spot;

[0026] The cross-sectional shape and size of the outlet end of the rear end tapered hole are consistent with those of the front end rectangular hole.

[0027] In one embodiment, the tapering angle of the rear end tapered hole is When: Under the conditions of mirror reflection between gas molecules and wall surface, the divergence angle and the convergence angle satisfy:

[0028]

[0029] in, Differential tube divergence angle designed for no rear tapered hole; Differential tube divergence angle for a rear tapered hole design.

[0030] In one embodiment, the filter differential tube is suitable for a multi-stage linear differential system, including an X-ray light source or a particle accelerator device.

[0031] In a second aspect, the present invention provides a gas filter cell, comprising:

[0032] The 12 vacuum chambers are arranged in series and are marked as vacuum chambers 11, 12, 13, 21, 22, 23, 24, 25, 26, 27, 28, and 29 respectively;

[0033] Adjacent vacuum chambers are connected via the above-mentioned filter differential tube;

[0034] The vacuum chamber No. 25 is filled with argon gas at a flow rate of 1300 SCCM;

[0035] The No. 24 vacuum chamber and the No. 26 vacuum chamber are evacuated by dry pumps, and the remaining vacuum chambers are evacuated by molecular pumps.

[0036] In one embodiment, the vacuum chamber No. 11 is connected to an upstream beam line;

[0037] The No. 29 vacuum chamber is connected to the downstream experimental station.

[0038] In one embodiment, the molecular pumps include molecular pumps numbered P-7 to P-2 and molecular pumps numbered P+2, P+3, and P+4; wherein:

[0039] Molecular pumps P-7 to P-5 correspond to vacuum chambers 11 to 13 respectively;

[0040] Molecular pumps P-4 to P-2 correspond to vacuum chambers 21 to 23 respectively;

[0041] Molecular pumps P+2, P+3, and P+4 correspond to vacuum chambers 27 to 29;

[0042] The vacuum chambers No. 21 to 23 and the vacuum chambers No. 27 to 29 are respectively evacuated by a shunt pump, each shunt pump having three extraction ports, which is equivalent to the above-mentioned molecular pumps No. P-4 to P-2 and molecular pumps No. P+2, P+3, and P+4.

[0043] In a third aspect, the present invention provides a method for reducing beam effects, which is applied to the above-mentioned gas filter cell, comprising the following steps:

[0044] S1. Replace the filter differential tube with the filter differential tube numbered 304 in the gas filter pool;

[0045] S2. Introduce 1200-1400 SCCM of argon gas into vacuum chamber 25;

[0046] S3. Start the molecular pump and dry pump to make the pressure of vacuum chamber No. 11 lower than 1×10 -5 Pa.

[0047] In one embodiment, the fluid domain from the filter differential tube No. 304 to the vacuum chamber No. 11 is simulated using Molflow+ software, and the boundary conditions include:

[0048] temperature;

[0049] Molar mass of gas molecules;

[0050] No. 304 filter differential tube inlet flow;

[0051] P-4 molecular pumping speed;

[0052] P-5~P-7 molecular pumps are from pumping speed.

[0053] The beneficial effects of the present invention are:

[0054] Due to the lack of divergence in traditional differential tubes, gas molecules move in a straight line and gather in the upstream vacuum chamber, resulting in a high pressure, which can reach 6.65×10 -6 Pa. The present invention increases the divergence angle of gas molecules after colliding with the wall by designing a tapered hole with a tapered angle of 3°. The proportion of particles with a small angle of 0-1.8° at the outlet is reduced from 0.8% to 0.7%, a decrease of 12.5%. Experimental simulation shows that the pressure of vacuum chamber No. 11 is reduced to 6.0×10 -6 Pa, the drop was 9.8%, and the outlet surface pressure of the gas filter pool was reduced from 3.45×10 - 5 Pa decreased to 3.04×10 -5Pa, decreased by 11.9%, vacuum stability was significantly improved, the contamination risk of beamline optical components such as gratings and mirrors was reduced, and the average annual maintenance times and operation and maintenance costs were significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments or the prior art.

[0056] Figure 1 A three-dimensional model of the gas filter cell at the synchrotron radiation vacuum ultraviolet beamline;

[0057] Figure 2 This is the differential cavity distribution diagram of the gas filter cell at the synchrotron radiation vacuum ultraviolet beamline;

[0058] Figure 3 This is the differential tube distribution diagram of the gas filter cell at the synchrotron radiation vacuum ultraviolet beamline;

[0059] Figure 4 Schematic diagram for comparison of two differential hole structures;

[0060] Figure 5 (a) Fluid domain model when the tapered angle is 0° before the No. 304 filter differential tube is replaced;

[0061] Figure 5 (b) The fluid domain model with a tapered angle of 3° after the No. 304 filter differential tube is replaced;

[0062] Figure 6 This is the angular distribution curve of the particles at the outlet before and after the replacement of the No. 304 filter differential tube;

[0063] Figure 7 The particle count and pressure at the inlet of vacuum chamber No. 11 before and after the replacement of filter differential tube No. 304;

[0064] Figure 8 The particle count and pressure at the outlet surface of the gas filter cell before and after the No. 304 filter differential tube was replaced;

[0065] Figure 9 Schematic diagram of the three-dimensional structure of the filter differential tube of the present invention;

[0066] Figure 10 It is a horizontal cross-sectional view of the filter differential tube of the present invention;

[0067] In the figure: 10, outlet surface of the gas filter cell; 11-13, vacuum chambers 11-13; 21-29, vacuum chambers 21-29; molecular pumps P-7-P-2, P-7-P-5; molecular pumps P+2, P+2; molecular pumps P+3, P+3; molecular pumps P+4, P+4; filter differential tubes 301-312, 301-312; 01, circular tube; 02, end plate; 03, differential hole; 03-1, front rectangular hole; 03-2, rear tapered hole. DETAILED DESCRIPTION

[0068] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0069] 1. Manufacturing and installation of filter differential tube

[0070] 1.1 Material selection and structural design

[0071] like Figure 9 and Figure 10 As shown, the core components of the filter differential tube include a round tube 01, an end plate 02 and a differential hole 03.

[0072] Round tube 01 can be made of 304 stainless steel and the total length can reach 100mm.

[0073] The differential hole 03 is opened along the axial center of the circular tube 01. The differential hole 03 is divided into two parts: a front rectangular hole 03-1 and a rear tapered hole 03-2. The length of the front rectangular hole 03-1 accounts for 0.1% of the total length of the differential hole 03. ;

[0074] The length of the rear end tapered hole 03-2 accounts for the total length of the differential hole 03 , the tapering angle is 3°, the cross section of the outlet end is consistent with the front rectangular hole 03-1, and the wall adopts a linear tapering design to ensure that the divergence angle of the gas molecules increases evenly after collision.

[0075] 1.2 Processing technology and quality control

[0076] The front rectangular hole 03-1 is machined using a slow-cut wire-cut process, specifically a Suzhou Sanguang Technology DK7740 lathe. After machining, the inner surface is polished at 2000 rpm using a nylon brush to remove burrs and reduce surface adsorption.

[0077] 1.3 Installation and Calibration

[0078] Turn off the exhaust system and release the vacuum. Use a torque wrench to loosen the flange bolts and remove the filter differential tube numbered 304 on the gas filter pool. Then install the new filter differential tube with the rear end tapered hole 03-2 described above. Leave the other filter differential tubes on the gas filter pool unchanged.

[0079] The filter differential tube No. 304 is located at the starting position of the molecular flow. The gas molecule number density is relatively high, and the molecular flow state is mainly dominated by collisions between gas molecules and the wall. The collision frequency between gas molecules and the wall in the filter differential tube No. 304 is high. Therefore, replacing the filter differential tube No. 304 with the new filter differential tube of the present invention can greatly enhance the divergence of the outlet particles.

[0080] When installing the novel filter differential tube of the present invention, the optical path is calibrated by a laser collimator (API XD Laser) to ensure that the deviation between the outlet axis of the rear end tapered hole 03-2 and the center of the downstream vacuum cavity No. 26 is ≤0.1°.

[0081] 2. Assembly and debugging of gas filter pool

[0082] like Figure 1 and Figure 2 As shown in FIG, the gas filter cell is composed of 12 vacuum chambers connected in series, which are numbered 11, 12, 13, 21, 22, 23, 24, 25, 26, 27, 28, and 29 from right to left.

[0083] Vacuum chamber No. 25 is the core gas absorption unit with a length of 256 mm.

[0084] like Figure 3 As shown, filter differential tubes No. 301 to 312 are connected to two adjacent vacuum cavities in sequence, among which filter differential tube No. 304 is located between vacuum cavity No. 24 and vacuum cavity No. 25 and is replaced by the new filter differential tube designed by the present invention, and the remaining differential tubes maintain the original design.

[0085] 2.2 Pumping system configuration The pumping system uses molecular pumps and dry pumps in a graded configuration. Molecular pumps are divided into three groups:

[0086] The molecular pumps P-7~P-5 can be Pfeiffer Vacuum Hipace 80 molecular pumps, and the pumping speed is adjusted to 65 L / s.

[0087] Connect to vacuum chambers 11 to 13 respectively;

[0088] The P-4 to P-2 molecular pumps are specifically Pfeiffer Vacuum Split Flow 310 split flow pumps, which have three pumping ports and are equivalent to the three molecular pumps P-4 to P-2. The P-4 molecular pump is connected to vacuum chamber No. 21 with an effective pumping speed of 160 L / s. The P-3 molecular pump and the P-2 molecular pump are connected to vacuum chamber No. 22 and vacuum chamber No. 23 respectively.

[0089] Molecular pumps P+2, P+3, and P+4 are connected to vacuum chambers No. 27 to No. 29 respectively. Molecular pumps P+2, P+3, and P+4 can also be replaced by the three extraction ports of a Pfeiffer Vacuum Split Flow 310 split flow pump.

[0090] The dry pump can be Leybold Vacuum ECODRY 65 plus, which is connected to vacuum chamber No. 24 and vacuum chamber No. 26. The speed is adjusted by frequency conversion control to adapt to the rapid extraction of high-flow gas.

[0091] 2.3 Gas injection and pressure control

[0092] Argon gas (purity 99.999%) was introduced into vacuum chamber No. 25 through a mass flow controller (MKS 1479A) with a flow rate set at 1300 SCCM.

[0093] During the initial vacuuming stage, the dry pump was run for 2 hours to reduce the pressure of vacuum chamber No. 25 from atmospheric pressure to 100 Pa, and then the molecular pump was started.

[0094] 3. Implementation and Verification of Beam Suppression Methods

[0095] 3.1 Fluid dynamics simulation

[0096] like Figure 5 As shown in the figure, the fluid domain model from the No. 304 filter differential tube to the No. 11 vacuum cavity is constructed using SolidWorks 2022, exported to STL format, and then imported into Molflow+ software.

[0097] The boundary conditions were set as a temperature of 293.15 K, an argon gas molecular molar mass of 40, an inlet flow rate of 0.0136 mbar·L / s at the filter differential tube No. 304, and a adhesion coefficient of 0.8 at the outlet surface 10 of the gas filter cell;

[0098] The pumping speed of the P-4 molecular pump is 160L / s, and the pumping speed of the P-5~P-7 molecular pumps is 65L / s.

[0099] The simulation results show that when the taper angle is 3°, the proportion of particles with an angle of 0-1.8° decreases from 0.8% to 0.7%, and the inlet pressure of the vacuum chamber No. 11 decreases from 6.65×10 -6 Pa dropped to 6.0×10 -6 Pa.

[0100] 3.2 Simulation data comparison and optimization

[0101] like Figures 6 to 8 As shown, for the tapered angle Comparative experiments were conducted for 1°, 2°, 3°, and 4°, and fluid domain models from the No. 304 filter differential tube to the No. 11 vacuum cavity were constructed respectively.

[0102] The results show that as the tapering angle Gradually increase, the particle divergence continues to increase, but limited by the standard outer diameter of the round tube 01 of 16mm, the preferred tapering angle is 3°. At this time, the proportion of particles with 0-1.8° drops to 0.7%, and the pressure of the vacuum chamber No. 11 is 6.0×10 -6 Pa, compared with the original structure ( =0°) decreased by 9.8%.

[0103] like Figure 4 As shown, structure 1 is the original differential hole structure, that is, there is no tapered angle ( =0°), while structure 2 is the differential hole structure of the present invention, that is, there is a tapered angle ( =3°). In both structures, there are two gas molecules with Assuming that the collision between the gas molecules and the wall is mirror reflection, the two particles are ejected from the right end outlet after two collisions. The angle between the movement directions of the two particles is the divergence angle of the gas molecules. The divergence angle of the differential tube without the rear end tapered hole design is The divergence angle of the differential tube of the present invention with a rear end tapered hole design is , we can know from the calculation that , The divergence angle of the differential hole of the present invention is greater than the divergence angle of the original differential hole structure, that is, the gas molecules can have a larger divergence angle when they collide with the wall in the differential hole of the present invention and are emitted from the right end, thereby achieving the purpose of enhancing the divergence of the gas molecules.

[0104] This invention significantly reduces the beam effect of synchrotron radiation vacuum ultraviolet beamlines, improves the vacuum level, and enhances the long-term stability of the beamline through innovative filter differential tube structures, optimized gas filter cell pumping systems, and beam suppression methods. This approach holds great potential for widespread industrial application.

[0105] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. Filter differential tube, characterized in that, include: Round tube with an outer diameter of 16 mm; an end plate fixed to one end of the circular tube; A differential hole is opened along the axial center of the circular tube, the differential hole consisting of a front rectangular hole and a rear tapered hole; The length of the front rectangular hole is the total length of the differential hole , the cross section is rectangular, and the size matches the incident spot to maintain the entrance particle number stable; The length of the rear end tapered hole is the total length of the differential hole , tapering angle It is 3°, which is used to enhance the divergence of gas molecules by deflecting the wall normal and reduce the proportion of particles with small angles at the outlet.

2. The filter differential transistor according to claim 1, characterized in that: The cross-sectional dimensions of the front rectangular hole match the dimensions of the incident light spot and are larger than the major and minor axes of the light spot; The cross-sectional shape and size of the outlet end of the rear end tapered hole are consistent with those of the front end rectangular hole.

3. The filter differential transistor according to claim 1, wherein: The tapering angle of the rear end tapered hole Determine by the following method: Under the condition of mirror reflection between gas molecules and wall surface, the divergence angle and the convergence angle satisfy: in, Differential tube divergence angle designed for no rear tapered hole; Differential tube divergence angle for a rear tapered hole design.

4. The filter differential transistor according to claim 1, wherein: The filter differential tube is suitable for a multi-stage linear differential system, including an X-ray light source or a particle accelerator device.

5. Gas filter cell, characterized in that, include: The 12 vacuum chambers are arranged in series and are marked as vacuum chambers 11, 12, 13, 21, 22, 23, 24, 25, 26, 27, 28, and 29 respectively; Adjacent vacuum chambers are connected via the filter differential tube according to any one of claims 1 to 4; The vacuum chamber No. 25 is filled with argon gas at a flow rate of 1200-1400 SCCM; The No. 24 vacuum chamber and the No. 26 vacuum chamber are evacuated by dry pumps, and the remaining vacuum chambers are evacuated by molecular pumps.

6. The gas filter cell according to claim 5, characterized in that: The vacuum chamber No. 11 is connected to the upstream beam line; The No. 29 vacuum chamber is connected to the downstream experimental station.

7. The gas filter cell according to claim 5, characterized in that: The molecular pumps include molecular pumps numbered P-7 to P-2 and molecular pumps numbered P+2, P+3, and P+4; wherein: Molecular pumps P-7 to P-5 correspond to vacuum chambers 11 to 13 respectively; Molecular pumps P-4 to P-2 correspond to vacuum chambers 21 to 23 respectively; Molecular pumps P+2, P+3, and P+4 correspond to vacuum chambers 27 to 29; The vacuum chambers No. 21 to 23 and the vacuum chambers No. 27 to 29 are respectively evacuated by a shunt pump, each shunt pump having three extraction ports, which is equivalent to the above-mentioned molecular pumps No. P-4 to P-2 and molecular pumps No. P+2, P+3, and P+4.

8. A method for reducing beam effects, applied to the gas filter cell according to any one of claims 5 to 7, characterized in that: The following steps are involved: S1. Replace the filter differential tube according to claims 1-4 with the filter differential tube No. 304 at the starting position of the molecular flow in the gas filter pool; S2. Introduce 1200-1400 SCCM of argon gas into vacuum chamber 25; S3. Start the molecular pump and dry pump to make the pressure of vacuum chamber No. 11 lower than 1×10 -5 Pa.

9. The method for reducing beam effect according to claim 8, characterized in that: The fluid domain from the filter differential tube No. 304 to the vacuum chamber No. 11 was simulated using Molflow+ software. The boundary conditions included: temperature; molar mass of gas molecules; inlet flow rate of the filter differential tube No. 304; pumping speed of the molecular pump No. P-4; and pumping speeds of the molecular pumps No. P-5 to P-7.

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